Skip to comments.Cyclic universe could explain cosmic balancing act
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.
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.
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."
"we live in a preposterous universe", says cosmologist Sean Carroll....
You wonder, then, why scientists have such a problem with religion. Why is one brand of incredulity better than another?
All this empty space and no one knows how it got here, let alone how some of it filled up with suns, planets, black holes, etc.(lots of theories but very little proof and changing all the time). No conclusion to reach from this post just a thought is all.
So, the universe is like Swiss cheese?..........
Big Science at its best! This is very interesting as it stands, I'm keen to see how the axion hunt goes!
After that verdict yesterday, who can argue?
"we live in a preposterous universe", says cosmologist Sean Carroll...."
Compared to what? Some other universe that isn't preposterous? LOL!
No, no, that's the moon.
The moon is Green Cheese.......
the bouncing ball theory (or, at least, hypothesis) has been around my whole life.
I keep wondering whether there's any evidence supporting the possibility that this sidereal reality is actually a composite of multiple contemporary or overlapping matter-energy eruptions at different loci.
On a deeper level, the scientists don't know what the heck they are talking about. Their theories and observations have led to a view of the universe that is way beyond common sense and starts to sound like magic, or God.
Just one teeny weeny example. The "cosmological constant" either doesn't exist, or they have no idea what it is. Their observations of the universe don't match what should be the behavior of the "stuff" they know to exist, so the cosmological constant is a number thrown in to make up for the difference. They have no idea what it is or if it is real.
Modern physicists especially enjoy coming up with explanations for things that don't make any sense, and then saying something like, "It doesn't have to make sense. It just has to describe reality. Reality doesn't necessarily make sense."
I think Einstein got that started when he came up with the Special Theory of Relativity, which seemed to contradict our common understandings. 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.
This makes me wonder if perhaps it's us living in the Bizarro Universe?
I don't suppose that any of you could recommend a good layman's guide to physics. I took a look at 'physics for dummies' (no, I'm not kidding), but I'm not certain that I really trust that series to be accurate.
Yeah, you should see my goody-goody bizarro twin.
Bottom line, it's not new and, still, no one has a clue.
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