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Time is a dimension, but not like space

(bigthink.com)
171 points belter | 1 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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amelius ◴[20 Oct 24 14:58 UTC] No.41895756[source]▶
Light traveling at infinite speeds, atoms and such not.
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andsoitis ◴[20 Oct 24 15:06 UTC] No.41895797[source]▶
If effects were instantaneous then atoms would not exist.
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tremon ◴[21 Oct 24 11:30 UTC] No.41902989{3}[source]▶
You're saying that an atom's decay rate is a function of the speed of light? What proof do we have of this? Does Newton's law of momentum also erroneously leave out the c component?
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1. lazide ◴[21 Oct 24 12:55 UTC] No.41903655{4}[source]▶
If decay rate is related to the elements composition (seems to be true), and the forces holding elements together include Electromagnetism and the Lorentz Force which also seems to be true, then yes. [https://en.m.wikipedia.org/wiki/Classical_electromagnetism_a....]

See also [https://en.m.wikipedia.org/wiki/Electromagnetic_four-potenti...]

Notably, light is a form of electromagnetism, so this shouldn’t be as surprising as it is. c is an explicit part of many formulas, interestingly. And electromagnetism was the first thing tackled in special relativity.