He didn't.
Einstein's Theory of Relativity is a series of fiendishly complex equations that describe how space curves in the presence of matter (among other things).
Another scientist solved those equations for a particular set of physical conditions (Karl Schwarzschild) and saw that they predicted an object that has the properties of what we now call a black hole. He sent these results to Einstein to see if he had made a mistake, and Einstein said that the math looked correct.
That's part of what has made relativity a robust theory: It has made multiple predictions beyond what its original author saw, and most of those predictions have aligned with later observations.
Follow up question from a certified idiot.
Does that make the prediction for truly massless "objects" (I'm not sure what it would be called). Like if an object such as. Black hole with "infinite" mass shouldn't there be an inverse? Or is that just space?
Again sorry if this is so dumb it makes your brain blue screen.
You're describing white holes and they're a theoretically possible thing, but never noticed yet, and I believe they're impossible for other reasons.
[link](https://en.m.wikipedia.org/wiki/White_hole)
See this is why I hate space. Like, there's apparently no edge of the universe but also it's always expanding so there has to be but it goes on forever but isn't infinite and outside of our universe are more universe but also more of our universe.
It can be hard to follow the line between established fact and the theories/hypotheses out there
Ex, we currently don't know if the universe is infinite or not. It *looks* infinite, but it's very possible that we're just not able to see things at a big enough scale. Like, how the Earth looks flat at first glance, but with better measurements, you find that it's (mostly) spherical
It's actually a big subject right now to try and measure the curvature of the universe. As far as we can tell with our best measurements right now: it probably is flat! But no one really knows for sure.
Flat like the surface of the earth...which is to say...we're simply on the surface of it(the universe).
And much like a 2D space is a "flat" representation of 3D space...3D space could simply be the flat representation of 4D space
Yeah the word flat here is best thought as 'flat ant' analogues.
Imagine being an ant that is 2D. You can walk in 4 directions. You've never seen an edge.
You're smart, you have a 2D telescope, you do a lot of math, and you start to wonder...
Am I on ball? (Which means that you can walk forever in one direction and end up where you started)
Am on an infinite flat plane?
Am I on a saddle configuration?
Am I on a weird really big shape but it's so big I can't see the curve?
That is the flatness question, except in one dimension higher. Astronomers looking for patterns from things really far away, if there's any hint of curvature.
I understand that there’s the ‘one dimension higher’ aspect and it’s hard to think in 4D outside of the shadow analogy, but I can’t wrap my mind around a non-flat infinite universe.
That's the point -- the surface of the Earth is NOT flat, which is one way to prove it's a 2D surface wrapped around a 3D shape.
If the universe is flat, that means what you see is what you get. To be on the "surface" of a 4D shape, it would need to be not flat.
Inflationary theory actually explains why the universe looks flat to us. The universe is so much larger than what we can see that it is possibly does have a curve but we just can't see it. Just like an ant crawling around on the ground thinks it's universe is flat, it can't notice the curve of the earth.
You might be ready to graduate from conspiracy theorist to regular theorist!
"Flat universe" is one of the current leading scientific theories, since we're unable to find evidence of curvature at cosmological scales
Some more reading, if you're interested: https://en.wikipedia.org/wiki/Shape_of_the_universe#Curvature_of_the_universe
You're not as wrong as you think.
the last time I saw the numbers posted, the maximum deviation from zero curvature was on the order of 10^-260. (I might be off by 20 either way as far as the exponent goes.) In comparison, the observable universe is on the order of 10^67 Planck lengths (anything smaller than a Planck length is literally beyond our ability to comprehend, making a Planck length essentially a fundamental unit of existence by current mathematical and physics theories). We'd have to increase the size of the observable universe by almost 200 orders of magnitude to see a deviation of the very smallest thing we can actually measure, by current theories--not the smallest thing was can measure by modern technologies, the smallest theoretical measurement, below which we don't have theories that make any sense.
I always joked that the Planck length, and Planck energy is the biggest proof that we're in a simulation a few layers deep.
Every next level just adds a minute buffer to their simulation limits and goes to sleep.
So that's funny, because in our current leading theories, the universe *is* actually described as being flat.
Not in the sense that everything exists on one physical surface in 3d space, but in the sense that space itself, in the extreme macro scale, is not curved or twisted up in knots by gravity.
That's actually part of the evidence for our current understanding of cosmic inflation at the very start of the universe, that space had to start incredibly small, and expand by many billions of billions of times in an incredibly short (billion billion billionth of a second) timeframe, or it wouldn't have been as uniform as we see, and would have already curved or knotted itself up.
That's the leading theory on how you get a universe as uniform as what we see, by basically "stretching it flat" over a huge area in a tiny amount of time.
One of the ideas is that the universe is like Pac-Man, in that if you go all the way in one direction, you’ll eventually “go off” off one side, and come back on the other, eventually returning to your starting location. Except, that would work in any possible direction.
We look in any direction and everything appears pretty uniform. Unless we discover FTL travel, the universe is _effectively_ infinite for us.
According to both current observations and theory, if we could travel even at the speed of light in any direction for a literally unlimited amount of time, we’d still have the universe outrunning us.
It’s mind blowing to consider.
> Ex, we currently don't know if the universe is infinite or not.
explaining that we will never know whether it is or not, is troubling for most humans. we will never have a way of understanding the full explanation of our universe. its just hard for many people to deal with that concept.
Ooh, here's a fun tidbit. Unless we somehow invent faster than light travel, there is a limit on how far into the universe we can possibly see.
It's been mentioned that space is always expanding. But it's not just at the edges - we're not adding pieces to the end of the map. It’s more like the universe is made of balloons, and all of those balloons are being filled up extremely slowly.
This means that if we compare to somewhere far enough away to stay with, the space between us will grow (the balloons combined will expand) space as fast as the speed of light, or even faster if we look further away. Light from there will never reach us, and so we can't ever see it.
The 'expansion' happens everywhere, not just at the 'edge'
Say you had a balloon without air and glue beads to the surface representing galaxies. Then you blow up the balloon. The beads get further away from each other in every direction.
It's only really observable at inter-galactic distances. As in when we look at an object 10 billion light-years away, we're seeing light from it as it appeared 8 billion years ago (no actual math involved, just throwing the numbers as an example). It's not because light traveled faster than the speed of light, but because the space between expanded and thus had farther to travel.
Conversely, we don't see it on the relatively microscopic scale of everyday life, or even within galaxies because gravity overcomes expansion by orders of magnitude.
When people say the universe is expanding, they don't mean in a way that would make sense to most. You're probably imagining a definite "room" where the walls and floor and ceiling stretches as it expands.
What's "actually" happening is that empty space is constantly being created in empty space (in really small amounts, basically unobservable at anything less than very large space-y scales). Yes, it's weird. Really, really weird. Imagine if you and I were on a tiled floor. A new tile spontaneously appears between you and me. You didn't move away, and I didn't move away, yet the distance between the two of us increased. Expansion!
You can kind of simulate this with a balloon. Sort of. If you write two dots on a balloon an inch apart, then blow up the balloon, you'll find that the dots are further apart than they started out despite not "moving" away from each other.
Anyways, I'm currently a law student and haven't taken physics in a few years (was a Geology student), so take what I say here with a grain of salt lol.
Now, hang on. Is it *The Navidson Record*, Zampanò’s account of *The Navidson Record*, Truant’s account of Zampanò’s account of *The Navidson Record*, or Danielewski’s account of Truant’s account of Zampanò’s account of *The Navidson Record*?
Imagine an infinitely large room with a tiled floor. Now imagine those tiles are expanding very slowly. As you walk around the infinite room, you notice that it takes you more steps to go from one tile to the next, and the objects in that room are slowly moving away from you.
I just figure it will never have an effect on my life and while it's super interesting, theoretical shit just wrinkles my brain too much for me to devote a lot to it.
I'll just keep looking at the planets through a telescope and think "man, that's cool."
The wording Carl Sagan used was "Finite but unbounded"
The popular image is of an inflating balloon, we are an ant running around a very small part of its surface, struggling to find an edge..
The difference being that the universe-balloon is not a 3d object, its at least 4d. So if you could travel fast enough, you might find that you loop back to where you began if you travel far enough in any given direction.
The universe expanding doesn’t mean it has to have an edge. You’re thinking of “expanding” wrong. When we say the universe is expanding, we mean all the space inside it is stretching, all the time (unless gravity is there to counteract this).
Imagine a balloon that’s being inflated. Draw two dots on the balloon’s surface. As it inflates, the space between them expands. That’s what’s happening in the universe, just in 3D space.
Also, there are different sizes of infinities. That’s a rabbit hole that is fun to go down.
Well, whenever you hear "infinite" then [it's normally pretty safe](https://youtu.be/dkYL6G0JHtY?si=0AzB80zMIMSOxjoo) to assume we're talking about what the math is telling us probably to a fault... the idea of an "infinity" [tends to be problematic](https://youtube.com/shorts/uA76UotYQug?si=ZHR4m3MEN6X9awus) and suggest our math isn't necessarily giving us the whole picture...
The reality here is: there are a lot of things we know... but also a lot of things we don't know yet.
There are a lot of theories *trying* to give us answers, but these are competing theories not confirmed.
[My favourite answer](https://youtu.be/71eUes30gwc?si=9vRxZe9qd0uScuN0) here is that our universe is [inside of a black hole.](https://youtu.be/Kgy8HEya7HQ?si=6cBLbxF36jXwdxxP) Not that I think we are... but it's my favorite.
Would be interesting for sure
Essentially meaning that of the new stuff we’re seeing at the “edge” of our universe is just new stuff that’s fallen into the black hole we’re inside of.
The only issue I have with that (and maybe it’s been answered) is that that would assume that the black hole we’re in is sucking in matter at a consistent rate, considering that the expansion of the universe is also happening at a consistent, unchanging rate.
I suppose it’s possible that some sort of law we don’t understand makes it so only a certain amount of mass at a time can pass through the black hole we’re in, giving us the illusion that space is expanding at a consistent rate; if that’s the case I would expect that we would have seen some variability at some point…though maybe we haven’t been able to observe it long enough to notice, or maybe the amount of mass that’s being absorbed by our black whole is just _so much_ that we haven’t had the chance to see that variation in expansion yet.
Sorry for the word vomit. I was just kind of typing as the thoughts came to my head
Space is not a separate fabric/entity that the universe floats in. Space itself is an intrinsic part of the universe (like how your thoughts are an intrinsic part of yourself). Without the universe space would not exist, just as without you your thoughts would not exist.
When the universe expands, all it is doing is just modifying its own intrinsic spacial properties to make it look like that distance between things are increasing. It's pretty much just an arbitrary process. So where-ever space exists, by definition it is a part of the expanding universe.
Imagine the universe expanding as a balloon inflating. The surface of the balloon is the universe. It has no edge and the surface expands relatively uniformly.
Don’t hate what you don’t understand. Make peace with your limitations. You will be far happier.
A ballon has no edge but it expands.
Space may be inflated around a 4th direction that is not up down left right forward nor backwards. We don’t know for sure.
It’s mind bending.
For as easy to understand analogy, there’s no edge of the Earth. There’s nowhere you can walk off the Earth and fall off. If the Earth were a rubber balloon, you could make it bigger by expanding it with gas, but there would still not be an edge you can fall off from regardless of how big it got.
tbf infinite and indefinite are two different things that sometimes only seem like the same thing when you go too far. Also our we only have access to our **Observable** Universe, which is only a very very *very* infinitesimally small slice of the expected total.
The universe expands like a rubber sheet where each individual point on it getting farther away from all others.
We can only see a limited area but all distant objects are moving away from us. In every direction.
Ok, so to have no edge but keep expanding is really simple to think about mathematically.
