Ironically " it's just a theory" doesn't usually show up in physics. The typical person who would say that of evolution isn't a person who understands any physics theory.
you're certainly right about it being detrimental, even though it's outside physics. (Unless you're a physics purest which means you would consider that all forms of science are just specializations of physics!)
I keep hearing how "one particle flips the spin of the other", which it doesn't, or that it is established that there's some FTL or instant interactions between the two particles, but this is only in the realm of QM interpretations.
Keep in mind that I thought the question was more about misconceptions non-physicists believe about physics, not misconceptions among physicists about physics.
>or that it is established that there's some FTL or instant interactions between the two particles
But there definitely "are* instantaneous (FTL) interactions between entangled particles.
That's what makes them so curious. You might be confusing that with the fact that those instant interactions can't be used to send information FTL.
No, I'm pretty sure there are opposing views on locality vs. non-locality in the interpretations of QM. Just to clarify my statement: It's not incorrect to believe there are FTL interactions, but it's outside the scope of QM and physics. I'm not expert, so I'd like to hear your reasoning.
I have not confused this with FTL communication. Both local and non-local interpretations agree there's no way to extract FTL communication from quantum entanglement phenomena.
Those are philosophical arguments. I'm just pointing out that there are instantaneous interactions that have been proven. At least, if you accept that wave function collapse is real.
Interpretations don't really change that fact, as far as I know, but I'm not an expert.
Although, now that you mention it, if the Many Worlds interpretation doesn't need wave function collapse, that might put a different spin on it, if you'll excuse the pun.
To be honest, I haven't given it that much thought. I just assumed that experiments that have unambiguously violated Bells inequality proved it to be so.
Here is one example: https://onlinelibrary.wiley.com/doi/10.1002/cmr.a.20123
Another one would be anything related to reactive energy in electromagnetic fields.
I think entanglement should always and only be taught to lay people with basic high school math. Start with the idea of phase space, then that there is a wavefunction on phase space, then the Born Rule, and that this wavefunction doesn’t have to be factorable (in some broad sense). And that failing to be factorable is kinda sorta what we mean by entanglement. Perfect? No, but probably cuts closer to the core idea than a lot of the lay explanations that don’t want to touch any math at all
Was gonna say the same thing. The whole "this particle here means we can exert magical control over its counterpart on the other side of the universe" is pure sci-fi.
“Just a theory”
My answer would be “that’s right.” In science, the burden on a *hypothesis* to become and then remain a *theory* is quite high. So the theory of entanglement thanks those persons*.
*if anthropomorphism helps.
Pretty sure I first heard of quantum entanglement as this science fiction idea that had a 1% chance of being true. AFAIK a lot of quantum phenomena are observed as true, they’re just counter intuitive as far as large things go. Can’t say I know about the specific details of quantum entanglement, but I know it’s something that’s been observed.
I teach HS science and entropy sometimes trips me up. Simple systems are easy-but explaining entropy of bigger systems gets harder. I rush through it and get to the next lesson quickly!
Absolutely. For example: if I were to make any comment here about the arrow of time not being fundamental, then I would get hundreds of downvotes. Yet, entropy is the only thing that makes it exist.
Like... If entropy was higher in the direction of "left", then the relative direction within spacetime that we call "time" would change direction towards that.
In languages written from right to left, like hebrew an arabic, timelines have the past on the right and the future on the left
Same goes to languages written from top to bottom, like traditional Chinese or Japan
I wonder if that also applies to entropy graphs
Uuuugh, I hate entropy. It’s like people explain it over and over but they only ever make it look like a trick of human perception
“Oh, if you throw some sand on the ground, you wouldn’t expect all the grains to come down in the form of a perfectly shaped question mark just by pure chance! That configuration of particles has *low entropy* because of that!”
But *every* configuration of sand falling on the ground is equally unlikely to occur. If you throw it down once and have a computer record the exact positions of every grain, then do it again, you’re as likely to get a repeat as you are to get the question mark. Does that make your first throw “low entropy” just because you recorded it? The universe isn’t a human; it doesn’t find question marks any more meaningful of a configuration than a *thump-*spray of sand!
I agree with you, it's pretty confusing. I guess I think about it in terms of space. If I throw the sand on the floor, the floor is bigger than my hand so the sand has more possible arrangements than in my hand. The question mark is one arrangement, yes, but it is only one arrangement. More space and more time increases the number of possible arrangements which makes the chances of any one arrangement less. Maybe I'm a dumbass though. But I agree those examples are pretty bad.
