Why Gravity is NOT a Force


4,1 M megtekintés929

    The General Theory of Relativity tells us gravity is not a force, gravitational fields don't exist. Objects tend to move on straight paths through curved spacetime. Thanks to Caséta by Lutron for sponsoring this video. Find out more at: www.lutron.com/veritasium
    Huge thanks to Prof. Geraint Lewis for hours of consulting on this video so I could get these ideas straight in my own brain. Check out his HUfast channel: ve42.co/gfl or his books: ve42.co/GFLbooks
    Amazing VFX, compositing, and editing by Jonny Hyman
    2D animations by Ivàn Tello
    Filmed by Steven Warren and Raquel Nuno
    Special thanks to Petr Lebedev for reviews and script consultation
    Music by Jonny Hyman and from Epidemic Sound epidemicsound.com
    Rocket made by Goodnight and Co.
    Screen images in rocket by Geoff Barrett
    Slow motion rocket exhaust footage from Joe Barnard at BPS.Space

    Közzététel: Hónapja


    1. Veritasium

      Here's a question I've seen a lot in comments: OK, I'm accelerating up but then shouldn't someone on the other side of the globe fall off? No, here's why: Either watch again from 8:28 or read what I've written below... Spacetime is curved - it curves the opposite direction on the other side of the Earth. Neither us on this side of the Earth nor they on the other side are changing our spacial coordinates - we're not moving up, they're not moving down - Earth isn't flying into one of us. BUT we both ARE accelerating. In curved spacetime you have to accelerate just to remain stationary. The traditional definition of acceleration is something changing its velocity. In general relativity you have to embrace a new definition of acceleration: it means deviating from a geodesic - not going on a straight line path through spacetime. Near the Earth a geodesic is a parabola so unless you're moving in a parabolic arc (like on a zero-g plane) you are accelerating. This definition is the same as the old one so if you're accelerating in deep space then your velocity is changing. *BUT*... if you are near a large mass you are in curved spacetime, now acceleration your velocity is changing. You can stay stationary relative to Earth's surface and still be accelerating. This is because your acceleration should be measured not relative to the Earth's surface but relative to free-falling objects - they are inertial observers. Imagine this - I'm in deep space and I make horizontal rows and rows of stationary golf balls. Then I hop in my rocket and accelerate up through them. Just think about what that looks like. Now my rocket is back on Earth just sitting there. I freeze time for a sec and make horizontal rows and rows of golf balls up into the atmosphere. Now unfreeze time. What do you see? If you just look at the golf balls and the rocket ship it looks the same as the situation in space where the golf balls were stationary and the rocket was accelerating. Einstein's point was the golf balls have the better claim as the "stationary" thing since their experience is just like the golf balls in deep space - no forces experienced. The rocket on Earth is just like the rocket in space. It feels a force and hence an acceleration.

      1. Mike80528

        Isn't this a circular definition problem due to the definition of force? Gravity provides the relative reference for force. But in an absolute sense, if you had two objects of a given mass in completely empty and flat space with no motion - they are completely at-rest. No kinetic energy. Exerting an external force would generate momentum. The gravitational distortion caused by their mases will also cause very slow but real acceleration towards each other. The net effect is the same unless there is an argument that the warpage of space gives-up energy to the objects to make them move, which creates serious issues...

      2. Trist Drew

        @Flare 72 because the moon curves space time too? I thought the tides caused friction (force) to the orbit anyway which over many years is what is reducing the angular momentum thingymcjiggy and hence means the moon gets further away?

      3. windwardpro

        @Veritasium Yes, constant velocity- not accelleration.

      4. CatastrophicNewEngland

        So is the universe only expanding in space time? If all galaxies were in roughly static physical locations in the universe they wouldn't be in an inertial frame of reference from each other, so they would be accelerating apart in space time? And since massive objects warp space time and bend light, wouldn't that also cause redshift? The more massive a galaxy, the more we would be accelerating away from each other in spacetime, and the more redshifted the light would be?

      5. Tanner

        @Veritasium What is the name of the field equation at 10:35 ? it seems to allude that time dilation is the main cause of gravity (not space & time).

    2. Revel Carlberg West

      4:39 I hear a Minecraft villager say something.

