Cosmology is the study of the evolution of our Universe as a whole – from birth to death, or maybe birth to death to rebirth. Stellar objects and events, like nova and supernovae are in the cosmic scheme of things almost insignificant in comparison. It’s like comparing the life and times of an individual insect to the life and times of Planet Earth. Still, there might be a lot to be gleamed from comparing the life and death of our Universe to the life and death of the stars within that Universe.
A cyclic universe – one with birth, death, rebirth, death, rebirth, death, etc. is a far more philosophically satisfying universe than a one-off born, live, and fade-away universe, which is what our Universe appears to be. A cyclic universe is probably more pleasing because such a concept more closely mirrors nearly all local reality – the cyclic four seasons endlessly repeating; day-night-day-night; New Moon – Full Moon – New Moon – Full Moon; evaporation – rainfall – evaporation – rainfall; the carbon cycle; the nitrogen cycle; you name it, it recycles. Okay, maybe you don’t. You maybe are like our Universe – born, live yet doomed to fade-away. But the broader human species continues to recycle – birth, death, birth, death, etc. The names and the faces change, but the human cycle continues. Actually all of your stuff will recycle too. Part of you today might be part of a cockroach 100 years down the track! That aside, the Big Question is how can you generate a cyclic universe, one which eventually goes from initial Big Bang expansion to one which contracts into a Big Crunch then rebounds again? How do you generate that from a Big Bang universe that’s apparently doomed to keep expanding, ever expanding, forever, and ever, amen?
The standard model of cosmology suggests that our Universe had a one-off moment of creation (the Big Bang) and will over trillions of years surrender to entropy (the evolution of a state of order to ultimate disorder) and die an eventual “heat death” (where the temperature – heat energy, the ultimate end product of all other forms of energy conversion – is exactly uniform throughout). So we go from Once Upon A Time/In the Beginning through to Cosmic Evolution through to The End. But that’s the narrow view. What if there were many universes, and they could interact? Then there might not be an overall Once Upon A Time/In the Beginning and ultimately The End. The parallel analogy with supernovae explains all.
THE STORY OF THE SUPERNOVAE: We’ve all heard of supernovae, and while quite rare, there has been one visible to the naked eye recently that occurred in the Large Magellanic Cloud (SN 1987A), a nearby companion mini-galaxy to our own visible from the Southern Hemisphere. It was first witnessed on Planet Earth after the light flash travelled thousands upon thousands of years, traversing intergalactic and interstellar space, to arrive locally on the 23rd of February 1987. It was the first visible naked eye supernovae event since 1604 – rare indeed.
Their cosmic story and cosmic significance is fairly straight forward. Stars form out of interstellar gas, dust and perhaps larger debris. This mix of stuff slowly but surely contracts, all under the mutual attraction of their individual gravities that eventually brings it all together in a lump sum – if massive enough an embryo star forms. The intense pressures heat up the interior, and if the embryo star is indeed massive enough, the heat and pressure will be enough to cause the gas, etc. to start to fuse, usually starting with hydrogen fusing to helium and releasing [solar] energy in that conversion – nuclear fusion is what powers the stars.
Now interstellar gas and dust clouds are not all uniform in size. So, some stars fire up with the bare minimum of stuff, other stars fire up with a lot of stuff in their core bellies, but not too much. These are sort-of like Goldilocks stars; stars like our Sun. A few stars formed from such a thick region of gas and dust that they were ‘born’ obese.
How massive newborn stars are will determine their lifespan and their fate. The relationship tends to be that the thinner you are at birth, the longer you’ll live. Very skinny stars are very frugal with their fuel. These misers have stellar life-spans perhaps measured in roughly a trillion or so years. When their fuel finally runs out, they just slowly, ever so slowly, fade away into a white dwarf then finally as a dark and cold black dwarf cinder. Average stars, like our Sun, are less thrifty, but even so manage a lifespan of roughly ten billion years. Average stars will go through a more complex evolution, but ultimately they too will settle down to a long retirement, cooling, ever cooling when the fuel is exhausted. They too will go out not with a bang but with a whimper.
However, some stars are born just plain fat! Some stars can also put on weight after-the-fact by stealing mass from a nearby companion star via their stronger gravity and close proximity. However the star gets fat, fat in a stellar sense (lots and lots of mass), the more massive a star is, the greater the temperatures and pressures in that star’s core, and the faster nuclear fusion reactions go. Really massive stars live life in the fast lane; they live fast; they die young. And they don’t go out with a whimper, but with a bang – sometimes endlessly hiccuping or burping or vomiting – novas; sometimes imploding due to massive gravity when their core fuel gets close to empty (leaving a bit of a void) which causes a massive rebound and a super-ultra-violent explosion called a supernovae. That really does spew their stellar guts back into the interstellar winds. While there are several different types of supernovae that have ultimately different origins, that’s of no concern in this context. The important bit is that stuff gets spewed back into space and eventually recycled.