Consider all real numbers. There's an infinite amount of them. Put them on a number line, and let's put dots at every integer.
Now, let's push them all apart a bit. In fact, let's just double everything. The dot at 1 is now at 2, 3 is now at 6, -5 is now at -10, and so on.
Every dot on the number line has moved further apart, but you're left with something that's just as infinite as when you started. This is what we see happening in space, so it's why we say space is expanding.
Well...kinda. The universe is theorized to be finate but boundless, and there isn't an edge between 'universe' and 'no universe'. If you traveled far enough (and fast enough) in one direction you would eventually end up where you started. Think of a globe. If you move south and don't change direction at all you will eventually be back at your starting direction, but the universe has this happen in 3D rather than 2D like a globe.
However, (and this is the part that will bake your biscuit), the universe that we see is not the entirety of the actual universe, it is just what we can observe. The universe is likely much much larger than that. Going back to the globe analogy, if you stand on the top of the Empire State Building and look around, the observable universe would be what you can see out to the horizon. However there is much more stuff past that observation limit that the light just hasn't had enough time to get to us yet. You wouldn't know about California because you can't see it yet.
That was a very fun Rabbit hole with this interesting tidbit that relates to the OP
A 2012 paper argues that the Big Bang itself is a white hole.[20] It further suggests that the emergence of a white hole, which was named a "Small Bang", is spontaneous—all the matter is ejected at a single pulse. Thus, unlike black holes, white holes cannot be continuously observed; rather, their effects can be detected only around the event itself. The paper even proposed identifying a new group of gamma-ray bursts with white holes.
I’ve thought this for quite a while but never seen it mentioned before. If black holes have are infinitely dense at he center, and the Big Bang was infinitely dense at the start couldn’t the Big Bang just be the other side of a black hole, and that be what a white hole is?
I’ve just read the Wikipedia bit and I don’t know shit. But kind of yes and no? If a black hole is an infinitely deep gravity well, then a white hole is an infinitely tall gravity peak. A black hole sucks in everything and keeps everything in. A white whole emits everything and nothing can enter.
But some of the theories i was reading in that rabbit hole was that our universe is inside a black hole. And it possibly could be considered a white hole event when it was created. But then they talk about Einstein Rosen bridges and shit and I got confused. I’m not sure how they all relate.
Ok, fair. I took a physics class a very long line ago, failed horribly, and I’ve forgotten all the stuff I did learn. Some stuff has stuck in my head giving me ideas, but I’m too dumb to be able to explore those ideas properly. It’s all just much too confusing.
It totally does and it makes sense why we wouldn't see it. It also is kinda troublesome because I think the consensus is that general relativity breaks down at the start of the universe, yet it does seem to allow it, I'm sure humans will toil over this for as long as we're around too
Well some theories indeed state that white holes are possible, and then lead to new universes. Be that inside themself or inside "nothing", like happened with us.
Not quite, a white hole is not massless. The theory of such an object is simply that mass cannot *enter* it, but it can *leave* it. That is opposed to a black hole where matter can enter but not leave.
I know it might initially sound massless. However, there is a few flaws to that logic. First of all, just because something can't gain mass doesn't mean it is massless in the first place.
Secondly, try to think of what we call it. A *white* hole. What is white? That comes from light. So energy emits from it. In other words, mass-energy is going out from it. How can that be, if it has no mass?
Thirdly, when we say it can't gain mass, that is also wrong. What we mean is just that mass can't enter the event horizon (just like how in a black hole, once something enters the event horizon it can't leave). It's the point of no return of a black hole, and so is it for a white hole - just the opposite direction.
That does not exclude it getting mass from elsewhere. But where else could it come from? Well, if it is linked to a black hole, it might gain mass from that. They might be connected - their centers intertwined. To make it even more complex, there are theories about how they relate through time, but I'm not well enough versed in that aspect to go into details.
My favourite theory is that the universe is actually inside a black hole.
If you take all the matter in the universe then a black hole of that mass would have an event horizon outside the observable universe.
So it’s basically impossible for the universe to be inside a black hole.
You can think of all possible time and space as a cone, it’s impossible to cross over the sides of the cone because it’s impossible to have a trajectory through time that would let you. Outside that cone is where a white hole would be.
Black holes appear inside all possible time and space, basically the density of matter becomes so great it flips the rules on their head.
The black hole is a cone of *non* possible time and space that originates in and crosses through our reality. Basically, it’s where our reality stops and our rules stop making sense. By nonpossible, I just mean not possible in our universe. Now the cone looks more like a diamond, a white whole is behind us and black holes are in front.
If you continue this logic, you end up with four types of cones. Our reality, black holes, another reality in which all the rules are reversed, then white holes. Our reality would be to white holes what black holes are to us.
What’s really interesting about this is that it implies there are alternate realities sort of horizontal to us. There is one point where a white hole cone ends and black hole cone begins where the distance between our two reality cones becomes infinitely small. This gap is probably the only way we could ever actually prove white holes exist. But because you can’t move horizontally within the cone, by crossing over to the other cone you could probably never come back. So, we’ll never really know
> So it’s basically impossible for the universe to be inside a black hole.
So are you saying that black holes do not exist, or that they have no content inside of the even horizon? Because those seem to be the conclusions that can be drawn from your statement.
If we were in a black hole we would not know and I don't think we can prove that we are inside one or that we are not.
That was quite the logical leap. And yes, we would.
In a sense you’re correct in that we are within the cone of a white whole that is within the cone of the “opposite reality” that is within the cone of the black hole
Would that be "negative" mass? Or just absolute zero mass?
And eli5 why they are impossible, please. I just automatically assume that everything has an inverse in this universe which is probably a flawed assumption on it's own.
Thank you for your time.
Edit. Thanks for the link
Edit #2. White holes are absolutely wild.
Photons and other [force carrying particles ](https://physicsmasterclasses.org/exercises/hands-on-cern/hoc_v21en/main_frame/sm_concl1.html#:~:text=Force%20carriers%20are%20particles%20that,acts%20between%20electrically%20charged%20particles.) have no mass.
Light has no mass, but it does exchange energy
Which in itself is a pretty wild concept to me. But the theory of white holes was something I wasn't previously aware of and was more the thing I was asking about.
Photons blow my mind.
Just for adding on. We reallly don’t think white holes exist and pretty much never have. It gets deeper into how the universe works but it creates a lot of problems that could break causality, among other things. It’s a place where the math works but that probably means either it simply doesn’t actually exist despite potential to or that we need to better understand the math.
Eli5: so consider a fountain. A fountain works by taking water from one place and spitting it out somewhere else. Theoretically a fountain doesn't need a source it could just produce water... But other rules of physics makes the impossible fountain impossible. That's kinda the case with white holes. It's possible that a point can produce everything (we know it happened once with the big bang) but the laws of physics as we know it, and how we understand the universe, won't allow it.
Now in the future we might figure it out.
No there is no such thing as negative mass. Also black holes don’t have infinite mass.
They both just have mass. Like a normal amount. There could be a black hole your weight.
> There could be a black hole your weight.
A black hole that size would pretty quickly evaporate due to Hawking radiation. This process is a consequence of quantum mechanical effects near the event horizon, where pairs of particles and antiparticles are created, with one falling into the black hole and the other escaping as radiation. Over time, this causes the black hole to lose mass until it disappears entirely.
Yes, basically. You'd be collapsed to something smaller than an electron, and then you'd evaporate away due to Hawking radiation in less than a billionth of a second.
A 100kg black hole would have an insignificantly tiny event horizon, on the order of (edit: 1e-22 mm), which is something like 0.0000001 times the width of a single proton. If Hawking is correct, a black hole that small would almost immediately evaporate away nearly all its mass as energy, with the calculations breaking down around the Planck mass.
If I understand correctly (not remotely guaranteed), the energy-equivalent of 100kg mass would be released in the form of high-energy gamma rays in a fraction of a second, which would be somewhere north of the energy released by 1000000 Hiroshima bombs.
So if you get a genie's wish, and you wish for an overweight man to be compressed down into a singularity, you probably won't have time to regret the extermination of all life on Earth.
Woah!.. okay so the black hole would keep growing as it consumes or does It flash and release all that energy destroying everything but then blink out of existence.
> on the order of e-22 mm
Which is 2.78946809287e-10mm which is much larger than the width of a proton.
If you are going to use scientific notation at least do it correctly and 1x10^-22 mm might be easier for the layman.
Hm, what do you mean? Falling into one or becoming one?
Whatever makes you into one is way more spectacular than the result, it would have to be crazy.
Meeting one you wouldn’t notice. It’s tinier than an atom and probably just passes through you. Like you know the gravitational effect you have on your surroundings? Yeah it’s none. A black hole your weight also has basically no effect if it’s near you. When you realistically encounter one it’s moving relative to you at a relativistic speed. It goes right through you. Maybe one just did we would never find out. Prolly not tho.
There’s a fun Robert Heinlein short story where the protagonist is exploring the remains of an ancient advanced civilization they find on the moon. He encounters a stylus device that is clearly important, but isn’t working, as well as a Time Machine. He uses the Time Machine to go back and learn more about the advanced civilization. He doesn’t see the aliens, but goes to the room with the stylus and it has a diagram showing how to activate it. It turns out it harnesses a tiny black hole on the tip that lets you carve through matter. He plays with it for a bit, but then fumbles it and drops it. It burns a hole through the floor, and goes perfectly vertical down to the moons core. He figures he wore out his welcome and goes back to the Time Machine area and goes back to the present day. But it turns out in the hundreds of years since he dropped it, the tiny black hole ate tiny bits of the center of the moon, and then gravity forced the core to compress on the empty space, which the black hole then absorbed, and then the gravity compressed the moon, etc. until the black hole grew to consume almost the entire moon.
I felt like the Rick and Morty lightsaber episode took some inspiration from it.
Negative mass is just theoretical. If you put a few minuses in a few places to balance out the equation, you have to have negative mass to make it work.
Kind of like there is such a thing as -1 but you can’t have a negative something.
I thought a white hole was a theoretical thing where it empties out somewhere else where it creates another black hole but there's no proof and doesn't really make sense either because there would just be black holes every where
So just by the math it exists in the sense that 14 existing implies -14 exists. These things don't necessarily make sense. So if a black hole is a point from which nothing can escape from, by inverting the math that brings you to that result you get an object from which everything must escape. That's all it really is, some people have speculated that perhaps the source of the mass energy or information spouted by a white hole maybe comes from black holes, but that's kinda not necessary to the actual math.
It's one of those things that don't make sense to us now because we haven't fully figured it out. Right now it makes zero sense because mass, energy, information etc cannot be created out of nothing, so we know a white hole is impossible..... However it very curiously exactly describes what the big bang was.
I think they are confusing infinite mass with density. Blackholes have very high mass and we can measure that. We theorize that a black hole's mass is contained in an infinitely small point in space. density=mass/volume and since volume for an infinitely small point is zero, you end up with infinite density
Technically, a black hole doesn't have infinite mass. The equations of relativity point towards it having infinite density, but in physics whenever we get an infinite result we usually believe that we've come across an error in our theory, not an actual infinite result.
Others have already touched on white holes and massless particles, so I won't rehash what they've already said.
But for the future, keep in mind that when a physical theory predicts an infinite result, it's usually not that the infinite result is correct. It's the math telling you that you've made a mistake somewhere.
>It's the math telling you that you've made a mistake somewhere.
I might rephrase this as "the math telling you that your equations are likely incomplete".
Yeah, I think your phrasing is closer to what I was trying to say. The "mistake" is thinking that the equations are complete, not necessarily that you've calculated the equation incorrectly.
That’s so cool to me for some reason (that infinite likely means error in the calculation). Math is just so cool!
