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Time Before Time [speculative cosmology]
Seed Magazine ^ | August 28, 2006 | Sean Carroll

Posted on 08/30/2006 1:01:48 AM PDT by snarks_when_bored

TIME BEFORE TIME

An event like the Big Bang is about as likely as billions of coin tosses all coming up heads. Explaining why that is might take us from empty space to other universes--and through the mirror of time.

by Sean CarrollPosted August 28, 2006 11:53 AM

From the SEPTEMBER issue of Seed:

  timebeforetime.jpg

The nature of time is such that the influence of the very beginning of the universe stretches all the way into your kitchen—you can make an omelet out of an egg, but you can't make an egg out of an omelet. Time, unlike space, has an obvious directionality—the view in a mirror makes sense in a way that a movie in reverse never would.

The arrow of time in our universe is puzzling because the fundamental laws of physics themselves are symmetric and don't seem to discriminate between the past and future. Unlike an egg breaking on the side of a frying pan, the journey of the planets around the sun would look basically the same if we filmed them and ran the movie backwards. Rather, it must be due to the initial conditions of the universe—a fact that makes the nature of time a question for cosmology. Remarkably, the answers we're beginning to discover are telling us there may be other universes out there in which the arrow of time actually points in reverse.

For some reason, our early universe was an orderly place; as physicists like to say, it had low entropy. Entropy measures the number of ways that you can rearrange the components of a system such that the overall state wouldn't change considerably. A set of neatly racked billiard balls has a low entropy, since moving one of the balls to another location on the table would change the configuration significantly. Randomly scattered balls are high entropy; we could move a ball or two and nobody would really notice.

Low-entropy configurations naturally evolve into high-entropy ones—as any billiards-break shows—for the simple reason that there are more ways to be high entropy than low entropy. The very beginning of time found our universe in an extremely unnatural and highly organized low-entropy state. It is the process by which it is inevitably relaxing into a more naturally disordered and messy configuration that imprints the unmistakable difference between past and future that we perceive.

Naturally, this leads one to wonder why the Big Bang began in such an unusual state. Attempts to answer this question are wrapped up with the question of time and have led me and my colleague Jennifer Chen to imagine another era before the Big Bang, in which the extremely far past looks essentially the same as the extremely far future. The distinction between past and future doesn't matter on the scale of the entire cosmos, it's just a feature we observe locally.

If time is to be symmetric—if the direction of its flow is not to matter throughout the universe—conditions at early times should be similar to those at late times. This idea has previously inspired cosmologists like Thomas Gold to suggest that the universe will someday recollapse and that the arrow of time would reverse. However, we now know that the universe is actually accelerating and seems unlikely to ever recollapse. Even if it did, there is no reason to think that entropy will spontaneously begin to decrease and re-rack the billiard balls. Stephen Hawking once suggested that it would—and he later called that the biggest blunder of his scientific career.

If we don't want the laws of physics to distinguish arbitrarily between past and future, we can imagine that the universe is really high-entropy in both the far past and the far future. How can a high-entropy past be reconciled with what we know about our observable universe—that it began with unnaturally low entropy? Only by imagining that there is an ultra-large-scale universe beyond our reach, where entropy can always be increasing without limit, and that if we went far enough back into the past, time would actually be running backwards.

Such a scenario isn't as crazy as it sounds. Our universe is expanding and becoming increasingly dilute, and the high-entropy future will be one in which space is essentially empty. But quantum mechanics assures us that empty space is not a quiet, boring place; it's alive and bubbling with quantum fluctuations—ephemeral, virtual particles flitting in and out of existence. According to a theory known as the "inflationary universe scenario," all we need is for a tiny patch of space to be filled with a very high density of dark energy—energy that is inherent in the fabric of space itself. That dark energy will fuel a spontaneous, super-accelerated expansion, stretching the infinitesimal patch to universal proportions.

Empty space, in which omnipresent quantum fields are jiggling back and forth, is a natural, high-entropy state for the universe. Eventually (and we're talking about a really, really big eventually) the fluctuations will conspire in just the right way to fill a tiny patch of space with dark energy, setting off the ultra-fast expansion. To any forms of life arising afterward, such as us, the inflation would look like a giant explosion from which the universe originated, and the quiescent background—the other universes—would be completely unobservable. Such an occurrence would look exactly like the Big Bang and the universe we experience.

The most appealing aspect of this idea, Chen and I have argued, is that over the vast scale of the entire universe, time is actually symmetric and the laws truly don't care about which direction it is moving. In our patch of the cosmos, time just so happens to be moving forward because of its initial low entropy, but there are others where this is not the case. The far past and the far future are filled with these other baby universes, and they would each think that the other had its arrow of time backwards. Time's arrow isn't a basic aspect of the universe as a whole, just a hallmark of the little bit we see. Over a long enough period of time, a baby universe such as ours would have been birthed into existence naturally. Our observable universe and its hundred billion galaxies is just one of those things that happens every once in a while, and its arrow of time is just a quirk of chance due to its beginnings amid a sea of universes.

