Posted on 08/30/2006 1:01:48 AM PDT by snarks_when_bored
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 Carroll • Posted August 28, 2006 11:53 AM
From the SEPTEMBER issue of Seed:
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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.
They answered that question. God racked the balls and then broke. I love that analogy! The universe is God's 4(+) dimmensional billard table.
I just hope we're not sitting on the 8 ball.
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I'll have to disagree..
There is a beginning and an end..
You are born and you will die..
The article mentioned entropy..
Possibly "time" would effectively end or stop if the universe reaches absolute zero throughout..
If there is no longer any energy transfer, no electron spin, no particle movement, only then could one suppose there is no longer any "time"..
But as long as there is heat, and activity, ( even on the quantum level? ) then one could use the progression of that sequential activity to measure time.. ( define time? )
Time may be "relative" to the physical state, but not arbitrary.. ( "physical" or atomic time, maybe a "quantum" time, or "probability" time, or "string" time.. )
Of course, this is just my opinion, demented rambling though it may be..
I don't expect anyone to simply accept it as scientific fact..
The universe is God's 4(+) dimmensional billard table.I just hope we're not sitting on the 8 ball.
The Magic 8-Ball weighs in on your theory:
Not sure.. When I said time is percieved in a relativistic sense, I was referring to human perception..
As to photons, I am unsure whether they "perceive" anything at all..
A photon is however, a light energy particle..
It is energy being transferred by a source to a "target" although not in the sense of an intended destination, but in the sense that anything that finds itself in the path of that energy will become the recipient..
I can imagine the photon experiences it's ejection from the source, and the impact on the target, but does not actually percieve a passage of time until impact occurs. I would best describe the interim passage as a state of flux..??
That's probably a weak explanation but it's the best I can do..
Of course, that depends on whether a photon's energy state remains constant or if it degrades with distance..
If entropy applies to photons then it would "experience" time as it grows older and weaker, eventually dying.. Maybe "flashing" out of existence, like a tiny, photonic supernova..
The constancy of the speed of light in a vacuum is a cornerstone of special relativity, an experimentally well-tested theory that we've found no cause to emend just yet.
It was once explained to me that two objects, both travelling at the speed of light and travelling on a direct path toward each other are still approaching each other at the speed of light, not twice the speed of light..
Special Relativity is indeed special if 1 + 1 does not equal 2..
I think that it will be found that special relativity does not always apply.. That there are states, dimensions, circumstances, applications, where the speed of light will not apply, or those "limits" can be adjusted.. Or simply bypassed completely....
It's not something I can adequately explain, but I have always felt that there were problems with Special relativity..
Not too bad a situation, really..
If we're the 8 ball, half the universe has to be eliminated before we are..
I just wonder if God has stripes or solids...
Sounds almost logical until one realizes that, while they may have a theory for old universes spitting out new universes, they ignore the real question: Where/when/how did the original one start?
If "membrane" theory is correct, we may never know..
Our universe may be the product of yet another universe, about which we know nothing..
So, "OUR" universe is like unto a raindrop in a puddle of water during a shower. Each splash drop is another "Big Bang" of it's own universe. Multiple universes are then separated by the space (puddle) and unobservable from each other's perspective?...................Naval contemplation.........
Time
Artist(Band):Pink Floyd
Ticking away the moments that make up a dull day
Fritter and waste the hours in an offhand way
Kicking around on a piece of ground in your home town
Waiting for someone or something to show you the way
Tired of lying in the sunshine staying home to watch the rain
And you are young and life is long and there is time to kill today
And then one day you find ten years have got behind you
No one told you when to run, you missed the starting gun
And you run, you run to catch up with the sun, but it's sinking
Racing around to come up behind you again
The sun is the same in a relative way, but you're older
Shorter of breath and one day closer to death
Every year is getting shorter, never seem to find the time
Plans like these that come to naught or half a page of scribbled lines
Hanging on in quiet desperation is the English way
The time is gone, the song is over, thought I'd something more to say
Home, home again
I like to be here when I can
When I come home cold and tired
It’s good to warm my bones beside the fire
Far away across the field
The tolling of the iron bell
Calls the faithful to their knees
To hear the softly spoken magic spell.
It's a little hard to grasp, but appears to be so.
It was once explained to me that two objects, both travelling at the speed of light and travelling on a direct path toward each other are still approaching each other at the speed of light, not twice the speed of light..Special Relativity is indeed special if 1 + 1 does not equal 2..
That velocities are not additive is one of the fundamental insights of special relativity. Of course, low velocities (very small fractions of the speed of light in a vacuum) are approximately additive; the divergence from additivity only begins to show itself at appreciable fractions of the speed of light. Proofs of this are simple and require only elementary algebra. Many websites go through the details.
NIV 1 Corinthians 2:7
No, we speak of God's secret wisdom, a wisdom that has been hidden and that God destined for our glory before time began.
NIV 2 Timothy 1:8-10
8. So do not be ashamed to testify about our Lord, or ashamed of me his prisoner. But join with me in suffering for the gospel, by the power of God,
9. who has saved us and called us to a holy life--not because of anything we have done but because of his own purpose and grace. This grace was given us in Christ Jesus before the beginning of time,
10. but it has now been revealed through the appearing of our Savior, Christ Jesus, who has destroyed death and has brought life and immortality to light through the gospel.
NIV Titus 1:1-4
1. Paul, a servant of God and an apostle of Jesus Christ for the faith of God's elect and the knowledge of the truth that leads to godliness--
2. a faith and knowledge resting on the hope of eternal life, which God, who does not lie, promised before the beginning of time,
3. and at his appointed season he brought his word to light through the preaching entrusted to me by the command of God our Savior,
4. To Titus, my true son in our common faith: Grace and peace from God the Father and Christ Jesus our Savior.
Sounds almost logical until one realizes that, while they may have a theory for old universes spitting out new universes, they ignore the real question: Where/when/how did the original one start?
There is no original one. The ground state of reality would be the quantum vacuum, which here and there, every now and then, coughs up a miniscule hair ball of dark energy (negative pressure), which hair ball then inflates into a cosmos.
That's all there is and there ain't no mo'...
Seems like they knew a lot of things they had know way of knowing or finding out.
Wait a minute here... What if two black holes collide? Would their consumed matter be expelled; or would they create a massive black hole?
I believe gravity will eventually smash all the galaxies with their own energy and mass. Not in the past, but in the future. Time rolls on.
Maybe so, maybe not. It could be that the universe is open and that all matter will ultimately be subjected to a 'big rip' as dark energy acceleration attains fantastically high values.
Wait a minute here... What if two black holes collide? Would their consumed matter be expelled; or would they create a massive black hole?
The coalescence of two black holes creates a more massive black hole, it's thought. Such an event should also be so violent as to produce gravitational ripples in spacetime, detectable in principle by us.
This set off my illogic alarm. What does he mean, "unnatural"? Isn't it nature itself that we're discussing? How many counterexamples can he offer? If he wants to say that the state of space in the distant past is different from the state of space now, that's fine, but calling it "unnatural" is a non-sequitur.
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...
Always beware when you see this construction. The "It was previously believed...However, we now know..." device is almost always the preface to a theorist asserting more than he can prove. What it actually means is "We have a better model than we used to have." Who is to say we won't have a still better model tomorrow? In that case, what we "now know" will become what we "previously believed."
I wish this guy would be more precise.
I've avoided Time ever since they put Hillary on the cover.
Bump to read later.
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