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Time is a dimension, but not like space

(bigthink.com)
171 points belter | 4 comments | 17 Oct 24 15:29 UTC | HN request time: 0s | source
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heed ◴[20 Oct 24 05:48 UTC] No.41893173[source]▶
Also consider the speed of light is also the speed of causality. If there was no such limit it means it would be possible for effects to precede causes which would lead to a very different kind of universe!
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MattPalmer1086 ◴[20 Oct 24 09:18 UTC] No.41894129[source]▶
How could an effect precede a cause if there were no speed limit to causality?

No matter how fast an effect propogates, it is always after the cause (with an infinite speed, I guess effects happen instantaneously, but not before).

Of course, this doesn't fit with a universe described by general relativity, where time can be different for different observers. But you wouldn't have a universe described by general relativity without that constraint in the first place.

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andsoitis ◴[20 Oct 24 14:30 UTC] No.41895599[source]▶
> How could an effect precede a cause if there were no speed limit to causality?

> No matter how fast an effect propogates, it is always after the cause (with an infinite speed, I guess effects happen instantaneously, but not before).

If everything happens instantaneously then there is no real cause and effect, and the universe would be over before it really got started.

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amelius ◴[20 Oct 24 14:48 UTC] No.41895699[source]▶
No speed limit does not mean that everything goes infinitely fast.
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lazide ◴[20 Oct 24 14:56 UTC] No.41895745[source]▶
If the speed limit is infinite, what else would you expect to happen?
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bryanrasmussen ◴[20 Oct 24 16:53 UTC] No.41896721[source]▶
old grannies driving at 30mph on the freeway, me at infinity.

on edit: not everything travels at the speed limit, if the speed limit right now is the speed of light - then why doesn't everything travel at the speed of light?

People say if the speed limit was infinite that everything would happen instantaneously - but they still need to explain why everything should go at the speed limit in this other universe, when not everything goes at the speed limit in ours.

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1. lazide ◴[20 Oct 24 17:31 UTC] No.41897011[source]▶
Almost everything (electrical fields, atomic radius, even speed of sound in materials) seems to derive in some way from the speed of light and related effects.
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2. ◴[20 Oct 24 18:11 UTC] No.41897301[source]▶
3. bryanrasmussen ◴[20 Oct 24 18:40 UTC] No.41897518[source]▶
perhaps this is an effect of having a speed limit in a universe, if a universe does not have any set speed limit (which is somewhat different than the phrasing speed limit is infinite) perhaps the discussed derivation of other speeds would not exist in the way it does in our universe.
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4. lazide ◴[21 Oct 24 13:16 UTC] No.41903846[source]▶
Anything is possible if anything is possible.

In this universe, fundamental forces like electromagnetism directly contain things like c, so if c is infinite, everything is going to work very differently.