@Nugatory Fair enough. But you are treating an hypothesis where we would do an experiment. The video I posted don't go this way. Think of it as if some external observer that could see everywhere clocks. I get your point though. Would you mind to give an analysis of the video?
Dale said:
I am not sure what you are asking for here. I have already told you that I don’t think statements of the type “time causes X” are usually right. So I am not sure how you think “time is responsible for X” differs.
So I am not sure that I even agree with the claim “the aspect of time of spacetime is responsible for gravity” let alone have evidence for it. Can you explain more what you are asking for, because I agree in principle that experimental evidence is essential to have.
That's good to read. What I'm asking is experimental proof for the statements, which I see often when reading/watching about relativity, that gravity is not a fundamental force the way the other 3 are and that is, instead, caused by the curvature of time. I've seen this more than once.
But, I think you didn't say that. In this case, let's take a step back and I ask you: Is gravity a fundamental force like electromagnetism, and nuclear weak and strong forces? And what is the cause of gravity?
Dale said:
You should. It is called a light cone, and it is a standard part of pseudo Riemannian geometry
Causes are always in the past light cone of effects and effects are always in the future light cone of causes. That is geometry, and it is geometry which constrains physical causality.
No. Geometry is used to represent the passing of time versus space. It's a representation to show that information cannot go beyond the past/future cones because its speed is limited by c. There is no light cone in our universe, it's just a way of explaining how it works. You can getrid of the cones by just explaining that nothing (including information) can travel faster than c, so if something is farther than 1 light-second away from you, you can't get any kind of contact/interaction with it in less than 1 second.
That's a very nice example of how you can explain something in our real world without using the math/geometry. And it's also an example of how the geometry is just a drawing that, sometimes, might help visualize or calculate things.
Dale said:
Yes, it is possible and many people’s brains are fully capable of it (including mine and most of the regulars on this forum). I cannot see what is in your head, but from what you write it seems that your difficulty stems more from a lack of willingness to accept the premises than any particular challenge of the material itself.
You are completely right. I was not asking if our brains were capable of understanding the theory of relativity, that is obvious. I was talking about we being able to trully comprehend and grasp what it means to live in a 4 dimensional universe, what exactly is spacetime and, of course, to understand (not accept) the premises and why they are true. Unless they are experimentally proven (that's why I asked before), in which case there is nothing more to understand than "we experimentally saw universe works this way", there must be a reason to believe it works that way.
@Nugatory , answering your second post, didn't want to make several quotes. I am not doubting the theory of relativity at all. I know about GPS, mercury orbit, etc. (even wrote those as examples in my posts). I'm specifically asking about the experiments about time and gravity. We can have the theory of relativity without having time to be responsibe for gravity.
@timmdeeg You answered with geodesics, which is related to the geometry of spacetime. My issue is the premisse that time can be treated as a spatial dimensional and curving it can do more than affecting the flow of time.
@anuttarasammyak Ok, what I understood from that is that space and time are related as if one can be a function of the other. I don't understand why you made that point in your last sentence.
@ersmith Great post. You had me until the last paragraph: "So it is perfectly reasonable to talk about "bending" a time axis, and in this case it really does mean mixing time and space coordinates. There is a limit to how much time and space can be mixed, and that limit is the speed of light (or the speed of causality)."
You painted two examples: one with a stationary clock, where it only moves throught the time axis (parallel to the time axis, perpendicular to space axis) and the other with a moving clock, having an angle between both axis. So, the moving clock will tick slower than the stationary clock, because part of that spacetime limit is now into the spatial axis and not only in the time axis.
I understand "mixing time and space" as being displaced in the spatial axis, which means changing the coordinates of both time and space. But not the bending of the axis. The axis are there just to measure the passing of time and distance. I don't understand what the heck it means to bend the line that is just used to count seconds.