The premises for my question are,

Gravity isn't a force but curved spacetime

"If gravity isn't a force, how does it accelerate objects?" (complicated answer)

If the answer below, to the question linked above, is correct, I feel it's easier to understand:

"Even objects "at rest" (in a given reference frame) are actually moving through spacetime, because spacetime is not just space, but also time: apple is "getting older" - moving through time."

Time is the result of causality -- to my understanding this means that something ages because of the interactions of its smaller parts, and at the speed of light for example, those interactions don't happen hence time doesn't pass.

So, a very cold object would move less through time (because its internal parts are moving slower, which means less causal interactions), and hence "feel less gravity".

  • $\begingroup$ I can't resist asking this, just for curiosity:).Because it has less internal energy, then it follows it has less mass, (a minute bit compared to its rest mass), shouldn't a very cold mass be the source of less gravity than if it was say, at room temperature.? $\endgroup$ – user214814 Dec 4 '18 at 22:18
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    $\begingroup$ Thanks for the question, but I feel at the moment it's rather vague. It's very hard to see exactly what you mean by 'move less through time', for example (for a cold object). Would it be possible to sharpen it all up a bit and thus ask a more specific and focused question? $\endgroup$ – Andrew Steane Dec 4 '18 at 22:21
  • $\begingroup$ If "moving less through time" means having less kinetic energy, then yes. What does it mean? $\endgroup$ – my2cts Dec 4 '18 at 22:38
  • $\begingroup$ Ah ok, I think I found the confusion I made. In the 3rd link the answer says that an object that is at rest relative to earth, still feels gravity because that object is moving through time (that object gets older) and so in general relativity that counts as motion and hence the object, that is moving in a straight line (forward in time) is following the bent spacetime. ----- My confusion was thinking that a cold object ages less because, due to the cold, its atoms and quarks would suffer less causal interactions (and according the video I linked, causality is responsible for time passed) $\endgroup$ – Harlequin Dec 4 '18 at 22:46
  • $\begingroup$ I'm sorry for the confusion everyone. What I am thinking is that a cold object feels less time because its internal parts are moving slower, and so it has less cause and effect. And if I am understanding it right, time is the result of causality $\endgroup$ – Harlequin Dec 4 '18 at 22:50

It is true that gravity acts on things that have mass and things that possess energy. But the energy content of mass is gigantic for macroscopic objects via $E = mc^2$. On the other hand, the difference in internal energy content of a massive object at two temperatures goes like $\Delta E = mC_p \Delta T$ where $C_p$ is the specific heat of the material. This amount of energy will create an immeasurably small amount of gravity in comparison.


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