Why General Relativity (and Newton's Laws) tell us The Sky is Falling Up

[@souvikchakraborty2019]

Misinformation. The equivalence principle says that a uniform gravitational field is indistinguishable from a freely falling reference frame. They are still two completely different things and you cannot claim that a uniform gravitational field is actually an accelerating reference frame. Objects in a uniform gravitational field move in a "straight" line towards lower gravitational potential, just like electrically charged objects in an electromagnetic field. The earth is not "falling up", and in fact there are clear differences between a gravitational field an an accelerating reference frame. Source: Physics postgrad working in general relativity.

[@kerrylittle7368]

Kinda like trying to calculate escape velocity from a black hole. (Humorous intent.)

[@MrBBywaters]

Thank God someone on here has a lick of sense!

[@MrBBywaters]

And I'll go you one further. I'll argue that a geodesic path by itself does not and cannot create gravitation. It is the contraction of spacetime toward the center of mass that creates both the paths and the potential gradient that causes an object to accelerate from regions of higher potential to regions of lower potential at the surface of the earth.

[@ScienceClicEN]

Yet again a fantastic video!

[@sgringo]

Coming from you, that is high praise! You're one of the best content providers for this subject matter (no pun intended).

[@dialectphilosophy]

Your support has made a world of difference for us. There isn't thanks enough we can give.

[@sgringo]

@@dialectphilosophy Your content is always superb. I've learned a lot from both you and ScienceClic.

[@abhir7823]

Was just thinking that Dialect's video style narration animation etc resembles Science Clic...😁

[@Name-js5uq]

If you're on board then I can trust everything in this video wholeheartedly. I love each and every single one of your videos. They truly are the benchmark for which all others must strive to become. You are at the top for helping others to become more enlightened about physics and spacetime. I think about your videos often and rewatch them just to stay current with my knowledge. I can never thank you enough. 😊 P.S. I love the background music so very much as it actually helps me to stay focused on your subject matter. Please don't change it. 🙏

[@spyros_77]

The ability to effectively explain complex concepts isn’t just extraordinary, it's a service to the world!

[@tonyennis1787]

1. What experiment shows that my local gravity disappears *instantly* when I step off the building, thus proving the ground is accelerating up? 2. I can't imagine convincing anyone that the apple isn't falling. Which part of this disproved gravity is a force pulling things down?

[@singh2702]

This is what you'll get when seeking answers to complex physics phenomena from KZbinrs. Newton's acceleration is one that is felt by a body when a force is applied to the body at a particular point, which compresses the body's matter i.e. all the atoms that make up the body exert a force on each other. This is not what is going on when a body is in a free fall in a gravitational field. Lets take for example , a person with a mass of 70kg free falling near the surface of the earth. This person is roughly made up of 7*10^27(seven billion billion billion) atoms. Since all these atoms are contained within the gravitational field, each atom will be accelerated individually by an individual force equal in magnitude for each atom. So there are no atoms exerting forces on each other hence no sensation of a force accelerating you like the force you would feel when you step on the gas pedal in your car and get pushed into your seat. When this person is standing on the surface of the earth, the surface is pushing up and since the individually accelerating atoms are obstructed from their path of travel, they are compressed, exerting forces on each other thus giving the sensation of a force accelerating you. The vector component at the center does not disappear and just leave the tidal force component.

[@warrenlancaster286]

I have watched many videos on gravity over the years and I think this was one of the best . Thanks

[@andrewbarrenger]

One of the few channels where I don't need subtitles, perfect diction! The switch-off gravity idea switched something on in my head. Thank you!

[@evrimagaci]

Great video! But: How does tidal forces towards the end of the video explain the problem with "earth falling up in all directions"? You asked the right question there but I am not sure if I understand how your explanation answers how the Earth can "fall up" in all directions? Also, you mentioned it's as if the objects are sucking the space-time around them. So this also goes against the Earth/sky falling up in all directions. Do they suck in or do they fall up?

[@-_Nuke_-]

Yes, those 2 things cancel each other out (after millions of years after the formation of the Earth) perfectly, so the Earth continues to have the same shape. The Earth is moving outwards in spacetime due to the Earth's own internal geological pressure, and spacetime itself, is falling inwards due to the Earth's energy density "sucking in" local spacetime. You could imagine that the Earth is flat and accelerating upwards but in a curved spacetime! All of a sudden, time at different altitudes runs either faster or slower and the entire shape of the flat Earth takes the shape of the local spacetime... Basically, a sphere. That doesn't mean that the superimposed spacetime, isn't equally Deus ex machina as it is with Newton's force of Gravity. It's just a more sophisticated Deus ex machina that takes more stuff into account, and gives an accurate result that respects the speed of light limit. But the explanation isn't any more or less "magical" than that of Newton.

[@edwardjenner1381]

I believe that it is the time-curvature in 'spacetime' curvature. Notice the gravitational subtractions were all done in space. The residual is the space curvature. Nearly all the effects of gravity near a body such as the earth or sun are due to the curvature of time. (I'm not 100% sure about this, because I would explain the concept differently, but I'm pretty sure that is what is explained). The earth accelerating 'up' is caused by the time curvature. If you are sitting on the earth in empty space, then relative to the earth you are stationary and thus not traveling through space, so you should not be influenced by space curvature, but you are still traveling in time, so you do experience time curvature. Falling off a building, you do then experience both space and time curvature since you are moving relative to the earth. But he space curvature is a tiny fraction of the overall gravitational effect. Here is the thing though with the above explanation at the end. If you consider that the earth is dragging spacetime into itself, then it seems more like objects that are stationary in that spacetime are indeed being pulled toward the earth, rather than the earth accelerating outwards. That is at odds with the video and the inertial frame of reference idea. - EXCEPT the inertial frame of reference is still local. Suppose you took the view of the earth as a whole as int he video with the apples on each side of the earth. You then have 2 people jumping off roofs in the US and Australia. Now has the act of jumping off the roof switched off the gravitational field? No, it has not. IDK, this then gets way deeper than a youtube reply. But locally the earth is accelerating up due to time-curvature - it is accelerating into you in time, not space.

[@justintime9714]

@@edwardjenner1381 The best explanation is, that gravity is a real force which obeys Einsteins equations. Like it would be if gravitons would exist.

[@juliavixen176]

The rocks, which make up this thing we call the Earth, are in currently in hydrostatic equilibrium between the outwards electrostatic forces in the atoms of the rocks, and the pressure of spacetime getting squeezed inwards by gravity. Gravity is making the space that the Earth occupies "physically shrink"... you don't see the Earth actually shrinking though, because the core of the Earth, the mantle, the crust, etc. are stretching out by exactly the same amount that space is shrinking. (Here on the surface, that stretching out is about 9.8m/s of linear acceleration... going "up") Smaller rocky bodies in our solar system, like asteroids and stuff, are not compressed enough by gravity for their rocks to get squished into a sphere. The electrostatic forces in the rocks are greater than the "force" of gravity, so they are not in hydrostatic equilibrium. (The rocks don't flow like a liquid.) I should also mention, the ~15PSI (760mm Hg) atmospheric pressure we have here on the surface of the Earth is also due to gravity compressing spacetime. Literally compressing a gas... Water pressure in the oceans is also for the same reason. We're all floating on top of a big ball of liquid rocks and metals. Also, below the surface of the Earth, the local acceleration that you feel -- your weight -- decreases until you reach the center of mass of the Earth, where you will feel weightless, as if you were floating in space (because you are). (This is assuming a hypothetical situation if there was a room at the core of the earth which was comfortable for a human being, and not actually a 9800°F blob of iron.)

[@aaronperelmuter8433]

@@justintime9714 That makes no sense at all. Firstly it most definitely is NOT the best explanation to say that gravity is a real force which obeys Einstein’s equations because the only way to obey said equations is for gravity to not actually be a force at all. And what exactly does it even mean “like it would be if gravitons exist”? What would actually change if gravitons existed and more to the point, how could you possibly have any idea whatsoever about how anything would change by postulating the existence of imaginary particles? Why do you believe there is any need for yet another imaginary and completely unnecessary particle? What would change if gravitons were discovered? It’s as if you’re insinuating that gravity has some requirement to be quantised, which is clearly incorrect. How do you know it’s not quantum mechanics which needs to be gravitised?

[@bobinthewest8559]

I need a better/more thorough explanation of how all points on the surface of a sphere can be accelerating “outward” simultaneously, while the sphere itself remains intact.

[@neilhopwoodsjugband]

Agreed. Where exactly is the acceleration happening if the surface is actually not moving relative to the sphere it is compromised of? Here's another one...if you are really at rest when you are falling in open space, why is the sensation of falling so internal and striking? That one has some explanations I think but it's interesting.

