Was There Only One Big Bang? 295
goldaryn writes "Physorg.com is running an interesting story about the work of Oxford-based theoretical physicist Roger Penrose. Penrose has been studying CWB radiation and believes it's possible that space and time did not come into being at the Big Bang but that our universe in fact continually cycles through a series of 'aeons.' He believes that he has found evidence supporting his theory that the universe infinitely cycles."
Before the Big Bang (Score:5, Informative)
Re:Old hat (Score:5, Informative)
Re:Old hat (Score:5, Informative)
Re:Old hat (Score:2, Informative)
Mm, but I meant detailed information as in "oh, there was a planet full of wonky aliens over there" or "there was another Earth in the previous universe!"
Consider that a black hole can be classically described by only 3 parameters: its mass, its charge and its angular momentum ... there ain't much detailed information there.
Been done (Score:3, Informative)
The Doctor already did it last season.
Re:New? (Score:3, Informative)
Basically. You're talking about the critical density of the universe. This is about 1, meaning that the universe is "flat" -- so it's infinite in extent and basically composed of a load of flat sheets rather than saddle shapes or spheres. So far as we can tell it's exactly 1. (It's pretty easy to tell, actually. We can look at the ripples in the universe back from when it was 370,000 years old, and then look at *those same ripples* from when the universe was about 10 billion years old. Those ripples have a particular wavelength, so from that we can tell how much the universe had to expand. It pins things down really quite nicely.)
Our problem comes from counting how much actual normal ("baryonic" though it includes more than just baryons) matter there is, by looking at everything that glows (and also by looking at the amount of hydrogen and helium, which was produced in the first few seconds of the universe's life; the ratio between the two is extremely sensitive to how much baryonic matter there was). It gives us a density parameter of about 0.05. Shit. So we then look at how much clumping matter we need, which would include "dark matter", whatever form that takes. We find that we need about a density parameter of 0.3 -- so 25% of the universe is dark matter.
Shit. We *still* only have 30% of the universe even accounting for dark matter.
So we're forced to add about 70% of the universe in something else. That can't clump and for other reasons it has to act as an "anti-gravity". That's called "dark energy".
Rather surprisingly, this model fits all the available data...
Re:if there are several Black Holes, why notBigBan (Score:3, Informative)
"the theorie of Black Holes gave the idea to the BigBang theory - they just applied time-reversal!."
No 'they' didn't. Black holes are based on inhomogeneous solutions to Einstein's equations -- the first being the Schwarzschild solution describing a spherical, uncharged body embedded in flat spacetime, with Reisser-Nordstrom, Kerr and Kerr-Newman adding in electromagnetic fields, rotation and then both respectively.
Cosmology is based on Friedman-LeMaitre-Robertson-Walker solutions, which impose maximal symmetry on spatial surfaces of constant time. You might be interested to note that no black hole solution can be maximally-symmetric since only three surfaces are -- normal flat space, a (hyper)sphere and a (hyper)saddle.
There really isn't much connection. "Reversing" time on a black hole solution (which happen when you take, for example, a Schwarzschild solution and allow it to exist all the way to the centre of the system instead of cutting it off with a stellar surface partway down, which is what happens in the solar system) gives you a white hole.
Re:Old hat (Score:5, Informative)
Milliseconds, not minutes, but yeah. At about t+4ms, the strong forces came into existence. Before that, the math completely falls apart, and we have no idea what was happening. We don't even know if time itself was constant, and as we percieve it those first 4ms could have taken a billion years or more.
This isn't, by any stretch, a new idea, though. It's very similar to the Hindu/Buddhist cosmologies, which have been around for thousands of years. Sure, the hindus do use the notion of Brahma and the Manus to explain the passing of cycles, but both faiths teach that the universe goes through an infinite cycle of expansion, stability, and collapse, and that time goes off into infinite in either direction from here. This scientist's "new idea"? It's been around for at least 5,000 years.
About the author... (Score:3, Informative)
Re:Pretty old theory (Score:5, Informative)
More people are alive today than all humans who have ever died.
That's an urban myth (how you defend it with flawed math probably nicely demonstrates our propensity to attaching to ourselves undue importance). 100+ billion homo sapiens dead already:
http://www.sciam.com/article.cfm?id=fact-or-fiction-living-outnumber-dead [sciam.com]
http://www.prb.org/pdf/PT_novdec02.pdf [prb.org]
http://www.prb.org/Articles/2002/HowManyPeopleHaveEverLivedonEarth.aspx [prb.org]
Re:Old hat (Score:5, Informative)
I saw Penrose speak on this topic at the Perimeter Institute about two years ago. He has been working on this for quite a while.
You captured the essence of his hypothesis. The idea is that in the latter stages of a universe, you eventually get two supermassive black holes orbiting each other - each containing half of the matter in the universe. As they rotate around each other, they're effectively ripping each other apart from the massive gravity wells. His theory is that the point at which they finally coalesce after billions of years of orbit, space and time "reset", and in that same instant the big bang takes place.
His premise is that not all of the energy has been completely contained within the singularity. When the big bang happens, the outlying energy causes rings in the background radiation.
Funny thing was, two days before his talk he got the first results back from the radiation survey. They didn't find rings, they found ovals. And in his words "we have no idea what that means".
It's great to see that he's making progress.
References (Score:1, Informative)
arXiv article by Penrose:
http://arxiv.org/abs/1011.3706 [arxiv.org]
Comment from Lee Smolin in a Nature review of coming Penrose book on the topic:
No living physicist has yet made a discovery as great as those of Isaac Newton or Albert Einstein, but Roger Penrose is in a better position to do so than most.
Further sample of Smolin's review in Nature:
We should pay attention because Penrose has repeatedly been far ahead of his time. The most influential person to develop the general theory of relativity since Einstein, Penrose established the generalized behaviour of space-time geometry, pushing that theory beyond special cases. Our current understanding of black holes, singularities and gravitational radiation is built with his tools.
His work in the 1960s on quantum gravity has borne dramatic fruit within the past five years. Penrose introduced two influential concepts: spin networks, which in 1988 seeded an approach called loop quantum gravity; and twistor theory, a recasting of space-time geometry that has generated a recent breakthrough in our understanding of gauge theories, the basic ingredients of the standard model of particle physics.
Penrose pulls one more trick out of his hat: the insight that physics in both the early and late regimes is insensitive to scale. Briefly, this is because massless particles move at the speed of light, at which point time stands still for them. Because there is no clock ticking, there is no reference against which they can measure a scale of length or time.
So if the only difference between the very early and late Universe is scale, and physics in both of these extremes is insensitive to changes of scale, then it is possible that our early Universe is the late Universe of a previous era. This is Penrose's big idea: deliciously absurd, but just possibly true. Moreover, it doesn't matter if such a transition took an eternity — photons are insensitive to the passage of time.
Penrose's concept joins several other proposals, such as loop quantum cosmology, that replace the Big Bang singularity and allow time to run before the Big Bang occurred, suggesting our Universe is the progeny of a previous one. Other ingenious mechanisms for making the history of the Universe cyclic — so that it repeatedly swells and contracts — have been proposed by physicists Paul Steinhardt and Neil Turok and their colleagues. But these exotic proposals involve theories of quantum gravity, which Penrose has no need for in his hypothesis.