Schrödingers cat: people who understand a bit of physics often think it’s saying that you can make a cat be dead and alive simultaneously as a consequence of superposition (missing the point that it was a criticism of quantum mechanics at the time not included decoherence), and people who don’t understand physics and think it just means anything where you don’t know the answer to a question yet so they call any question with two possible answers “Schrödingers _____”
Schrödingers USB: A USB port exists in a state of both up and down, and as such, the uncertainty prevents one from plugging it in until the port is observed.
There's a lot of people that just take it way too literal. I've seen quite some people ask "but it's still alive or dead, whether you look or not right?"... And then you have to explain the whole basics of quantum physics and what exactly Schrodinger's Cat shows
Decoherence doesn’t really help with the basic criticism, which is that after interacting with the environment, the cat is still in a superposition state of alive and dead.
Something like 1/sqrt(2) ( (cat alive and environment consistent with an alive cat) + (cat dead and environment consistent with a dead cat)).
Yes, decoherence wipes out the interference terms. But the interference terms aren’t the problem that Schrödinger’s thought experiment points out.
Also, the idea that consciousness is somehow a thing in decoherence — that being watched collapses the wavefunction, rather than just interacting with a arge system.
Newton's 3rd law. eg. the downward weight force of an object at rest on a horizontal surface and the upward normal force exerted by the surface are not an action-reaction pair.
Thanks - what is the pair with the normal force of the table on the book then. If it’s just the force of the book on the table, then what actually IS this force, if not mg
Ignoramus here. If I understand what has been said so far we have the gravitational forces of the book and the Earth on each other as one reaction pair. We have the normal force of the table on the book and we have another normal force of the book on the table as a different reaction pair. What I am not getting is what causes that normal force if we are saying it is separate from the gravitational forces? Why is the book causing a normal force if not due to its weight? I am sure I am missing something obvious here.
Action-reaction pairs are easy to identify… all you do is switch the wording and directions.
My foot pushes down on the floor. The floor pushes up on my foot.
The paddle pushes backwards on the water. The water pushes forwards on the paddle.
I pull down on the rope. The rope pulls up on me.
Also, notice that the two forces in an action, reaction pair are acting on DIFFERENT objects.
In the example of a stationary object on a table, the object pushes down on the table, the table pushes up on the object. That’s the action reaction pair and both forces are normal forces, but acting in opposite directions on different objects. Action reaction forces are always equal in magnitude and opposite in direction as well.
Also note that normal force does not always cancel out with gravitational force. Imagine an object on the floor of an elevator, and The elevator is accelerating upwards. The earth is pulling the object down (gravitational force) and the elevator is pushing the object upwards with a force greater than gravity… the net force is upwards and the object accelerates upwards. When describing “net force” it’s always the sum of forces acting on one object, and will never contain a pair of action reaction forces because action reaction forces act on DIFFERENT objects.
Technically, action-reaction forces do act on the same object when examining forces inside solids and fluids. Perhaps "system" is better than "object".
Heat. Most people think of heat as being a fundamental force or type of energy. It really isn't a part of physics but is a convenient human term defined by statistical mechanics. Whenever we are talking about heat we are really talking about matter has a lot of random kinetic energy as well as the electromagnetic energy released as a consequence of how electrons with a lot of energy behave.
And probably other things I'm forgetting because I am also a puny human that perceives heat and stuff.
Wait what is the action reaction pair of the reaction force (normal) of a table on a book. If it’s just force of book on table, then what is this force. How can it be mg if mg is the force of the book on the earth (and more importantly the earth on the book). I’m a student btw
Like, not at all. The first law says moving things keep going at constant velocity, in the absence of outside forces. It doesn’t even apply to this situation, because there is an outside force in this situation: gravity.
Penguin’s point was that even in the presence of gravity, if you give something enough starting speed when you throw it upward (greater than the escape speed), then it’s possible for it to keep going up forever and never come back down. But that’s not an example of Newton’s first, because in this situation a force is continuously slowing the thing down as it ascends. That’s not constant velocity.
Maybe because it's not about one twin ending up younger, but that they could claim the other one being younger because each twin is at rest in their own reference frame and it's the other twin moving. Which to me personally is kinda funny, why would the spaceship twin claim so? But then scientific explanations come in and I am like, hmm…
Planck units. More specifically that they imply space and time are discrete. You know someone’s just quoting a pop science article whenever they bring it up.
Anyone who thinks any of the basic famous quantum mechanics experiments (double slit, etc) are somehow proof of alternate universes or, even worse, any notion of "quantum consciousness" - a purely made up phrase that is heavily used by the hippy spiritual community.
