Is There Anything Outside The Universe?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

14 August 2005

After speculating on what was there before the beginning and what will be there after the end of the universe, a reader has posed another related question: “What exists outside the universe?”

The quick answer is nothing. The reason lays in the definition of the term universe. It means everything – planets, moons, stars, etc, and whatever other things that may exist and we don’t know about yet! Any new object discovered, wherever it is found, is still part of the universe. Therefore, the question of “outside the universe” should never arise.

Now that brings another question – is the universe, therefore, infinite in size? There is still no agreement on that. However, it is generally accepted that the observable universe is limited by its age. This is how:

For us to see anything, light must travel from the object to our eyes or telescopes. It takes time from the instant the light is emitted to the moment it reaches us. Therefore, if the universe is was one year old, we would not be able to see anything located more than about 9,500 billion kilometres. This is the distance that light travels in one year, so anything outside that would no be seen because its light will not have had enough time to reach us.

It is estimated that the universe is 13.7 billion years old. Therefore the limit of the observable universe is 13.7billion multiplied by 9.5 trillion kilometres = 130,000 billion-billion kilometres. This is simplified to 13.7 billion light years.

If there is anything outside that limit, then we shall never know unless we discover a new entity to use for observation that travels faster than light (and electromagnetic waves). On the other hand if something is found outside the limit, then it shall mean that the universe is older than previously thought. Currently, the most distant object known is some 13 billion light years away.

But there is another limitation: the universe is known to be expanding. That is, galaxies of stars are not stationary; they are flying away from each other. Moreover, the farther away the galaxy is, the faster it moves. Since the speed of light is the fastest that can be reached by anything, the question then arises, how far would a galaxy be if it were moving at the this speed?

The answer is about 14 billion light years. For a galaxy to exist farther than this, it would have to be flying away faster than light. But that is impossible! Nothing can travel faster than light, therefore none of the things that we know can exist outside this limit.

One must not confuse the universe with the observable universe. The former includes everything (known and unknown) while the latter is limited to what we can possibly observe (whether we have found it or not). These two are, of course, also different from the known universe. That is, every thing that we can see using the most powerful telescopes available,