Theories of the Universe: The Accelerating Universe

The Accelerating Universe

We'll begin this section by picking up were we left off, completing our analysis of the big bang theory. Here you'll get a chance to see the two or three significant obstacles that prevent complete acceptance of it. Be that as it may, since it is the most popular theory right now, we'll also look at the consequences of how the universe will end, if the big bang theory is the correct one. It's not a happy picture and raises a number of philosophical questions about the meaning of human existence. But again, the view of how the cosmos will eventually end is a projection of a theory, not the way it will necessarily end.

Within the context of this section, we'll also examine another theory that has been put forth over the last decade, the theory of plasma cosmology. It supplies answers to some of the questions that the big bang has problems dealing with. And after all of that, we'll look at the three possible fates of the universe and the geometrical shape that coincides with what cosmology knows about the structure of the cosmos at the beginning of the twenty-first century.

It's Bigger Than We Thought

There are two basic assumptions in conventional cosmology that new observations have posed problems for:

• The universe is, at the largest scale, smooth and homogeneous.
• This smooth universe is dominated by gravity alone and therefore must either contract to or expand from a single point, a singularity.

However, our universe is anything but smooth, it's clumpy. But what are these clumps? They turn out to be galaxies grouped together in vast supercluster complexes. These are huge ribbons of matter a billion light years long. And these clumps would not warp all of space or cause it to expand or contract. Each of these superclusters would just dimple the space around it.

The idea of homogeneity has always been a problem for the big bang because for decades astronomers have known that the universe is not smooth. The usual answer to account for this clumpiness has been that even though the universe started out smooth, there were very tiny clumps in its early period. And through gravitational attraction these clumps gradually grew bigger and bigger, forming the stars, galaxies, and clusters that we have today.

The only problem with this is that the bigger the clump, the more time it takes for it to form. The age of the universe has been determined to be between 15 and 20 billion years old. Cosmologists realized that it would have taken much longer for these superclusters to form, longer than 20 billion years. It works like this. By observing the redshift (we covered that in the last section) of galaxies, astronomers can calculate two things: how far away the galaxies are and how fast they are moving relative to one another. And as it turns out, galaxies very seldom move faster than 1,000 kilometers per second, or one three hundredth the speed of light.

What this means is that in the 20 billion years since the big bang, a galaxy could have only moved about 65 million light years. Well, in order for these huge clusters to form, the matter contained in them would have moved at least 270 million light years, which would have taken at least 80 billion years, or four times as long as allowed by the big bang. But wait—there's more. Because the matter contained in these galaxies would first have to accelerate up to speed and the seed mass located in these regions of space would also have to form to attract matter these big distances, it would take at least 100 billion years for this all to happen. So the 20 billion years that the big bang estimates is far too short a period of time for the universe to have formed into the way it is right now.