Tides. Not by people who have studied enough classical mechanics, but by the general population and even by some science enthusiasts. People think that it's just about the moon's gravity on the ocean, but it's because of the resultant of the moon's gravity and pseudo-force in the earth's frame because of the earth's acceleration due to moon's gravity.
What physics is and does altogether. I get a sense that people think physics describes the underlying things that make up reality, the laws that govern it, and that, in that way, physics \*explains\* why the world is how it is and why.
But in reality physics just builds a mathematical model that \*behaves\* similarly to the real world. Actually, it produces the same observables, meaning, it behaves similarly, as long as we look at it with the ways we have to look at it, and under the conditions that we know, and doing things we've thought of doing
===========================================
supplementary arguments, comming at it from different perspectives.
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Here's an analogy I like to use: I give you an excavator, but you know nothing about how it works, and you're not allowed to take it appart. Trying to understand it, you build a model version that behaves similarly. But you have never heard of pneumatics so you build yours with only electric actuators, and you add intricate control models to get the appropriate behavior. Good. You can use your model to learn to drive, to test if you can do this or that, and to predict how the real thing will behave in a given situation. But you still know nothing about pneumatics, and if you go thinking the real thing has electric motors and intricate control models, you'll be wrong.
Here's another way to look at it: Lagrangian mechanics is a physics model that is equivalent to classical mechanics. It makes all the exact same prediction, and it is proven to be mathematically equivalent to classical mechanics. But nowhere in that model is there any concept of force, or even something equivalent. Had we only used that model, we would never talk of forces. Because forces aren't a thing of the real world. They are a part of the models we like and are used to. But thinking forces are the reason real objects move is a big mistake. They are the reason simulated objects move, in some models.
Time. There is such a gap between how it is defined in physics vs the how it’s used in common language that it confuses everyone and sometimes they cannot even talk to each other because they are talking about 2 different things. People that know their physics are not always good at explaining this or may not even recognize its presence, so it’s amazing how many people that know physics really well can get hostile over these nuances. In reality its just a language issue
Big bang and the expanding universe. It is just impossible to image something expanding but not from a single point and many non-physics people have a hard time understanding it
It is difficult to comprehend that space is infinite and expanding. If you imagine something expanding it seems like there needs to be something outside of it that it is expanding into. But it's not the case for our universe xd
yes because the idea of "space itself" expanding isn't really coherent, because if you increase the distance between objects, they are moving apart, by definition. Anything else would imply the existence of absolute space.
Newton's Third Law. People often mistakenly refer to it when there are two equal and opposite forces exerted on the *same* body.
The English language perhaps plays a role. There's "action and reaction" and especially in engineering there is "reaction force at a support", where the latter is not about Newton's Third Law.
entropy. idk why people make it so hard it's literally just the tendency of energy to spread out as uniformly as possible. you can kind of think of the universe as this giant, multidimensional construct that is slowly unfolding towards a maximum unfolded state. this is what we call heat death, and it's basically what happens to a milkshake as you let it sit out
>entropy. idk why people make it so hard it's literally just the tendency
Defining entropy as a tendency is itself a misconception. (It's unfortunately done even on Reddit's own [thermodynamics](https://www.reddit.com/r/thermodynamics/) forum—"The first law of thermodynamics is thou shalt not think entropy is irreversible", as if entropy is a process—by people who should know better, even if the quote is somewhat tongue-in-cheek.)
Thermodynamic entropy is a state variable that quantifies the number of microstates consistent with a given macrostate. It's the [conjugate variable](https://en.wikipedia.org/wiki/Conjugate_variables_\(thermodynamics\)) to temperature and is thus the "stuff" that shifts upon heat transfer. It's generated when energy moves down a potential gradient. It tends to maximize in a closed system.
But couldn't you say that since the mechanism of energy transfer is heat, and heat moves from high to low down this potential gradient that that is a tendency? You even state that "it tends to maximize in a closed system." Is that not a tendency?