    3. Anthony Christ

      Now. You have mentioned a man falling out of the sky but what about a body submerged underwater? If we didn’t need oxygene could practically “defy gravity” permanently? Just another example how gravity does not exist In the ways society teaches D:

    4. Harsh Mishra

      Derek, I Enjoy your videos ! I have observed many a times whenever There is a plot of any random event then it seems to follow the normal distribution be it:- 1. Maxwell-Boltzmann Distribution in GASES or 2. Nationwide Trend of Marks obtained by students in any University entrance exam or 3.Rates of reaction vs Temperature . How does it relate ? How does normal distribution relate to randomness of nature ?

    5. Glen Jennett

      I see gravity in a different way that would take too long to explain here, but I agree that gravity is not a force. I think I understand what gravity is and how it works.

    6. Sharon Stanphill

      I have questions. I lived and worked on a large cruise ship. When I got off I noticed while standing in line to pay a guy ahead of me was rocking back and forth very slowly. Guested he worked on the ship to and discovered I to was slow rocking. So I have the motion of the wobbling whole earth spinning, the solar system moving, universe expanding, and wave action rocking my ship. Does that change things and how? My body changed to keep me balanced. I couldn't feel the changes when off the ship.

    7. Christopher Turner

      Yah Terrence Howard already did this lol 😂

    8. Chelsye LittleWing

      So can quantum loop gravity still possibly work as a contender up there with string theory in how quantum mechanics could possibly unite with TGR one day ?

    9. Kevin Wells

      Could the same thing not be said about the other forces (EM, strong, and weak)? It would be easy enough to explain magnets pulling together as a warping of space rather than as a real force right? If not then what is the difference between them?

    10. UnknownCleric2420

      "What made Einstein so happy about this wasn't Schadenfreude." Every Scunt ever: "B A H A H A"

    11. Tim S.

      Ok, I can accept this. Now my understanding of time is broken.

    12. sudhindra nath

      no, I don't think free falling charge will radiate. I think the charge will only radiate when actual force like magnetic or electric force will apply on it. Yes, now I really think gravity is not a force.

      1. Narf Whals

        Then it should radiate when sitting on the table. The table applies a real force to it. The answer is that whether you see the charge radiate also depends on your own reference frame. If you are freely falling with it you don't. If you are sitting in the lab with it, you don't. But it you see it fall you do. And if you fall while you see it sit you do. Google paradox of an electric charge in a gravitational field.

    13. Animesh

      If light is slightly bending downwards coz of acceleration then we can measure the one way path of light to calculate the speed of light coz if we let the light to bend then the light will cover a circular path and hits the point from where it has been emited!!!!!!

    14. Elemental Golem

      One quick question. When it ties to thw tides and the moons effect on water how would it look when using this way of explaining gravity? Would it be that the moon further curves space time on top of earths curvature of space time?

      1. Narf Whals

        Everything with mass/energy curves spacetime. Tidal forces happen when one part of an object has a different geodesic than another. That is what the moon causes on earth(and vice versa). Spacetime is curved more on the side that is nearer to the moon so.

    15. Akos Nadas

      The other night a question popped into my head regarding this video. I did watch it a while go so excuse me if i remember things wrong. I do recall saying that you couldn't tell the difference between earth's gravity and accelerating on a spaceship with 1G in outer space. This seems legit so far, then it hit me. A water droplet on earth would fall in it's teardrop shape towards the ground, however i suspect that on a spaceship accelerating with 1G it would be the shape it usually is in space, bubble like. In conclusion you could tell the difference i think. What do you think?

      1. Akos Nadas

        @Narf Whals yup, seems legit. The more i look into it, the more sense it makes.

      2. Narf Whals

        @UCVxhBLtia7sQBXC9IbRdMSA that shape is actually very aerodynamic. People tried to build cars that way, they're just ugly. Look up air flow models for it. But again, because raindrops are very soft they don't actually have that shape. They get squished in the middle and bulge at the sides. Their shape does not come from gravity. You can see this from videos of scientists on the space station letting water float around. It is falling freely and gravity is not significantly weaker there. It tries to collect onto a sphere. The difference is that the air is not rushing past it.

      3. Narf Whals

        A raindrops shape comes from air resistance(it also isn't actually a teardrop shape more like a smooshed bean). If there is air in the rocket it will have the same effect there as it has on earth because it is being pushed past the water droplet by the rocket.