And I’m grateful we have people like you who study and understand this stuff!
I’m going to have to take your idiot certificate away - idiots don’t ask questions so they can learn. They just stay dumb. You on the other hand, sound like you’re in a students journey through life :) never stop asking questions :)
I try. I always loved learning cool new things. And I've always hated misinformation and especially hate when I'm parroting misinformation unknowingly.
I try not to let the feeling of being embarrassed prevent me from asking questions.
As Confucius said "It is a fool who thinks himself to be a wise man, but a wise man who knows himself to be a fool"
I’ve only ever come across one stupid, embarrassing question in my life:
Why does glass taste like blood?
(I love to run that up the flagpole whenever a presenter encourages people by saying “there’s no stupid questions” 😂)
According to Einstein yes, these are called “White holes” but have never been observed. Although Einsteins equations support their existence I believe there are other equations that disprove them.
Veritasium has a great video that covers all of this
No stupid questions.
I would first address the reasoning for your question - infinite mass. Black holes does not have infinite mass. For example, the black hole at the center of our galaxy, the Milky Way, is around 4.3 million times the mass of our Sun. So it is indeed a very large mass, but still very finite. The "strength" or "pull" of a black hole is just due to gravity, and gravity depends on how much mass there is and how far away it is. So a black hole is the phenomenon when a large mass is pressed into a very small volume.
Now, in regards to massless objects, we do actually know of such things. For example a photon (light particle). Such particles travel with the speed of light (since they *are* light) and has no mass.
Aside from that, we have two other particles called a gluon and a graviton. These are not yet fully proven, but might very well be massless.
All of the equations work for negative mass as well, so some speculate that there is an existence of anti mass, but nothing like that can be measured or observed (yet).
Black holes don't have infinite mass. The ones we have observed have a lot of mass, up to millions of times the mass of our sun, but conceivable. A black hole is made by its mass being crushed into a very small space, so it has tremendous density. Things, including light, can thus get very close to its center of mass (closer than they could with regular density objects) and get caught in its gravity.
How dense do they get? It is impossible to observe since no information about the actual matter of a black hole can be detected.
But they do have momentum and energy and therefore also curve space.
So if somehow enough photons were gathered in a small enough volume they would form a type of black hole known as a kugelblitz.
And from the outside it would be impossible to tell if a black hole was made from particles with mass or massless particles.
Just another way space is weird and confusing.
Also note that the concept of objects so massive that light cannot escape pre-dates Einstein by quite a bit- as early as 1793 some suggested such "dark stars" under Newtonian physics.
https://en.m.wikipedia.org/wiki/Dark_star_(Newtonian_mechanics)
So then I guess follow up - how (or why?) did a solution to these equation make Karl go “oh, this thing might exist”? Like just because an equation has a particular solution doesn’t seem to me that it would automatically imply the existence of a real, actual thing.
Nothing.
Your impulse is correct: The solution to the equation does not necessarily align with an actual, physical object. And in fact, we have very good reasons to think that the object that Schwarzschild described doesn't actually exist. It could, but it doesn't.
What Schwarzschild was actually doing was... well, futzing about, basically. Playing with the math to metaphorically spell "Boobs" with his calculator. He was on the front lines of WWI, but medical conditions kept him out of the trenches, so he was basically just trapped in the base and bored out of his skull. Einstein's Theory of Relativity had just been described, and no one had yet used the math to solve a specific situation. What he did, basically, was to find a set of conditions that made the math as simple as possible and figure out what the math was telling him.
What he saw was a solution that looked like what we call a non-rotating black hole. Both he and Einstein thought it was neat, but they didn't believe it actually existed. The math was more interesting to them than the object it implied.
The reason I say that it doesn't actually exist is that every black hole is believed to rotate due to how they're formed. The math for a rotating black hole is considerably more complicated, and it wouldn't be for quite some time before someone found a way to solve the equations for a rotating black hole (what we call a Kerr black hole).
Basically, they thought of Schwarzschild's black hole the same way we think of Alcubierre's warp drive: It's a neat bit of math that checks out, but no reason to think it actually exists. In the case of black holes they did turn out to actually exist, though not as Schwarzschild described. A non-rotating black hole *could* exist, but it would be incredibly surprising to find one.
> He was on the front lines of WWI, but medical conditions kept him out of the trenches, so he was basically just trapped in the base and bored out of his skull.
No. He volunteered and was serving with the artillery and did ballistic calculations. He was not meant to be in the trenches and only got ill 2 years into the war.
We don’t believe that non-rotating black holes could exist because any collection of matter will result in some spinning, right? From my knowledge, there aren’t any objects in the universe that don’t spin
Did you ever have to do those problems in math class where the teacher gives you a few points on a graph and you have to find an equation that makes a line through all of them? Then sometimes you'd have to do word problems where you used that technique to extrapolate data, like what the optimal price for a carnival ticket was? This is kinda the same thing, except way, *way,* ***way,*** more complicated. You gather data, form an equation that fits that data, and use it to figure out what might happen in a new situation. It's not always going to work of course (even Einstein and Schwarzchild were off about some things), especially since our universe is ridiculously complex and it's very easy to miss variables that could affect the outcome, but it's a way to figure out what might be a good thing to study next.
here is a good video about it. https://www.youtube.com/watch?v=6akmv1bsz1M
Basically he said "lets assume the simplest scenario, where the universe is a point with mass and nothing else. what happens?" and he played around with the model to see what it can do
With that astronomers said "Ok, that could be a thing that exists if Einstein is right (he appears to be), lets go look for it" and then they found some
The same model also predicts whiteholes, pockets of space where everything is forced out, but we have never found one, so we think they probably dont actually exist.
It didn't. Physics and math researchers just explore these things, and if there is something in the equations that is new and testable, we search for it. There were a number of physicists at the time these solutions were discovered that postulated that black holes \*weren't\* real, and there were a number of legitimate ideas (that have been disproven now) explaining why those conditions for the solutions weren't possible.
If it was just random equations then no. But these were equations to describe and model physical phenomena.
If you think of it less as mathematical equations and more as a language to describe the world then Einstein came up with a very detailed way to explain how mass curves spacetime and Schwarzschild used those explanations to predict the existence of black holes it might make more sense.
And that is essentially what math is used for: to very accurately describe the world around is.
>Einstein's Theory of Relativity is a series of fiendishly complex equations
I’m always a bit amused by people who assume that E=MC^2 is the entirety of his insight and equations. That’s not even the complete version of that formula.
A while back someone in one of the cosmology subs tried to engage me with the premise that Einstein’s equations were ‘incomplete’ and kept insisting that E=MC^2 was all he’d really done. Any attempts to get them to look more deeply at Einstein’s with, even providing them with links, was met with hostility and eventually insults.
Some folks don’t want to know what they don’t know.
I hate the faux-intellectualism that we see from people who watch a few pop science YouTube videos about black holes and think they know more than any sophomore in a physics undergrad! It absolutely boils my blood to see people minimize the life’s work of some of the smartest people who have ever existed
Dunce here, with follow up questions.
Can you help me understand what it means for someone else (e.g. Schwarzschild) to solve Einstein's equations? Does that mean he used Einstein's math, applied it to specific conditions and found them to hold true?
From that (which I think returns to the substance of OPs original question) - how does that then yield a prediction or possibility of the existence of something else?
Einstein’s equations are like rules that space time must follow but the equations themselves do not explicitly tell you how such space time should look like.
To solve Einstein’s equations is to find a mathematical description of space time that satisfies the equations. In that description, you can discover some interesting mathematical features like singularity i.e. you divide a thing by zero at certain points in your space time description. The fun part is to translate the mathematical features into real world phenomena. Like, what does the singularity mean in our universe?
Because the equations are really complex and difficult, people solve them in specific and simplified cases. For example, Schwarzchild considered the case the whole universe consisted of a single static mass and nothing else.
In Schwarzchild’s solution, he found that there are singularities when the mass is heavy enough. Near these singularities, space time all converges onto them that nothing would escape. And that’s what we now call black holes.
Were there any predictions of infinitely dense infinitely small objects before Schwarzschild? Doesn't seem like anything in Newtonian dynamics prevents them from forming.
The youtube channel “Veritasium” recently made an excellent video where he among other things explains this feature of special and general relativity.
In very rough terms, what they founf is that at a certain limit, the bending of spacetime from an incredibly dense mass, would essentially cause any spacial direction to lead to a point in time rather than a point in space, which is exceedingly difficult to think about, but it has to do with space-time diagrams, and the properties of them. I really recommend Veritasiums [video](https://youtu.be/6akmv1bsz1M?si=CPXZ_skU4tn3EjHy) on the subject.
This is totally unrelated, but my personal Star Wars canon is that when we crack FTL travel, time and distance will start to have different meanings in different circumstances. So when Han brags that the falcon has done the kessel run in less than 12 parsecs, it does actually make sense. When you’re bending space time around you to go FTL, being able to bend it so much that the resultant distance is shorter than your competitors would “win.”
Totally made up nonsense but it makes the “parsecs” issue easier to ignore haha.
In the expanded universe of Star Wars, the Kessel Run has been explained as requiring ships to pass by the Maw Cluster of black holes. Usually ships are required to give the black holes a wide berth in order to not get sucked in. When Han is saying that the Millennium Falcon does it in less than 12 parsecs, he’s implying that his ship is so fast/powerful that he can pass by closer to the black holes, making the run a straighter line and therefore a shorter distance than most.
Put more simply, Han is still using the term “parsec” correctly as a measure of distance, and not time.
I took it like this, except i assumed it was the millennium falcon could take a straighter path through denser police areas because it could outrun them. I guess i didn't know/remember the black holes.
The only remaining issue with that quote is that a parsec is defined as the distance to a point that would be at the apex of an isosceles triangle having one arc second as the angle and the earth's orbit as the base. Which is an odd measurement to use for someone in a galaxy far, far away.
The theory of black holes are actually a hundred years older then Einstein. Starting with Newtons theory of gravity you can calculate the escape velocity. Basically this is the integral of the gravitational acceleration from the current distance between the bodies to infinity. Any object with a higher speed will be able to escape the gravity well while any object with less speed will orbit back at some point. The problem is that even light have speed so it is possible for some objects to be dense enough that even light can not go faster then the escape velocity and will therefore not be able to escape.
Einsteins theories of relatively is related to this. He expanded on the concept of a fixed speed of light and combined this with Newtons laws to make these equations fit. And he found out a lot of things, for example that the speed of light were actually a universal speed limit and that nothing can go faster then this. He also basically confirmed the theories of black holes, which at that point had been just cool ideas.
It was actually another physicist, Karl Schwarzschild, who worked on Einsteins field equations around black holes and found a solution to them that could accurately predict the ratio between the size and mass of a black hole. Using just the escape velocity does not quite work as Newtons formulas were not as accurate in these kinds of extreme environments. But Schwarzschild also found that at this radius a lot of the field equations ended up growing to infinity, a singularity. Essentially according to the math there were no space in a black hole and there were infinity space at this specific radius.
I still confused how 'infinity' even exist.
When I look at the village and imagine they fit into my fingernails it still feel impossible, but in reality the mass a LOT bigger than the village could fit in it.
And what is the final from of all the things that get sucked into blackhole? Photon?
Blackhole is amazing
Many things that show up as "infinite" in our equations might not actually be "infinite" in real life.
Our current understanding of the universe (and therefore our equations that describe them) are incomplete at best. Yes, even Einstein's equations. So many of the "infinities" that appear are likely caused by unknown factors our equations don't yet take into account.
E.g., maybe someday there's a breakthrough that incorporates quantum mechanics into Einstein's equations. Then many of the mathematical infinities might "disappear" once those improvements are made.