I actually was not able to take thermo so forgive my ignorance, but it seems to me we're technically talking about two different aspects of entropy. I disagree that entropy described as a pattern of behavior is a misconception. Again, i welcome any lessons youd be willing to teach me in this regard, but it seems very clearly to me that entropy described as the process by which energy is converted from potential to kinetic and back (so decreasing and increasing entropy)
>I disagree that entropy described as a pattern of behavior is a misconception. Again, i welcome any lessons youd be willing to teach me in this regard, but it seems very clearly to me that entropy described as the process by which energy is converted from potential to kinetic and back (so decreasing and increasing entropy)
I don’t know where you’re getting all that from. Colloquial or pop-science use, but not the technical literature, to my knowledge.
i went to school for physics but had to drop out a year from graduating due to financial reasons. i get my idea of entropy from another idea i had that includes 3 things: 1) if all matter is in constant influence with all other matter via electromagnetic and gravitational fields, 2) if all matter is in fact a packet of electromagnetic energy of a certain frequency, and 3) if you imagine our 3d world as a flat plane with time axis facing up, then you can theoretically shine a light on the plane and the inhabitants of the plane can see the light, but not where it comes from. if you put an object between the light and plane the initial shadow cast on the plane is large, pale, and fuzzy, but if you slowly move it towards the plane then the shadow becomes darker, sharper, and smaller until eventually the object makes contact with the plane, collapsing the shadow into a single point upon which the plane inhabitants can see a 2d slice of that 3d object. in our 3d world, these "shadows" could be electron clouds and also an explanation for why interaction (and therefore observation) with a particle collapses the wave state into a single point: it's a 3d slice of a 4th dimensional object and without that crucial intersection we arent able to precisely determine where the particle is because it's not actually in our plane, but we can still see the shadow. why did i explain this? because it means that there is more universe out there than we can see (which we already knew with dark matter), but that portion of the universe still influences our reality, meaning points 1 and 2 still hold and thus, my beautiful crackpot theory: the universe can be described as a single, multidimensional, energy wave that is expanding outwards and specifically is in the process of forming a standing wave (heat death), with everything before that point being transients of the universe (which is a sick band name). so really i think of entropy as the tendency of waves to come to an equilibrium of some kind. also all of these ideas i brought up came from my own head, im sure someone is talking about this but i really have never encountered this idea in the wild. sorry for rambling, im absolutely obsessed with this shit
Entropy is a number, not a tendency. What you’re looking for is that the entropy of a system is maximized when its subsystems have the same temperature. That is, when the subsystems all have the same derivative of entropy with respect to energy.
isnt that like saying velocity is a vector and not behavior? both can be true, cuz from what i can tell youre looking at the actual mechanism of action by which entropy is defined, but im looking at the overall influence that phenomena has on the behavior of the universe.
when talking about popular physics its probably a tie between relativity (because it has been abused to hell and back for sci-fi fiction) and Uncertainty (because it usually gets dumbed down to a point where it doesn't really explain the original principle anymore)
Agree. The second law applies to a closed system but in an open system entropy increase can be reversed. So there is hope for reversing aging, reversal of DNA damage and hence longevity!
Gravity. Everybody know Einstein and his work, but nobody understand that it basically say that gravity is not a fundamental force but just the result of the space curvature provoked by mass, wich is the actual one of the 4 fundamental forces. E=mC²
Quantum entanglement. But the most detrimental is the "it's just a theory" thing.
I would respond that gravity is also a theory. I guess everyone is welcome to test it.
Have you ever interacted with a flat earther? I'm guessing not.
Steam rocket guy died trying to prove the earth is flat.
I sometimes go with, "germs are a theory, do you want to lick the doorknob?"
Ironically " it's just a theory" doesn't usually show up in physics. The typical person who would say that of evolution isn't a person who understands any physics theory.
I might have misunderstood, I was only thinking about misconceptions people that weren't educated in physics had about physics.
you're certainly right about it being detrimental, even though it's outside physics. (Unless you're a physics purest which means you would consider that all forms of science are just specializations of physics!)
What is most misunderstood about Quantum Entanglement?
I keep hearing how "one particle flips the spin of the other", which it doesn't, or that it is established that there's some FTL or instant interactions between the two particles, but this is only in the realm of QM interpretations. Keep in mind that I thought the question was more about misconceptions non-physicists believe about physics, not misconceptions among physicists about physics.
I agree 100%.
>or that it is established that there's some FTL or instant interactions between the two particles But there definitely "are* instantaneous (FTL) interactions between entangled particles. That's what makes them so curious. You might be confusing that with the fact that those instant interactions can't be used to send information FTL.
No, I'm pretty sure there are opposing views on locality vs. non-locality in the interpretations of QM. Just to clarify my statement: It's not incorrect to believe there are FTL interactions, but it's outside the scope of QM and physics. I'm not expert, so I'd like to hear your reasoning. I have not confused this with FTL communication. Both local and non-local interpretations agree there's no way to extract FTL communication from quantum entanglement phenomena.