    16. Daniel Palanker

      If gravity is not a force, what attracts two static masses to each other?

      1. Daniel Palanker

        @Narf Whals Thanks for the link! Here is even better illustration, in my view: hufast.info/plan/vide/rKjZnK6fpoe9h5c

      2. Narf Whals

        @Daniel Palanker There are no static objects in spacetime. Everything always has a velocity. If it doesn't have a velocity in space it is moving in time. Two balls that are not moving relative to each other in space are moving at the same speed through time. Which basically means their clocks tick at the same rate. And it is not actually space curvature that is responsible for gravitational attraction as we know it, but time curvature. hufast.info/plan/vide/e2uym8-otJamq5s

      3. Daniel Palanker

        @Narf Whals I’m asking about static objects (e.g. touching balls). Their relative positions do not change in space and time, even though the space is curved.

      4. Narf Whals

        Spacetime curvature. Their geodesics are curved towards each other. They don't need to be moving relative to each other for that. They are on parallel paths through spacetime. If they are not moving in space then they are moving through time that much faster. Those parallel paths curve towards each other. Imagine the surface of the sphere again but the direction towards the pole is time.

    17. TheLethalOne

      yo meh brain

    18. Luca Mancinelli Degli Esposti

      When we look from the outside at a laser beam crossing the rocket shouldn't we see it hit the opposite wall at a lower level due to the fact that the rocket is accelerating towards the beam?

      1. Narf Whals

        Yes. But the path it travels will be a straight line.

    19. Bolt D. Etherion

      So the people beneath.. Ahm.. Don't they fall of then?

    20. 69keniu

      So Newton wasn't right?

      1. Narf Whals

        Not about gravity. But he was right enough for everything people may come across in everyday life. His formula is much simpler than General Relativity and good enough to get you to the moon. That is why it is still taught in school.

    21. Nechar Joshi

      I was having a hard time understanding some of the concept. But became more apparent after I watched this. hufast.info/plan/vide/n57SgLqW1HuXlI0

    22. ramansh paliwal

      Acelliration is same as gravity or acceleration is same as gravity. Se the elevator clip of the movie the genius/Albert Einstein great movie. Great vidio,thanks and appreciate the great cgi

    23. Butchness

      no? it's an acceleration?

    24. Archie Doughman

      GRAVITY is a subjective matter especially relative to the earth surface and its rotational movement base on its axis... now, how about magnetic field that we have on earth..what do the earth magnetic field does?..If the earth is rotating and there is no gravity why the object on the earth surface is not being thrown outward due to centrifugal force of the earth rotation...what force that holds the object on earth's surface..?

      1. Narf Whals

        The rotation of earth is basically negligible. It makes you weigh about 0.3% less at the equator than at the poles. The video explains why we feel drawn towards the surface. That's just where our natural motion takes us.

    25. Commander ZiN

      I actually learnt something new and yet it's been around for years. Makes perfect sense just never thought of it that way before.

    26. Time Factor Theory of Gravity and Relativity.

      There is even more to Time! Added a challenge with a prize to Time Factor Theory!

    27. 1s4


    28. Foxste Gamer

      I think this was the video which made me think how we are in a simulation probably

    29. Harsh Mudgil

      Help me with this one. Are you basically saying that, instead of us being accelerated towards the Earth, we experience an acceleration away from the Earth due to the fact that we are moving with the Earth on a straight line path on a curved space around the sun. Is that right or am I missing something?

      1. Narf Whals

        @Harsh Mudgil Yes. That force is the electromagnetic force between the atoms in the ground and our feet. That is what is keeping us stationary relative to the ground. Without it we would be freely falling with no forces on us.

      2. Harsh Mudgil

        @Narf Whals he says in his pinned comment that, on a curved space time you have to accelerate to be stationary. Before he mentioned in the video that Gravity isn't a force. But if indeed, in a curved space, we have to accelerate to be stationary then it means to be stationary there has to be a force acting on us.

      3. Narf Whals

        No. When standing still on the earth surface we are experiencing an acceleration "upward" due to the atoms in the ground pushing against the atoms in our feet. This has nothing to do with the earth's motion around the sun or its rotation. He explains in the pinned comment what it means to accelerate while standing still.

    30. Oscar Rotili

      what is that general relativity formula at 10:15 called?