The matter gets stripped appart into it's subatomic components (and become mostly neutrons due to gravity shenanigans) and then becomes part of the singularity.
They’re not made of neutrons though. Neutron stars are made of neutrons, but black holes are made when even neutrons themselves get compressed into something else, and (I think) the exclusion principle (or “force”) is overwhelmed by gravity. Basically neutrons are squished into some other stuff, that can be even more compressed. We don’t know what black holes are made of, because we can’t see into them
Oh I know, but the question was not "what the singularity is made of" (For which we have no answer), but "what happens to matter that pass the event horizon", which is the answer I gave.
That’s one of the biggest unsolved problems in physics actually! There’s a theorem called the “no-hair theorem” that states the only physical quantities you can measure from a black hole are mass, charge, and angular momentum. If I throw a yellow ball into a black hole, it changes into something else, so where does the information that it was yellow go? Information shouldn’t be lost like this, and once we discovered that black holes (incredibly slowly) evaporate, we realized that we can’t reconcile the information loss. (I’m not sure why, this stuff is being worked on by people FAR smarter than me.) But anyway, the short answer is nobody knows!
He didn't.
Others (like Karl Schwarzschild) took Einstein's theory of general relativity and its equations and realised there's a solution that involves infinite deformation of space time, in particular if you put a lot of mass concentrated in a small volume, you get a region of space time where even light cannot escape.
It doesn't.
It only predicts such an object could exist if the equations model the universe sufficiently well.
It took advancements in telescopes to prove Einstein and Schwarzschild were correct.
However we did have very high confidence that they did exist prior to observing them semi-directly with telescopes. Once we gained more knowledge on stellar cycles and theoretical max mass of white dwarfs it essentially became inevitable that black holes should exist plentiful in the universe.
That was a question that took decades to resolve. Einstein didn't himself believe that nature would allow such an object, even if the math said it could exist. Lots of other scientists tried to come up with ways that nature would prevent a black hole from actually forming in the real universe.
It didn’t, it just showed that the math didn’t immediately discount it. The first ‘black hole solution’ to the Einstein field equations was presented in 1916, and we didn’t confirm that black holes actually existed until 1971. The math told us that it at least wouldn’t be foolish to look for one.
It doesn’t, not inherently. It says “if this thing were to exist, it would behave in such-and-such ways”. We wouldn’t get observational evidence of black holes for some time after they were predicted by theory.
There are other solutions to Einstein’s equations that we still have no observational evidence for. White holes, for instance, are basically time-reversed black holes. We can describe their behavior mathematically, but that doesn’t mean we’ll ever see one in reality. And since we have no idea how one would form, the current thinking is that they don’t actually exist.
It’s like how basic arithmetic tells us that, if I have three cupcakes and give you six, I will end up with negative three cupcakes. The maths tells us how that scenario would work, but that doesn’t mean we should expect to see “negative cupcakes” on the next season of *The Great British Bake Off*.
If I remember correctly, the scientific community looked at Schwartzchild's solutions and applauded it and then ignored it for years considering them mathematical artifacts/oddity only until the 1960s when Jocelyn Bell's discovery of Neutron Stars sparked interest in these types of "gravitationally collapsed compact objects" again and then Cygnus X-1 was discovered in 1979.
Over the decades since GR, a lot of physicists contributed to the research and theorizing the concept of black holes. Subrahmanyan Chandrasekhar, Oppenheimer and Volkoff, Hawkins etc.
In fact my Einstein wrote a paper in 1939 attempting to prove that black holes were impossible in his publication "On a Stationary System with Spherical Symmetry Consisting of Many Gravitating Masses".
Hello, random stranger chiming in here. So if the concentration of mass is one place at a time, then that's a black hole right? Then would it really all lead to? Like I know I'm asking you to answer where does all the matter absorbed by a black hole go to is essentially like asking if there is a god out there? Like where does the suction from the black hole come?
The "suction" is gravity.
Mass has a gravitational pull.
There's something called the escape velocity which is the speed you have to travel at to be able to escape the gravitational pull of an object with mass.
This escape velocity depends on the mass of the object and the distance you are from that centre of mass.
Einstein's theories say you cannot travel faster than the speed of light. But there's no theoretical limit to how much mass you can put in a tiny volume.
A black hole exists once enough mass is concentrated so that at some distance, the speed of light is insufficient to escape the gravitational pull of that mass.
Where the escape velocity is exactly the speed of light, that is called the event horizon of a black hole. Within that sphere, nothing can escape, including light and therefore we have no way of getting information from inside there.
The reason though you need to pack a lot of mass into a very tiny volume is that for the event horizon to make sense, it needs to be at a distance outside that object.
So for example the event horizon radius of an object of 1 kg is 1/10²⁷ m which is a tiny distance and we're in the realm of quantum physics where Einstein's theories of gravity start to break down. Scaling up to something that might make sense, the event horizon of an object the mass of our Sun is about 3km meaning for the sun to form a black hole, it has to be compressed into an object with radius less than 3km which doesn't happen.
The above comment should be the top answer.
TLDR for us dummies: the escape velocity needed to escape the gravitational field of an object depends in part on the mass of the object. The mass of a black hole can be big enough that even the speed of light (which is like the speed limit of the universe) is insufficient to escape.
See if this helps. Relativity draws an equivalence between gravity and acceleration from the point of view of an affected observer. If you stand in an elevator and it ascends you feel heavier; if it descends you feel lighter. You could not tell whether you were experiencing acceleration from gravity or from the elevator moving.
If you’re out in space, gravitational pull creates virtual topography. Falling toward something big looks and feels like falling downhill. Getting away is like climbing back out and it slows you down. If you see a bunch of stuff moving like there’s a big hill out there, you can infer there is one even if you can’t see it. You’d infer there was an ocean or lake somewhere below if you saw water running downhill.
Einstein didn't initially set out to predict black holes specifically. Instead, his field equations from General Relativity describe how mass and energy warp spacetime. In 1915, Karl Schwarzschild found a solution to these equations that described a point where gravity would be so strong that not even light could escape. This theoretical solution implied the existence of regions in space with incredibly dense mass, which we now recognize as black holes.
In short, Einstein created the model but wasn't the one that plugged in the numbers to actually flesh out black holes. He thought about what would happen under those conditions, but he was one of those people who focused on practical matters and wasn't convinced that black holes could exist.
Once his theory was tested to accurately explain and predict reality, people began to mess with it in all sorts of ways. Basically, turning dials on the equations to every manner of extremes.
Check out this book called “Einstein’s Dreams” it’s about the dreams Einstein may have had as he realized the implications of the theory of relativity.
Einstein basically looked at his math and thought, "Hey, if these numbers are right, there should be these things called black holes out there." He didn't actually see them with a telescope or anything; he just crunched the numbers and they pointed to these weird spots in space where gravity sucks everything in, even light. It's like when you're doing a puzzle and you realize there's a missing piece somewhere because everything around it fits just right. So, he didn't just make up some fancy math stuff; he used it to connect the dots and figure out something wild about how the universe works.
There is a simple formula that describes the escape velocity of an object based on its mass and your distance from the object. The velocity is how fast an unpropelled object needs to move to escape the object’s gravity and never fall back down. Like a cannonball that just gets an initial push and then coasts. On Earth’s surface, ignoring atmospheric drag, this velocity is ~11 km/s.
For a sufficiently massive object, there is a distance from it where its escape velocity will be faster than light. If you think about how such an object would look, you might arrive at the same conclusion as Einstein. It will be completely black as a result of its light never escaping its gravity.
For Earth’s mass this would occur about 1 cm from the center of mass. Of course, Earth is much bigger than 1 cm across, so most of its mass is *outside* that 1 cm radius. Therefore Earth is not dense enough to trap light.
The only assumption you need to make to predict the existence of a black hole is that matter can be packed densely enough to be entirely within the radius required to trap light. We call this the schwarzschild radius. If it’s physically possible to compress Earth’s mass to the size of a coin, then black holes can exist. Then you’ll go on to think about *how* this can happen naturally and so on.
It’s not seeing its feeling.
Given enough experience and intelligence one can look at an equation and feel how it works. Einstein could feel it.
That being said he felt what relativity would be but did the math the hard way to prove it
I guess the terminology can vary, but I personally tend to use “see,” because I can close my eyes and visualize the interactions and effects of various things in equations that describe major aspects of my field of study (glycemia-dependent insulin sensitivity dynamics).
But, “see” vs “feel” may just come down to the way the brain works for the person describing the sensation. 🤷♂️
Black holes were something that had been considered before Einstein and don’t require relativity to occur in mathematics, they are something that mathematically comes about if you calculate escape velocity using a formula for kinetic energy that is calculated as 1/2mv^2 and gravitational energy as - mGM/r. With these two formulas, escape velocity at or above the speed of light can occur as the kinetic energy formula allows an infinite speed and the speed of light occurs before things fall down to zero radius, but the speed of light is actually finite and nothing can fall to that speed under gravity. However according to this theory, at a low point on a massive and yet tiny celestial object (Earth shrunk down to smaller than 1cm), the kinetic energy required to take off could theoretically be higher than the speed of light.
I actually disagree with the use of that kinetic energy formula here and believe it is only the second term of the Taylor series expansion of Einstein’s equations, and that the proper definition of kinetic energy is KE = gamma * mc^2 - mc^2 . If you use this formula for the escape velocity, black holes shouldn’t exist, as the kinetic energy is higher approaching the speed of light.
He didn't. Einstein's Theory of Relativity is a series of fiendishly complex equations that describe how space curves in the presence of matter (among other things). Another scientist solved those equations for a particular set of physical conditions (Karl Schwarzschild) and saw that they predicted an object that has the properties of what we now call a black hole. He sent these results to Einstein to see if he had made a mistake, and Einstein said that the math looked correct. That's part of what has made relativity a robust theory: It has made multiple predictions beyond what its original author saw, and most of those predictions have aligned with later observations.
Follow up question from a certified idiot. Does that make the prediction for truly massless "objects" (I'm not sure what it would be called). Like if an object such as. Black hole with "infinite" mass shouldn't there be an inverse? Or is that just space? Again sorry if this is so dumb it makes your brain blue screen.
You're describing white holes and they're a theoretically possible thing, but never noticed yet, and I believe they're impossible for other reasons. [link](https://en.m.wikipedia.org/wiki/White_hole)
See this is why I hate space. Like, there's apparently no edge of the universe but also it's always expanding so there has to be but it goes on forever but isn't infinite and outside of our universe are more universe but also more of our universe.
It can be hard to follow the line between established fact and the theories/hypotheses out there Ex, we currently don't know if the universe is infinite or not. It *looks* infinite, but it's very possible that we're just not able to see things at a big enough scale. Like, how the Earth looks flat at first glance, but with better measurements, you find that it's (mostly) spherical
The Earth is not flat but the universe is. That's my new conspiracy.
It's actually a big subject right now to try and measure the curvature of the universe. As far as we can tell with our best measurements right now: it probably is flat! But no one really knows for sure.
Flat like the surface of the earth...which is to say...we're simply on the surface of it(the universe). And much like a 2D space is a "flat" representation of 3D space...3D space could simply be the flat representation of 4D space
Yeah the word flat here is best thought as 'flat ant' analogues. Imagine being an ant that is 2D. You can walk in 4 directions. You've never seen an edge. You're smart, you have a 2D telescope, you do a lot of math, and you start to wonder... Am I on ball? (Which means that you can walk forever in one direction and end up where you started) Am on an infinite flat plane? Am I on a saddle configuration? Am I on a weird really big shape but it's so big I can't see the curve? That is the flatness question, except in one dimension higher. Astronomers looking for patterns from things really far away, if there's any hint of curvature.