Exploding stars, the novae but especially the supernovae return not only gas and dust and debris back to the interstellar medium, but enriched gas, dust and debris since the enormous temperatures and pressures cook up the heavier elements (elements more complex than helium), elements that are essential for life to ultimately grace the cosmos with its presence.
Gas and dust from one star’s ‘burp’ intersect with gas and dust from another star’s ‘hick-up’ and maybe intermingle with the ‘spewing vomit’ from a supernovae, all ultimately contracting again under mutual gravity to form a second, even third generation star and stellar planetary system. Our Sun is at least a third generation star and is made up of former spewed stuff, some of which is now heavier than just hydrogen and helium; ditto the Sun’s family of planets, including Planet Earth. If it weren’t for supernovae, we wouldn’t be here. The late astronomer, Carl Sagan, said it best when he stated that we are indeed the end product of “star-stuff”.
So the basic cosmic cycle is stars form from interstellar gas and dust; stars live; some stars spew their guts of gas and dust back out into interstellar space, providing the raw materials for the next generation of stars. You get creation – destruction – creation – destruction, over and over again, albeit at different times in different places.
THE PARALLEL COSMOLOGY ANALOGY: So what the hell does the above have to do with cosmology? There’s lots of stars; only one Universe – or is that really the case?
One set of assumptions has to be made from the get-go. I postulate that the cosmos, all that is and ever will be, is infinite in both space and in time. This assumption is more philosophical than scientific. If you ever postulate a finite cosmos, a cosmos with a boundary, a fixed volume, you must, of necessity, deal with that maverick who asks, “Well, what exists beyond that boundary?” If you postulate a beginning and/or an end, that same maverick will annoy you with, “Well, what happened before that or after that?” It’s just easier to wrap your head around a cosmos that is infinite; a cosmos that had no beginning and will have no end. Unfortunate, the standard model of cosmology postulates a beginning, and a fade-away ending and a finite amount of stuff and space to stuff it into.
We all know the standard scientific spiel to the creation of our Universe – no, not the Biblical Book of Genesis, but the Big Bang event. Well, already we have a parallel analogy – supernovae are mini big bang events.
Now the Big Bang and other associated real time events like an additional oomph of an in the beginning “inflation” have resulted in our Universe expanding, ever expanding. There’s lots of observational evidence for the Big Bang and the expansion. So, lots of stuff has been vomited out into the cosmos from a unique point in time – 13.7 billion years ago. But if there was a finite Big Bang, then there must also have been a finite amount of space to stuff that vomit into. That violates my philosophical ideals of not only no boundary in time, but no bounds in space for our Universe to strut its stuff in.
Anyway, we have expansion of stuff spreading out through space. Well, that’s a parallel analogy with the spewing out of gas and dust via stars going nova and supernovae. Now commonsense might suggest that the original oomph of the Big Bang would eventually run out of puff as the one-way attraction of gravity would slow the expansion down, and down, and down and eventually cause the expansion to come to a grinding halt – then reverse, as gravity would cause everything to contract once again back into the configuration from which the Big Bang arose from. In other words, the expected fate of our Universe was to be born from a Big Bang, live and evolve, and die in a Big Crunch.
Alas, life isn’t that simple – Mother Nature is a baseball pitcher with a wicked curveball or knuckleball. Mother Nature’s a real Hall-of-Fame bitch. A bunch of astronomical party-poopers discovered that the expansion of the Universe isn’t slowing down; it bloody well accelerating! Thus, no Big Crunch is on the horizon in the far future, only a “Heat Death” as entropy ends up ruling the roost. So runs the standard spiel. So how are you going to eventually generate a second or third or one-hundredth generation universe out of that mess? But that’s the limited view. Let’s climb the cosmic mountain for the grander picture.
What comes now to the rescue is that there is more than one Big Bang (maxi nova or supernovae) universe; more than one expansion event, because, there’s more than one universe, more than just our Universe, within that infinite (in space and time) cosmos referred to above.
And so, while from our limited point of view there is our Universe, and thus we assume the one-and-only-Universe, in fact there is more – much, much more. If you have a lot of universes in the infinite cosmos, all of which started off with a supernovae-like Big Bang, then, sooner or later, the spew of one (or more) will intersect with the spew of another (or more).
Thus, a lot of expanding regions of individual universes will intersect, eventually. That intersect region will, under combined gravities, start to slow things down. That region will slowly, but surely, start to contract. That contraction will eventually collapse into a Big Crunch. It seems something cyclic has happened. Lots of Big Bangs have generated a Big Crunch – actually a lot of Big Crunches when you look at the total 3-D picture. Big Bang A’s expansion might intersect with Big Bang expansions B, C, and D in one direction, say left. Big Bang A’s expansion might intersect with Big Bang expansions E, F and G in the opposite direction. Big Bang A’s expansion might intersect with Big Bang expansions H, I, J and K in the up direction; Big Bang A’s expansion might intersect with the L, and M Big Bangs in the downward direction, and so on and so forth. The Big Crunches (resulting in the Mother of all Black Holes) will be symmetrical, turning inside out into newly vomiting Big Bangs, or White Holes.