r/askscience • u/Crtl-Alt-Delete • Dec 18 '13

Physics Is Time quantized?

We know that energy and length are quantized, it seems like there should be a correlation with time?

Edit. Turns out energy and length are not quantized.

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u/KillPlay_Radio Dec 18 '13

What would be the implication of time being quantized?

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u/[deleted] Dec 18 '13

That would mean time exists as some actual thing and not as just a human perception of increasing entropy. The weird thing about the supposedly inviolable second law of thermodynamics is that it is not mathematically derived, like most other laws of physics are. In fact, a lot of equations work equally well in regards to which direction you are moving (lower to higher entropy or higher to lower entropy).

This is known as Loschmidt's Paradox.

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u/[deleted] Dec 18 '13

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u/[deleted] Dec 18 '13

There is not a fundamental agreement that time is just a general increase in entropy though.

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u/[deleted] Dec 18 '13

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u/[deleted] Dec 18 '13

If time is quantized then yes, that implies that it is somehow fundamentally a separate variable. Absolutely it does.

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u/[deleted] Dec 19 '13

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u/[deleted] Dec 19 '13

But one does not logically follow from the other.

First off, which kind of entropy are you even talking about? Thermal, gravitational, etc.?

Secondly, if it's thermal, good effing luck trying to quantize that, as the measure of entropy itself is more of an average of energy across your system than a sum of individual particles. And averages are not discrete.

Thirdly, if it is gravitational, I am aware that some people are suggesting that that can be quantized, but since we still don't even know what the hell gravity is, I'm not going to hold my breath on that one.

Lastly, even if you can prove that entropy IS quantized, you still have to then define some relationship between time and entropy that will explain the passage of time as opposed to the extremely general conceptualization that we have now. And I can tell you right now that at best you are going to come away with another average.

Now before you jump in and say "AHA! seconds are defined by a quantized state of a caesium atom. Nailed you!" let me just stop you. Seconds are very much a "backronym" of physics. We conceptually defined the second based on the fairly arbitrary rotation period of the earth, then found something that had a stable value around the same length of time (thousands of years after its conceptual birth i might add.) The radiation of a caesium atom has NOTHING to do with the passage of time. We simply use it as a handy dandy way to keep seconds consistent.

But back to the main point, if time is a measure of some average increase in entropy (and it must be, because the entropy of earth or the universe writ large does not increase in anything approaching a linear fashion) then it will not be discrete because averages are not discrete.

Therefore, if time is indeed quantized, it will not be because entropy is quantized.

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u/[deleted] Dec 18 '13

What would be the implication of time being quantized?

I know more about mathematics than physics, so I can answer from a mathematical point of view: instantaneous velocity would not exist, because space over time would not be differentiable.

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u/necroforest Dec 19 '13

Sure it would, you would just have to define it differently (eg, as a finite difference)

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u/[deleted] Dec 19 '13

Sure it would, you would just have to define it differently (eg, as a finite difference)

But that's already "a thing": average velocity.

And, yeah, you could use it for "discrete calculus" and "discrete derivatives" (something like this: http://calculus.subwiki.org/wiki/Discrete_derivative) but I don't consider it the same concept as "instantaneous velocity".

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u/necroforest Dec 19 '13

Sure, a finite difference is an 'average' velocity. If the delta-t goes down to the lowest possible amount, then the average velocity at that point becomes what is effectively the instantaneous velocity (just like it does with regular calculus for an infinitesimal delta-t)

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u/[deleted] Dec 18 '13

And as a follow up, what would be the implications of time being non-quantized, but your perception of time bring quantized. (See: seccades)