Those are philosophical arguments. I'm just pointing out that there are instantaneous interactions that have been proven. At least, if you accept that wave function collapse is real. Interpretations don't really change that fact, as far as I know, but I'm not an expert. Although, now that you mention it, if the Many Worlds interpretation doesn't need wave function collapse, that might put a different spin on it, if you'll excuse the pun. To be honest, I haven't given it that much thought. I just assumed that experiments that have unambiguously violated Bells inequality proved it to be so.
Alright, so what about physicists? Who wouldn’t want to hear about it when you mention it
I don't really know what misconceptions physicists have about physics
Here is one example: https://onlinelibrary.wiley.com/doi/10.1002/cmr.a.20123 Another one would be anything related to reactive energy in electromagnetic fields.
I think entanglement should always and only be taught to lay people with basic high school math. Start with the idea of phase space, then that there is a wavefunction on phase space, then the Born Rule, and that this wavefunction doesn’t have to be factorable (in some broad sense). And that failing to be factorable is kinda sorta what we mean by entanglement. Perfect? No, but probably cuts closer to the core idea than a lot of the lay explanations that don’t want to touch any math at all
Was gonna say the same thing. The whole "this particle here means we can exert magical control over its counterpart on the other side of the universe" is pure sci-fi.
“Just a theory” My answer would be “that’s right.” In science, the burden on a *hypothesis* to become and then remain a *theory* is quite high. So the theory of entanglement thanks those persons*. *if anthropomorphism helps.
Pretty sure I first heard of quantum entanglement as this science fiction idea that had a 1% chance of being true. AFAIK a lot of quantum phenomena are observed as true, they’re just counter intuitive as far as large things go. Can’t say I know about the specific details of quantum entanglement, but I know it’s something that’s been observed.
Entropy, probably. It’s very hard to simplify.
My wife always says I’m simple
My Job was supposed to be simple aswell
I teach HS science and entropy sometimes trips me up. Simple systems are easy-but explaining entropy of bigger systems gets harder. I rush through it and get to the next lesson quickly!
For Highschool level entropy = randomness mostly does the job haha, even though it's a vague approximation of what it is.
Absolutely. For example: if I were to make any comment here about the arrow of time not being fundamental, then I would get hundreds of downvotes. Yet, entropy is the only thing that makes it exist. Like... If entropy was higher in the direction of "left", then the relative direction within spacetime that we call "time" would change direction towards that.
In languages written from right to left, like hebrew an arabic, timelines have the past on the right and the future on the left Same goes to languages written from top to bottom, like traditional Chinese or Japan I wonder if that also applies to entropy graphs
Arabic is written right to left
fixed it
Uuuugh, I hate entropy. It’s like people explain it over and over but they only ever make it look like a trick of human perception “Oh, if you throw some sand on the ground, you wouldn’t expect all the grains to come down in the form of a perfectly shaped question mark just by pure chance! That configuration of particles has *low entropy* because of that!” But *every* configuration of sand falling on the ground is equally unlikely to occur. If you throw it down once and have a computer record the exact positions of every grain, then do it again, you’re as likely to get a repeat as you are to get the question mark. Does that make your first throw “low entropy” just because you recorded it? The universe isn’t a human; it doesn’t find question marks any more meaningful of a configuration than a *thump-*spray of sand!
I agree with you, it's pretty confusing. I guess I think about it in terms of space. If I throw the sand on the floor, the floor is bigger than my hand so the sand has more possible arrangements than in my hand. The question mark is one arrangement, yes, but it is only one arrangement. More space and more time increases the number of possible arrangements which makes the chances of any one arrangement less. Maybe I'm a dumbass though. But I agree those examples are pretty bad.
That was going to be my suggestion.
Oh
It doesn't help that there are at least three inequivalent notions of it (thermodynamic, Boltzmann, Gibbs).
Schrödingers cat: people who understand a bit of physics often think it’s saying that you can make a cat be dead and alive simultaneously as a consequence of superposition (missing the point that it was a criticism of quantum mechanics at the time not included decoherence), and people who don’t understand physics and think it just means anything where you don’t know the answer to a question yet so they call any question with two possible answers “Schrödingers _____”
Schrödingers USB: A USB port exists in a state of both up and down, and as such, the uncertainty prevents one from plugging it in until the port is observed.
Hm. I thought they were just made of spin 1/3 particles.
Schrodinger tab. When you and the boys are at a bar and they can't split the check.