[@tyedee7552]

When you have a cloud of gas in empty space, it expands, due to the gases' internal pressure, which occurs in every direction. This explains how the earth is accelerating in every direction, because the materials inside the earth exert pressure outward. Now to explain why the earth does not fall apart, we can't use the "force of gravity", because it is fictitious. So instead, we are forced to conclude that the volume of the spatial region encompassed by the earth is shrinking over time due to spacetime curvature(more precisely Ricci curvature). If you are wondering where this spacetime curvature comes from, it is shown in the Einstein Field Equations that mass and energy density cause spacetime curvature.

[@carultch]

This is something he does a horrible job at explaining, and you have the a knee-jerk reaction anyone should have from hearing his ideas. There isn't any acceleration of the surface of our planet, in the kinematic sense of the word "acceleration" that you ordinarily experience. But there IS acceleration, in the sense that there is a net non-gravitational force, which is equivalent from the observer's point of view of being in deep space and actually accelerating. What's really going on, is that spacetime is collapsing in on itself, in the region of a gravitational field. Constraint forces "accelerate" objects on the surface of this planet outward, against the space collapsing. We are therefore "running to stay still" as a consequence of constraint forces preventing us from following the collapsing spacetime.

[@dontmeansquat]

Two points on opposite sides of the earth have been accelerating away from each other at what appears to be a fairly constant rate for quite a while now. Even in just one year, their relative velocities were approaching c. Isn't that what's called "exploding"?

[@carultch]

​@@dontmeansquat He has a new video out that explains this, called "The River Model of General Relativity", and it's very similar to what I described in my previous comment.

[@atila8623]

This Chanel is a paradise for physicists and who are interested in physics. You're doing great. I don't know how to thank you.

[@messi8459]

being able to come up with effective analogies is a hella underrated skill, and you have it in spades, terrific video 10/10

[@ImpShimadon]

Wow, I knew the equivalence principle was locally true for a homogeneous field, but I never thought about it using the tidal forces and the subtraction of vector component. Well done !!!!!

[@hiZarki]

for a homogenous field isn't it globally true?

[@anuman99ful]

@@hiZarki Indeed

[@walterchavez3081]

One of the best videos I've seen explaining how the equivalence principles of freefall to zero-G and gravity to acceleration can still work despite facts like gravity gets weaker over distance and causes things to fall radially.

[@michaeldelaney1058]

Just found this channel and love its content. However, I'd appreciate a better explanation by the idea that the ground accelerates up toward objects we would normally consider as falling down. I understood everything this video said from the standpoint of vectors and so forth, and even learned a few new ways to think about GR. But when we got to the question about how Earth, a solid sphere, can accelerate upward in all directions, I felt the answer was glossed over. I'm not saying the answer isn't there, it was just rushed past. Having thoroughly enjoyed all four videos about how easy it is to pick apart solutions for the Twin Paradox by asking simple questions pointing out contradictory or incomplete answers, it is my feeling that saying that Earth, or at least the local ground, accelerates up makes way for contradictory or incomplete answers. After all, this video even points out how strange it would be for two apples to be released on opposite ends of the planet, implying Earth is accelerating in two opposing directions at the same time. Again, I'm not saying the explanation isn't there or doesn't make sense, I'm just saying it would be nice to revisit this idea I'm greater depth. Is saying the ground accelerates up merely a colloquial tool to make sense of the various vectors which add in some directions and eliminate themselves in others? Or are we to literally expect huge columns of dirt and rock to shoot up from beneath our feet every time an apple lets loose from a branch? Or is there a third way of phrasing it which a future video can explore? Thank you for considering my query as I would be very interested to learn this topic in greater depth, which I'm sure there is much yet to cover.

[@dialectphilosophy]

Glad you're enjoying the content! And you're right that a lot of information is glossed over -- we didn't want a 40-minute video on our hands, so we're breaking the topic into multiple videos (like we did with the twin paradox series). The next video in the series will tackle the question of how the earth can accelerate in many directions at once... stay tuned!

[@michaeldelaney1058]

@@dialectphilosophy Thanks for the response. Can't wait to see what's next.

[@davidzombori54]

@@dialectphilosophy It defies common sense that channel with such quality is in fact proposing rather radical idea as earth accelerating up. It is so contraintuitive and propostereus that it should be backed with some serious evidences. So far you have not provide any. That said, everything else is among best of the best on youtube regarding relativity and physics...

[@pigdog126]

The idea that we are accelerating at the surface of the earth is not a new idea invented by the creators of this channel. This has been the understanding of proponents of general relativity for decades

[@billyshawjr4038]

From what I understand, standing on Earth is LIKE traveling in a ship with an acceleration of 9.81 m/s/s. It does not make the ship the same mass as the Earth or the Earth the same mass as the ship. Having a large mass can curve the spacetime around it, but the ship has accelerated motion which is a curve through spacetime. To me it seems more plausible that all objects with mass are "falling" though time and objects with large mass can slow time increasingly with proximity, causing other nearby objects with mass "fall" through time towards the massive object until they hit and then continue "falling" through time parallel with the massive object. If you stop accelerating through spacetime then you stop the curvature and "gravity". Jumping off a building does not stop the curvature of spacetime that the mass of Earth has affected, it only removes the object that was keeping you from "falling" through time to the Earth. It seems unlikely, to me, that the surface of the Earth is racing outward thousands of feet in all directions to meet every object within thousands of feet. That's an incredibly large bat hitting a lot of small balls, not to mention the surface of the Earth rushing outwards to meet every air molecule in the atmosphere. However, I'm no genius, so please direct me to where can I read the peer reviewed proofs of this theory of the surfaces of massive objects racing outward in all directions?

[@singh2702]

Newton's acceleration is one that is felt by a body when a force is applied to the body at a particular point, which compresses the body's matter i.e. all the atoms that make up the body exert a force on each other. This is not what is going on when a body is in a free fall in a gravitational field. Lets take for example , a person with a mass of 70kg free falling near the surface of the earth. This person is roughly made up of 7*10^27(seven billion billion billion) atoms. Since all these atoms are contained within the gravitational field, each atom will be accelerated individually by an individual force equal in magnitude for each atom. So there are no atoms exerting forces on each other hence no sensation of a force accelerating you like the force you would feel when you step on the gas pedal in your car and get pushed into your seat. When this person is standing on the surface of the earth, the surface is pushing up and since the individually accelerating atoms are obstructed from their path of travel, they are compressed, exerting forces on each other thus giving the sensation of a force accelerating you. The vector component at the center does not disappear and just leave the tidal force component.

[@zBernie12345]

So if two people on opposite sides of the earth simultaneously drop an apple, the Earth would be moving in two different directions right? I just don't think this interpretation of gravity represents reality, mathematics and thought experiments notwithstanding.

[@King.Mark.]

That's what I taught ,😅

[@rickandrygel913]

I thought they figured out a long time ago that gravity isn't a force... What every mechanic and some engineers know is that just because it makes sense on paper or works in a computer simulation doesn't mean it actually applies to reality.

[@Jackie-wn5hx]

That's only true in the framework of _general_ relativity and classical mechanics.

[@singh2702]

Newton's acceleration is one that is felt by a body when a force is applied to the body at a particular point, which compresses the body's matter i.e. all the atoms that make up the body exert a force on each other. This is not what is going on when a body is in a free fall in a gravitational field. Lets take for example , a person with a mass of 70kg free falling near the surface of the earth. This person is roughly made up of 7*10^27(seven billion billion billion) atoms. Since all these atoms are contained within the gravitational field, each atom will be accelerated individually by an individual force equal in magnitude for each atom. So there are no atoms exerting forces on each other hence no sensation of a force accelerating you like the force you would feel when you step on the gas pedal in your car and get pushed into your seat. When this person is standing on the surface of the earth, the surface is pushing up and since the individually accelerating atoms are obstructed from their path of travel, they are compressed, exerting forces on each other thus giving the sensation of a force accelerating you. The vector component at the center does not disappear and just leave the tidal force component to be real.

[@Jameshazfisher]

"The river model of general relativity, where mass eats space" - aha, that's exactly how I've been making sense of it! I need to see more about this interpretation!

[@dexter8705]

They mostly only refer the river model to black holes but it should be used for all matter, black holes only do it on a more intense scale.

[@gtitboij2586]

Does it " eat" space or is it a diffrent form of space ? Space in a different state

[@dexter8705]

@@gtitboij2586 don't know, probably just returns to its previous state or dimension. Space and matter are most likely anti-pair states of something. Were use to hearing about anti particles and they destroy each other releasing energy, but gravity is space being erased or converted, but the matter stays. Most likely converted to the time dimension.

[@gtitboij2586]

@@dexter8705 we all know that matter and energy in the universe are conserved so I am of the opinion that it is a diffrent form of space , the wave model suggest that space is excited via electromagnetic waves therefore there must be a quantized point where space becomes matter thus allowing for the formation of non- degenerate bosonic particles ...