      1. Narf Whals

        The Geodesic Equation en.wikipedia.org/wiki/Geodesics_in_general_relativity

    31. Tommaso Bianchi

      the first time I held my girlfriend's hand and kissed her I felt weightless, does that mean I was an inertial observer?

    32. Ian williams

      G'Day,,,Hmmmmmm,,, why does space time bend around a object,??So what you are saying is that space time cannot go through solid objects and need to go round it ,thus appearing to bend time around object, Finally if Gravity didn't exist then why do we fall,??and if acceleration is to blame how come the earth isn't doing a couple of millions miles an hour and increase speed in time,,years would be shorter and days near vanish,,But none of this has occurred,, as for your proton dropping giving off charge,,simple static electricity generated by friction as it move's,as we all know atoms are made up neutron and electrons,,and each atom can only hold so many electrons,as the atom moves it capture more free electrons,, cannot hold this extra charge and then releases charge to atmosphere,,so discharging effect show Giving of energy,,+ One More to think about,,as the atom falls it collides with other atoms,thus gathering extra charge, Now assuming we can indeed see the smallest partical,,,????Does the charged partical,deviate in the fall,,?? Don't give me vacuum stuff as we are not in a vacuum,,The space ship,is,and we all know about inertia,,body at rest tends to stay at rest unless acted on by another force,,in this case acceleration,, were as here on the planet..we seem to be sucked to the ground,,Gravity,?? Why does any thing with mass attract others mass,, Could it be,magnetic waves we cannot see,, might explain why time bends,,but not light,,try to bend light with a magnet,,Yer nup,,doesn't deviate, same as your laser pointer experiment,,Gravity has no effect on light,,and acceleration would not either,,If what you are saying is correct,,

    33. hothaifa tayeh

      I have a question i hope it'd reach you, What is the source that makes planets and galaxies move if gravity is an illusion, also is the whole universe static or moving, does it have any relation to the fact the universe is expanding, and what is the reference position in the universe to express the relative position for any object in the universe, as in the example of the accelerating rocket-ship the floor of it was the reference for the objects inside it, and is that reference if it exists moving? sorry for the long questions but i have so many questions but the ideas that you shared in the video are fascinating leaving me helpless but to start wondering about

      1. Narf Whals

        Movement is always relative. Everything in the universe is moving relative to something else. When you ask "is the whole universe moving" you must ask "relative to what could it be moving?" There is no absolute reference frame to give absolute movement or absolute position. A useful reference frame is the one that is moving along with the expanding motion of the galaxies en.wikipedia.org/wiki/Comoving_and_proper_distances#Comoving_coordinates In a gravitational field of a planet a useful frame is the surface of the planet or a freely falling one. The surface of the planet is similar to the inside of the accelerating rocket with its thrusters turned on. While freely falling would be the rocket falling towards the planet.


      Wrong. hufast.info/plan/vide/q363Zs-L2qWZhnU

    35. Nesto

      My physics teacher disagrees

    36. Paul Turner

      They say Gravity is a bitch.

    37. You Forever

      This is all B.S. A time-waster!

    38. Dyida

      Amazing. You can regurgitate from religious books.

    39. Vaibhav B shet

      What about flat earth society

    40. Rudisbashar

      Blackhole:...just another brainfart....

    41. Dhairye Shekhawat

      Can we say that gravity is the bending of spacetime or why cant we say it

    42. Bopsop

      13:58 I need a bit of explanation here. So light is bent when measured relative to an accelerating frame of reference? I thought this whole time that light was bent because of lights traveling through a straight line, through curved spacetime created by the object. What did I miss here?

      1. Narf Whals

        The reasoning is that those scenarios should be the same. Standing still in the curved spacetime near a massive object should be the same as accelerating "up" with the same g. Light bends in both scenarios. In the acceleration scenario it happens because the observer is accelerating away from the light. Around the massive object it happens because of spacetime curvature.