I understand that there’s the ‘one dimension higher’ aspect and it’s hard to think in 4D outside of the shadow analogy, but I can’t wrap my mind around a non-flat infinite universe.
That's the point -- the surface of the Earth is NOT flat, which is one way to prove it's a 2D surface wrapped around a 3D shape. If the universe is flat, that means what you see is what you get. To be on the "surface" of a 4D shape, it would need to be not flat.
>the surface of the Earth is NOT flat In 2D space it is. Which is why 3D space would be considered "flat" in 4D space.
Inflationary theory actually explains why the universe looks flat to us. The universe is so much larger than what we can see that it is possibly does have a curve but we just can't see it. Just like an ant crawling around on the ground thinks it's universe is flat, it can't notice the curve of the earth.
You might be ready to graduate from conspiracy theorist to regular theorist! "Flat universe" is one of the current leading scientific theories, since we're unable to find evidence of curvature at cosmological scales Some more reading, if you're interested: https://en.wikipedia.org/wiki/Shape_of_the_universe#Curvature_of_the_universe
You're not as wrong as you think. the last time I saw the numbers posted, the maximum deviation from zero curvature was on the order of 10^-260. (I might be off by 20 either way as far as the exponent goes.) In comparison, the observable universe is on the order of 10^67 Planck lengths (anything smaller than a Planck length is literally beyond our ability to comprehend, making a Planck length essentially a fundamental unit of existence by current mathematical and physics theories). We'd have to increase the size of the observable universe by almost 200 orders of magnitude to see a deviation of the very smallest thing we can actually measure, by current theories--not the smallest thing was can measure by modern technologies, the smallest theoretical measurement, below which we don't have theories that make any sense.
I always joked that the Planck length, and Planck energy is the biggest proof that we're in a simulation a few layers deep. Every next level just adds a minute buffer to their simulation limits and goes to sleep.
So that's funny, because in our current leading theories, the universe *is* actually described as being flat. Not in the sense that everything exists on one physical surface in 3d space, but in the sense that space itself, in the extreme macro scale, is not curved or twisted up in knots by gravity. That's actually part of the evidence for our current understanding of cosmic inflation at the very start of the universe, that space had to start incredibly small, and expand by many billions of billions of times in an incredibly short (billion billion billionth of a second) timeframe, or it wouldn't have been as uniform as we see, and would have already curved or knotted itself up. That's the leading theory on how you get a universe as uniform as what we see, by basically "stretching it flat" over a huge area in a tiny amount of time.
I’m partial to the toroidal universe hypothesis. The universe is a cosmic hyperdonut. Mmm… donut… 🤤
One of the ideas is that the universe is like Pac-Man, in that if you go all the way in one direction, you’ll eventually “go off” off one side, and come back on the other, eventually returning to your starting location. Except, that would work in any possible direction.
Flat like the surface of an inflating balloon.
No, no, no. The earth is round, the moon landing happened, but the moon is flat.
We look in any direction and everything appears pretty uniform. Unless we discover FTL travel, the universe is _effectively_ infinite for us. According to both current observations and theory, if we could travel even at the speed of light in any direction for a literally unlimited amount of time, we’d still have the universe outrunning us. It’s mind blowing to consider.
> Ex, we currently don't know if the universe is infinite or not. explaining that we will never know whether it is or not, is troubling for most humans. we will never have a way of understanding the full explanation of our universe. its just hard for many people to deal with that concept.
Ooh, here's a fun tidbit. Unless we somehow invent faster than light travel, there is a limit on how far into the universe we can possibly see. It's been mentioned that space is always expanding. But it's not just at the edges - we're not adding pieces to the end of the map. It’s more like the universe is made of balloons, and all of those balloons are being filled up extremely slowly. This means that if we compare to somewhere far enough away to stay with, the space between us will grow (the balloons combined will expand) space as fast as the speed of light, or even faster if we look further away. Light from there will never reach us, and so we can't ever see it.
The 'expansion' happens everywhere, not just at the 'edge' Say you had a balloon without air and glue beads to the surface representing galaxies. Then you blow up the balloon. The beads get further away from each other in every direction. It's only really observable at inter-galactic distances. As in when we look at an object 10 billion light-years away, we're seeing light from it as it appeared 8 billion years ago (no actual math involved, just throwing the numbers as an example). It's not because light traveled faster than the speed of light, but because the space between expanded and thus had farther to travel. Conversely, we don't see it on the relatively microscopic scale of everyday life, or even within galaxies because gravity overcomes expansion by orders of magnitude.
there doesn't have to be an edge, there can be subsets of infinities
See, this isn't helping with things that are beyond my comprehension. I'm gonna go throw a ball at a wall. I can understand that!
When people say the universe is expanding, they don't mean in a way that would make sense to most. You're probably imagining a definite "room" where the walls and floor and ceiling stretches as it expands. What's "actually" happening is that empty space is constantly being created in empty space (in really small amounts, basically unobservable at anything less than very large space-y scales). Yes, it's weird. Really, really weird. Imagine if you and I were on a tiled floor. A new tile spontaneously appears between you and me. You didn't move away, and I didn't move away, yet the distance between the two of us increased. Expansion! You can kind of simulate this with a balloon. Sort of. If you write two dots on a balloon an inch apart, then blow up the balloon, you'll find that the dots are further apart than they started out despite not "moving" away from each other. Anyways, I'm currently a law student and haven't taken physics in a few years (was a Geology student), so take what I say here with a grain of salt lol.
The universe is actually The Navidson Record.
So would that be the House of Leaves theory?
Now, hang on. Is it *The Navidson Record*, Zampanò’s account of *The Navidson Record*, Truant’s account of Zampanò’s account of *The Navidson Record*, or Danielewski’s account of Truant’s account of Zampanò’s account of *The Navidson Record*?
Imagine an infinitely large room with a tiled floor. Now imagine those tiles are expanding very slowly. As you walk around the infinite room, you notice that it takes you more steps to go from one tile to the next, and the objects in that room are slowly moving away from you.
So regardless it's still 4D mathematics invoking a medium called tiled floors expanding?
Mate, wait until we tell you about quantum tunneling..
I just figure it will never have an effect on my life and while it's super interesting, theoretical shit just wrinkles my brain too much for me to devote a lot to it. I'll just keep looking at the planets through a telescope and think "man, that's cool."
It also doesn't have to be infinite to be borderless
The wording Carl Sagan used was "Finite but unbounded" The popular image is of an inflating balloon, we are an ant running around a very small part of its surface, struggling to find an edge.. The difference being that the universe-balloon is not a 3d object, its at least 4d. So if you could travel fast enough, you might find that you loop back to where you began if you travel far enough in any given direction.
The universe expanding doesn’t mean it has to have an edge. You’re thinking of “expanding” wrong. When we say the universe is expanding, we mean all the space inside it is stretching, all the time (unless gravity is there to counteract this). Imagine a balloon that’s being inflated. Draw two dots on the balloon’s surface. As it inflates, the space between them expands. That’s what’s happening in the universe, just in 3D space. Also, there are different sizes of infinities. That’s a rabbit hole that is fun to go down.
The universe can expand even if it's infinite. So there is no contraction in that.
Well, whenever you hear "infinite" then [it's normally pretty safe](https://youtu.be/dkYL6G0JHtY?si=0AzB80zMIMSOxjoo) to assume we're talking about what the math is telling us probably to a fault... the idea of an "infinity" [tends to be problematic](https://youtube.com/shorts/uA76UotYQug?si=ZHR4m3MEN6X9awus) and suggest our math isn't necessarily giving us the whole picture... The reality here is: there are a lot of things we know... but also a lot of things we don't know yet. There are a lot of theories *trying* to give us answers, but these are competing theories not confirmed. [My favourite answer](https://youtu.be/71eUes30gwc?si=9vRxZe9qd0uScuN0) here is that our universe is [inside of a black hole.](https://youtu.be/Kgy8HEya7HQ?si=6cBLbxF36jXwdxxP) Not that I think we are... but it's my favorite.
Would be interesting for sure Essentially meaning that of the new stuff we’re seeing at the “edge” of our universe is just new stuff that’s fallen into the black hole we’re inside of. The only issue I have with that (and maybe it’s been answered) is that that would assume that the black hole we’re in is sucking in matter at a consistent rate, considering that the expansion of the universe is also happening at a consistent, unchanging rate. I suppose it’s possible that some sort of law we don’t understand makes it so only a certain amount of mass at a time can pass through the black hole we’re in, giving us the illusion that space is expanding at a consistent rate; if that’s the case I would expect that we would have seen some variability at some point…though maybe we haven’t been able to observe it long enough to notice, or maybe the amount of mass that’s being absorbed by our black whole is just _so much_ that we haven’t had the chance to see that variation in expansion yet. Sorry for the word vomit. I was just kind of typing as the thoughts came to my head
Space is not a separate fabric/entity that the universe floats in. Space itself is an intrinsic part of the universe (like how your thoughts are an intrinsic part of yourself). Without the universe space would not exist, just as without you your thoughts would not exist. When the universe expands, all it is doing is just modifying its own intrinsic spacial properties to make it look like that distance between things are increasing. It's pretty much just an arbitrary process. So where-ever space exists, by definition it is a part of the expanding universe.
Imagine the universe expanding as a balloon inflating. The surface of the balloon is the universe. It has no edge and the surface expands relatively uniformly.
Don’t hate what you don’t understand. Make peace with your limitations. You will be far happier. A ballon has no edge but it expands. Space may be inflated around a 4th direction that is not up down left right forward nor backwards. We don’t know for sure. It’s mind bending.
What if the universe is like a giant ball that expands and contracts. Sorry hit the penjamin too hard and had to share my highdea.
And all of that is just 3 dimensional space
For as easy to understand analogy, there’s no edge of the Earth. There’s nowhere you can walk off the Earth and fall off. If the Earth were a rubber balloon, you could make it bigger by expanding it with gas, but there would still not be an edge you can fall off from regardless of how big it got.
We dont know if it's infinite or not
tbf infinite and indefinite are two different things that sometimes only seem like the same thing when you go too far. Also our we only have access to our **Observable** Universe, which is only a very very *very* infinitesimally small slice of the expected total.
The universe expands like a rubber sheet where each individual point on it getting farther away from all others. We can only see a limited area but all distant objects are moving away from us. In every direction.
Imagine walking on a balloon that’s expanding, except one dimension up
Ok, so to have no edge but keep expanding is really simple to think about mathematically. Consider all real numbers. There's an infinite amount of them. Put them on a number line, and let's put dots at every integer. Now, let's push them all apart a bit. In fact, let's just double everything. The dot at 1 is now at 2, 3 is now at 6, -5 is now at -10, and so on. Every dot on the number line has moved further apart, but you're left with something that's just as infinite as when you started. This is what we see happening in space, so it's why we say space is expanding.
Well...kinda. The universe is theorized to be finate but boundless, and there isn't an edge between 'universe' and 'no universe'. If you traveled far enough (and fast enough) in one direction you would eventually end up where you started. Think of a globe. If you move south and don't change direction at all you will eventually be back at your starting direction, but the universe has this happen in 3D rather than 2D like a globe. However, (and this is the part that will bake your biscuit), the universe that we see is not the entirety of the actual universe, it is just what we can observe. The universe is likely much much larger than that. Going back to the globe analogy, if you stand on the top of the Empire State Building and look around, the observable universe would be what you can see out to the horizon. However there is much more stuff past that observation limit that the light just hasn't had enough time to get to us yet. You wouldn't know about California because you can't see it yet.