[@dexter8705]

@@gtitboij2586 I like that idea but wouldn't that cause other objects to be push away and not pulled in? I'm trying to visually imagine and physic'ally because sound can do something similar but thats due to the compression of the atmosphere, I wonder if the excited state of matter and space from the electromagnetic wave are doing something similar but with enough force to pull it in...

[@micry8167]

I appreciate that you acknowledge the left over questions most viewers are left with. Just that makes me comfortable accepting the model for now. Great presentation and work.

[@immagnusandreas]

When an apple falls to the Earth, the apple *is* accelerating down, while at the same time, the Earth *is* accelerating up (the sky is falling up at the same time the apple is falling down). The center of “pull” (acceleration) between those two objects is well within the Earth, so from our standpoint above the surface of the Earth, it is hard to see the Earth moving(accelerating) at all because: we can't see the central reference point the Earth and apple are accelerating to, and the Earth is moving much slower than the apple. Better to visualize two objects of the exact same size, density, etc. “falling” toward each other (one on 'top' the other on 'bottom'). Imagine two large balls of some pliable substance (perhaps blobs of some fluid) in space. They start moving (falling/accelerating) towards each other, toward the center of the common acceleration/gravitational point. As the spheres move toward each other (neglecting tidal forces), when the surface points closest to each other meet, you can now see the center point of the acceleration. The surrounding soft material on each side will still be accelerating toward that center. As the material of each sphere starts to interact (electromagnetic push and pull, strain between the atoms of the two spheres) they experience (feel) the acceleration(deceleration) of the motion they already had. That center point continues to cause acceleration of the rest of the material until the forces balance out and a new single sphere is created. The point is, both the Earth *and* the apple are accelerating (experiencing free-fall, Up-Earth, Down-Apple) toward the common center of mass. Lines of gravitational force should be diagrammed through the Earth and any satellite (like the moon or even an apple) with an exaggeration to shown the central point of gravity. Diagram a 2 body system like the Earth and Moon to more easily see the central gravitation point the both bodies accelerate to ~(1700 kM / 6371 kM = about a quarter the distance from the surface down to the center of the Earth in an Earth/Moon diagram).

[@FalkFlak]

this is a great explanation/ correction of the concept depicted quite inaccurate in the video.

[@davidowen4816]

One of the best graphic demonstrations of this subject I've ever seen. I'm old, I've seen a lot of them. Don't miss this one.

[@Dragonblaster1]

Galileo didn't actually drop balls from the Tower of Pisa, he rolled them down inclined planes.

[@peterdevalk7929]

Actually it was Simon Stevin who did the proof years earlier. But he wasn't Italian.

[@mikev4621]

@@peterdevalk7929 Dutch

[@williamsmith4709]

I am not a cosmologist, but I logically can't understand that if the earth's surface is accelerating at 32 feet per second squared, then why isn't the earth expanding. I mean if the earth is coming up to push me and there is someone in China being pushed in the opposite direction, the earth, being a sphere, would have to expand, wouldn't it?

[@dialectphilosophy]

Hey, thanks for watching! We recommend checking out the follow-up video to this one, "The River Model of General Relativity" for answers to your questions!

[@williamsmith4709]

@@dialectphilosophy So, you don't know the answer? Now I know where not to go to get an answer. Thanks for trying, anyway.

[@josephdennie6503]

The earth is actually pushing against space simply because it is a solid mass... gravity is greater at the surface of the because it is the surface of the earth that is doing the pushing....further away from the surface gravity weakens....where there is mass there is gravity

[@OGTimeBandit]

Space is being “sucked” in at the same rate.

[@davidkent2804]

Breakthrough concepts for the layman patiently and convincingly explained. Kudos

[@dialectphilosophy]

Thanks for your support!

[@DarkSkay]

12:27 Reducing the acceleration of the reference frame obviously means that it will no longer accelerate at e.g. 9.81m/s^2. That's not primarily an "experiment" within the reference frame, but altering the crucial parameter of the reference frame itself.

[@tombisson3186]

Thanks. The best explanation yet. Two questions: Why do "falling" objects stop moving? Why don't they continue to move through space at the same speed as the earth? The earth is moving at a constant speed and not accelerating. If you toss a ball in a vehicle moving at a constant speed, it does not fly backwards toward the rear. Two: Is the earth actually moving or is it sucking in space all around it?

[@jmcsquared18]

21:44 I don't think putting this as a footnote is pedagogically wise. The intuition that the ground is accelerating upwards, for everyone on earth's surface, is clearly impossible unless space is doing something funny (which it absolutely is doing funny in general relativity). Thus, the river model of spacetime curvature is vital to understanding this viewpoint. If you're going to cover it in a future video (which I am excited for), then that's great, but in terms of good educational practices, "just trust us" is practically blasphemy.

[@jmcsquared18]

​@@narfwhals7843 yeah but that is the entire reason why this viewpoint can even sensibly work. I would've started with that, and then analyzed the implications of the equivalence principle in light of that understanding of spacetime. Plus, I've been wanting a video on the river/flow model from this channel for a while. Really different but valid viewpoint of the way general relativity describes spacetime curvature.

[@-_Nuke_-]

You need to understand that both Newton and Einstein basically say that magic makes the apple fall towards the Earth. The only difference, is that for Newton the explanation doesn't include a speed limit, where for Einstein it does. And thus, we can say, "look, the Earth is exploding outwars but at the same time spacetime is imploding inwards, so the whole thing balances each other out, and any free from any other forces body will hit the Earth because it's basically caught between 2 opposing events that counter each other. But that is still an explanation that at some level, still requires the use of "magic". The true difference from Newtons magical force of gravity, is that Einstein's magic is more sophisticated than Newton's magic, because Einstein takes into consideration the limitations of the speed of light and the hyperbolic geometry of spacetime. And that is true for all science. Quantum Mechanics uses similar kings of magic itself too. Fields, particles etc... All made us mathematical abstract objects and models to probe deeper into the unknown truth of the Universe, that still remains unrevealed.

[@jmcsquared18]

​@@soopergoof232 I think you're missing something, which is that the flow model is a MODEL. It's a way to view the equations. There is also the B-theory of time (also known as the block universe model). These are analogies, ways we make more sense of the mathematics. And the idea that spacetime is a superfluid is not anywhere near a proven statement. It's an interesting conjecture that some physicists are working with.

[@jmcsquared18]

@@-_Nuke_- all I will say to that is, neither Newtonian nor Einsteinian gravitation remotely qualify as "magic." Magic is something human beings control with their thinking or actions. The laws of physics, on the other hand, are blind and apathetic to our will.

[@Wagon_Lord]

Combining slapstick with general relativity. Brilliant as always.

[@PhuongNguyen-oy8sj]

One of the few channels that have a dark sense of humor in physics explanation.

[@MrBBywaters]

The idea that the ground is accelerating UP toward "falling" objects... all over the world, at the same time, in every direction, is stupid beyond comprehension.

[@stewiesaidthat]

Modern science can't get past the flat earth/stationary frame, earth is the center of universe of their ancestors. Rotating frames accelerate the mass outward and forward at the same time. This is the centrifugal force. Since the top of the frame has more acceleration than the bottom, everything is constantly falling inwards. This is the centripetal force. With rotating frames your are going in circles without going anywhere. As the planet rotates, everything is going in a forward direction. Add in the planets orbit around the sun and you get the main direction of travel. As the planet rotates, you go from a clockwise direction of travel to a counterclockwise direction but your overall motion is still in a forward direction around the sun. No different than pacing back and forth on a moving train. Toss a ball out the window and it's no longer being accelerated by the train. Toss it off the top of a building and the building is no longer accelerating it so it free falls back to the ground. E=mc. Acceleration defines everything. In a universe defined by acceleration, there is only more or less acceleration.

[@jnhrtmn]

I think the use of frames illustrates where people are confused about position in space relative something akin to mass. Space is massless (novel concept). You know acceleration is absolute. When you fall, you are accelerating, so all of those games in frames are confusion. On the surface of the planet, you see a different manifestation of acceleration. There are infinite definitions for any velocity which is just like saying NO DEFINITION. Velocity is like a potential energy that you can see, and it is how we define our world being the largest effect on our brain, but I don't think nature sees velocity at all.

[@leapdaniel8058]

This was really good, thank you. I had always been bothered by the fact that most people discussing the equivalence principle almost never mentioned its locality, and it needlessly confused me for years. The "kill engine switch" idea was really cool. It's also very nice to see that the tidal forces are like a less extreme version of the "spaghettification" that occurs when falling into a black hole.

[@ivoryas1696]

@Science Revolution Interesting?

