These Ekpyrotic scenarios have already gone through a number of revisions as deficiencies in them have been exposed. In the most recent revision called the cyclic Ekpyrotic model, we are asked to envision two 3-dimensional membranes (sometimes these are called branes for short) existing in a 5-dimensional space. These 3-dimensional membranes which exist in this higher 5-dimensional state are supposed to be parallel to each other and to be in an eternal process of approaching one another and colliding and then receded from one another. Then they re-approach, collide, and recede from one another in an eternal cycle. That is why it is called a cyclic Ekpyrotic model. Each time the two membranes collide and spank together that causes one of the membranes to expand. That membrane is our universe. So with each collision, the expansion of our universe is renewed, keeps on going, thus the universe never had a beginning, never came to exist. Even though our 3-dimensional universe is expanding, this whole 5-dimensional setup is eternal and never had a beginning.
It hardly needs to be said that this is little different than science fiction. It is so speculative, its speculation builds upon speculation. There are all kinds of problems with it but some of these are so technical that I don’t think I will go into them. Let me just mention one of the problems. What this model really amounts to is our old friend the oscillating model writ large in 5-dimensions. As such it faces the same problem that the oscillating model did; namely, it is impossible for the universe to go through a singularity from a contraction and come back to a new bounce. Rather, the universe would just end at the end of one of the cycles. So this model has not been able to deliver on its promises to explain the large scale structure of the observable universe. In light of all of these problems, Andrei Linde has recently complained that while this cyclic Ekpyrotic scenario is very popular among journalists, it has remained “unpopular among scientists.”
But let’s not get into all those technical difficulties. I think the more important point is this: It turns out that just like the chaotic inflationary model that we discussed last time, the cyclic Ekpyrotic universe cannot be eternal in the past. In September of 2001, Borde and Vilenkin in cooperation of Alan Guth (the father of inflationary cosmology) were able to generalize their earlier results which show that inflationary models cannot be eternal in the past. They were able to extend these conclusions to other models of the universe. Specifically they said “our argument can be straight forwardly extended to cosmology in higher dimensions, specifically brane cosmology.” So according to Vilenkin, “It follows from our theorem that the cyclic universe is past incomplete” – that is to say, it goes back to an initial singularity. The need for the initial singularity has not been eliminated. Therefore, even despite its other problems, if those can be solved the cycle Ekpyrotic scenario cannot be past eternal.
That brings us right up to the current edge of cosmological speculation today. As I said last time, the history of 20th century cosmology has in a sense been a history of the failure of one theory after another to avert the beginning of the universe predicted by the standard Big Bang model. So when people say to you, “You can’t trust this scientific evidence, it comes and goes,” that is a half truth.[11] What comes and goes are all of these theoretical attempts to try to avoid the beginning of the universe predicted by the standard model, but the standard model first proposed back in 1920s by Friedman and Lemaitre continues to survive. So it has been one confirmation after another of the prediction of the standard model that the universe began to exist. Laypeople who think the results of contemporary cosmology are fleeting and uncertain have mistaken the enduring stability of the standard model for the transitory and fleeting quality of all of these challenges to the standard model that have been proposed over the decades.
Science is always provisional, and therefore the evidence is always tentative and our conclusions are tentative. Nevertheless, I think it is hard to deny that the best evidence does stubbornly continue to indicate that the universe began to exist.
Read more:
reasonablefaith.org/defenders-1-podcast/transcript/s05-05#ixzz47ukbEyum
