David Spence asked:
If the Universe is comprised of 96% of dark matter/dark energy, do we have concrete proof the big bang actually created dark matter/dark energy?
Could it not be the case dark matter/dark energy already existed, and it was an interaction with an unknown particle and dark matter/dark energy which caused the big bang to occur?
If dark matter/dark energy is so dominant within the Universe, why should be hypothesize the big bang created dark matter/dark energy? We are basing this hypothesis on the 4% of matter we can see.
Chris Smith put this to professor Andrew Norton, astronomer from the Open University...
Andrew - Well, yeah. Dark energy, dark matter Ė these are names that we give to things that we really have no idea what they are. We see the evidence for it in the way that galaxies rotate, in the way that galaxies move through space. There must be some other matter there thatís controlling how things move through the effect of its gravity, but we have no idea what it is. Dark energy on the other hand, itís not anything to do with dark matter. It just happens to have a word in common. But that seems to be some stuff Ė again, we donít know what it is Ė that is causing the expansion of the universe to accelerate. Now, the simple answer of where they came from is to say, ďWell, if the universe began in a Big Bang about 14 billion years ago, the dark matter - whatever it is - and the dark energy - whatever it is - were created there along with time and space, and everything else.Ē Now, thatís an easy answer perhaps but itís not a very satisfactory one. There is another theory. Now, I'm not saying that everybody believes this by any means, but itís an intriguing theory. Itís called the ekpyrotic universe theory. I think itís from a Greek word meaning borne out of fire. So, weíre familiar with four dimensions. Three dimensions of space Ė up, down, left, right, backwards, forwards, and one dimension of time. Four dimensions weíre familiar with, thatís fine. In the ekpyrotic universe theory, the universe has 11 dimensions. Bear with me. Six of these dimensions are curled up too small. We can't see them. Letís forget those, but there's another dimension, a fifth dimension which is a dimension of space that we can't experience. The idea is our universe sits on what's called a brane. This is not a b-r-a-i-n, brain.
Chris - Laura was getting all excited then.
Andrew - Sorry, Laura no. this is a b-r-a-n-e, brane Ė a four dimensional brane.
Chris - Membrane.
Andrew - Membrane, yeah. We think of two dimensional membranes like the skin of a drum. Well, a four dimensional brane, our universe then in this theory sits on a four dimensional brane. And there's another four dimensional brane separated from us across this invisible fifth dimension, this hidden brane. What we think of as the Big Bang was not a creation of time and space. It was actually a big clap when these two branes last came together. And ever since then the two branes have been stretching apart and the tension between those branes is what we see today as dark energy. Also, the matter on that other brane on the hidden brane that is the dark matter thatís influencing our universe. And the idea is that these two branes stretch further and further apart. Eventually, sometime in the future, the two branes will spring together, make another big clap and the whole thing will start all over again.
Chris - Effectively then gravity can propagate between or the influences of gravity can propagate between these brains but other stuff can't. So we see the effects of gravity but not other stuff.
Andrew - Yeah. So the leakage of the gravity from this matter on the other brane maybe is what the dark matter is. Now I say, ekpyrotic universe theory, not everyone believes it by any means but I think itís a good fun theory.
Chris - I've learned a new word this evening already Ė ekpyrotic universe theory. David, does that assuage your hunger?
Dave - Well, I'm just wondering if this new theory, is this based on string theory?
Andrew - It is very closely linked to string theory. You're absolutely right, yeah. As you probably know the idea of string theory is again, tied up with these multidimensional objects, these branes. So itís an attempt in a way to link the cosmology to the string theory. Who knows? It could be right.
Every discussion of dark matter and dark energy that I have ever seen, presupposes the existence of space and time in which they occur. A key question is whether, prior to the big bang, space and time even existed. If they did not, then the existence of dark matter and dark energy also become doubtful. Atomic-S, Fri, 8th Apr 2016