[@tomszabo7350]

The tidal forces are purely geometric in a classical, Newtonian sense, whereas the idea of upward acceleration of the ground doesn't actually exist in (Newtonian) geometry and thus the theory he presents is inconsistent and flawed. Just consider that a falling object experiences acceleration (weightlessness) not just at its lower contact point (feet) but also internally (e.g. butterflies in the tummy). How does the acceleration of ground upwards cause this??? Also look at floating in water, or gravity inside the earth's core ... it is 4.3m/s² IN EVERY DIRECTION ... which implies the earth is "falling inwards" but you won't have any actual or apparent motion at all, and you can't "turn off gravity" by jumping off something (you float without being weightless).

[@bobinthewest8559]

@@tomszabo7350 … Re: “butterflies in the tummy”… Ever drive your car at speed, over a hump (such as a railroad crossing)? You are driving along at a constant speed, and in a “uniform” direction (therefore, experiencing little or no acceleration)…. Until you encounter the hump. At that point, you experience an upward acceleration, followed by a very brief moment of “weightlessness”, then a “downward” movement, followed by an abrupt “halt” of “downward motion”. The point at which you feel the “butterflies”…. Is during that brief moment of “weightlessness”, which (from one perspective) can be described as being the moment in which “your acceleration is switched off”. If interpreted in this way…. It can be argued that “butterflies” are not caused by acceleration, but instead by the “switching off” of acceleration. I’m not claiming to have a better understanding of all of this than you do…. Nor am I saying that I fully agree with the claims of this video… Just pointing out how “interpretation” can influence one’s “conclusions”. Personally…. I need a much more thorough explanation of how all points along the surface of a sphere can be accelerating “outward” simultaneously, while the sphere remains “intact”.

[@tomszabo7350]

@Bob in the West A roller coaster or even an elevator can give you the same feeling ... never mind a fighter jet! It is a nervous system reaction in the abdominal wall to a change in acceleration. My point was that the ground "falling upward" can't explain it. Gravity is not indirect. The creator of the video does have it partially correct though. In the time domain the ground and everything else "falls" up (expands outward). This happens at the speed of light. If there is no mass present, then the time domain expands smoothly and space-time is "flat". The presence of mass creates "kinks" in the time domain which causes space-time to curve. It is tricky to visualize time like this ... perhaps try imagining the universe as a diorama that you can somehow observe from outside. Now zoom in on Earth ... you are still outside the universe diorama but all of a sudden everything is much bigger. Now zoom back out to billion light year scale ... everything now appears relatively smaller. That is essentially time (though it only seems to zoom in). But to everybody inside the universe diorama there is no change (expansion) in scale since in 3 dimensions all observed objects are relative. We only detect the "passage of time". Yet the expansion itself is very real including the generation of actual quanta of space (that we can't detect in 3 dimensions). The mechanics of how this time domain expansion actually happens remains to be solved though string theory and the holographic principle are probably on the right path.

[@ayushdeshmukh284]

One rebuttal: the accelerator pedal (or any theoretically perfect apparatus) cannot instantaneously make the gravity vanish. Kinda like how when you release the top of a long hanging spring, the bottom stays stationary until the top of the spring reaches the bottom at the speed of sound. Letting go of the force moving the car will not mean that the ball pendulum stops accelerating faster than the speed of light, in fact it doesn't even happen faster than the speed of sound. (Speed of sound travelling through a car metal frame) So rather than giving allowing the pendulum to seem like an example, it should be made explicitly clear that only gravity vanishing far away would be a problem. (For example, say the car travelled 1km from a starting point, then stopped accelerating at an ending point. Looking from the ending point, the gravity at the starting point vanish at a response speed that's faster than the speed of light.)

[@hdskbdjsksndjssm]

bro the “sky is falling up” is a great name for some horror movie

[@lucaozymandis479]

What you are doing here and ScienceClic English on his channel (by the way ScienceClic, your last clip called "The Electromagnetic field, how Electric and Magnetic forces arise" is extraordinary) is THE REAL DEAL. I'm really surprised that you only have so few subscribers. Much closer to the value of the content promoted here would be at least 3 - 4 million subscribers, but if you keep it up, you will get there in the shortest time, which is what I wish for you from the bottom of my heart. I only ask you to maintain this rigor in the future and we want as many and more frequent videos like this from you (and from ScienceClic as well!). I can't wait to watch the videos in which you treat the topics you opened up with the questions at the end of this video. All the best in the future in your journey through ... space time (SIC!).

[@Speedcuber6969]

Saying this video is brillliant is an understatment. The way it is written and the logic that flows is so good. Brilliant writing whicuh translates to brilliant understanding

[@GuyAtTheSix]

Your channel and ScienceClic are by far the best channels on this subject. Keep up the good work. Look forward to seeing new videos from your channel!

[@ReasonMakes]

5:20 Tiny mistake here. Astronauts orbiting earth are NOT in zero-gravity. The gravity from Earth is actually about the same where the ISS orbits as it is at sea level (0.89x to be precise). They are floating because they are in *free fall,* because they are orbiting. Which, appropriately for your video, is indistinguishable for the observer within that frame.

[@dialectphilosophy]

"Zero-gravity" was actually coined to describe astronauts in orbit, so it's conflation with free-fall has existed since its origin. However, since there is no difference between free-fall and zero-gravity, both terms are appropriate in the situation.

[@LeoH3L1]

@@dialectphilosophy No, they're not appropriate.

[@MisterPoopyButthole]

"Zero Gravity - Noun the state or condition in which there is no apparent force of gravity acting on a body..." Zero gravity doesn't mean there is no gravity, just that it is not apparent. His usage of the term was correct.

[@Epicus5]

​@@LeoH3L1 how so, please expand.

[@ronsandgren1]

I don't understand the math or expanation of this and everything falls down and I don't feel the Earth moving up.

[@nickallbritton3796]

A lot of the explanations are very good but the idea that earth is accelerating up is completely unfounded in this video.

[@SotGravarg]

So what you're saying is "I do not understand this, therefore it must be wrong.", you probably also think the earth is flat don't you?

[@moixemi]

i believe “you feel the earth moving up” as weight, as in how much you may weigh in lbs or kgs. however idk

[@kakudmi]

Modern scientists are trying to brainwash ppl to believe their theories instead of our senses.

[@neoanderson7962]

Interesting how well presented logical fallacies smoothly take us down the road of inaccuracy 😮😮😮

[@JackPullen-Paradox]

But one must ask how the Earth can perpetually, eternally accelerate up (in all directions)? By the way, why doesn't the Earth accelerate toward a feather at the same rate as to a steel ball?

[@mikev4621]

Air resistance still applies

[@JackPullen-Paradox]

@@mikev4621 The Earth and its atmosphere move as one do they not? The Earth would move toward the feather at an inexorable accelerating rate, while the feather would experience a "wind" that would not have the same characteristics as air resistance. So, we would see somewhat different behaviors in the two ways of looking at the effects of gravity. At least, that is what sticks in my mind about this.

[@mikev4621]

@@JackPullen-Paradox Yes, but the atmosphere under the feather would act like a cushion and push it upwards relative to the steel ball. Therefore the Earth would reach the feather and the ball at different moments.

[@JackPullen-Paradox]

@@mikev4621 My point is, there would be a different equation of motion in the two scenarios.

[@mikev4621]

@@JackPullen-Paradox it would be the same equation for the ball and the feather; but the resistance term for the feather would be greater

[@Rick.Sanchez]

I still don't get _why_ the surface is accelerating "upward". Isn't this just mearely a consequence (of the hen-egg -type) of repulsion of matter attracted to the same center of mass, i.e. pushing off of each other when "falling" in the same direction of space curved by matter? Edit: confirmed in the follwoing videos 👍

[@ivoryas1696]

Man this is _really _*_really_* one of those moments in which I wish I had happily and accidentally stumbled upon a mostly completed KZbin series... I actually didn't even have as many questions as were shown in the end, and I _still_ feel like I've been left on a cliff-hanger. I'll agree that the explanatory power of this video and it's production quality are *_well_* above its weight class in subs and views, but then again, I doubt many don't...

[@dialectphilosophy]

Thank you for the kind words, glad you found us!

[@ritemolawbks8012]

This was a very good video. The caption @ 21:31 describes my first impression of the channel. I'm happy to be proven wrong, and as a new subscriber, I'm excited to finish the learning journey with you!

[@dialectphilosophy]

Thank you 😂. The journey will continue!

[@Justwantahover]

I actually checked the date of upload. And was surprised it wasn't April the first!

[@kaleijuka8532]

Gravity pulls things down to Earth center. Electrons keep you from phasing through. The normal force is pushing you up because of the pressure exerted downward. Do you have information that could add more to this?

