2. Time dilation has been experimentally established as correct, and correctly described by relativity, so you would need to take it into account in your calculations.

Certainly, but this has *nothing* to do with the statement:

"as you approach the speed of light time slows down".

Do you want a prove? Here it is: My time flows as always, exactly in the same way, but in this moment I am travelling at almost light speed, with respect to some extremely energetic cosmic ray, and at the same time I'm obviously stationary, with respect to another frame of reference co-moving with me.

Time flows exactly in the same way independently of speed.

Time dilation is a consequence of the fact 2 different bodies makes different paths in spacetime between two events. But time for every of the 2 bodies flows exactly as before.

A metaphor.

Let's say you with your car A and you friend with his car B go from Rome to Paris, starting simultaneously at 00:00:00 (you have synchronized your perfectly identical clocks) from Rome. You travel *at the same exact constant speed*.

At the end you compare your clocks: your signs 15:00:00, the one of your friend signs 13:00:00.

Has time flowed differently for you and your friends?

Or is it, maybe, that you have taken two different paths to go to Paris?

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