    43. Sam Mullins

      Curved space-time is non-sense same as religion. Religion says I need religion instead of saying, I could progress within equals' togetherness for building God's FAITH within both of us, both individually plus OUR religion! Otherwise it is Satan's anti-Servant republicly mis-used Occult. Definitively Speaking, it is my turn to pray for me:: Communism/Socialism like USA is when authoritarians count ONLY upon centralized (mainstream) decider's voice (opinion), whilst silencing everyone else's. Corruption addicts' senses like Republicans, Democrats, & Libertarians are as stupefied as that Helen Keller astronaut, whom are isolated thereby "their" impoverished exosphere. Predicamented Sin-Slavery has factoried REPUBLIC astronaut-ed NON-sensed to extent, they actually misbelieve propaganda Human Society is bouncing off the ceiling. They welcome the next discovery thinking nothing can escape their senseless damnings(if presented hidden within politically correct superficials). Anyone not desensitized will tell you planet-size gravity compounded by nearest star horizontally dived/impacted that spaceship into casualty.

    44. UnkieRich

      Isn't this the same theory the flat Earthers have? They claim there is no gravity and the Earth is accelerating up at 9.8 meters per second squared. You have chosen poorly!

      1. Narf Whals

        Flat earthers chose a little truth to misrepresent and build a lie around. That is common practice among liars.

    45. United Digital Solutions

      Before Rocket Veritasium crash lands on the moon, wouldn’t Rocketman feel the rocket accelerating into the moon? You made it seem otherwise.

      1. Narf Whals

        Not from inside the rocket. He can look outside and see that the moon is coming closer, but inside the rocket there is nothing that indicates an acceleration.

    46. cardayz

      What about electrostatics? Is that a force? Mathematically it is identical to gravity. Do charged balls feel a force as they accelerate towards each other?

      1. Narf Whals

        @cardayz I'm not actually sure. An object of perfectly even density, or a point charge, would possibly not notice a force because the acceleration would be perfectly equal everywhere. But any real object would notice a force because any volume with different mass in it feels a different acceleration. An accelerometer would register an acceleration.

      2. cardayz

        @Narf Whals Good point. That answers a lot of what I was wondering. However, the video uses the argument that falling in free fall is equivalent to free floating (the onboard accelerometer would not record acceleration). Does the same apply to charges accelerating towards each other?

      3. Narf Whals

        It is not actually identical to gravity because the mass doesn't cancel out. F=qq/r²=ma The force is proportional to only charge, so when you divide by m to get the acceleration you can't cancel anything in the middle term. That being said there is a theory that phrases the electromagnetic force as curvature in an extra dimension. en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory

    47. fessit

      If 1g acceleration is the same as 1g on earth why does a person age less accelerating at 1g than someone on the earth. Clearly they don't have the same effect.

    48. Nixon

      That’s why time ticks slower near objects

    49. thomas aquinas

      Well, technically gravity is the effect of matter curving space without energetic events. However, in his thought experiment, Einstein showed that gravity was in fact indistinguishable from force...

      1. Narf Whals

        He showed that it was indistinguishable from _acceleration_ not from force.

    50. Craig Fordyce

      Great! Now that gravity is eliminated, can we do the same with death and taxes?

    51. King Celestial

      It's is what it is

    52. Sigurd Breivik

      But if we are constantly accelerating upwards, doesn't that mean that our speed is constantly increasing? Or does that only apply to Newtonian?

      1. Narf Whals

        Yes that doesn't really apply. He explains in the pinned comment what it means to accelerate while standing still.


      12:32 KNOCK OUT

    54. Kyle Mcmullen

      So here is my understanding, and my crazy question: I imagine this description of gravity and space-time as a 3D or 4D grid in the universe. lines representing space time, all equal. when there are bodies of varying size and density (planets, stars, etc) this grid compresses around them; essentially the lines of the grid are pulled into the body, becoming closer but not changing in relative time, giving curvature to spacetime relative to their pull on the lines of this grid. My description is lacking, but imagine a giant grid with black holes of various sizes pulling those lines into the centre. The relative space-time of these spaces doesnt change, even though they are more compressed closer to the centre. If that is correct, in terms of space travel, could you essentially move longer distances in the universe, relative to the enormous grid, the farther one gets away from the planets, stars, and galaxies?

      1. Kyle Mcmullen

        or i guess a better description would be inserting these bodies inbetween the spaces in the grid and expanding them, compressing the grid around them.

    55. Holophrazeinikos

      Wow- Science can be fun- and you can even understand some of it! Thanks

    56. John G

      So if there is no force, what is causing the acceleration?

    57. John G

      Was he and his house in a vacuum?