[@riccardovacchi1362]

Mi viene da piangere per quanto è semplice e intuitiva la spiegazione in questo video. Cancella completamente e in un solo colpo l'errata e insoddisfacente visione intuitiva avuta da sempre. Ora è chiaro che sia tutto sulla terra ad essere accelerato verso l'alto, ed è chiaro che buttare qualcosa da un grattacielo significa fargli raggiungere istantaneamente uno stato inerziale, cancellando definitivamente il fantomatico campo gravitazionale che immaginavamo, sottraendo l'accelerazione verso l'alto, la scomposizione delle forze radiali lascia lo spazio per una minuscola forza, che è la vera forza mareale, che da sempre mi aspettavo piccola altrimenti gli astri, invece di orbitare, si sarebbero dovuti schiantare fra loro. Dover essere accelerati a 9,8 m/s2 verso l'alto per rimanere fermi e contrastare la curvatura dello spazio-tempo ora mi sembra così logico. Grazie a questo e ai video precedenti di Dialect, sono impagabili!

[@ramimehyar481]

You blew my mind! However, there is always going to be the argument that the objects falling towards the ground do not lose (pull the plug on) the gravitational field, it only appears so because the measuring methods and tools are also accelerating with it and the complete system within the frame of reference seems to do so, at the end all of the objects are relative to each other in the same frame of reference.

[@davestorm6718]

Exactly. The analogy does fail with another respect: The objects with the monkey DO feel downward force due to acceleration because that frame is NOT moving at a constant velocity. Implying that it does, is incorrect from both a relativity standpoint and a Newtonian one. The "force" is not actually "turned off". There is a massive difference between constant velocity and constant acceleration - pun intended.

[@singh2702]

@@davestorm6718 Newton's acceleration is one that is felt by a body when a force is applied to the body at a particular point, which compresses the body's matter i.e. all the atoms that make up the body exert a force on each other. This is not what is going on when a body is in a free fall in a gravitational field. Lets take for example , a person with a mass of 70kg free falling near the surface of the earth. This person is roughly made up of 7*10^27(seven billion billion billion) atoms. Since all these atoms are contained within the gravitational field, each atom will be accelerated individually by an individual force equal in magnitude for each atom. So there are no atoms exerting forces on each other hence no sensation of a force accelerating you like the force you would feel when you step on the gas pedal in your car and get pushed into your seat. When this person is standing on the surface of the earth, the surface is pushing up and since the individually accelerating atoms are obstructed from their path of travel, they are compressed, exerting forces on each other thus giving the sensation of a force accelerating you. The vector component at the center does not disappear and just leave the tidal force component.

[@davestorm6718]

@@singh2702 Newton's laws were derived by the motion of an object in a gravitational field - the object moves faster and faster over time - meaning acceleration - until it crashes into the Earth. When I say "feel", I mean affected by. You don't actually "feel" anything. To say that the Earth is pushing up makes no sense (and no evidence of that). It may be have a force exerted on it by the small object causing it to move, imperceptibly towards that object, but, as per Newton's Law again, the acceleration of the small object is directly proportional to the force pulling on it. You have to consider inertia (both linear and rotational), for the Earth to push up, a ridiculous amount of force (that the small object cannot provide) would be required to overcome the inertia of the Earth (including the rotational inertia). There's no magic here. The Earth is not expanding "upwards" - this is nonsense and easily provable otherwise as any expansion would be non linear!

[@singh2702]

@davestorm6718 I have provided the answer in detail of how you can be accelerated yet feel no force. This effect of accelerating and feeling no force can only be achieved in free fall in a gravitational field. The curvature of Spacetime is a force that acts on every single atom , sub-atomic particle, and light. The force field acts on them individually, i.e., no net forces by fellow atoms applying pressure on each other. When you stand on the surface of the earth, the surface is preventing those atoms from traveling through their geodesic path. They thus have no path to accelerate, so they can't help but exert forces on each other. This is when you feel the force of gravity. All your organs , muscles, etc. are squeezed against each other(inertia) due to the obstruction of the surface of the earth. I did not say the earth is expanding and accelerating you. I said it's an obstruction to your path of travel dictated by gravity.

[@davestorm6718]

@@singh2702 There IS a differential between the atoms furthest away from the source vs the atoms closest (in the same body). The effect is so minuscule you wouldn't feel a thing, regardless, unless you were hypersensitive. With regards to extreme pull (e.g. black hole), and were falling in, feet first, I promise you will then feel it. Curvature of space and time differentials are one way to explain this (i.e. there is no gravitational force, only warped space-time), but, believe it or not, simple attractors (not requiring 'space-time') can explain the same thing (the way things were explained for a couple of centuries before Einstein's ideas hit the scientific circles) and explain relativity as a whole. Space-time concept fails to explain observations in so many fields, it's amazing that anyone who really dug into it, cannot conclude that it's invalid (in the tangibility sense) - sure, some works on paper (if you make enough "adjustments" for infinities), but it needs to be laid to rest. When the alleged "confirmations" are off by orders of magnitude (e.g. dark matter, gross error in the Gravity B probe experiment, orders of magnitude difference in light bending from prediction, multiple astronomical observations being 2-3 O.O.M. off w/ James Webb, the failed conclusions of the Michelson-Morley experiment that, while it may indicate an ether-less Universe, it also would necessarily disprove frame-dragging), it should be obvious that Einstein's version of relativity needs to be trashed so we can move forward in a productive direction. Einstein contributed greatly to science, but, he was correct when his intuition kept leading him to the VSL theory, even to the postulation G might not be a constant in later life. The science is not settled. I can't wait until someone finally figures out that a star cannot create a singularity - an externally compressed system is not the same thing as an attractor compressed system and they can grow almost indefinitely, until acted on by something else, of course. The zone of highest density is not in the center, but in a shell between the surface and the center. We made models, over 3 decades ago, via finite element analysis -style program that used attractors. The results indicated this. I'm hiring a mathematician and some devs later this year to recreate the model graphically, and run it on thousands of cores, snap shotting the true evolution of stars (and proving they cannot create singularities) vs the Fortran mod where we had pallets of printouts much to the chagrin of the computer dept (we never got to complete the run, which would take about a year, but did get indicators of our predictions). I promise a massive upheaval of the mainstream physics in the next few years, partially fueled by AI advances, and a re-visit to the classical physics (e.g. Maxwell's equations) with more rigorous analyses than humanly possible (including the search for anomalies in derived work) and extrapolations to real world observations with little error (none of this "well his theory is 100% correct, so we must tweak it when it doesn't work" nonsense).

[@ozachar]

Thank you for an amazing video with insightful delicate points highlighted. It would be nice if you add a segment or another video showing explicitly how we can glean this from the metric tensor mixing parameters under the effect of mass, so we see the flow of space expressed in the rather simple algebra. There is an audience here that is not afraid of seeing math.

[@Nibor999]

None of the examples that you give where the gravitational field is "instantly" turned off are correct. You cannot instantly remove your foot from the car's accelerator and even if you could the car's engine does not instantly turn off. The same applies for the rocket's kill switch. You also cannot instantly step off a building unless you travel at the speed of light. In each case the gravitational field will gradually (not instantly)diminish (if you choose to view it that way) .

[@bradbadley1]

I think the point stands. It doesn't have to be "instantly." The point is that it's FTL and if it's FTL then that should throw up red flags and alarm bells.

[@-_Nuke_-]

You can step off the pedal at a velocity of a m/s. At some distant part of space, gravity will turn off for you faster than light. So the a velocity isn't important here.

[@salvatronprime9882]

@@bradbadley1 it's never FTL, he is flat out wrong.

[@salvatronprime9882]

@@-_Nuke_- no, there is no point in the universe where gravity will deactivate FTL. There is a spacetime contraction/decontraction that flows through the atoms in your body as you accelerate or decelerate. His explanation is bad and Eugene Koryanki had it right the first time.

[@Nibor999]

@@bradbadley1 My point is that it cannot be FTL. How can your foot move of the accelerator FTL?

[@ProgressiveEconomicsSupporter]

I am not sure if it is correct to bring the ISS as an example of an inertial system moving with constant velocity. Isn't ISS rather constantly free falling around the earth but just quick enough, that is why it seems zero gravity on board although there isn't.

[@tricky778]

I have a theory of the genesis of flat earthers. When we combine what's stated independently into an independent model rather than depending on a basis for our philosophical view we get the flat earth. Since one educator says the ground is moving up, but others say the planet is not getting larger and the speed of light is constant, not increasing exponentially, along with the permittivity and permeability of free space, particle masses, etc, then the earth's radius must be infinite and thus its surface is flat.

[@hugoballroom5510]

Just seeing this one now after commenting on the animation on one of the twin paradox videos. Again, superlative work on these concepts and representing them. At 17:03 i noticed the moving coordinate grid in the background and then at the end the animated coordinates which to me visually represents the concept of i think it's referred to as the "river model" in the video? I had not heard of that term, but it makes the thinking-shift the sequence of videos strives for very clear. One of the things that i'm still hung up on is how there are arguments attributing a cause to the phenomenon of gravity. I"m remembering a Feynman crack in one of the audio lectures about how the old theory of planetary motion was angels beating their wings to push the planets around, which has now been "slightly modified. The angels push the planets toward the sun and don't have wings." His point being that while the phenomenon can be more and more accurately described (over a wider regimes), the CAUSE of gravity is not something that is yet known. Causality being a whole other level of explanation.

