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what is gravity?

Anonymous Sat 27 Feb 23:41:12 2021 No.12764887 View Reply Original Report

Quoted By: >>12765000 >>12765684 >>12765798 >>12767351

Hello,/sci/
what is gravity? is it the deformation of space around mass? is it the density of mass that curves space? is it an undetectable particle that gathers around the atoms? is there any alternative to gravity we can use on the future to make space less hostile to us? i.e. magnetic force

Anonymous

Anonymous Sun 28 Feb 2021 00:15:58 No.12765000 Report

Quoted By: >>12765068 >>12765092

>>12764887
>what is gravity? is it the deformation of space around mass?
To our best knowledge, yes. Energy-momentum curves spacetime.
>is it the density of mass that curves space?
It is the energy content. E = mc^2 and all that. Any form of energy curves spacetime, even massless electromagnetic waves.
>is it an undetectable particle that gathers around the atoms?
What? It is the atoms themselves. The majority of atoms' mass (like 97%) comes from the strong interactions between quarks in the nucleus, i.e. potential energy.
>is there any alternative to gravity we can use on the future to make space less hostile to us? i.e. magnetic force
What? Your question is nonsense. What's wrong with gravity making space "less hostile"? Also electromagnetic forces are a much bigger problem for astronauts and spaceprobes. It fuck with electronics and can kill people if exposed for long. Google things like the van Allen belt.

Anonymous

Anonymous Sun 28 Feb 2021 00:38:26 No.12765068 Report

Quoted By: >>12765088

>>12765000
Instead of curvature you can also use cartesian tensors to end up with the same einstein hilbert action:
https://arxiv.org/abs/1405.4728
Isn't it a better definition to simply define gravity as the einstein hilbert action? That meshes much better with our other field theories, but it might miss some stuff.
Also what about mond, do we really need something like mond if we can't explain the velocities of galaxies with what we get from GR?
https://en.m.wikipedia.org/wiki/Modified_Newtonian_dynamics

Anonymous

Anonymous Sun 28 Feb 2021 00:45:03 No.12765088 Report

Quoted By: >>12765322

>>12765068
>Isn't it a better definition to simply define gravity as the einstein hilbert action?
emm...It is the definition, anon. The Einstein field equations are the equations that lead to minimization of that action. It's just that if you tell a non-physics person about action they will have no fucking clue what you mean, because it is a very technical term.
>Also what about mond, do we really need something like mond if we can't explain the velocities of galaxies with what we get from GR?
All this "modified" nonsense is literally 100 years old and was used to predict (unsuccessfully) Mercury's precession, while utterly failing at predicting things like bending light. GR predicts all these with astonishing accuracy as well as modelling dark energy (cosmological constant) and dark matter (just add more matter to your energy tensor, lol) very well. While GR is an incomplete theory and we need quantum gravity, the correspondence principle requires that we don't just throw it the fuck away like many crackpots want to. Nobody threw away Newtonian gravity when GR became a thing, it was shown that it is a good approximation for sufficiently weak gravitational fields.

Anonymous

Anonymous Sun 28 Feb 2021 00:46:19 No.12765092 Report

Quoted By: >>12765112

>>12765000
>is there any alternative to gravity we can use on the future to make space less hostile to us?
what i meant to say is: is there any alternative to gravity we can use in an hypotetical space station? i mean, since microgravity has effects on muscle mass and bone i figured it is necessary to have something that generates gravity, i.e. an electro magnetic field that can be used to create the illusion of gravity, just saying.

Anonymous

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Anonymous Sun 28 Feb 2021 00:53:02 No.12765112 Report

Quoted By:

>>12765092
>is there any alternative to gravity we can use in an hypotetical space station?
Ah, as to imitate gravity? I see what you were trying to say. Yes. Einstein noticed that gravity and acceleration are one and the same thing and not just a coincidence. Therefore someone accelerating in an elevator in space at 9.8 m/s^2 feels the exact same force that someone on earth would from gravity. A common sci-fi way of imitating gravity is via a rotating ring. You can see it for instance being used in Kubrick's Space Odyssey. Realistically however you need the diameter of such a ring to be in a hundreds of meters so that the difference in acceleration between your head and your legs is small enough not to make you dizzy.

Anonymous

Anonymous Sun 28 Feb 2021 02:23:12 No.12765322 Report

Quoted By:

>>12765088
Ok cool so that action is the rigorous way to say it and yes that's true you can just add more mass to account for dark matter. But there's definitely gotta be more there.

Anonymous

Anonymous Sun 28 Feb 2021 04:53:38 No.12765684 Report

Quoted By: >>12765739 >>12765869

>>12764887
We don't know. They like to say it's caused by space-time curvature but I find that answer very unsatisfying and incomplete.

Anonymous

Anonymous Sun 28 Feb 2021 05:13:46 No.12765739 Report

Quoted By: >>12765771

>>12765684
Nobody who knows anything about physics says that. Gravity is the curvature, the curvature is gravity.

Anonymous

Anonymous Sun 28 Feb 2021 05:21:40 No.12765771 Report

Quoted By:

>>12765739
Meaningless statement.

Anonymous

Anonymous Sun 28 Feb 2021 05:24:43 No.12765784 Report

Quoted By:

Not even GR say the susposed curve makes gravity. Gr expects gravity be teue and makes adjustments.

The real reason is electrical. Gravity field changes at speed of light. So it must be electrical.

Anonymous

Anonymous Sun 28 Feb 2021 05:30:18 No.12765798 Report

Quoted By: >>12767064

>>12764887

Imagine 3d object have widths height length on another 3d space, time and gravity

Space and time have opposit (180 degrees ) direction and gravity is (90 degrees) direction that is why you can't see gravity dimensions but you can feel it.

Anonymous

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Anonymous Sun 28 Feb 2021 06:09:14 No.12765869 Report

Quoted By:

>>12765684
>We don't know.
FUCKING STOP!!! STOP WITH THIS *WE* SHIT.

*YOU* DON'T KNOW!!!

IT IS **YOU** THAT DOES NOT KNOW!!!

GET IT? YOU POPSCI FAGGOT.

FUCK

Anonymous

Anonymous Sun 28 Feb 2021 15:17:58 No.12767064 Report

Quoted By:

>>12765798
So gravity could be a 5th physical dimension? So the QFT might be onto something. Now we just have to find the other 5. Could light or energy itself be another dimension?

Anonymous

Anonymous Sun 28 Feb 2021 16:35:47 No.12767351 Report

Quoted By:

>>12764887
Useful fiction created by the curvature of space-time by massive objects.

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