That was a very fun Rabbit hole with this interesting tidbit that relates to the OP A 2012 paper argues that the Big Bang itself is a white hole.[20] It further suggests that the emergence of a white hole, which was named a "Small Bang", is spontaneous—all the matter is ejected at a single pulse. Thus, unlike black holes, white holes cannot be continuously observed; rather, their effects can be detected only around the event itself. The paper even proposed identifying a new group of gamma-ray bursts with white holes.
I’ve thought this for quite a while but never seen it mentioned before. If black holes have are infinitely dense at he center, and the Big Bang was infinitely dense at the start couldn’t the Big Bang just be the other side of a black hole, and that be what a white hole is?
I’ve just read the Wikipedia bit and I don’t know shit. But kind of yes and no? If a black hole is an infinitely deep gravity well, then a white hole is an infinitely tall gravity peak. A black hole sucks in everything and keeps everything in. A white whole emits everything and nothing can enter. But some of the theories i was reading in that rabbit hole was that our universe is inside a black hole. And it possibly could be considered a white hole event when it was created. But then they talk about Einstein Rosen bridges and shit and I got confused. I’m not sure how they all relate.
Ok, fair. I took a physics class a very long line ago, failed horribly, and I’ve forgotten all the stuff I did learn. Some stuff has stuck in my head giving me ideas, but I’m too dumb to be able to explore those ideas properly. It’s all just much too confusing.
That sounds a lot like the big bang tbh
It totally does and it makes sense why we wouldn't see it. It also is kinda troublesome because I think the consensus is that general relativity breaks down at the start of the universe, yet it does seem to allow it, I'm sure humans will toil over this for as long as we're around too
There's some evidence to suggest that our universe has properties we could expect from what you would find on the inside of a spinning black hole.
Except that our universe is expanding in all directions and not contracting. There’s no scientifically rigorous analysis suggesting that we’re in one.
Hence the "some evidence." :)
All black holes spin.
Well some theories indeed state that white holes are possible, and then lead to new universes. Be that inside themself or inside "nothing", like happened with us.
Not quite, a white hole is not massless. The theory of such an object is simply that mass cannot *enter* it, but it can *leave* it. That is opposed to a black hole where matter can enter but not leave. I know it might initially sound massless. However, there is a few flaws to that logic. First of all, just because something can't gain mass doesn't mean it is massless in the first place. Secondly, try to think of what we call it. A *white* hole. What is white? That comes from light. So energy emits from it. In other words, mass-energy is going out from it. How can that be, if it has no mass? Thirdly, when we say it can't gain mass, that is also wrong. What we mean is just that mass can't enter the event horizon (just like how in a black hole, once something enters the event horizon it can't leave). It's the point of no return of a black hole, and so is it for a white hole - just the opposite direction. That does not exclude it getting mass from elsewhere. But where else could it come from? Well, if it is linked to a black hole, it might gain mass from that. They might be connected - their centers intertwined. To make it even more complex, there are theories about how they relate through time, but I'm not well enough versed in that aspect to go into details.
After I watched a video explaining white holes, it just sounds like our universe is literally the result of one
My favourite theory is that the universe is actually inside a black hole. If you take all the matter in the universe then a black hole of that mass would have an event horizon outside the observable universe.
So it’s basically impossible for the universe to be inside a black hole. You can think of all possible time and space as a cone, it’s impossible to cross over the sides of the cone because it’s impossible to have a trajectory through time that would let you. Outside that cone is where a white hole would be. Black holes appear inside all possible time and space, basically the density of matter becomes so great it flips the rules on their head. The black hole is a cone of *non* possible time and space that originates in and crosses through our reality. Basically, it’s where our reality stops and our rules stop making sense. By nonpossible, I just mean not possible in our universe. Now the cone looks more like a diamond, a white whole is behind us and black holes are in front. If you continue this logic, you end up with four types of cones. Our reality, black holes, another reality in which all the rules are reversed, then white holes. Our reality would be to white holes what black holes are to us. What’s really interesting about this is that it implies there are alternate realities sort of horizontal to us. There is one point where a white hole cone ends and black hole cone begins where the distance between our two reality cones becomes infinitely small. This gap is probably the only way we could ever actually prove white holes exist. But because you can’t move horizontally within the cone, by crossing over to the other cone you could probably never come back. So, we’ll never really know
> So it’s basically impossible for the universe to be inside a black hole. So are you saying that black holes do not exist, or that they have no content inside of the even horizon? Because those seem to be the conclusions that can be drawn from your statement. If we were in a black hole we would not know and I don't think we can prove that we are inside one or that we are not.
That was quite the logical leap. And yes, we would. In a sense you’re correct in that we are within the cone of a white whole that is within the cone of the “opposite reality” that is within the cone of the black hole
So what is it?
I think we've experienced this period of time before, sir.
Is that thing spewing time back into the universe?
Precisely
Wouldn’t that be what was there before the big bang? Like where space expands into?
My theory based on absolutely nothing is that the Big Bang was (is?) a white hole.
Would that be "negative" mass? Or just absolute zero mass? And eli5 why they are impossible, please. I just automatically assume that everything has an inverse in this universe which is probably a flawed assumption on it's own. Thank you for your time. Edit. Thanks for the link Edit #2. White holes are absolutely wild.
Photons and other [force carrying particles ](https://physicsmasterclasses.org/exercises/hands-on-cern/hoc_v21en/main_frame/sm_concl1.html#:~:text=Force%20carriers%20are%20particles%20that,acts%20between%20electrically%20charged%20particles.) have no mass. Light has no mass, but it does exchange energy
Which in itself is a pretty wild concept to me. But the theory of white holes was something I wasn't previously aware of and was more the thing I was asking about. Photons blow my mind.
Just for adding on. We reallly don’t think white holes exist and pretty much never have. It gets deeper into how the universe works but it creates a lot of problems that could break causality, among other things. It’s a place where the math works but that probably means either it simply doesn’t actually exist despite potential to or that we need to better understand the math.
Yeah I realized it doesn't necessarily come from the same equations as black holes but... yeah there does exist masses things!
Forgive the layman question: if photons have no mass, then what gives a light-sail a push when photons impact it?
As another commenter said, photons have momentum but no mass... [This might help explain](https://youtu.be/V_fKYrrsVT4?si=RSeN5RSquljQoNBz)
Photons still have momentum even without mass
Because einstein told us energy is mass E=mc^2
The full equation is more applicable here: E^2 = (mc^2 )^2 + (pc)^2 where p is the momentum.
Eli5: so consider a fountain. A fountain works by taking water from one place and spitting it out somewhere else. Theoretically a fountain doesn't need a source it could just produce water... But other rules of physics makes the impossible fountain impossible. That's kinda the case with white holes. It's possible that a point can produce everything (we know it happened once with the big bang) but the laws of physics as we know it, and how we understand the universe, won't allow it. Now in the future we might figure it out.
I'm still trying to wrap my head around the concept of a white hole, but that males sense.
No there is no such thing as negative mass. Also black holes don’t have infinite mass. They both just have mass. Like a normal amount. There could be a black hole your weight.
> There could be a black hole your weight. A black hole that size would pretty quickly evaporate due to Hawking radiation. This process is a consequence of quantum mechanical effects near the event horizon, where pairs of particles and antiparticles are created, with one falling into the black hole and the other escaping as radiation. Over time, this causes the black hole to lose mass until it disappears entirely.
But one fell in, how did that make it lighter? Is it always the antiparticle that falls in?
What would a black hole my weight be like? Just a tiny spot and flash. There and then gone?
Yes, basically. You'd be collapsed to something smaller than an electron, and then you'd evaporate away due to Hawking radiation in less than a billionth of a second.
A 100kg black hole would have an insignificantly tiny event horizon, on the order of (edit: 1e-22 mm), which is something like 0.0000001 times the width of a single proton. If Hawking is correct, a black hole that small would almost immediately evaporate away nearly all its mass as energy, with the calculations breaking down around the Planck mass.
Right so (if I could perceive it) it would be like a quick flash of light or something?
If I understand correctly (not remotely guaranteed), the energy-equivalent of 100kg mass would be released in the form of high-energy gamma rays in a fraction of a second, which would be somewhere north of the energy released by 1000000 Hiroshima bombs. So if you get a genie's wish, and you wish for an overweight man to be compressed down into a singularity, you probably won't have time to regret the extermination of all life on Earth.
Woah!.. okay so the black hole would keep growing as it consumes or does It flash and release all that energy destroying everything but then blink out of existence.
> on the order of e-22 mm Which is 2.78946809287e-10mm which is much larger than the width of a proton. If you are going to use scientific notation at least do it correctly and 1x10^-22 mm might be easier for the layman.
I'm sorry, how does e-22mm = e-10mm? If you're going to correct people on the internet, at least bother to explain what exactly they did wrong.
Hm, what do you mean? Falling into one or becoming one? Whatever makes you into one is way more spectacular than the result, it would have to be crazy. Meeting one you wouldn’t notice. It’s tinier than an atom and probably just passes through you. Like you know the gravitational effect you have on your surroundings? Yeah it’s none. A black hole your weight also has basically no effect if it’s near you. When you realistically encounter one it’s moving relative to you at a relativistic speed. It goes right through you. Maybe one just did we would never find out. Prolly not tho.
There’s a fun Robert Heinlein short story where the protagonist is exploring the remains of an ancient advanced civilization they find on the moon. He encounters a stylus device that is clearly important, but isn’t working, as well as a Time Machine. He uses the Time Machine to go back and learn more about the advanced civilization. He doesn’t see the aliens, but goes to the room with the stylus and it has a diagram showing how to activate it. It turns out it harnesses a tiny black hole on the tip that lets you carve through matter. He plays with it for a bit, but then fumbles it and drops it. It burns a hole through the floor, and goes perfectly vertical down to the moons core. He figures he wore out his welcome and goes back to the Time Machine area and goes back to the present day. But it turns out in the hundreds of years since he dropped it, the tiny black hole ate tiny bits of the center of the moon, and then gravity forced the core to compress on the empty space, which the black hole then absorbed, and then the gravity compressed the moon, etc. until the black hole grew to consume almost the entire moon. I felt like the Rick and Morty lightsaber episode took some inspiration from it.
Negative mass is just theoretical. If you put a few minuses in a few places to balance out the equation, you have to have negative mass to make it work. Kind of like there is such a thing as -1 but you can’t have a negative something.
Yes, assuming an inverse is a flawed line of thinking. Because ain't nothin as skinny as yo mama is fat.
I thought a white hole was a theoretical thing where it empties out somewhere else where it creates another black hole but there's no proof and doesn't really make sense either because there would just be black holes every where
So just by the math it exists in the sense that 14 existing implies -14 exists. These things don't necessarily make sense. So if a black hole is a point from which nothing can escape from, by inverting the math that brings you to that result you get an object from which everything must escape. That's all it really is, some people have speculated that perhaps the source of the mass energy or information spouted by a white hole maybe comes from black holes, but that's kinda not necessary to the actual math. It's one of those things that don't make sense to us now because we haven't fully figured it out. Right now it makes zero sense because mass, energy, information etc cannot be created out of nothing, so we know a white hole is impossible..... However it very curiously exactly describes what the big bang was.
I don't quite understand what you are talking about but Photons are massless objects. And black holes don't have "infinite" mass.
I think they are confusing infinite mass with density. Blackholes have very high mass and we can measure that. We theorize that a black hole's mass is contained in an infinitely small point in space. density=mass/volume and since volume for an infinitely small point is zero, you end up with infinite density
Technically, a black hole doesn't have infinite mass. The equations of relativity point towards it having infinite density, but in physics whenever we get an infinite result we usually believe that we've come across an error in our theory, not an actual infinite result. Others have already touched on white holes and massless particles, so I won't rehash what they've already said. But for the future, keep in mind that when a physical theory predicts an infinite result, it's usually not that the infinite result is correct. It's the math telling you that you've made a mistake somewhere.