    58. Duck

      This made me THINK dude

    59. Nahulanham

      In curved space analogy using the ball orbiting (for a while) the central point, aren't the going in a straight line, though they appear to travelling in a circular orbit (or in Keplar's sense and ellipse?) I have John Wheeler's book on this curve.

    60. Perry Winkle Elliott

      if gravity is not real as you say then why do you fall at different rates of speed in different gravity say for example if you jump off a 100 story building on jupiter or the same hight building on earth different mass of planet = different gravity readings different rate of acceleration toward the ground on witch ever planet and if your on a planet that's not spinning then you would fall in a straight line as well so its all relative to the viewer gravity is just a way to measure mass really and bending of light could just be because photons have mass and mass is attracted to mass might not really be bending time and time is also relative to the viewer if you were in an event horizon but somehow alive and unharmed you would perceive time as going buy at normal speed to you the viewer but if you looked out the universe mite seem to have stopped moving

      1. Perry Winkle Elliott

        also things don't fall at the same rate on earth drop a feather and a rock and the rock hits the ground first i have done it lots you meant to say in a vacuum i'm sure in a vacume its true but don't forget about the thick air around us it affects things of little mass a lot get rid of the air tho and its the same

    61. I

      No time has nothing to do with it, because time is only a calculation of motion, a calculation acts upon nothing, what scientists call gravity is actually "counter space" True "space" AKA volume, mass, something that takes up a spatial footprint, always has a opposite reaction called "counter space" it's only "space" and "counter space" Also known as the "ETHER"

      1. I


    62. Bobbie

      Ok my problem to understand here is that if one person stands on something tall on the north pole and someone else is standing on something tall on the south pole they will both be making contact with the floor. But that means it accelerates in two different direction. Please can someone explain?

      1. Narf Whals

        It does accelerate in all directions. And it does so while standing still. He explains more about that in the pinned comment.

    63. John McKown

      So there is no gravitational field, like there is a electromagnetic field. And there are no gravitons, like there are photons. So there cannot be an anti-gravity device. The closest might be a space "straighter" device? Or perhaps some device which pushes all the particles in its area of effect in a specific direction, which would mean that nothing in that field would feel any acceleration, kind of like free fall.

    64. Hung Su

      How are the ocean tides involved in this explanation?

      1. Hung Su

        @Narf Whals Thank you.

      2. Narf Whals

        Tidal forces happen when the geodesics aren't the same for all parts of an object. The moon changes what the geodesics around earth look like, but it does so more on the side that is closer to it than on the other.

    65. Samer Najjar

      At 13:15 you said that an external observer will still see the light travel in a straight line inside the accelerating rocket ship. Why though?

      1. Narf Whals

        The external observer will see the light travel in a straight line because there are no forces on the light. So it just moves in a straight line as things with no forces on them do. He will see the light hit a lower spot on the opposite wall because that spot accelerates "up" to meet the light beam.

    66. Naeem Baluch

      i am actually amazed 😮. Since school we were told Gravity is real but damn gravity doesn't exist.

    67. Das Kuch

      the way you visualize light and how it seemingly "bends" is so unbelievably cool.

    68. Adikara Maulana

      thats explaining how naruto's sage mode really works

    69. Ihsahn Åkerfeldt

      If gravity is just an illusion and it's actually the earth accelerating upwards, answer this question: why is it that air resistance manages to slow down the fall of light objects with considerable surface area like a paper or a feather but not rocks? This is a factor that is clearly dependent on the falling object, which according to this Einsteinian view is actually inertial while the earth is accelerating upwards. Makes no sense. Does anybody have any idea?

      1. Narf Whals

        @Ihsahn Åkerfeldt The air doesn't get in the way of the ground. It moves with the ground and gets in the way of the falling object. Just like the ground does when you're standing on it. The terminal velocity through the ground is 0.

      2. Ihsahn Åkerfeldt

        @Narf Whals The supposed acceleration of the ground should not be affected by air being there because the former is so massive and, again, we're told here it's the ground that's actually moving.

      3. Narf Whals

        @Ihsahn Åkerfeldt The ground pushes the air along. So it also rushes up to meet the falling object. And in doing so it pushes on the object.

      4. Ihsahn Åkerfeldt

        @Narf Whals Why does air matter when it's supposedly the massive ground rushing up to meet the "falling" object?

