It is impossible to determine the shape of the universe?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

10 May 2009

If the world (or the earth) is round, then what is the shape of the universe? Now that’s a difficult question to answer, but it seems that the most sensible shape would be a (approximately) sphere.

However, before going that far out, let us take things one step at a time. Some people argue that, by strict definition, the planet Earth includes its moon. Thus, it is not accurate to state that the Earth is round. The area occupied by these bodies has the shape two plates placed “mouth-to-mouth” – it is not a sphere!

Now the Earth goes around the Sun but it is not alone in doing this: there are another eight planets (sorry, seven – after Pluto was declassified in 2006) in this so-called solar system.

The Sun is a large sphere measuring about 1.5 million kilometres in diameter. All the orbits of the planets lie on the same flat plane (approximately). The evidence for this fact is easy to see: Go outside on a clear night and look out for planets in the sky. (You will distinguish them from ordinary stars in that they don’t “twinkle”.)

You should see at least four this month if you stay out long enough. You will notice that they lie within a fairly narrow “line” running across the sky from East to West.

Now, since the rotation of the Earth is helping in scanning your view all the way around, the positions of the planets (as viewed from Earth) mean that they all lie on the same plane – approximately. Thus the shape of the solar system is a thin flat disc (a few million kilometres thick and a few billion kilometres wide) with a large dot at the centre.

The solar system is not the whole universe – not by a long shot! The Sun exists in a group of a few hundred billion other stars in what is known as the Milky Way Galaxy.

Observations with telescopes reveal that the Milky Way is also the shape of a thick disc with big blob at the centre. This disc is 100,000 light-years across (or one billion-billion kilometres).

Now, the Milky Way is not the only galaxy: there are many others, hundreds of billions of them! And they come in different shapes – spherical, ellipsoidal, etc. These galaxies make up the observable universe and they are arranged in clusters all over.

There is no one direction that seems to have more galaxies than the other thus it is reasonable to assume that, for now, the universe is approximately spherical in shape. Perhaps as more powerful telescopes are developed, a different shape might emerge.

Still, there is a philosophical angle to this discussion: when we talk about the shape of an object, we assume that it is possible to stand far enough to view it in full. Indeed, when we say the Milky Way is a disc, we mean the shape one would see if they were viewing it from another far-away galaxy.

Now, it is impossible to get outside the universe. The reason is that, by definition, wherever you go, you will still be in the universe since you are part of it. Thus it is impossible to answer the question of the shape of the universe!