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What is gravity?
(mander.xyz)
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this post was submitted on 05 Sep 2023
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gravity applies to everything with mass. But also light which has no mass.
Photons have no rest (invariant) mass, and gravity doesn't directly affect photons, but does warp the spacetime that the photons travel through. That said, photons do possess energy which can also affect things gravitationally, even other photons.
So… you're saying we don't know what gravity is
Well you can say that about anything can't you?
We can name thousands of variations of the color red, we can measure the wavelength of the light that produces the color red, we can build machines and devices that manipulate matter at the quantum level to produce the color red, and yet... it's still impossible to actually say what red is, and no one knows if what they perceive as red is the same as what others perceive.
So ya we don't "know" the ultimate true nature of gravity, and yet...
...even babies and simple animals learn and understand that gravity exists, and we can measure gravity to astonishing levels of accuracy, and we understand gravity enough that we can launch a rocket up into space that then launches a probe that can travel millions of kilometers through space over several years and land on the surface of a comet that's travelling tens of thousands of kilometers an hour, but ya... "we don't know what gravity is"
If you can spend your entire life studying the mountains of data and literature that we have amassed about a topic, then is it honest to say we know nothing about that topic?
https://youtu.be/6HlCfwEduqA?si=QV8HMlUEPXHLIEm7
Yeah.. about that.. I have nothing clever to say.
Our laws of physics aren't really suited for it, and everything seems so round-about that it looks like that time when people tried to argue for having Earth be the centre of the solar system. It's all just patches to something that we know isn't that simple.
This isn't the first time, I'm hearing about light being affected by gravity, but like, are we saying that electric fields and magnetic fields are not affected by gravity... except they are, when they oscillate back and forth in the form of an electromagnetic wave?
My understanding of EM fields compels me to say that they are affected by gravity because the mediating particles are.
I'm guessing by "mediating particles", you don't mean those affected by fields, but rather those 'propagating' the field, i.e. photons.
And well, my research tells me that photons don't really exist. 🙃
Well, particles don't really exist, in the traditional sense. They're not solid balls flying through space. They're rather just peaks in the EM and gravitational fields. And then, if you've got a disturbance in a field, a peak or wave will travel along the field, which propagates that disturbance. And if you've got all that internalized, then you could call that peak/wave a "particle" again.
Here's a rough source / different explanation of those claims: https://physics.stackexchange.com/a/201
But yeah, I don't think this particle analogy is helping us here. We're ultimately still just talking about a field being affected by gravity.
(Still, thanks for the input. I'm sorting my thoughts as I go, and reading that I've also been subjected to an unhelpful analogy is helping it make sense.)
I also like to say that particles don't really exist in any sense one would associate to the word. And to be pedantic, we can't even say that particles are peaks in a field because that is merely how we model it, and that model is incomplete.
Since we don't know what gravity is or does, nor what (or if) a field is or what particles are, it's hard to answer a question like whether a particular field is affected by gravity other than in terms of a specific model and hope that corresponds to real observations.
In this case, our best bet is to reason in terms of known properties of what we think of as particles mediating the field in question. Photons are subject to gravitational influence, and so we expect EM fields to be as well.
Interesting points. I was thinking, we're generally treating EM fields like they're unaffected by gravity, because we've measured the field strength around a magnet and saw that it wasn't drooping to the ground.
But I guess, the influence of gravity is so weak on EM fields, that it only becomes apparent near a black hole and therefore, it's hardly possible to actually measure a deformation on Earth. And therefore, we just don't know.
Plus, of course, other reality-bending stuff, like the EM-waves we use while measuring (e.g. visible light) being affected by the gravitational pull.
Do you know, if there's anything for which we've secured that it's unaffected by gravity?
Apparently, there's a few particles/field-peaks/whatever, which are deemed massless, but given that no mass does not mean unaffected by gravity, that's kind of moot...
I don't think we know of anything not affected by gravity. If we did, General Relativity would be considered incorrect (not merely incomplete).
Awesome. Slowly, but surely, this General Relativity thing starts to make sense to me.