      5. Narf Whals

        Falling through air is not actually inertial. The air does the same thing as the ground. It pushes objects off their geodesic with a force that is proportional to the surface area that is exposed to the air. Only falling in a vacuum is inertial motion, which is why all objects fall at the same rate in a vacuum.

    70. SalaryMan

      it makes me thinking back to moon landing. if planet earth is accelerating up (which is relatively true, by mathematical calculations and observations), why did armstrong was in a "floaty-state" when he was allegedly on the surface of the moon? (by which, doesn't seems to be complementing this equation?) or am i too thick to understand this now? somebody please enlighten me!

      1. Ihsahn Åkerfeldt

        Iirc the astronauts were not floating weightlessly. They could jump higher and stuff (because of weaker gravity) but they would land back.

    71. Usama Iftikhar Butt

      Having difficulty understanding this video. Watch this one hufast.info/plan/vide/rKjZnK6fpoe9h5c This guy create really good visuals.

    72. The observer 1

      I prove gravity by telling you a story of place I can't be but if you assume I'm right then you too can believe in gravity


      Nice video

    74. Mister Super Cool

      Gravity isn’t a force because Gravity is a potential of Inertia in disguise under the veil of curved space hufast.info/plan/vide/qGPDhJiOmnzaep8

    75. juma Abu Nasser

      Gravity is a hoax

    76. mizo mint

      I feel like 390lbs...

    77. Felipe Gaete Román

      I think that's exactly why we see the earth flat, because the space-time is curved, and the sphere looks flat.

      1. Felipe Gaete Román

        @Narf Whals Yes I know this is because perspective, but when you approach from space, at the beginning you see the earth round, and as you come closer, you start to fall into the ground and the sphere is transformed into a horizon (sky up earth down). I don't know how to explain well.

      2. Narf Whals

        We see the earth as flat because we are tiny and the earth is large. The curve of the earth is too big to see from our perspective.

    78. Dennis Madderra

      If I understand this, does that mean that terminal velocity is dead stopped? Letting space/time pass you by. If that's the case it makes falling collisions interesting because of which body actually contains the energy.

      1. Narf Whals

        Which body contains the energy has always been a matter of perspective.

    79. RISHI MODI

      What if stationary charges emits radiation but for detection we have to observe it from inertial frame...

    80. Phillip Peng

      R.I.P. Rocket Man 1982 - 2020 "Ha, nice tweet. Wait is that a pla-"

    81. M M

      How can you present a person who didn't pay attention about what happened? He is on his phone Yaah😥💔

    82. DIEGO ARCH

      what about black holes?

    83. Nathanial Reed

      So a more accurate name for this video would be “gravity is not a force when your reference point is yourself”

    84. Robert Kemper

      The John Wheeler quote does not resolve what gravity is, does it? Force or not, what does it mean to curve spacetime? What is the mechanism that does the curving? If gravity is not a force, then what is causing the curvature? How does Spacetime, whatever that is, know to "curve" or as a better explanation, to cause matter to move in a geodesic in the presence of mass (or energy)? In the case of an imploding star, where the nuclear fuel is insufficient to prevent collapse, what is it that is collapsing? Could it be said that it is spacetime that is the force that causes the accelerations and collapses?

    85. Robert Nielsen

      The Big Bang feels like one big experiment where they set mass to determine time, so the biggest places’ time accelerates more quickly I want to know can humans conceive time difference, aka can you think faster in low overall mass, do you stop thinking in a black hole or think infinitely more quickly?

    86. Rob Shaw

      If gravity is not at all a force, then why are scores of genius physicists trying to unify gravity with the other three quantum forces: electro-weak and strong nuclear forces?

      1. Rob Shaw

        @Narf Whals Ok. I can get behind that. A complete theory of gravity will predict observations when large, gravitating masses approach the scale at which quantum effects predominate, say around a few orders of magnitude of the Planck length or smaller. The Einstein field equations are continuous functions and not discrete like the wave functions of a high-gravity, particle-sized body.

      2. Narf Whals

        ​@Rob Shaw They aren't forces in the classical sense. They are interactions with exchange bosons. If you're looking at a quantum level, forces basically don't exist at all. So the question is; is general relativity compatible with quantum field theory? And that is the big question of current physics research. It looks like it isn't.

      3. Rob Shaw

        @Narf Whals Huh? Of course they are - as they involve the exchange of bosons when they interact. The boson for gravity - the graviton - is purely theoretical.