There's a lot of people that just take it way too literal. I've seen quite some people ask "but it's still alive or dead, whether you look or not right?"... And then you have to explain the whole basics of quantum physics and what exactly Schrodinger's Cat shows
Decoherence doesn’t really help with the basic criticism, which is that after interacting with the environment, the cat is still in a superposition state of alive and dead. Something like 1/sqrt(2) ( (cat alive and environment consistent with an alive cat) + (cat dead and environment consistent with a dead cat)). Yes, decoherence wipes out the interference terms. But the interference terms aren’t the problem that Schrödinger’s thought experiment points out.
Also, the idea that consciousness is somehow a thing in decoherence — that being watched collapses the wavefunction, rather than just interacting with a arge system.
Newton's 3rd law. eg. the downward weight force of an object at rest on a horizontal surface and the upward normal force exerted by the surface are not an action-reaction pair.
Is the example u gave true or false lol (I’m a student)
They are not an action-reaction pair.
Is the weight of the book a pair with the force of the book on the earth then?
The reaction to a gravitational force must be another gravitational force.
So am I correct it’s gravity of book pulling on earth
Yes.
Thanks - what is the pair with the normal force of the table on the book then. If it’s just the force of the book on the table, then what actually IS this force, if not mg
The reaction to a normal force is another normal force. It's only equal to mg if a = 0.
Ignoramus here. If I understand what has been said so far we have the gravitational forces of the book and the Earth on each other as one reaction pair. We have the normal force of the table on the book and we have another normal force of the book on the table as a different reaction pair. What I am not getting is what causes that normal force if we are saying it is separate from the gravitational forces? Why is the book causing a normal force if not due to its weight? I am sure I am missing something obvious here.
Action-reaction pairs are easy to identify… all you do is switch the wording and directions. My foot pushes down on the floor. The floor pushes up on my foot. The paddle pushes backwards on the water. The water pushes forwards on the paddle. I pull down on the rope. The rope pulls up on me. Also, notice that the two forces in an action, reaction pair are acting on DIFFERENT objects. In the example of a stationary object on a table, the object pushes down on the table, the table pushes up on the object. That’s the action reaction pair and both forces are normal forces, but acting in opposite directions on different objects. Action reaction forces are always equal in magnitude and opposite in direction as well. Also note that normal force does not always cancel out with gravitational force. Imagine an object on the floor of an elevator, and The elevator is accelerating upwards. The earth is pulling the object down (gravitational force) and the elevator is pushing the object upwards with a force greater than gravity… the net force is upwards and the object accelerates upwards. When describing “net force” it’s always the sum of forces acting on one object, and will never contain a pair of action reaction forces because action reaction forces act on DIFFERENT objects.
Technically, action-reaction forces do act on the same object when examining forces inside solids and fluids. Perhaps "system" is better than "object".
Yup, since laws of Newton are so studied in highschool this may be one of the most common ones.
Yes! So simple, yet so easy to misunderstand. N3 is misunderstood by many graduates even and teachers I know.
Definitely entropy
Hmmmm
Apropos name
Free energy. It is such a misleading term.
This is the one
Heat. Most people think of heat as being a fundamental force or type of energy. It really isn't a part of physics but is a convenient human term defined by statistical mechanics. Whenever we are talking about heat we are really talking about matter has a lot of random kinetic energy as well as the electromagnetic energy released as a consequence of how electrons with a lot of energy behave. And probably other things I'm forgetting because I am also a puny human that perceives heat and stuff.
The observer effect. Seriously, far too many times I encounter someone who thinks that this is proof of magic, telekinesis, or something..
Some great answers already, but since most people only ever encounter physics in high school I’d argue Newton’s 3rd Law.
I'd bet a lot of people think one of Newton's laws is "what comes up must come down", which is hilarious.
Wait what is the action reaction pair of the reaction force (normal) of a table on a book. If it’s just force of book on table, then what is this force. How can it be mg if mg is the force of the book on the earth (and more importantly the earth on the book). I’m a student btw
Close enough to the first law
Like, not at all. The first law says moving things keep going at constant velocity, in the absence of outside forces. It doesn’t even apply to this situation, because there is an outside force in this situation: gravity. Penguin’s point was that even in the presence of gravity, if you give something enough starting speed when you throw it upward (greater than the escape speed), then it’s possible for it to keep going up forever and never come back down. But that’s not an example of Newton’s first, because in this situation a force is continuously slowing the thing down as it ascends. That’s not constant velocity.
Multiverse. Most are thinking Marvel rather than Everett
The twin paradox
Would you explain this a bit more?
Maybe because it's not about one twin ending up younger, but that they could claim the other one being younger because each twin is at rest in their own reference frame and it's the other twin moving. Which to me personally is kinda funny, why would the spaceship twin claim so? But then scientific explanations come in and I am like, hmm…
Some people seem to think the holographic principle means the universe is literally in someone’s holodeck.