[@dialectphilosophy]

You raise some good points. No one knows what gravity really is, or why it is linked to mass - makes many people susceptible to theories of causation that are often just poorly applied analogies. Thanks for watching!

[@boidaemon8733]

another great vid keep em coming, i can guarantee that this channel will blow up once people start seeing the quality in these vids.

[@androstern]

"GRAVITIY MAKE FALL - DOESN'T THINGS"

[@Jiggerj01830]

I didn't get the part about the earth rising up to meet the apple in the east, while at the same time rising up to meet the apple in the west.

[@pascalguerandel8181]

After researching, i find that there is still disagreement on this subject in Academia. Example...a free falling object is pulled downwards to the ground and that the ground is not moving upwards. 😮😮😮

[@SemiStableUniverse]

One time when I was drunk, I could actually see spacetime flowing through me into the Earth.

[@tomisaacson2762]

How do I get some of what you were drinking?

[@chiraggowda4928]

We have all been there.

[@tombisson3186]

I think I was with you, it was on 4-20.

[@yagvtt]

I have been trying to make sense of GR for many years now, yet each of your videos is an eye opener to me. It must be nice to be clever, i'll never know. Thank you very much for sharing this understanding and for the great animations. Do you have any knowledge/opinion about Laurent Nottale's Scale Relativity ? From the little i understand of it, it is very elegant. At its core it's an extension of GR to scales (=>there's no such thing as zooming/unzooming), it leads to many experimentally verified results both in micro and astro scales, and yet for some reason it has been completely ignored by the scientific community since it came out in the early 90s. I'm not intelligent enough to decide or claim that it is right or wrong, but it is so impressive that it should at least deserve some interest, even if only for debunking.

[@bernardputersznit64]

the very same for me - i spent years trying to understand tensor calculus - that is a very intuitive way to attempt to grasp GR. This makes it so much more LUCID 🙂

[@bernardputersznit64]

BTW I had a look at your YAG videos - VERY Good - Kudos

[@bernardputersznit64]

However I was reminded by the insanity of heterogeneous dice systems of resolution -- this and other long standing issues of most RPGs simply rub me wrong -- I am creating my own RPG system that utilizes a much simpler method of ordinary playing cards (which can be digitized as in YAG) - Face Cards allow for 'now for something different' - several face cards in a row result in something TOTALLY different.

[@yagvtt]

@@bernardputersznit64 Hi, thanks a lot for the kind words about Yag :-) There is unfortunately no card management system in Yag atm because i still haven't got a good idea of how to correctly make this. It's a difficult subject^^ Anyway, i'll stop talking about Yag here as it would be impolite to take the focus out of this video. Feel free to contact me outside of those comments if you want to talk about this. Cheers.

[@dialectphilosophy]

We have a little bit of knowledge of that theory -- mostly cause Sabine Hossenfender bashed rather hard on it lol -- but the desire to understand theories like that also motivated our desire to better understand GR in the first place. So we can't say much about it atm but will probably be looking into it in the future. Cool gameboard design, btw.

[@Robinson8491]

If it's the earth that's moving upwards instead of the apple falling down, then how do you explain when something falls to the earth, *its distance to the moon increases*

[@carultch]

Because the Earth's surface doesn't have a kinematic acceleration as we normally experience it, that is upward toward the moon. The Earth has an acceleration as General Relativity defines the term, but not as introductory kinematics defines the term. What really is happening, is that spacetime collapses inward on massive objects that are the source of gravitational fields. The normal force is accelerating you upward, so that you are "running to stay still" in this collapsing field of spacetime that we normally consider to be a gravitational field.

[@Robinson8491]

@@carultch if spacetime collapses inward, and normal force accelerates outward, you are adding two accelerating forces: so which one is it: the earth moving outwards or the space flowing inwards? You can't have both, and you are mixing them up in your answer! Double acceleration!

[@carultch]

@@Robinson8491 The answer is that they add up to zero, when looking at it from our point of view and the Newtonian explanation. Or more specifically, very close to zero, after you account for all the kinematic acceleration associated with the planet's motion. That's why I say "running to stay still". Spacetime is collapsing inward on itself, when in a gravitational field. Constraint forces accelerate you outward, relative to the collapsing spacetime. The net result is that you aren't falling toward the center, or expanding outward, but that Earth maintains a constant size and keeps you on its surface from the equilibrium of structural forces and the gravitational field. When you stop "accelerating upward" from the normal force, you are forced to follow the collapsing spacetime. It feels as if there are zero forces acting on you, from your point of view, because unless you are sensitive enough to feel tidal forces, you cannot feel gravity.

[@FalkFlak]

it appears to me this is all just convention and if you switch signs and say the mass is accelerating "inwards" and spacetime "outwards" everything stays the same just by the arbitrary definition of those words. Its like those engineere who insist the earth on which they found their building is pushing with a negative sign against their buidling. It just doesnt matter it you dont mix it up.

[@todradmaker4297]

@@carultch This man gets a gold star. The surface doesn't fall up. Actually we don't really fall down either, but rather we fall in.

[@spaciousflame]

13:00 No solid body is truly rigid. The acceleration doesn't stop everywhere instantaneously. The lack of acceleration ripples outwards at lightspeed at the fastest, meaning that for the front of the car, the apparent gravity will vanish, while at the back, the gravity will remain slightly longer.

[@hosh1313]

8:00 This is not the same thing. If we are on the accelerating ship and a piece of the ship breaks away from the ship that piece gets left behind. But if we now have a rock falling in a G field and it splits, both pieces of rock continue to accelerate identically! The idea that you can't tell if you're accelerating in a G field is because G acts through every particle in your body (there is no apparent force on you like if you're sitting in a chair and being pushed into it by G) If you're in a G field and there is nothing to counter that force then you are indeed accelerating! Being able to realise it is irrelevant!

[@AWSVids]

You're conflating the effects WITHIN the ship with effects OUTSIDE the ship. If "a piece of the ship breaks away", that would be analogous to a piece of the Earth breaking away... not to two objects acting within Earth's gravitational effects. This is why the analogy is being INSIDE the accelerating ship, not somehow breaking away to outside of it. If you somehow "break away" from Earth, you'll "get left behind" too.

[@singh2702]

Exactly. Newton's acceleration is one that is felt by a body when a force is applied to the body at a particular point, which compresses the body's matter i.e. all the atoms that make up the body exert a force on each other. This is not what is going on when a body is in a free fall in a gravitational field. Lets take for example , a person with a mass of 70kg free falling near the surface of the earth. This person is roughly made up of 7*10^27(seven billion billion billion) atoms. Since all these atoms are contained within the gravitational field, each atom will be accelerated individually by an individual force equal in magnitude for each atom. So there are no atoms exerting forces on each other hence no sensation of a force accelerating you like the force you would feel when you step on the gas pedal in your car and get pushed into your seat. When this person is standing on the surface of the earth, the surface is pushing up and since the individually accelerating atoms are obstructed from their path of travel, they are compressed, exerting forces on each other thus giving the sensation of a force accelerating you. The vector component at the center does not disappear and just leave the tidal force component.

[@marcuslowe9556]

Good video. I was just thinking about how gravity works recently. This "charge" that gravity exerts would be a mirror of mass equivalence when a force F is applied to an object O for time T. Mass M defined by a volume V would have an energy equivalence that causes its center of gravity to accelerate towards the sky. IMO it's more akin to mass folding space inwards based on this energy equivalence, so we get the same time dilation effects that would occur with velocity. I think this "folding space inwards" would be how matter stays matter through time. Escape velocity would be to essentially escape from one guy folding in space, only be attracted by another guy folding in space. Since the edge of our observable expands at c(and where time stops) it's akin to an event horizon and will be the ultimate attractor for those that leave their home bodies, which would also explain why galaxies stretch further and further apart.

[@potawatomi100]

Outstanding video production and exceptionally well narrated. You presented information in a compelling, interesting and engaging way. I get your point, …absolutely, but my intuition still struggles with the reality of the matter.

[@blurta2011]

It's presented well but is it TRUE

[@Roberto-REME]

@@blurta2011 The concept is not intuitive, thus, hard to get my full understanding. But, so was Relativity when Einstein presented it in 1905 - he was ridiculed, insulted, etc. Today, w/out the necessary adjustments mandated by Relativity, geopositioning would not work (GPS), and many other tech advances.

[@misterlau5246]

The production level with so many animations is superb. Way to go!

