Cosmological Limits

by Abigail Barnhart

April 5, 1999

Limits of Comprehension

Finite speed of light

Entire space

Observable universe





Our universe

Chaotic inflation

One or many

Entire universe(s)



10-15 m


1 m






1026 m


When discussing the limits of cosmology, there are scientific limits, technological limits, perceptual limits, and limits of knowledge. Some limits we think of may only be perceived. The limitation science has is due to the limits of our knowledge and resources. We use new knowledge to expand our current knowledge even further, but in order to find this knowledge we devise instruments. The microscope allows us to view the subatomic world, and the telescope gives us a view of the observable universe (as demonstrated by the table above). We, as the human race are in the middle of this continuum. In order to observe the subatomic structures, it is necessary to have an immense amount of energy. This brings more limits into play; our lack of energy, as well as economical and technological limits. We do not have the ability, as of yet, to pool our resources together to answer these questions.

With the theory that there is a finite speed of light arose more questions about the limits of our cosmological research. As we look farther away, beyond a certain distance no light can have reached us yet. The universe is approximately 15 billion years old, and therefore light from distances larger than 15 billion light years did not have enough time to travel to us yet. Since this is true, we will never see beyond a distance equivalent to the age of the universe. So we will never know what is beyond the boundary of the "observable universe". Hence, we will never see the edge of the entire universe and know the limits it offers.

The theory of inflation proposes more questions. The theory of inflation argues that the universe started with a large explosion that propelled everything quickly, and then the motion started to slow down. There is no quantitative theory in this, and it needs more testing to answer the questions it provokes. If this did occur, inflation would have acted like an anti-gravity force to increase the initial momentum. If this theory is true, then we could not define our universe and make inferences about others. Under the theory of inflation, if we asked the question of whether or not we had an open universe, it would be impossible to answer. If inflation is true, then our method of counting galaxies would not be a valid method, for the whole geometry of the universe would be different.

Chaotic systems seem to be unpredictable at their higher levels, but predictable in the lower levels. If we, as humans, are on the lower levels, we may say that we are predictable through biology. We know what we are made up of and how we work, for the most part. On the other hand, our universe in its entirety is unpredictable. Chaos states that small fluctuations in the universe can affect the whole universe or some distant part in some way. This means that our universe is an interactive system, and we may never be able to explain it.

At this point in the discussion, we started talking about principal limits of knowledge. The scientists' knowledge about the universe being flat was questioned. It was concluded that before this century scientists 'made rules' to make this theory possible. They did not know before this century that the universe was actually flat, they simply assumed it was due to the physical laws they had come up with. Now, at this point, we still can not be sure the universe is flat because we can not see into the future. Our knowledge is limited now to give these questions definite answers. We assume that there was enough matter to slow gravity, but how much is there, we won't know because we can not see our entire universe, only the observable universe. Also, we will never have the knowledge to have the precision to figure out where the universe came from.

We may never know everything about our universe and ourselves. We will never get the proof we need because we will never look beyond the boundary of the observable universe or see it from outside. We have no way of knowing where our universe fits anywhere. We may never answer the questions about the universe because we have these limits. We are looking for deterministic knowledge from a reductionistic view. Yet, how do we know that these are limits and if they will ever change enough so that we are able to answer them. There are too many variables in the equation to have an answer now. Too many things change in an unpredictable manner for us to ever have the answers. We all interact in different manners, and some day it may all click and we'll have all the answers, but we can not know that.