Friedmann's Three Assumptions For The Evolution Of The Universe

May be it is misleading to claim that "all this" will end one day, so I would rather ask "how this universe will look like after a VERY long time". For purpose I do not mention any exact time, just an abstract "very long time". Shortly said, I would like to understand what our universe will look like after billions of years, hundreds of billions of years or even more (after a VERY long time).

Few years ago my wife gave me Stephen Hawking's book "A Brief History of Time" as a present. It is a very interesting science book, and I completed in a couple of days. In the book Hawking discusses about the three possibilities of the evolution of our universe. That is an interesting chapter to which I would like to refer in this post.

When we talk about the evolution of the universe, we should consider the various models developed. Hawking does not discuss about all the models, instead he refers to Friedmann's model. Alexandr Friedmann was a Russian mathematician who developed so called "Friedmann's model of the evolution of universe". Friedmann claimed that the universe either expands, contracts or is even. There are other models as well, such as "big bang model", but let's focus into the Friedmann's model.

Friedmann's first assumption for the evolution of the universe is that it continues expanding so slowly that finally the gravitational forces of galaxies will stop the expansion. Soon after that the universe starts to contract until all the matter is again "together" (the big crash). The universe is not infinite but it has no edge. This assumption makes me thinking "is this the first time the universe acts like this or is this a repeating process"? As we all know, it is quite difficult to answer..

Friedmann's second assumption says that the universe continues expanding so fast that the gravitational forces of the galaxies cannot stop the expansion. This means the universe continues expanding to infinity, forever. People tend to think "heyyy, some day it must end. The MUST be a start and the end for everything". Well, as amazing as it is, some researchers claim that there is no "start" neither "end". There is no time out there. Without time "start" and "end" has no meaning. This really makes me confused..

Friedmann's third assumption says that the universe continues expanding exactly with a speed that can hardly stop the expansion. The result is that the universe stays "stopped forever". This one is really grazy. I just cannot imagine what it means to "stop forever".

Hawking's book is great and I recommend buying it (I will post a whole book review later on). It really makes you thinking about the universe. It is really a fascinating book. The three assumptions of Friedmann are interesting. It is really interesting to think about the evolution of the universe.

Marko Pyhajarvi is an amateur astronomer and enthusiastic blogger from Finland. He is interested in skywatching and astronomy discussions. His biggest interest within astronomy is in deep space and especially in nebulae and galaxies. For more articles from Marko Pyhajarvi, please visit his astronomy blog http://homeboyastronomy.com