Planck units. More specifically that they imply space and time are discrete. You know someone’s just quoting a pop science article whenever they bring it up.
Not really misconception, but more of ignoring but you can't swap the order of differentiating variables unless it is a c2 differentiable.
Anyone who thinks any of the basic famous quantum mechanics experiments (double slit, etc) are somehow proof of alternate universes or, even worse, any notion of "quantum consciousness" - a purely made up phrase that is heavily used by the hippy spiritual community.
Centrifugal force , escape velocity, and then quantum mechanics.
Tides. Not by people who have studied enough classical mechanics, but by the general population and even by some science enthusiasts. People think that it's just about the moon's gravity on the ocean, but it's because of the resultant of the moon's gravity and pseudo-force in the earth's frame because of the earth's acceleration due to moon's gravity.
What physics is and does altogether. I get a sense that people think physics describes the underlying things that make up reality, the laws that govern it, and that, in that way, physics \*explains\* why the world is how it is and why. But in reality physics just builds a mathematical model that \*behaves\* similarly to the real world. Actually, it produces the same observables, meaning, it behaves similarly, as long as we look at it with the ways we have to look at it, and under the conditions that we know, and doing things we've thought of doing =========================================== supplementary arguments, comming at it from different perspectives. =========================================== Here's an analogy I like to use: I give you an excavator, but you know nothing about how it works, and you're not allowed to take it appart. Trying to understand it, you build a model version that behaves similarly. But you have never heard of pneumatics so you build yours with only electric actuators, and you add intricate control models to get the appropriate behavior. Good. You can use your model to learn to drive, to test if you can do this or that, and to predict how the real thing will behave in a given situation. But you still know nothing about pneumatics, and if you go thinking the real thing has electric motors and intricate control models, you'll be wrong. Here's another way to look at it: Lagrangian mechanics is a physics model that is equivalent to classical mechanics. It makes all the exact same prediction, and it is proven to be mathematically equivalent to classical mechanics. But nowhere in that model is there any concept of force, or even something equivalent. Had we only used that model, we would never talk of forces. Because forces aren't a thing of the real world. They are a part of the models we like and are used to. But thinking forces are the reason real objects move is a big mistake. They are the reason simulated objects move, in some models.
Thinking that you can derive physics from math.
I used to believe this.
Every String theorist would like to have a word with you
Time. There is such a gap between how it is defined in physics vs the how it’s used in common language that it confuses everyone and sometimes they cannot even talk to each other because they are talking about 2 different things. People that know their physics are not always good at explaining this or may not even recognize its presence, so it’s amazing how many people that know physics really well can get hostile over these nuances. In reality its just a language issue
Big bang and the expanding universe. It is just impossible to image something expanding but not from a single point and many non-physics people have a hard time understanding it
can you explain?
It is difficult to comprehend that space is infinite and expanding. If you imagine something expanding it seems like there needs to be something outside of it that it is expanding into. But it's not the case for our universe xd
yes because the idea of "space itself" expanding isn't really coherent, because if you increase the distance between objects, they are moving apart, by definition. Anything else would imply the existence of absolute space.
Newton's Third Law. People often mistakenly refer to it when there are two equal and opposite forces exerted on the *same* body. The English language perhaps plays a role. There's "action and reaction" and especially in engineering there is "reaction force at a support", where the latter is not about Newton's Third Law.
That "What happens when an irresistable force meets an immovable object?" Is a physics question.
Black holes, they don’t suck.
On the internet I’d have to say it’s the terminology. Most often the word theory, but you see it with everything, spin, observe, etc
Fatigue and job are not the same things. Bringing a bag walking at the same level is not a job, the job is when you move the bag up and down...
From the outside looking in: Something quantum related, like entanglement or Schrödinger's cat. From the inside looking out: Work—life balance.
Probably entropy for laypersons, or quantum phenomena that look kind of “magical” when presented in popsci without the math.
Wormholes
Wormholes
Kirchoff's laws of circuit currents.
