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In the physics we've studied upto and including special relativity, space and time are considered real physical objects each, and something like length contraction and time dilation were considered real physical effects. Indeed time dilation is experimentally confirmed using atomic clocks and more.

When studying more advanced books on relativity and covariance however, the only real thing is the space-time interval, while the spatial components and time component of the interval depend on the coordinate system used, and something like time dilation and length contraction is no longer a profound physical effect but merely an artifact of the use of coordinates.

Besides, different inertial frames are merely considered coordinate systems rotated with respect to each other. In this sense, space-time transformation is nothing profound and is just as profound as the transformation between cartesian and polar coordinates.

So my questions is, which of the two points of view is true and why?

Scibo
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Ahmed Samir
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which of the two points of view is true and why?

“True” is primarily the purview of mathematicians and priests. In science we use the scientific method. This compares the prediction of a theory to an experiment.

Both points of view produce predictions that are consistent with experimental evidence. They are therefore both scientifically validated. So you can use whichever you prefer, or even switch between them as desired. I personally prefer the second, but I also use the first whenever it is convenient.

In my philosophical view, that means that the distinction we draw between these two points of view is a human mental construction, not a natural distinction.

Dale
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I think you are creating an imagined distinction. The two points of view are just that- different perspectives. Length contraction is a real effect. It happens because the time axis in a frame in which a long object is moving is rotated relative to the time axis in the frame in which the object is at rest. The frames are not 'merely' rotated, they are rotated, and the rotation leads to physical effects. It's not simply a free and arbitrary choice of coordinates- if you are moving relative to me, your time axis physically points in a different direction to mine, the degree of tilt being determined by your relative speed.

Professor Sushing
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GR is more simply formulated when described via 4d spacetime rather than space and time separately. This is why the 4d spacetime interval is said to be more real rather than the associated spatial contraction and the temporal dilation.

However, it is impossible for us to see 4d spacetime directly, we are limited to 3d space and 1d time. Thus, I would say both perspectives are equally real.

Mozibur Ullah
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I assume with "philosophy" you mean "intuitive interpretation" or something along those lines. There is no separate "Philosophy" about the contents of Physics Science proper - in the old days, Physics was considered a proper subset of Philosophy.

That said, reality does not care about what mathematical theory we use to describe it. None of those two regimes (special relativity vs. general relativity) is more correct than the other as long as the results we achieve with calculations we are doing with them match observations. SR just comes with some limitations about where it is valid to use it (i.e., better don't use it if gravity is involved)

So my questions is, which of the two points of view is true and why?

There is only one area where speaking about a truth value of a theory makes sense, and that is when comparing its predictions to observation. In that respect, as you mentioned, certain things (like time dilation in atomic clocks flying being observed with the help of atomic clocks) seem to "work" in special relativity already, and thusly for that particular question, SR is "true". Same as Newtonian Physics is still "true" (or maybe "true enough") unless you venture into relativistic regimes.

If you are asking more along the lines of "what interpretation is useful to explain the theory to laypersons, without the need for any formulas" then the simpler one is probably the most useful. So in that respect, both interpretations are useful as descriptions within the context of their particular theory.

And as a last point: awful little of what Physics describes actually tells us what reality "actually" is. Physics, even the standard model + GR, only ever makes predictions about behaviour of stuff, and except for doing experiments/observations and checking whether the predictions are true, they don't actually give us any insight of what reality "really" is. After all, I could still just be a brain floating in a vat...

AnoE
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