What Is Time?

Posted on Thursday, March 11th, 02010 by Camron Assadi - Twitter: @teiwaz
link Categories: Long Term Science, Long Term Thinking   chat 0 Comments

What is time?

Wired Science has posted a thought-provoking interview with Caltech theoretical physicist Sean Carroll about the arrow of time, which points from past to future. We all perceive this arrow and can measure its passage with clocks, but very little is understood about how and why it works that way. Carroll explains:

We remember the past but we don’t remember the future. There are irreversible processes. There are things that happen, like you turn an egg into an omelet, but you can’t turn an omelet into an egg.

And we sort of understand that halfway. The arrow of time is based on ideas that go back to Ludwig Boltzmann, an Austrian physicist in the 1870s. He figured out this thing called entropy. Entropy is just a measure of how disorderly things are. And it tends to grow. That’s the second law of thermodynamics: Entropy goes up with time, things become more disorderly. So, if you neatly stack papers on your desk, and you walk away, you’re not surprised they turn into a mess. You’d be very surprised if a mess turned into neatly stacked papers. That’s entropy and the arrow of time. Entropy goes up as it becomes messier.

So, Boltzmann understood that and he explained how entropy is related to the arrow of time. But there’s a missing piece to his explanation, which is, why was the entropy ever low to begin with? Why were the papers neatly stacked in the universe? Basically, our observable universe begins around 13.7 billion years ago in a state of exquisite order, exquisitely low entropy. It’s like the universe is a wind-up toy that has been sort of puttering along for the last 13.7 billion years and will eventually wind down to nothing. But why was it ever wound up in the first place? Why was it in such a weird low-entropy unusual state?

That is what I’m trying to tackle. I’m trying to understand cosmology, why the Big Bang had the properties it did. And it’s interesting to think that connects directly to our kitchens and how we can make eggs, how we can remember one direction of time, why causes precede effects, why we are born young and grow older. It’s all because of entropy increasing. It’s all because of conditions of the Big Bang.

For a deeper exploration of the arrow of time and the cosmology of why it exists, Carroll’s recently published book is From Eternity to Here: The Quest for the Ultimate Theory of Time.

  • jmrowland

    So the Big Bang was an Entropy Reset.

    One effect of the Arrow of Time is that we think of the Big Bang as something that “happened” in the past. It’s an explosion wave that we’re still riding.

  • Was the universe orderly or just very simple? Or is that the same thing?

  • Sebastian Formoso

    Time does not exist. It is a human concept, our own way of measuring change. Change exists but time…it’s just in your clock and no where else. That’s why we can’t remember the future. We can’t remember it because we have yet to make changes to the present.

  • Karl

    I just love that graphic (and all things time-related). Is it available as a poster anywhere … or can I get a high resolution file?

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  • Dennis Ludlow

    There are many more out there besides Ludwig Boltzmann and Sean Carroll. Have any of you read the books: ‘Living Time’ by Maurice Nicoll or ‘Tertium Organum’ by the Russian mathematician, P.D.Ouspensky? These two books delve into this question of ‘What is time.’ from the point of view of a dimension beyond the third.

  • isingularity

    Who says you can’t remember the future? That’s a remarkably lineal argument. How do we know time is lineal. Perhaps in the physical realm..but what if?

    It’s not so far fetched, most physics around time seems fairly theoretical….what of metaphysical understandings of time?
    Not science I understand but even quantam physics in some circles is getting a little bit wacky and unscientific.

    Time as a loop not a line? What really happens in the centre of a black hole?

    Just thoughts based on some personal (non drug effected) experiences.

  • Raphael

    Time is one manifestation of universal intent, the other three being space, energy and matter. Time is the spreading out of materialisation, past is that which is materialised, future is that which is potential. The present is that glowing moment at which both are one. In other words, the present moment is the means to go from time back into universal intent that caused time, because in the present the opposites have been brought into a fusion.

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