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So I have been thinking about some subjects and one of it involves time.

And I tried writing a story/question on here to summarize the bigger picture but it's not going to happen it's too complicated for that.

But basically one of the questions in that bigger picture was based on a comment I heard from a physicist in a video that said "people sometimes say that time is there to stop everything from happening all at once".

And that was a pretty weird comment in my opinion. But it got me thinking about it.

So then one of more basic questions that I had was, if you speed everything in the universe up with the same amount. Like, speed it up by the same magnitude. Wouldn't that be like going faster and everything ending up the same way that it will now, only faster?

Or would it alter things?

And in the end, my bigger picture ended up with kind of like... a link appearing between time itsself and the subjective experience of being alive. Consciousness. But I don't know if such a question is really answerable. So... Is there a link in that? Or is it too complicated for that?

  • Related: http://physics.stackexchange.com/q/15371/2451 , http://physics.stackexchange.com/q/71823/2451 and links therein. – Qmechanic May 25 '15 at 15:20
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    I'm not sure what the actual physics question here is. Asking "Why does X exist?" is, regardless of X, not a physics question. – ACuriousMind May 25 '15 at 16:59
  • A link to a conference where that question is tackled: https://www.youtube.com/watch?v=ODAngTW8deg Two difficulties: - it's a very mathematical approach - Alain connes has a very strong accent... but to summarize (actually that's about all I got out of this talk) there is a "canonical" one parameter automorphism on the algebra of observables... that's time – Noix07 May 25 '15 at 20:24

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Snap your fingers. Wait. Snap them again. Physically speaking, time is a measurement which distinguishes between these two different events (finger snaps) which happen non-simultaneously (snap, wait, snap) at the same spacial location. There is no reference frame in which these events happen simultaneously.

That's the simplest way I know to define time. Why does time exist? Because there are events which will always be non-simultaneous, no matter the reference frame. Time measures non-simultaneity.

Bill N
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    Hmm, +1 but we don't know what order they happened in. We know that a glass smashes after you throw it, but we don't know what order you filled 10 glasses. – Tim May 25 '15 at 15:13
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    @Tim Non-simultaneous events which happen at a common location ($\Delta x = 0$) in one reference frame will always happen in the same order in other reference frames (but in different locations). And what 10 glasses are you talking about??? – Bill N May 25 '15 at 15:23
  • As in if you fill 10 glasses, and you don't have to fill one to fill another, the order you filled them is unknown isn't it? – Tim May 25 '15 at 15:29
  • This answer seems a bit circular to me. How would you define simultaneous? – RedGrittyBrick May 25 '15 at 22:13
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    Simultaneous events in a given reference frame have the property that $\Delta t = 0$. Just because they are simultaneous in one reference frame doesn't mean they are simultaneous in others. I understand the tendency toward circularity, but time is still a measurement which we make regarding events. – Bill N May 25 '15 at 22:56
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"Why" is never a physics question, but we can replace it with "What is time?", which is.

"Time" is that which a suitable clock shows.

It's not some abstract, undefinable philosophical notion that magically "makes things happen". Time in physics is a stream of steadily increasing numbers coming from suitable experiments that measure time. We call those experiments "clocks". The definition of "time" is inseparable from the definition of "clock" in just the same way as the definition of "distance" is inseparable from the definition of "yardstick".

Once we have built good (enough) clocks, we can then correlate other numbers against the time numbers and that's how we do all physical dynamics. Now your question comes down to "When can I build clocks?" and the answer to that is given by thermodynamics: as long as the universe is not in thermodynamic equilibrium. If it were, there would be no useful notion of "time".

CuriousOne
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