[joslin01]

I guess I don't see the equivalence. Time very much depends upon duration and the terms might as well be synonymous. Does space depend upon displacement? If we froze a single instance of space & time, we would see a universe sitting still. Space and all its fillings would still be there but would time? I believe it quite bold to call space time and time space just because duration and displacement seem similar.

[ben_w]

You’re calling one dimension special because if you remove it you don’t get to use the special words you use for that dimension.

If updown was a special named dimension and you took a single 2-space+1-time slice of the universe at fixed radius from the Earth, your argument wouldn’t really be different, only words and phrases like “sitting still”, which is inherently about the dimension being removed, because it’s convenient for us.

And that’s ignoring questions like “can particles have momentum if there is no time?” which might actually be important in the unlikely event that I understand what a black hole’s singularly does to time.

[joslin01]

I think what you're saying is fair and I realize it might be pushing it to remove the dimension of time to articulate my position.

Regarding the last question, if I understood forces correctly, it's that they remain in motion until an equal or greater force stops them right? Why do we need time for that out of curiosity?

[ben_w]

Thanks. Velocity is the derivative of position with regard to time. Does it exist if there is no time? It might be that momentum is the fundamental thing and velocity is just a consequence of it. Or not, I don’t know.

Momentum has a direct influence on Einstein field equations, and I don’t know enough maths to follow GR (just two A-levels) so I have no idea if that “direct” influence is still present at a no-more-future boundary condition.

My insufficient maths skills are, amongst other things, why I don’t trust my understanding that a black hole singularity really is a no-more-future boundary condition.

[haZard_OS]

Don't you think the concept of "motion" presupposes time? For that matter, every verb in existence presupposes time.

A fascinating book on this topic is "Philosophy in the Flesh" by George Lakoff:

https://amzn.to/2vCkS9s

[TuringTest]

> If we froze a single instance of space & time, we would see a universe sitting still.

I don't believe that mental experiment proves what you think. If you freeze time, there wouldn't be anyone that could make observations. You might as well choose one fixed point in the universe, eliminating space considerations, and think about its whole story from the beginning to the end of time; that would be as real as a frozen universe.

I think of reality as a goo of vibrating stuff, encompassing all matter and energy. Matter creates space, and the vibrations of change create time.

[jhayward]

The problem you may be having is there is no separate thing called 'space'. There is only 'spacetime'.