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The Question

(Submitted January 14, 1998)

I have seen programs and read books about the Universe. Mainly they speak of it either being constant, never-ending or ever-expanding with the end of the universe happening when it finally collapses upon itself. Could the "Big Bang" be a continuous cycle of collapse and expansion, collapse and expansion....? It goes against everything in me to believe that one day it could end. I don't know how well I have stated my question, but I have always understood that matter is a constant. That paper can be burned and its composition changed, but the atoms are all still present only in a different form. I also understand that change is the only certainty in the universe as we know it, so an end does not seem possible. Has someone who has a respected opinion in this regard discussed it or disregarded this idea?

The Answer

I think this is a question that has occurred to many people contemplating the Big Bang. Historically, cosmologists have fallen into 2 fairly clear categories: those who are very reluctant to contemplate a 'one-shot' universe (we might call them recyclers), and those who are not. Right now there is a preponderance of evidence that the universe will not collapse, based on measurements of the rate of expansion and the mass density. I agree with you that this is somewhat less appealing than recycling. However, I also am interested in how science often challenges my preconceived ideas, and so I am personally interested in keeping my mind open on this subject. Die-hard recyclers will undoubtedly be able to suggest ways of bringing about collapse. You can read more about the Big Bang on our site, for example at:

I hope this helps,

Tim Kallman
for the Ask an Astrophysicist Team

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