Posted on 05/04/2006 12:02:17 PM PDT by PatrickHenry
Big bounces may make the Universe able to support stars and life.
A bouncing universe that expands and then shrinks every trillion years or so could explain one of the most puzzling problems in cosmology: how we can exist at all.
If this explanation, proposed in Science1 by Paul Steinhardt at Princeton University, New Jersey, and Neil Turok at the University of Cambridge, UK, seems slightly preposterous, that can't really be held against it. Astronomical observations over the past decade have shown that "we live in a preposterous universe", says cosmologist Sean Carroll of the University of Chicago. "It's our job to make sense of it," he says.
In Steinhardt and Turok's cyclic model of the Universe, it expands and contracts repeatedly over timescales that make the 13.7 billion years that have passed since the Big Bang seem a mere blink. This makes the Universe vastly old. And that in turn means that the mysterious 'cosmological constant', which describes how empty space appears to repel itself, has had time to shrink into the strangely small number that we observe today.
Cosmic disagreement
In 1996, it was discovered that the universe is not only expanding but is also speeding up. The cosmological constant was used to describe a force of repulsion that might cause this acceleration. But physicists were baffled as to why the cosmological constant was so small.
Quantum theory suggests that 'empty' space is in fact buzzing with subatomic particles that constantly pop in and out of existence. This produces a 'vacuum energy', which makes space repel itself, providing a physical explanation for the cosmological constant.
But the theoretically calculated value of vacuum energy is enormous, making space far too repulsive for particles to come together and form atoms, stars, planets, or life. The observed vacuum energy, in contrast, is smaller by a factor of 10120 - 1 followed by 120 zeros. "It is a huge problem why the vacuum energy is so much smaller than its natural value," says Carroll.
You're special
One of the favoured explanations is the 'anthropic principle'. This suggests that in the apparently infinite Universe, the cosmological constant varies from place to place, taking on all possible values. So there's bound to be at least one region where it has the right size for galaxies and life to exist - and that's just where we are, puzzling over why our observable Universe seems so 'special'.
But this runs against the grain for physicists, who prefer to be able to explain our Universe in one shot. "Relying on the anthropic principle is like stepping on quicksand," Steinhardt and Turok write. They think they have a more satisfying explanation.
They have seized on an idea first proposed by physicist Larry Abbott in 1985: that maybe the vacuum energy was once big but has declined to ever smaller values. Abbott showed that this decay of the vacuum energy would proceed through a series of jumps, with each jump taking exponentially longer than the last. Over time, the Universe would spend far longer in states with a vacuum energy close to zero than with a high vacuum energy.
A long, long time ago
The problem was that Abbott's calculations implied that by the time the vacuum energy decayed to very small values, the expansion of space would have diluted all the matter within it so much that it would effectively be empty.
The cyclic universe gets around this problem, say Steinhardt and Turok. With cycles of growth and collapse taking a trillion years or so, and no limit to how many such cycles have preceded ours, there is plenty of time for the vacuum energy to have decayed almost to zero. And each cycle would concentrate matter during the collapse phase, making sure that the Universe doesn't end up empty.
Steinhardt and Turok say that their idea is testable. The cyclic model predicts that the Big Bang induces gravity waves in space, which physicists are now hunting for. And the decay of the vacuum energy predicts new types of fundamental particles called axions, which may also be detectable.
"It's an interesting idea," says Carroll. He confesses that he has other worries about the cyclic-universe model that temper his enthusiasm. But the wackiness of it doesn't bother him. "Any explanation is quite likely to be extreme," he says, "because all the non-extreme possibilities have already been thoroughly explored."
Why? If some force, like gravity, makes it collapse, it will do so. If something else makes it go Bang, it will do so. Why couldn't this continue eternally? Where would the energy loss due to some kind of friction go?
"But the irony is that Einstein insisted that the Theory of Relativity not only made sense, but it was the only possible explanation that did make sense."
I'm not so sure about that.
He also stated his first theories were totally incorrect.
The smartest man in the world is the one who realizes that he knows nothing.
They always say that. Of course it is testable, so is gravitational blue-shift. If nothing else we can wait and see what happens.
"but I think understanding and accepting these concepts has more to do with intuition than anything.
"
Now, you, are a very smart person.
New theories, new inventions, come not from our individual brilliance over and above other humans.
It is given to many at the same time. Most do nothing with the info. The few are the ones that 'invented' it in history books.
I think Michio Kaku, author of "Hyperspace", fits into that category, judging by his quips and quotes in the book: "Therefore, unicorns do not necessarily have to exist. And neither does God".
I skipped most of those sections, but it is a useful book overall.
"paired photons"="entangled photons"
"If I knew God I'd be Him..." and know how and why the universe is.
Don't ask me for the math; I had it all noted down but it got misplaced in the same spot where Hillary keeps all those missing FBI files.
Not necessarily counter intuitive. If you consider what intuition is, or could be. I think it those thoughts and ideas that cannot be clearly expressed in language which is based upon all our past knowledge and experiences. It is those math ideas, for example, or ideas about an oscillating universe that cannot be formally expressed yet you know intuitively, are true.
If you consider the survival of the fittest, the universe that survives is the universe that is self-perpetuating. Thus a universe that is a one-time affair might be doomed for self-destruction.
Life itself can be viewed as innately oscillating if you consider yin and yang, positive-negative charges, magnetism, binary zero sum, plus minus instances...and nature abhoring a vacuum so that it is constantly in flux and thus perpetuating life. (OK, time for a nap... ;))
Apparently, intuition is a relative thing.
If you've really mastered that sort of physics, you should be able to invent a yoyo which requires no energy imput from the user. There should be lots of money in something like that.
"We do not know the actual mechanism of space respiration; we merely observe that all space alternately contracts and expands..."
"The cycles of space respiration extend in each phase for a little more than one billion years..."
We always knew the universe was expanding.
It was trying to get away from Chuck Norris!
"Why, it's dirt, of course. Dirt, all the way down."
1000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000
00000000000000000000000000000.
Not nearly as much as numbers of the form 1720....
"that is the nature of the quantum universe..."
Well, you and I are not going to settle that here. That's what Eistein and Bohr spent years arguing about. Bohr won, according to modern physicists, but I still think Einstein was right that God does not play dice. Part of the problem with physics is that there is a degree of orthodoxy. There are some things you can't argue without being labeled a quack. That's one reason why Aristotle's view that the Earth is the center of the universe prevailed for almost 2,000 years. A lot of physicists will tell you that if you've got a theory that works in the sense that it predicts the right result, then that's all you need, even if it's wrong. They aren't going to change it until they get to a point where they just can't explain something.
Of course, some of us would say that they are already there inasmuch as they can't explain gravity. That doesn't seem to bother them though.
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