[@peterburkhalter6344]

I may have missed the point of this video but doesn't acceleration imply that you move to a new location?

[@hieronymusvonlipschitz]

No it means a change of speed and/or direction. Twirling around in a circle at a constant speed is still accelerating because you're constantly changing direction

[@peterburkhalter6344]

@@hieronymusvonlipschitz I don't think so. I think we're misinterpreting "change of direction". I think a force has to be applied to something for it to accelerate

[@ausblob263]

It's not totally indistinguishable when your on a rocket ship vs. being on the earth but very hard to tell, the earth is curved and the field projects radially outward, but on a ship its linear, it's a small thing but I'm fairly sure of that *** edit*** well I should have watched the whole video

[@TTGTanner]

GRAVITY THINGS DOESNT FALL MAKE

[@jack.d7873]

@15:10. This is the most intuitive explanation of Einsteins equivalence principle I've ever seen. Brilliant work as usual

[@annamariacarusone6619]

Excellent video with comprehensible explanations and great animations! Astonishing job at making hard concepts of our physical world easily accessible! Thank you!

[@spacecadet9852]

Near the end you say that mass sucks space in like a vacuum, but isn't that the opposite of what it's doing? Like if space is falling up, it's like mass(energy) emits space more like a faucet than a drain. Here's a good analogy: think of bubbles in a fluid, rising to the surface. Now imagine mass as bubbles in the fluid of space, and falling becomes similar to rising. Another cool way to shift your perspective is to imagine that a fire's upward trending shape is a result of motion through space rather than gravity.

[@maaaaaaaaarcel]

I don't understand how the "earth is falling into all directions"-paradox was answered in the end...

[@duality4y]

this video is really really great! but could you put some sources/references in the description ?

[@souvikchakraborty2019]

He can't because this is classic pseudoscience. He picked one statement and completely misinterpreted it, made it sound sciencey, and claimed he was an expert.

[@duality4y]

@@souvikchakraborty2019 that is why i asked for them :D

[@green65eyes]

KZbin is overrun by AI-voiced pseudoscience videos these days. What even motivates creating something like this?

[@PronatorTendon]

Sounds like a good defense for a car accident "I wasn't accelerating, my frame of reference was"

[@UhrBushaltestelle]

😂🤣🤣😂😭

[@m.c.4674]

daily dose of relativity contradictions ☕😮‍💨.

[@frankclough380]

I think I get it. The Universe and everything in it is expanding so the earth is getting bigger, that means that as you stand on the expanding Earth you will feel it pushing you in the direction of its expansion. Likewise if you fall off a high building the expanding Earth will be accelerating towards you giving you the illusion you are falling. That makes it all clear now, thanks!

[@Skullbro-bd4ue]

Not at all. Earth is not expanding. In order for earth to stay still. Earth has to accelerate in curved to stay still. And so Earth accelerating in all directions is not expa.ding because spacetime is curved. But in flat spacetime that would be true.

[@Skullbro-bd4ue]

No

[@theoriginaltroll4truth]

G force and Gravity are pressure mediation of aether. G force, acceleration causes a pressure gradient in the uncompressed aether, in the direction of motion. High pressure builds in front, low pressure builds behind. Gravity is a result of uncompressed aether/space flowing/accelerating towards compressed aether/matter. Pressure builds above, while decreasing below.

[@HarpSeal]

May i ask if you have a degree or any sort of certificates on physics?

[@kylelochlann5053]

In watching their other videos I am quite certain the content creators have no formal training in physics and if you asked them to solve a random end-of-chapter question out of Wald or Schutz even, they wouldn't have any idea whatsoever on how to solve it, but that said, this video is quite good and fairly consistent with relativity.

[@green65eyes]

Are you asking the person behind the video or the AI voice narrating it?

[@tomusic8887]

Sounds so crazy theoretical....you give no good answering to the sky falling up, just that it is a theoretical trick.....still confused

[@nickallbritton3796]

That's because this is absolutely bullshit. A lot of real physics poisoned by really flawed logic. Like how he pointed out which way up is would have to be every direction simultaneously all the time and then moved past it without ever explaining it. Then he concluded the earth is accelerating "up" 2 min later anyway. "As I have just showed for you 2+2 can be described very beautifully and abstractly in this new formalism. Some people say that 2+2=4 because if you take 2 of something and another 2 of that something you end up with 4 of it. Anyway with this new paradigm 2+2=5 and it's great."

[@FootlooseNomad]

I think it boils down to our motion being determined by pressure difference, maby. Makes sense in my mind anyway

[@nickallbritton3796]

@@FootlooseNomad no it doesn't

[@TheMijoAaron]

@@nickallbritton3796doesn’t the internal pressure of a mass push outward in all directions. From my understanding planets and stars don’t collapse upon themselves from gravity because they are exerting just enough force to stay stable against the flow of spacetime. So the earth is pushing outward in all directions at 9.8m/s^2 or whatever the number is

[@nickallbritton3796]

@@TheMijoAaron its pushing out against you but perfectly balanced so it's not moving. Why don't you get accelerated upwards then? Because of gravity. The math and physics just doesn't make sense without it

[@romantrix]

BELIEVING that the same results mean the same cause is a MISTAKE

[@zedred8075]

Great video, really clear and helped me get a better understanding of GR. One point though. It’s unfair to claim that if Galileo and Newton had just thought about things a bit more they could have come up with GR. I would posit it was impossible for them to do so. They didn’t have the benefit of 250 odd years of maths and physics discoveries to help as Einstein did. There was no Maxwell or Minkowski or Hilbert or Lorenz to help them. Einstein himself said that without Maxwell and Newton he wouldn’t have been able to devise GR. Einstein also said that what Newton did with his universal law of gravitation was just about the only way a human being with the highest intellect could do to make sense of gravity in his time. So kudos to Galileo and Newton for laying the foundations for Einstein.

[@dialectphilosophy]

Actually! -- believe or not -- Newton was at very cusp of formulating the equivalence principle. In his works he explicitly stated that a collection of bodies all accelerated in the same manner might look, from another perspective, as if they were at rest. This is of course not that surprising given how much Newton wrote about apparent vs. actual forces. Yes, without the mathematical machinery of Riemannian geometry, formulating a precise version of GR would have been impossible. But notice that nowhere in this video did we bring up anything about higher-dimensional curvature or geometry; everything we present here can be deduced simply from the equivalence principle, which Newton very likely in essence understood. Also we never state that Newton could have come up with GR, only that he could have realized, through assiduous application of his own laws, that it was ground which was accelerating up.

[@zedred8075]

Thanks. I wonder if Newton had the benefit of knowing about Maxwell’s equations he might have had more confidence to go down this path? There probably wasn’t any way of rigorously proving that hypothesis though in his time. His ‘laws’ worked for everything he could see, knew about or could experience. But I bet that backward jerk he may have got from being on a horse or carriage in his time probably made him think! Pretty sure I read that he knew action at a distance wasn’t going to be the final answer. Imagine Einstein explaining GR to Newton. From what you say he probably wouldn’t have been surprised! Anyhow, thanks again for your fantastic videos on gravity. They are the best I’ve come across on this subject.

[@dialectphilosophy]

@@zedred8075 Maxwell's equations were undoubtedly the necessary prod towards the theory of relativity, and it would have been hard to justify those theories in their absence. And given how much Newton achieved in his own lifetime, asking that he would have developed even a rudimentary conception of GR would be demanding too much -- still, one could wonder, if he had devoted the remainder of his life to furthering his theories of gravity, rather than, say, becoming obsessed with alchemy, what additional insights he might have contributed to physics. Thanks for the compliments and for watching! New video on GR drops tomorrow, make sure to catch it!

[@zedred8075]

Can’t wait!!

[@stevegriffin1535]

These videos are all great. They almost instantly stir up competing / debunking videos which are also interesting.

[@Moon-Labs]

This is nonsense.

[@friedmule5403]

Really great video, I have added some comment that try to explain my confusion:-) 8:20 "Accelerating or on Earth" If I take two atomic clocks, let one be on the floor and raise one above my head: If on Earth, will there be a difference due to the change in gravity. If I do the same in the rocked ship, will there be no difference, since gravity does not change that much. 13:45 Accelerating: The Earth is moving through space at a constant speed. Let's now take the rocket, blast off from Earth in the opposite direction of the Earth's motion through space, and let's do it with exactly the same speed as the Earth is moving. Now, can I fully postulate that I am exactly where the Earth were, and I have not moved out of that place. If I now start to apply break, will I still feel the slowing down, even it is in fact Earth that has moved.

[@peterburkhalter6344]

And if the ground is always moving up, wouldn't the volume of the Earth increase continuously?