Such a scenario is obviously speculative, but it fits in well with modern ideas of a multiverse with different regions of possibly distinct physical conditions. Admittedly, it would be hard to gather experimental evidence for or against this idea. But science doesn't only need evidence, it also needs to make sense, to tell a consistent story. We can't turn eggs into omelets, even though the laws of physics seem to be perfectly reversible, and this brute fact demands an explanation. It's intriguing to imagine that the search for an answer would lead us to the literal ends of the universe.


—Sean Carroll is a cosmologist at the University of Chicago and the author of a popular textbook on general relativity. He is also a regular contributor to the physics blog Cosmic Variance.


TOPICS: Culture/Society; Extended News; Miscellaneous; Philosophy
KEYWORDS: cosmology; multiverse; physics; space; spacetime; stringtheory; thomasgold; time
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To: jennyp
Red-fonted oberver should read observer in the Aguirre & Gratton passage, of course...
121 posted on 08/31/2006 3:09:04 AM PDT by snarks_when_bored
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To: grey_whiskers; taxed2death
I thought relativity said that there is no preferred inertial reference frame.

By arranging to act simultaneously, they placed themselves in the same reference frame.

BTW, could that IRF be described as "approximately SunTime + [(1/c) X 1AU]" ? '-)

Regards!

122 posted on 08/31/2006 4:57:57 AM PDT by TXnMA ("Allah": Satan's current alias...)
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To: TXnMA
Hmmm -- I note that I referred to position [of the earth's center] (an average radius of 1AU from the sun) -- which impies an position on a sphere of radius = 1AU, centered on the Sun.

To be more accurate, I suppose that position would have to be defined including the date to derive relative motion between earth and sun, since the earth's orbit is not circular...

But, you are correct -- inasmuch as I had to refer to position (relative to the Sun, whch has its own [constantly changing WRT the Galaxy center, etc.] position)...

Of course, by convention, "earth time" is measured at the Prime (Greenwich) Meridian. Your watches merely indicate your angular displacement (± 7.5 degrees) from the Prime meridian. Again, as you point out -- position...

123 posted on 08/31/2006 5:35:39 AM PDT by TXnMA ("Allah": Satan's current alias...)
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To: TXnMA

Yup, your use of the word position better suits this discussion than my use of location, I agree.


124 posted on 08/31/2006 6:17:39 AM PDT by taxed2death (A few billion here, a few trillion there...we're all friends right?)
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To: taxed2death
LOL!! I wasn't "playing semantics" ("location" versus "position"). I just 'mis-remembered' the exact term you used and employed the synonym that came to mind...

I guess we can agree that "where you is" and "where you is a-headed" and "how fast you is a-goin'" all have a bearing on this "relative time" thingy... '-)

At any rate, thanks for getting me started thinking!

Regards...

125 posted on 08/31/2006 8:40:44 AM PDT by TXnMA ("Allah": Satan's current alias...)
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To: RightWhale
The object was very small, smaller than an atom, and not heavy, 10 kilograms.
 
 
 
Albert said -
 
E= Mc2
 
rearranging...
 
M=E/c2
 

NOW the question is:
 
"Where did the ENERGY come from?"

126 posted on 08/31/2006 11:10:00 AM PDT by Elsie (Heck is where people, who don't believe in Gosh, think they are not going....)
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To: Salamander

I might have seen an Aard when he wasn't varking......


127 posted on 08/31/2006 11:12:17 AM PDT by Elsie (Heck is where people, who don't believe in Gosh, think they are not going....)
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To: Elsie

Aquinas commented on that 700 years ago. No need to rehash what cannot be resolved.


128 posted on 08/31/2006 11:12:23 AM PDT by RightWhale (Repeal the law of the excluded middle)
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To: RightWhale
No need to rehash what cannot be resolved.

Cannot?

129 posted on 08/31/2006 6:28:12 PM PDT by Elsie (Heck is where people, who don't believe in Gosh, think they are not going....)
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To: Elsie

Disagree with Aquinas? I'm not that adept, nor did I study in Albertus Magnus' class.


130 posted on 09/01/2006 7:36:16 AM PDT by RightWhale (Repeal the law of the excluded middle)
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131 posted on 06/10/2008 8:50:50 AM PDT by SunkenCiv (https://secure.freerepublic.com/donate/_________________________Profile updated Friday, May 30, 2008)
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