Jul 19

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The Expanding Universe

The first person to discover that the universe is expanding was Edwin Hubble in the 1920s. This happened when scientists began to be able to measure the distance of far away galaxies. As they looked at the light coming from these galaxies, they saw that they were red-shifted. This means that the wavelengths of the light coming from them had been stretched to the red end of the spectrum, just as sound waves are stretched, giving the Doppler Effect when a train speeds past you. Therefore other galaxies are moving away from us and each other, and the whole universe is expanding. Gloria uses a lovely analogy, which I have asked her if I can borrow. Imagine the universe as a lump of dough with raisins in. As the dough rises, the raisins move apart. Easy.

There was so much going on in astronomy and cosmology (the study of the origin and nature of the universe) in the 1920s and 1930s. Everyone wanted to know how the universe was born and how it would die. Fred Hoyle was one of the chief exponents of the Steady State theory. He proposed that the universe had always been there and had always looked much the same. But this was then proved to be untrue when Hubble’s Big Bang theory came along. According to this theory, by winding back the clock, everything in the universe, space, matter, energy and time were all compressed into a single point, called a singularity, of infinite density, pressure and temperature. About 13.7 billion years ago, this point exploded, to create everything in our universe today. What was there before? Nothing?’before’ doesn’t exist, as there was no time before time came into existence. Mind boggling, I agree, but that doesn’t make it impossible.

Do we have any proof of this theory? The closest we can get to proof is that in 1967, two scientists measured a very small amount of microwave radiation which seemed to exist in whatever direction they looked. From the intense heat following the Big Bang, which since then has been gradually cooling, they were able to calculate that by now, it would have decreased to the exact amount of the radiation they had measured.

Cosmologists still can’t tell us what caused the singularity to explode and why then. Insights into quantum physics and the amazing antics of the smallest particles that exist, are presenting some possibilities. If you really want to go there, a book by Paul Davies called The Goldilocks Enigma sets out the latest thinking on these matters. However, it’s likely to leave you more baffled than before. The Uncertainty Principle, anti-matter, dark energy and String Theory are not for the likes of us ordinary mortals. If God caused it all to happen, then where did God come from?

However, we can still toy with the possibilities of how the universe may end, even if we can’t do the mathematics to prove it. It’s possible that it will go on expanding for ever. We can’t know this, as we can’t actually see the edges of the universe?if there are edges. It’s not just that our telescopes aren’t powerful enough. Obviously light from whatever we’re looking at can only travel at the speed of light, so if those farthest objects are moving away from us, we can never see past them. The speed of expansion has slowed down dramatically since the start, as the gravity produced by large bodies such as stars and planets counteracts the outwards movement. Maybe one day, it will stop and start to move back in on itself. Perhaps it will all end in a Big Crunch. Or perhaps eternity holds an endless cycle of Big Bangs and Big Crunches.

Or the weirdest idea of all?our universe may be one of many in a multiverse?a bubble or pocket universe, complete in itself, and totally unaware of all the others. Theories, pie-in-the-sky philosophy, or just plain rubbish, it’s all fascinating.

If you’d like to know more about all this, just type ‘origins of the universe’ in your browser and be ready for a fascinating read.

? Wendy Ogbourne


Wendy writes for Bonzer! magazine. Please visit www.bonzer.org.au

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