What if God dropped you at a random spot in the universe?
The Sunday Nation
Nairobi,
13 April 2014
After last week’s illustration of the size of the Solar System, the next obvious question is how big the universe is; not just its size but more how we can appreciate its vastness. To tackle that, let’s get some basics out of the way.
We live on Earth, which revolves around the Sun together with another seven planets and thousands (if not millions) of other bodies to make what is known as the Solar System. The sun is located in the Milky Way galaxy – together with another 200 billion stars.
There are about 200 billion to 500 billion galaxies in the universe; most of them smaller than our Milky Way. In short, the universe is vast.
So vast that distances cannot be conveniently expressed in kilometres: they are quoted light-years (Ly). This is simply how far a beam of light travelling at one billion km/h would cover in one year.
One light year comes to about 10 trillion kilometres! The nearest star to the sun is about 4.25Ly or 42.5 trillion km. Mind blowing, isn’t it?
Now, to date, the most distant “object” ever observed by astronomers is about 13 billion Ly. It is a galaxy containing a few hundred million stars. Discovered in 2011, this galaxy is believed to lie at the outermost fringes of the observable universe.
One point that rarely appreciated is that universe is quite sparsely populated. Planets, for example, are thousands of kilometres in diameter but millions and billions of kilometres apart – Venus, our nearest neighbour is 42 million km away at its closest. The orbits of Jupiter and Uranus are more than 2 billion km apart.
Therefore, if God was to throw you into the universe with His eyes closed, chances are that you would end up in empty space; but what kind of place would that be?
The 300 billion or so galaxies in the universe exist in a spherical space measuring about 13bn light years in radius. Of course, that is assuming that our galaxy (the Milky Way) is at the centre of the universe, which may or may not be the case!
Nevertheless, the volume of this universal sphere is about 10,000 billion-billion-billion cubic Ly. Therefore the average volume of space around a galaxy is about 30 billion-billion Ly. This we get by dividing the volume of the universe by the number of galaxies.
The cube-root of this average volume gives the average distance between galaxies. This comes to about 3 million light years. So what does that mean?
If God dropped you into the universe at random you’d end up about 3 million light years away from any galaxy. Chances are that from there, you’d be too far away to see anything… It would be pitch-dark all around with not a single star in view. Isn’t it surprising then that our planet is only 150 million kilometres from a star; and the night sky is full of stars? Not a random place when you think about it.
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