I wish I had a better sense of where gravity comes from. Anyone have good intuition that they could explain?
I obviously get what it is: apple falls from the tree, etc. And I think I more or less get how it is: Newtonian mechanics, general relativity, curved spacetime, etc.
But I do not get why it is. Why does gravity exist? Why do large accumulations of mass naturally pull other mass toward them? π§
One theory I’ve heard is that there’s a universal field, like the Higgs, with particles traveling in all directions and colliding with mass. If you’re near a massive body like a star or planet or moon, it blocks some particles on its side from hitting you, but not from the other side, so the net effect pushes you toward it.
That would make gravity related to volume instead of mass, though, which obviously isn’t right. Still, I don’t remember hearing any other explanations. Does anyone know of any?
I could be wrong but I think if you answer this question you solve a lot of physics
I’m just generally happy that we have it
I think of the whole universe as a sort of survivorship bias. If our universe didn’t have gravity (or it worked differently), we wouldn’t exist to ponder such questions in the first place.
I think with fundamental forces at some point you run out of “why” and you end up with “that’s the way nature is”
But I also think in the case of gravity, it sort of has to be that way, or we would not be here to discuss it [con’t]
Say we lived in a world where every bit of matter repelled every other bit of matter. It would be much less likely to result in complex systems that interact and evolve
I think we need mass to agglomerate to form environments for complex systems to evolve
You can get a bit of a sense of this by playing with Conways Game of Life. Most rulesets are very uninteresting, but some spawn “life” (for some definition of life, heh)
A physicist would say because mass bends space around it, and demonstrate with a heavy weight on a rubber sheet. Idk why they all have rubber sheets though.
Higgs field causes bosons to have mass through the Higgs mechanism, otherwise everything would be massless.
“Spacetime tells matter how to move; matter tells spacetime how to curve.” – John Wheeler
Specifically matter with mass causes spacetime to curve.
if you can answer ‘why is gravity’ and ‘why is magnetism’ I believe you can answer everything we don’t know about physics
*I should have said matter with mass-energy causes spacetime to curve.
Yes! Both of you have a great point here.
I wish it was a bit more satisfying, though. I mean, yes, sure, it’s probably a necessary condition for stars, planets, life etc existing. But even given that, I still wish I had a more mechanical explanation or intuition for what causes it physically.
@mickeykats.bsky.social is probably right though: once you go low enough down into laws of physics, those kinds of explanations don’t exist so much. Which is fine, if maybe a bit frustrating intellectually. π
Yes! I absolutely get that that’s the right description, ie provides more detail on the how. I just wish I understood why matter with mass-energy causes spacetime to curve.
I think when people look for intuition with fundamental laws, the best we can do is analogies + connections, rather than explanations
For example, it might be comforting to you that the force of gravity falls off as 1/distance^2 just like the electrostatic force drops off as 1/distance^2
@snarfed.org Sometimes you have to seperate the “why” from the “how” and be satisfied with just asking the questions themselves.
Not all questions have answers but we’ve got marbles!
Marbles were one of my earliest demo on how gravity works and I love using it for teaching. It’s still a model and as they say
“All models are wrong, but some are useful”! :Blobhaj:
#physics #classroom
https://m.youtube.com/watch?v=MTY1Kje0yLg
#classroom
#physics
@snarfed.org I meant to investigate this thoroughly as a teenager, and got to a book on general relativity — that was in the STEM desert long before the internet — whose math was waaayyy above my league at the time. They had me at “Einsteinian summation convention” with volume integrals when I had barely seen a volume integral before.
P.S. A Why question here may not make much sense. IMHO to be able to form a Why answer, you’d have to step out of the descriptive system of physics.
@snarfed.org I stopped studying this before getting quite that far, but when physicists say ‘spacetime curves’, that’s in four dimensions if I’m not entirely mistaken.
If you look at it as space over time, it’s more like space itself is flowing towards gravity wells, I think. We can’t measure that directly though, just changes in it to an extent.
(I’m fairly certain we don’t actually know what’s going on, but this should be a mathematical model that at least mostly makes sense.)
@snarfed.org We basically don’t know why this happens! π π π€£
The explanation of general relativity is more or less this: if every body that has a mass “moves” in spacetime “towards” its own future, when it encounters another body, the two masses converge towards the same spacetime future.
If one of the two bodies has a “much” greater mass than the other, the larger body exerts on the smaller one a modification of spacetime such that it totally affects the smaller body.
In this case, when the two masses touch, the smaller mass deviates totally from its own spacetime direction, taking the direction of the larger mass
Waaat
So gravity is basically our version of Eve Online’s time dilation
That is so cursed. Thanks, I hate it π
not what you asked for but i absolutely love this video http://www.youtube.com/watch?v=wrwg...
Youβre not a climber
High-gravity days are the worst
You donβt wanna know
@hankgreen.bsky.social
Besides being a curvature in space/time caused by something that has mass? No idea. Reality is fucking weird.
curved space shoves you around, I don’t think anybody understands it, it’s just what we see happening
Okay so everything exists within the fabric of spacetime, which is 4-dimensional (x, y, z, time). Like a bowling ball on a trampoline, things with mass bend spacetime in toward themselves. (Continued…)
Like a marble on the edge of the bowling ball’s divot in our trampoline, things tend to fall along that curvature toward the centre. Everything is just falling toward something else. But if it moves fast enough, centrifugal force counters the falling motion, or even overcomes it.
Had to double-check some things! The curvature is caused by the stress-energy tensor, but…nobody knows why the tensor causes spacetime to curve. AFAIK we’re now talking about a point where quantum mechanics and relativity can’t be reconciled so we just don’t know.
It comes from nowhere. It doesn’t exist. Bosons are allured to the information conveyed to them and bend reality to try and get to the origin. Because all their friends existed everywhere all at once– then rapidly moved away. Now they’re far away from their friends and lonely. QED gravity is love.
Yes! The quantum mechanics vs gravity/general relativity conflict, I’m familiar with, but that didn’t quite feel like the reason we can’t explain “why gravity.” However, “nobody knows why the tensor causes spacetime to curve”…bingo! Thank you!
Pingback: snarfed.orgsnarfed.orgBlueskyBluesky
@snarfed.org The canonical explanation, per Einstein, is that mass bends space, and everything follows space.
It comes from mass.
Beyond that, we don’t really know.
there is a science feed which I think you get to with π§ͺ emoji
my stupid answer is that is how our universe works; why is hard to say (I mean you cna trot out math and so forth)
@snarfed.org Itβs all math. Remember:
“Nothing Unreal Exists” -T’Planahath, Vulcan Philosopher