[@KipIngram]

The reappearance of gravity is NOT faster than the speed of light. When the soles of your feet stop moving, your scalp is still falling. It takes a finite time for the effect to reach your head. Granted it's tiny compared to what you can "sense," but it's still non-zero and it is most definitely slower than light - quite a lot slower, actually. If you hold a Slinky off the top of a tall building, let it stretch out and become stationary, and then let the top go, the bottom will not immediately begin to fall. The top will - you can watch this on a video. It takes time for the upward tension operating on the bottom turn of the Slinky to disappear. That's a visible example of the same thing I was just talking about in more "rigid" bodies.

[@TallinuTV]

A straight path through spacetime, near something like the earth, is an ellipse. That's how being in orbit works... Go sideways fast enough and the ellipse spreads out till you dodge the ground even though it keeps trying to rush towards you! Standing on the surface, the sideways component of your ellipse matches the rotation of the earth so that from your perspective, the ellipse narrows into a straight line pointing at the center of the earth... And if you could pass through it, you'd ascend through the other side, and repeat in reverse. In the absence of acceleration (in free fall), that is your "remains in motion" path. But there's a whole bunch of stuff in the way. And that stuff has other stuff in the way of it, in turn. None of it can follow that straight path, because the stuff below is compressed by all the stuff landing on top of it, until it pushes back upward with sufficient force to keep it at a relative standstill by accelerating it away from that straight line path, forcing it away from the Earth's center of mass (think of that spring accelerometer standing upright). This propagates upward until we leave the solid and liquid layers and get into the gaseous layer, in which it is relatively easy to propel yourself upward by pushing off of the solids below you with greater force, briefly breaking contact with all that stuff pushing up on your feet and putting you just barely on the rising arc of your elliptic straight line path... Until, no longer obstructed, that path brings you right back down to the ground. At which point the ground suddenly and forcibly redirects you again, by virtue of being much more massive than you (and, usually, having nowhere it can easily go in response to the impact, unlike air or water).

[@nathannopants3157]

Except you said that bodies in a gravity field arent free bodies, so while you are in freefall in a gravity field, you still cant perform the free body test, because none of you are free bodies. Gravity is formed from the curvature of spacetime, making an object appear to fall, because its straight line has been curved into the earth, and its “motion through time” appears as a constant acceleration into the curved spacetime as the object continues to try to follow that straight line (that now points to the surface of the mass)

[@beansnrice321]

I took 4 years of Aikido classes and you spend half your time throwing people to the floor and the other half of your time being thrown to the floor. I have probably spent more time in free-fall than most pilots. Heck, I may have spent more time in free-fall than some astronauts. We had a physics professor in our class and most aikido is done at a pace that you can talk still and we used to have all kinds of conversations about physics. From that I used to think of the equivalence principal frequently and lets just say that, if you take tens of thousands of falls, you really start to feel that ground rushing back up to meet you. I also wanted to mention that one of the reason we were falling so often was because we would have to dodge attacks from wooden swords and the swords were supposed to come down like a normal sword, so fast. So generally the only way you could move quickly enough was by falling in the correct direction. In fact, in Aikido, that's usually how you move everywhere, by pulling the support out from underneath the side of yourself that you want to move and you start falling in the direction you want to go. So why fall everywhere? Why use falling so much? because falling is instant acceleration. If I wanted to hop or skip out of the way, I would first have to fall a little bit and then push up, away from the the ground to start moving. that makes you have to do two things before you start moving in the direction you want to go. So instead you just do the first step, the falling step and you try to steer your fall into a step or a roll into a new superior position. Another part of Aikido that's relevant to relativity is how important posture is, if for no other reason than that it takes less energy to stand with proper posture. Think of it with the equivalence principal. Think of standing on the nosecone of an accelerating rocket. Do you think that a balanced beam will stand with less effort or do you think that an imbalanced beam would? One last thing, the equivalence principal tells you that up is the true forward. So if you want to look forward, look up! That's the direction you're constantly accelerating in, even if you're sleeping. =D

[@kaceesnow]

Why does a scale or with a seasaw, the heavier person touch the ground, when the seasaw stand is being pushed up? Unless while moving up, the force or friction will pull an with bigger mass down? Also, why don't we reach the sky?

[@heromaiker4414]

one thing i dont get If you put a scale at the bottom of the building and have one monkey drop from the rooftop and one from the middle floor, the scale will give diferrent readings at the moment of impact for each monkey. Does that mean for rooftop monkey the ground is moving faster than for 5fth floor monkey even if they impact at the same time and both are at the same inertial frame?

[@marcoantoniazzi1890]

It's amazing how there are constant twists and turns in this video.

[@epicenter5126]

I'm still not sure you answered how the earth can be accelerating out in all directions. If 2 apples on either side of the earth "fall" at the same time, does the earth expand outward to meet them both? And shouldn't the earth have blown itself apart if it's been accelerating outward all this time?

[@juliavixen176]

This exact same question has been asked and answered a dozen times in other comments on this video.

[@micry8167]

Thought experiment: the person in the spaceship but with the ship scaled up to the mass of Earth. Now when they toss the object away from them, it ‘falls’ and sticks to some part of the craft. Regardless of whether that massive ship is accelerating. They can kill the thrusters and then jam then on again, but they won’t get a dramatic ‘gravity-canceling’ effect. The mass of the giant ship is exactly what makes its influence detectable to human eyes and guts and springs. And now they are back where they started, trying to get away from the familiar, interfering gravity their ship has and their new efforts become self-referential. If the Earth had the mass of a spaceship, I think we wouldn’t consider that it’s accelerating up to meet our feet.

[@benbam6519]

If earth is falling Up, and the other side of earth also falling up. Will the earth be torn apart?

[@KipIngram]

Well, in fact the acceleration does instantly vanish when you take your foot off of the accelerator. The accelerator doesn't move instantaneously. When you push on one end of a metal rod, for instance, the other end doesn't move immediately - that force propagates through the material of the rod. So none of this happens fast enough to violate local causality - the whole process is bound by local causality.

[@davestorm6718]

The leaning Tower of Pisa experiment incorrectly concludes that all objects fall at the same rate. They only appear to do so because the falling objects masses are incredibly small (even if 1 was 1kg and another was 1000kg) with respect to the Earth's mass (6x10^24kg). If one of those objects (say balls) was comprised of, say, highly dense matter, say from a neutron star, it would accelerate [fall] faster (>>9.8m/s/s). This is also easy to conclude as the acceleration due to gravity is mass dependent (not independent as Galileo's conclusion states). If you were to do the same experiment on the moon, your acceleration is 1.6m/s/s and on a larger mass (Jupiter), it would be much higher. Newton was correct in computing the force between 2 masses and that it is a 2-body problem (always). In fact, this equation is embedded in general relativity formula! The sky is falling up concept fails to conclude the fact that the object, that no longer appears to feel gravity, is in it's own frame (with respect to itself). With respect to the ground, that frame is accelerating. The clocks emitting light experiment in inertial frames (and frames within frames) utilize this concept as well. It also fails to conclude that the "tidal forces" (the other components of gravity) won't actually make things coalesce (geometrically, they make things spin and fly away - not coalesce!). The geometric model of Special Relativity should be abandoned as it requires 2 components (warped space AND another "gravity") for it to work. (why most will use the field equations, not the geometric ones) Lastly, Einstein was on the verge of abandoning Special Relativity, later in life, because of temporal paradoxes, but his colleagues backed him into a corner (they had already spent time and resources on their derivative works and urged him to stop). He was working on his original stuff, namely VSL (variable speed of light) and G[constant] variants to eliminate prior mathematical infinities. Special Relativity fails to describe Newton's spinning bucket experiment (that, alone, was enough reason to abandon it), a.k.a. the inertia problem.

[@vimal-cliobconsulting]

Wow, this is one of the best videos I've seen on gravity and general relativity.

[@petersmythe6462]

It's interesting mass is continuously causing the reference frames inside its bulk to shrink, yet reference frames outside the bulk of an object do not shrink. They stretch isovolumetrically.

[@john-vv1ln]

if you take a magnet and a coin and place them on a flat surface far enough apart that the coin doesn't snap to the magnet, then slowly slide the coin towards the magnet, at some point the coin will snap (fall) to the magnet. The magnet is not falling up to the coin. Q: how fast is the coin accelerating to the magnet?

[@greypilot2430]

Great explanation. I was ok until I figured out (only a few seconds before the video explained it) that the earth can't fall in two different directions. I get lost with the tidal stuff but I'm sure a lot of people understood the explanation. I'm going to watch it again and hopefully understand a little more. Thanks!

[@watamatafoyu]

Neither is falling, but to the apple the earth is accelerating upward; to someone orthogonal the apple is falling to the earth. To math, warped space draws objects together over time. This video's explanation of the earth falling upward is over-complicated and based only on the falling thing's perspective, not an outer perspective.

[@bunyu6237]

I like the fact that you counter-argument your counter-argument to your counter-argument of your argument