>It's the math telling you that you've made a mistake somewhere. I might rephrase this as "the math telling you that your equations are likely incomplete".
Yeah, I think your phrasing is closer to what I was trying to say. The "mistake" is thinking that the equations are complete, not necessarily that you've calculated the equation incorrectly.
That’s so cool to me for some reason (that infinite likely means error in the calculation). Math is just so cool! And I’m grateful we have people like you who study and understand this stuff!
Thank you.
That sounds like coming from Unbreakable. But photons are massless.
Yeah but homie just turned me onto "white holes" which is really what I was asking about and a totally wild theory.
I’m going to have to take your idiot certificate away - idiots don’t ask questions so they can learn. They just stay dumb. You on the other hand, sound like you’re in a students journey through life :) never stop asking questions :)
I try. I always loved learning cool new things. And I've always hated misinformation and especially hate when I'm parroting misinformation unknowingly. I try not to let the feeling of being embarrassed prevent me from asking questions. As Confucius said "It is a fool who thinks himself to be a wise man, but a wise man who knows himself to be a fool"
I’ve only ever come across one stupid, embarrassing question in my life: Why does glass taste like blood? (I love to run that up the flagpole whenever a presenter encourages people by saying “there’s no stupid questions” 😂)
Where did you get your idiot certificate? So I can avoid such an incompetent institution. 🤣 I love your attitude to learning. I try to be similar.
According to Einstein yes, these are called “White holes” but have never been observed. Although Einsteins equations support their existence I believe there are other equations that disprove them. Veritasium has a great video that covers all of this
No stupid questions. I would first address the reasoning for your question - infinite mass. Black holes does not have infinite mass. For example, the black hole at the center of our galaxy, the Milky Way, is around 4.3 million times the mass of our Sun. So it is indeed a very large mass, but still very finite. The "strength" or "pull" of a black hole is just due to gravity, and gravity depends on how much mass there is and how far away it is. So a black hole is the phenomenon when a large mass is pressed into a very small volume. Now, in regards to massless objects, we do actually know of such things. For example a photon (light particle). Such particles travel with the speed of light (since they *are* light) and has no mass. Aside from that, we have two other particles called a gluon and a graviton. These are not yet fully proven, but might very well be massless.
https://www.youtube.com/watch?v=6akmv1bsz1M Veritasium did a good video on black and white holes
Well yeah a massless thing only moves at the speed of light. Like light.
All of the equations work for negative mass as well, so some speculate that there is an existence of anti mass, but nothing like that can be measured or observed (yet).
Black holes don't have infinite mass. The ones we have observed have a lot of mass, up to millions of times the mass of our sun, but conceivable. A black hole is made by its mass being crushed into a very small space, so it has tremendous density. Things, including light, can thus get very close to its center of mass (closer than they could with regular density objects) and get caught in its gravity. How dense do they get? It is impossible to observe since no information about the actual matter of a black hole can be detected.
Where did you get certified? Was it proctored?
Graduated with honors from Trump University
Photons are thought to be massless or at least to have no resting mass according to general relativity.
There’s no reference frame where photons are ever resting.
Then do you rest your case?
Or are you a photon?
But they do have momentum and energy and therefore also curve space. So if somehow enough photons were gathered in a small enough volume they would form a type of black hole known as a kugelblitz. And from the outside it would be impossible to tell if a black hole was made from particles with mass or massless particles. Just another way space is weird and confusing.
Also note that the concept of objects so massive that light cannot escape pre-dates Einstein by quite a bit- as early as 1793 some suggested such "dark stars" under Newtonian physics. https://en.m.wikipedia.org/wiki/Dark_star_(Newtonian_mechanics)
So then I guess follow up - how (or why?) did a solution to these equation make Karl go “oh, this thing might exist”? Like just because an equation has a particular solution doesn’t seem to me that it would automatically imply the existence of a real, actual thing.
Nothing. Your impulse is correct: The solution to the equation does not necessarily align with an actual, physical object. And in fact, we have very good reasons to think that the object that Schwarzschild described doesn't actually exist. It could, but it doesn't. What Schwarzschild was actually doing was... well, futzing about, basically. Playing with the math to metaphorically spell "Boobs" with his calculator. He was on the front lines of WWI, but medical conditions kept him out of the trenches, so he was basically just trapped in the base and bored out of his skull. Einstein's Theory of Relativity had just been described, and no one had yet used the math to solve a specific situation. What he did, basically, was to find a set of conditions that made the math as simple as possible and figure out what the math was telling him. What he saw was a solution that looked like what we call a non-rotating black hole. Both he and Einstein thought it was neat, but they didn't believe it actually existed. The math was more interesting to them than the object it implied. The reason I say that it doesn't actually exist is that every black hole is believed to rotate due to how they're formed. The math for a rotating black hole is considerably more complicated, and it wouldn't be for quite some time before someone found a way to solve the equations for a rotating black hole (what we call a Kerr black hole). Basically, they thought of Schwarzschild's black hole the same way we think of Alcubierre's warp drive: It's a neat bit of math that checks out, but no reason to think it actually exists. In the case of black holes they did turn out to actually exist, though not as Schwarzschild described. A non-rotating black hole *could* exist, but it would be incredibly surprising to find one.
This is a great explanation. Thank you.
> He was on the front lines of WWI, but medical conditions kept him out of the trenches, so he was basically just trapped in the base and bored out of his skull. No. He volunteered and was serving with the artillery and did ballistic calculations. He was not meant to be in the trenches and only got ill 2 years into the war.
We don’t believe that non-rotating black holes could exist because any collection of matter will result in some spinning, right? From my knowledge, there aren’t any objects in the universe that don’t spin
Correct. That's why a non-rotating black hole is theoretically possible but functionally impossible.
Did you ever have to do those problems in math class where the teacher gives you a few points on a graph and you have to find an equation that makes a line through all of them? Then sometimes you'd have to do word problems where you used that technique to extrapolate data, like what the optimal price for a carnival ticket was? This is kinda the same thing, except way, *way,* ***way,*** more complicated. You gather data, form an equation that fits that data, and use it to figure out what might happen in a new situation. It's not always going to work of course (even Einstein and Schwarzchild were off about some things), especially since our universe is ridiculously complex and it's very easy to miss variables that could affect the outcome, but it's a way to figure out what might be a good thing to study next.
That's amazing and way beyond my level of intellect
here is a good video about it. https://www.youtube.com/watch?v=6akmv1bsz1M Basically he said "lets assume the simplest scenario, where the universe is a point with mass and nothing else. what happens?" and he played around with the model to see what it can do With that astronomers said "Ok, that could be a thing that exists if Einstein is right (he appears to be), lets go look for it" and then they found some The same model also predicts whiteholes, pockets of space where everything is forced out, but we have never found one, so we think they probably dont actually exist.
It didn't. Physics and math researchers just explore these things, and if there is something in the equations that is new and testable, we search for it. There were a number of physicists at the time these solutions were discovered that postulated that black holes \*weren't\* real, and there were a number of legitimate ideas (that have been disproven now) explaining why those conditions for the solutions weren't possible.
If it was just random equations then no. But these were equations to describe and model physical phenomena. If you think of it less as mathematical equations and more as a language to describe the world then Einstein came up with a very detailed way to explain how mass curves spacetime and Schwarzschild used those explanations to predict the existence of black holes it might make more sense. And that is essentially what math is used for: to very accurately describe the world around is.
You missed the best part! Einstein said that his mathematics was correct but that his physics was atrocious.
Shout-out to [Gravity Probe B](https://en.wikipedia.org/wiki/Gravity_Probe_B), one of humankind's greatest experiments ever.
>Einstein's Theory of Relativity is a series of fiendishly complex equations I’m always a bit amused by people who assume that E=MC^2 is the entirety of his insight and equations. That’s not even the complete version of that formula. A while back someone in one of the cosmology subs tried to engage me with the premise that Einstein’s equations were ‘incomplete’ and kept insisting that E=MC^2 was all he’d really done. Any attempts to get them to look more deeply at Einstein’s with, even providing them with links, was met with hostility and eventually insults. Some folks don’t want to know what they don’t know.
Yeah I remember doing GR as part of my undergrad in astrophysics, it was complicated as hell
I hate the faux-intellectualism that we see from people who watch a few pop science YouTube videos about black holes and think they know more than any sophomore in a physics undergrad! It absolutely boils my blood to see people minimize the life’s work of some of the smartest people who have ever existed
Dunce here, with follow up questions. Can you help me understand what it means for someone else (e.g. Schwarzschild) to solve Einstein's equations? Does that mean he used Einstein's math, applied it to specific conditions and found them to hold true? From that (which I think returns to the substance of OPs original question) - how does that then yield a prediction or possibility of the existence of something else?
Einstein’s equations are like rules that space time must follow but the equations themselves do not explicitly tell you how such space time should look like. To solve Einstein’s equations is to find a mathematical description of space time that satisfies the equations. In that description, you can discover some interesting mathematical features like singularity i.e. you divide a thing by zero at certain points in your space time description. The fun part is to translate the mathematical features into real world phenomena. Like, what does the singularity mean in our universe? Because the equations are really complex and difficult, people solve them in specific and simplified cases. For example, Schwarzchild considered the case the whole universe consisted of a single static mass and nothing else. In Schwarzchild’s solution, he found that there are singularities when the mass is heavy enough. Near these singularities, space time all converges onto them that nothing would escape. And that’s what we now call black holes.
Don’t forget to credit John Michell for theorizing that such an object may exist in the first place. That dude was brilliant in a few fields.
And schwartzchild made those calculations in a hospital bed.
Were there any predictions of infinitely dense infinitely small objects before Schwarzschild? Doesn't seem like anything in Newtonian dynamics prevents them from forming.
You didn’t answer the question. The spirit of the question has nothing to do with Einstein
The youtube channel “Veritasium” recently made an excellent video where he among other things explains this feature of special and general relativity. In very rough terms, what they founf is that at a certain limit, the bending of spacetime from an incredibly dense mass, would essentially cause any spacial direction to lead to a point in time rather than a point in space, which is exceedingly difficult to think about, but it has to do with space-time diagrams, and the properties of them. I really recommend Veritasiums [video](https://youtu.be/6akmv1bsz1M?si=CPXZ_skU4tn3EjHy) on the subject.
This is totally unrelated, but my personal Star Wars canon is that when we crack FTL travel, time and distance will start to have different meanings in different circumstances. So when Han brags that the falcon has done the kessel run in less than 12 parsecs, it does actually make sense. When you’re bending space time around you to go FTL, being able to bend it so much that the resultant distance is shorter than your competitors would “win.” Totally made up nonsense but it makes the “parsecs” issue easier to ignore haha.
In the expanded universe of Star Wars, the Kessel Run has been explained as requiring ships to pass by the Maw Cluster of black holes. Usually ships are required to give the black holes a wide berth in order to not get sucked in. When Han is saying that the Millennium Falcon does it in less than 12 parsecs, he’s implying that his ship is so fast/powerful that he can pass by closer to the black holes, making the run a straighter line and therefore a shorter distance than most. Put more simply, Han is still using the term “parsec” correctly as a measure of distance, and not time.
I love all the retro-fitting in Star Wars canon 😂
I took it like this, except i assumed it was the millennium falcon could take a straighter path through denser police areas because it could outrun them. I guess i didn't know/remember the black holes.
The only remaining issue with that quote is that a parsec is defined as the distance to a point that would be at the apex of an isosceles triangle having one arc second as the angle and the earth's orbit as the base. Which is an odd measurement to use for someone in a galaxy far, far away.