      4. Narf Whals

        Because those aren't forces either.

    87. Vishnu Sagar

      Captain help, Person inside a rocket approaching a nearby planet would definitely see his rocket accelerating as it enters the curved spacetime and his rocket is no more moving with a constant velocity. Wouldn't he?

      1. Ken Hoffman

        I should clarify that the video makes that claim at the start before the planet is brought into the picture later. Once the planet is introduced, it is then a different situation.

      2. Ken Hoffman

        @Narf Whals The video claims that the falling man is the same as the Rocket man, a true inertial observer. I suggest the falling can make that incorrect conclusion, but unlike the rocket man, who could never determine if he has any velocity, the falling man can confirm otherwise. The claim that they are equal is what is not valid. Yes, the planet can claim the acceleration and neither is a true IRF.

      3. Narf Whals

        @Ken Hoffman The whole point is that there is no measurement he can make without looking outside the rocket. Inside the rocket there is no indication of acceleration. Inside the rocket is an IRF. The changing velocity relative to the planet might as well mean that the planet is accelerating.

      4. Ken Hoffman

        @Narf Whals Yes, he can "look outside" the rocket with a light beam to the planet to measure. The point is that he can make a determination of distance/time/velocity/acceleration. Thus, he can confirm he is no longer in an IRF.

      5. Narf Whals

        @Ken Hoffman Which distance can he measure without looking outside the rocket?

    88. Vishnu Sagar

      'Gravity isn't a force'. Now I feel way smarter, just enough to recommend this video to anyone who says otherwise

    89. Vishnu Sagar

      Now it's itching to watch interstellar again.

    90. dasireddy sai joshan

      Then moon should be going in same speed as earth , then why the gravity on moon is less

      1. Narf Whals

        @dasireddy sai joshan No they are not expanding. They are accelerating _while standing still_ . Again it is explained in the pinned comment.

      2. dasireddy sai joshan

        Then the distance between moon and earth should vary if the moon and earth are accelerating in with different accelerations

      3. dasireddy sai joshan

        @Narf Whals what , the surface is expanding ?

      4. Narf Whals

        It isn't about the velocity of the earth or moon. The surface is accelerating outwards in all directions while standing still. He explains more about this in the pinned comment. The moons gravity is weaker because it has less mass. It is its mass that curves spacetime.

    91. AJ PuzzleFerret

      10:12 the moment my brain said, "Nope!" and decided to think about computer games instead. I wish I could follow this, its fascinating :D

    92. S. Husen

      I knew it😏

    93. Rajat Rathore

      Can I Go For Bsc Maths Or For Bsc Physics

    94. Flamebuster32

      gravity is the friends we made along the way

    95. Reap420HM

      A whole different way of looking at life. You dont fall to the ground, its hitting you in the back! Literally!!

    96. KTVX.94

      So basically gravity is psychological

    97. Trist Drew

      So if it was possible to drill a small tunnel from through the whole of earth and I jumped down I would no longer be accelerating and instead be following a geosic straight line through space. Where would the free fall stop? Would it still be the centre of the core of the earth despite the fact it had accelerated past me from my frame of reference for about 8000 miles and then come to a halt? Or is it irrelevant because of the pressure inside the earth

      1. Narf Whals

        @Trist Drew Yea you can actually use a pendulum formula for it. If there is some damping, like from air resistance, the pendulum will eventually come to rest at the center. You get essentially the same result if you use newtonian gravity hufast.info/plan/vide/e2bcirSYvoCapH0

      2. Trist Drew

        @Narf Whals so basically like a pendulum until you eventually reach the centre or just keep going back and forward. Interesting thought

      3. Narf Whals

        Well lets ignore the pressure and air resistance and gravitational waves. If you dig a tunnel through earth and jump in your geodesic will point towards the center and will keep doing until you pass it. Then it will point outwards because of your velocity relative to earth and be bent back until it turns you around at the exact height you jumped from. Apparently this will take 42 minutes. You will fall up and down until the end of time.

    98. Lumiens

      What if physicists identify a "graviton"?

      1. Narf Whals

        Then the theory of gravitons has to reproduce the results of general relativity.

    99. Jeremy Basil

      Imagine all this is just the imaginings of a delusion mind!

    100. Harith Fernando