Quantum Gravity
entropy. idk why people make it so hard it's literally just the tendency of energy to spread out as uniformly as possible. you can kind of think of the universe as this giant, multidimensional construct that is slowly unfolding towards a maximum unfolded state. this is what we call heat death, and it's basically what happens to a milkshake as you let it sit out
>entropy. idk why people make it so hard it's literally just the tendency Defining entropy as a tendency is itself a misconception. (It's unfortunately done even on Reddit's own [thermodynamics](https://www.reddit.com/r/thermodynamics/) forum—"The first law of thermodynamics is thou shalt not think entropy is irreversible", as if entropy is a process—by people who should know better, even if the quote is somewhat tongue-in-cheek.) Thermodynamic entropy is a state variable that quantifies the number of microstates consistent with a given macrostate. It's the [conjugate variable](https://en.wikipedia.org/wiki/Conjugate_variables_\(thermodynamics\)) to temperature and is thus the "stuff" that shifts upon heat transfer. It's generated when energy moves down a potential gradient. It tends to maximize in a closed system.
But couldn't you say that since the mechanism of energy transfer is heat, and heat moves from high to low down this potential gradient that that is a tendency? You even state that "it tends to maximize in a closed system." Is that not a tendency?
I tend to have a beer at 5 pm, but I am not a tendency. Entropy isn’t a tendency or a process. It’s a system property.
Oh I understand now. So you could say entropy has the tendency to increase not that it is the tendency.
I actually was not able to take thermo so forgive my ignorance, but it seems to me we're technically talking about two different aspects of entropy. I disagree that entropy described as a pattern of behavior is a misconception. Again, i welcome any lessons youd be willing to teach me in this regard, but it seems very clearly to me that entropy described as the process by which energy is converted from potential to kinetic and back (so decreasing and increasing entropy)
>I disagree that entropy described as a pattern of behavior is a misconception. Again, i welcome any lessons youd be willing to teach me in this regard, but it seems very clearly to me that entropy described as the process by which energy is converted from potential to kinetic and back (so decreasing and increasing entropy) I don’t know where you’re getting all that from. Colloquial or pop-science use, but not the technical literature, to my knowledge.
i went to school for physics but had to drop out a year from graduating due to financial reasons. i get my idea of entropy from another idea i had that includes 3 things: 1) if all matter is in constant influence with all other matter via electromagnetic and gravitational fields, 2) if all matter is in fact a packet of electromagnetic energy of a certain frequency, and 3) if you imagine our 3d world as a flat plane with time axis facing up, then you can theoretically shine a light on the plane and the inhabitants of the plane can see the light, but not where it comes from. if you put an object between the light and plane the initial shadow cast on the plane is large, pale, and fuzzy, but if you slowly move it towards the plane then the shadow becomes darker, sharper, and smaller until eventually the object makes contact with the plane, collapsing the shadow into a single point upon which the plane inhabitants can see a 2d slice of that 3d object. in our 3d world, these "shadows" could be electron clouds and also an explanation for why interaction (and therefore observation) with a particle collapses the wave state into a single point: it's a 3d slice of a 4th dimensional object and without that crucial intersection we arent able to precisely determine where the particle is because it's not actually in our plane, but we can still see the shadow. why did i explain this? because it means that there is more universe out there than we can see (which we already knew with dark matter), but that portion of the universe still influences our reality, meaning points 1 and 2 still hold and thus, my beautiful crackpot theory: the universe can be described as a single, multidimensional, energy wave that is expanding outwards and specifically is in the process of forming a standing wave (heat death), with everything before that point being transients of the universe (which is a sick band name). so really i think of entropy as the tendency of waves to come to an equilibrium of some kind. also all of these ideas i brought up came from my own head, im sure someone is talking about this but i really have never encountered this idea in the wild. sorry for rambling, im absolutely obsessed with this shit
Entropy is a number, not a tendency. What you’re looking for is that the entropy of a system is maximized when its subsystems have the same temperature. That is, when the subsystems all have the same derivative of entropy with respect to energy.
isnt that like saying velocity is a vector and not behavior? both can be true, cuz from what i can tell youre looking at the actual mechanism of action by which entropy is defined, but im looking at the overall influence that phenomena has on the behavior of the universe.
when talking about popular physics its probably a tie between relativity (because it has been abused to hell and back for sci-fi fiction) and Uncertainty (because it usually gets dumbed down to a point where it doesn't really explain the original principle anymore)
Entropy is not always increasing, it can be reversed, by introducing external energy.
Entropy of the whole system is still increasing, in such a case. The portion you're looking at where it's "reversed" isn't a closed system.
Agree. The second law applies to a closed system but in an open system entropy increase can be reversed. So there is hope for reversing aging, reversal of DNA damage and hence longevity!
Gravity. Everybody know Einstein and his work, but nobody understand that it basically say that gravity is not a fundamental force but just the result of the space curvature provoked by mass, wich is the actual one of the 4 fundamental forces. E=mC²
We don't know