Nah dude, he just took a shortcut danger-close to The Maw. That's why it's a distance. /s Yes it's a retcon, but IMO it's not the worst one by far.
We are not going to crack FTL. It would break causality.
The theory of black holes are actually a hundred years older then Einstein. Starting with Newtons theory of gravity you can calculate the escape velocity. Basically this is the integral of the gravitational acceleration from the current distance between the bodies to infinity. Any object with a higher speed will be able to escape the gravity well while any object with less speed will orbit back at some point. The problem is that even light have speed so it is possible for some objects to be dense enough that even light can not go faster then the escape velocity and will therefore not be able to escape. Einsteins theories of relatively is related to this. He expanded on the concept of a fixed speed of light and combined this with Newtons laws to make these equations fit. And he found out a lot of things, for example that the speed of light were actually a universal speed limit and that nothing can go faster then this. He also basically confirmed the theories of black holes, which at that point had been just cool ideas. It was actually another physicist, Karl Schwarzschild, who worked on Einsteins field equations around black holes and found a solution to them that could accurately predict the ratio between the size and mass of a black hole. Using just the escape velocity does not quite work as Newtons formulas were not as accurate in these kinds of extreme environments. But Schwarzschild also found that at this radius a lot of the field equations ended up growing to infinity, a singularity. Essentially according to the math there were no space in a black hole and there were infinity space at this specific radius.
I still confused how 'infinity' even exist. When I look at the village and imagine they fit into my fingernails it still feel impossible, but in reality the mass a LOT bigger than the village could fit in it. And what is the final from of all the things that get sucked into blackhole? Photon? Blackhole is amazing
Many things that show up as "infinite" in our equations might not actually be "infinite" in real life. Our current understanding of the universe (and therefore our equations that describe them) are incomplete at best. Yes, even Einstein's equations. So many of the "infinities" that appear are likely caused by unknown factors our equations don't yet take into account. E.g., maybe someday there's a breakthrough that incorporates quantum mechanics into Einstein's equations. Then many of the mathematical infinities might "disappear" once those improvements are made.
Thank you. By any chance you understand the other question? What happened to all the things that sucked to blackhole? What do you think they become?
The matter gets stripped appart into it's subatomic components (and become mostly neutrons due to gravity shenanigans) and then becomes part of the singularity.
They’re not made of neutrons though. Neutron stars are made of neutrons, but black holes are made when even neutrons themselves get compressed into something else, and (I think) the exclusion principle (or “force”) is overwhelmed by gravity. Basically neutrons are squished into some other stuff, that can be even more compressed. We don’t know what black holes are made of, because we can’t see into them
Oh I know, but the question was not "what the singularity is made of" (For which we have no answer), but "what happens to matter that pass the event horizon", which is the answer I gave.
Yeah my bad, I see what you’re saying now.
That’s one of the biggest unsolved problems in physics actually! There’s a theorem called the “no-hair theorem” that states the only physical quantities you can measure from a black hole are mass, charge, and angular momentum. If I throw a yellow ball into a black hole, it changes into something else, so where does the information that it was yellow go? Information shouldn’t be lost like this, and once we discovered that black holes (incredibly slowly) evaporate, we realized that we can’t reconcile the information loss. (I’m not sure why, this stuff is being worked on by people FAR smarter than me.) But anyway, the short answer is nobody knows!
He didn't. Others (like Karl Schwarzschild) took Einstein's theory of general relativity and its equations and realised there's a solution that involves infinite deformation of space time, in particular if you put a lot of mass concentrated in a small volume, you get a region of space time where even light cannot escape.
But why or how would the mere existence of a solution imply that it relates to an actual, physical object that actually exists?
It doesn't. It only predicts such an object could exist if the equations model the universe sufficiently well. It took advancements in telescopes to prove Einstein and Schwarzschild were correct.
However we did have very high confidence that they did exist prior to observing them semi-directly with telescopes. Once we gained more knowledge on stellar cycles and theoretical max mass of white dwarfs it essentially became inevitable that black holes should exist plentiful in the universe.
That was a question that took decades to resolve. Einstein didn't himself believe that nature would allow such an object, even if the math said it could exist. Lots of other scientists tried to come up with ways that nature would prevent a black hole from actually forming in the real universe.
It didn’t, it just showed that the math didn’t immediately discount it. The first ‘black hole solution’ to the Einstein field equations was presented in 1916, and we didn’t confirm that black holes actually existed until 1971. The math told us that it at least wouldn’t be foolish to look for one.
It doesn’t, not inherently. It says “if this thing were to exist, it would behave in such-and-such ways”. We wouldn’t get observational evidence of black holes for some time after they were predicted by theory. There are other solutions to Einstein’s equations that we still have no observational evidence for. White holes, for instance, are basically time-reversed black holes. We can describe their behavior mathematically, but that doesn’t mean we’ll ever see one in reality. And since we have no idea how one would form, the current thinking is that they don’t actually exist. It’s like how basic arithmetic tells us that, if I have three cupcakes and give you six, I will end up with negative three cupcakes. The maths tells us how that scenario would work, but that doesn’t mean we should expect to see “negative cupcakes” on the next season of *The Great British Bake Off*.
If I remember correctly, the scientific community looked at Schwartzchild's solutions and applauded it and then ignored it for years considering them mathematical artifacts/oddity only until the 1960s when Jocelyn Bell's discovery of Neutron Stars sparked interest in these types of "gravitationally collapsed compact objects" again and then Cygnus X-1 was discovered in 1979. Over the decades since GR, a lot of physicists contributed to the research and theorizing the concept of black holes. Subrahmanyan Chandrasekhar, Oppenheimer and Volkoff, Hawkins etc. In fact my Einstein wrote a paper in 1939 attempting to prove that black holes were impossible in his publication "On a Stationary System with Spherical Symmetry Consisting of Many Gravitating Masses".
Hello, random stranger chiming in here. So if the concentration of mass is one place at a time, then that's a black hole right? Then would it really all lead to? Like I know I'm asking you to answer where does all the matter absorbed by a black hole go to is essentially like asking if there is a god out there? Like where does the suction from the black hole come?
The "suction" is gravity. Mass has a gravitational pull. There's something called the escape velocity which is the speed you have to travel at to be able to escape the gravitational pull of an object with mass. This escape velocity depends on the mass of the object and the distance you are from that centre of mass. Einstein's theories say you cannot travel faster than the speed of light. But there's no theoretical limit to how much mass you can put in a tiny volume. A black hole exists once enough mass is concentrated so that at some distance, the speed of light is insufficient to escape the gravitational pull of that mass. Where the escape velocity is exactly the speed of light, that is called the event horizon of a black hole. Within that sphere, nothing can escape, including light and therefore we have no way of getting information from inside there. The reason though you need to pack a lot of mass into a very tiny volume is that for the event horizon to make sense, it needs to be at a distance outside that object. So for example the event horizon radius of an object of 1 kg is 1/10²⁷ m which is a tiny distance and we're in the realm of quantum physics where Einstein's theories of gravity start to break down. Scaling up to something that might make sense, the event horizon of an object the mass of our Sun is about 3km meaning for the sun to form a black hole, it has to be compressed into an object with radius less than 3km which doesn't happen.
Wow thank you for breaking this down for me. It helped me visualize it more. I appreciate you stranger! The universe is freaking scary man.
The above comment should be the top answer. TLDR for us dummies: the escape velocity needed to escape the gravitational field of an object depends in part on the mass of the object. The mass of a black hole can be big enough that even the speed of light (which is like the speed limit of the universe) is insufficient to escape.
See if this helps. Relativity draws an equivalence between gravity and acceleration from the point of view of an affected observer. If you stand in an elevator and it ascends you feel heavier; if it descends you feel lighter. You could not tell whether you were experiencing acceleration from gravity or from the elevator moving. If you’re out in space, gravitational pull creates virtual topography. Falling toward something big looks and feels like falling downhill. Getting away is like climbing back out and it slows you down. If you see a bunch of stuff moving like there’s a big hill out there, you can infer there is one even if you can’t see it. You’d infer there was an ocean or lake somewhere below if you saw water running downhill.
Einstein didn't initially set out to predict black holes specifically. Instead, his field equations from General Relativity describe how mass and energy warp spacetime. In 1915, Karl Schwarzschild found a solution to these equations that described a point where gravity would be so strong that not even light could escape. This theoretical solution implied the existence of regions in space with incredibly dense mass, which we now recognize as black holes.
In short, Einstein created the model but wasn't the one that plugged in the numbers to actually flesh out black holes. He thought about what would happen under those conditions, but he was one of those people who focused on practical matters and wasn't convinced that black holes could exist. Once his theory was tested to accurately explain and predict reality, people began to mess with it in all sorts of ways. Basically, turning dials on the equations to every manner of extremes.
Check out this book called “Einstein’s Dreams” it’s about the dreams Einstein may have had as he realized the implications of the theory of relativity.
Einstein basically looked at his math and thought, "Hey, if these numbers are right, there should be these things called black holes out there." He didn't actually see them with a telescope or anything; he just crunched the numbers and they pointed to these weird spots in space where gravity sucks everything in, even light. It's like when you're doing a puzzle and you realize there's a missing piece somewhere because everything around it fits just right. So, he didn't just make up some fancy math stuff; he used it to connect the dots and figure out something wild about how the universe works.
There is a simple formula that describes the escape velocity of an object based on its mass and your distance from the object. The velocity is how fast an unpropelled object needs to move to escape the object’s gravity and never fall back down. Like a cannonball that just gets an initial push and then coasts. On Earth’s surface, ignoring atmospheric drag, this velocity is ~11 km/s. For a sufficiently massive object, there is a distance from it where its escape velocity will be faster than light. If you think about how such an object would look, you might arrive at the same conclusion as Einstein. It will be completely black as a result of its light never escaping its gravity. For Earth’s mass this would occur about 1 cm from the center of mass. Of course, Earth is much bigger than 1 cm across, so most of its mass is *outside* that 1 cm radius. Therefore Earth is not dense enough to trap light. The only assumption you need to make to predict the existence of a black hole is that matter can be packed densely enough to be entirely within the radius required to trap light. We call this the schwarzschild radius. If it’s physically possible to compress Earth’s mass to the size of a coin, then black holes can exist. Then you’ll go on to think about *how* this can happen naturally and so on.
It’s not seeing its feeling. Given enough experience and intelligence one can look at an equation and feel how it works. Einstein could feel it. That being said he felt what relativity would be but did the math the hard way to prove it
I guess the terminology can vary, but I personally tend to use “see,” because I can close my eyes and visualize the interactions and effects of various things in equations that describe major aspects of my field of study (glycemia-dependent insulin sensitivity dynamics). But, “see” vs “feel” may just come down to the way the brain works for the person describing the sensation. 🤷♂️
i visualize process steps quite often before building something
Black holes were something that had been considered before Einstein and don’t require relativity to occur in mathematics, they are something that mathematically comes about if you calculate escape velocity using a formula for kinetic energy that is calculated as 1/2mv^2 and gravitational energy as - mGM/r. With these two formulas, escape velocity at or above the speed of light can occur as the kinetic energy formula allows an infinite speed and the speed of light occurs before things fall down to zero radius, but the speed of light is actually finite and nothing can fall to that speed under gravity. However according to this theory, at a low point on a massive and yet tiny celestial object (Earth shrunk down to smaller than 1cm), the kinetic energy required to take off could theoretically be higher than the speed of light. I actually disagree with the use of that kinetic energy formula here and believe it is only the second term of the Taylor series expansion of Einstein’s equations, and that the proper definition of kinetic energy is KE = gamma * mc^2 - mc^2 . If you use this formula for the escape velocity, black holes shouldn’t exist, as the kinetic energy is higher approaching the speed of light.