The Universe is back in the news again, as it transpires that Big Bounce is the new Big Bang, at least according to Martin Bojowald, assistant professor of physics at Penn State. One of the main tenets of comsology these past few decades has been that this Universe is a single event phenomenon, the result of a vast and cataclysmic explosion from a tiny point of virtual nothingness around 13 -15 billion years ago.
Before that, it was popularly assumed that there was no time, no space, no matter, no life – absolutely nothing at all, anywhere – leaving us to wonder how an entire Universe, replete with galaxies, black holes, and at least one solar system capable of supporting life, was created out of what was effectively nothing. For his part, Martin Bojowald contends that there was a Universe before ours, and that we may be one result of that Universe undergoing something like a Big Crunch event, a process that might have spawned our own Universe. As we see…
Now, however, Bojowald and other physicists at Penn State are exploring territory unknown even to Einstein — the time before the Big Bang — using a mathematical time machine called Loop Quantum Gravity. This theory, which combines Einstein’s Theory of General Relativity with equations of quantum physics that did not exist in Einstein’s day, is the first mathematical description to systematically establish the existence of the Big Bounce and to deduce properties of the earlier universe from which our own may have sprung. For scientists, the Big Bounce opens a crack in the barrier that was the Big Bang.
My knowledge of quantum cosmology and theories of relativity in general, is patchier than the arm of a drinker in a British pub since the smoking ban kicked in, but I’m not sure it’s correct to say there are equations around today that did not exist in Einstein’s time – the equations existed, it’s just that no-one had discovered them. Back to the theory…
Scientists using this theory to trace our universe backward in time have found that its beginning point had a minimum volume that is not zero and a maximum energy that is not infinite. As a result of these limits, the theory’s equations continue to produce valid mathematical results past the point of the classical Big Bang, giving scientists a window into the time before the Big Bounce.
Quantum-gravity theory indicates that the fabric of space-time has an “atomic” geometry that is woven with one-dimensional quantum threads. This fabric tears violently under the extreme conditions dominated by quantum physics near the Big Bounce, causing gravity to become strongly repulsive so that, instead of vanishing into infinity as predicted by Einstein’s Theory of General Relativity, the universe rebounded in the Big Bounce that gave birth to our expanding universe. The theory reveals a contracting universe before the Big Bounce, with space-time geometry that otherwise was similar to that of our universe today.
Bojowald reached an additional conclusion after finding that at least one of the parameters of the previous universe did not survive its trip through the Big Bounce — that successive universes likely will not be perfect replicas of each other. He said, “the eternal recurrence of absolutely identical universes would seem to be prevented by the apparent existence of an intrinsic cosmic forgetfulness.”
I’m not sure from reading this how different from each other successive Universes might be, whether the same laws of physics would apply, or whether there would even be galaxies and other components we have thus far observed in this Universe, and there’s no mention here either of the origin, let alone the roles of dark energy and dark matter. These are two theoretical phenomena, which between them are said to comprise around 95% of the Universe; dark energy, which is believed to have suddenly appeared from an unknown origin around 9 billion years ago, is causing our Universe to expand at an accelerating rate in runaway mode, exactly the opposite of what should be happening – after the initial expansive stage of the Universe, it was previously predicted that gravity would eventually exert a stranglehold over the whole, causing the Universe to begin contracting until eventually collapsing to a single point wherein all energy and matter would be concentrated.
Loop Quantum Gravity would appear to be a function of such a collapse, with the possibility that this very collapse will be the birth pangs of another nascent Universe – but the fate of our Universe at present is estimated to be one where everything eventually ends up so far away from everything else, that stars and galaxies will no longer be able to form, black holes will have nothing to feed on and so dissipate, with the Universe eventually winding up as a vast cloud of irradiated dust – unless of course dark energy disappears as mysteriously as it appeared, and the Universe falls back in on itself.
We still have no confirmation that life exists elesewhere in our own Universe, although it seems highly likely that there is at least microbial life extant, for example on Mars; but complex life may be harder to track down. But the possibility of one or more Universes that have existed before ours does raise the possibility that other types of (intelligent) life, governed by entirely different laws of nature, could have existed billions of years ago, or will exist in future Universes, is one that remains intriguing, albeit one we’ll probably have no way of confirming one way or the other. As Bojowald explains, the ‘cosmic forgetfulness’ would seem to be a mechanism which wipes the slate clean at the incept of each new Universe, giving each one a new set of laws, types of evolution, and interpretations of life that we could barely imagine.
On the human scale it could be argued that none of this really matters – at present, we cannot access most of our own Universe, let alone those that might exist in the past or future – but it’s just possible that through advances in a wide range of science disciplines, humans may be able to live greatly longer lives, possibly even becoming in some sense immortal – the ageing process is stopped, disease is defeated and even planetary disasters and extinction events would cease to be factors, were we spread widely enough across the cosmos.
Michio Kaku envisages a situation whereby humans could live sufficiently long that the destruction or entropy of our current Universe, which in any event is already in the process of becoming cold and dark would give us sufficient cause to seek out other ‘warmer Universes’ , hopping through numerous such environments over the course of hundreds of billions of years – it would be interesting to see if by then there remained any vestige of ourselves that would be recognisable to us today. (TJ)
see also: Centauri Dreams – A Big Bounce After All?