The Universe — in 500 words! (Article 71)
There is one thing everyone knows about the Universe: it is big, so big that our earth based measurements of distance and time cannot cope with its unimaginable size. For example, the distance to the Sun, our near neighbour in space, is 150,000,000 kilometres. Figures like that are pretty meaningless in our workaday world, so astronomers call this distance 1 astronomical unit (AU). This works fine out to Pluto, which is about 40 AU from the Sun, or 40 times the Earth — Sun distance. After that, it is a big jump to the nearest star, Alpha Centauri: 277,600 AU away. As you see the numbers are again getting out of hand, which brings us to the standard unit of measurement from here to the far end of the universe: the Light Year. This system of measurement takes the distance travelled by a beam of light in a vacuum in one year as one unit of distance. When you realise light travels 300,000 kilometres per second, the distance it covers in one year is difficult to imagine! Yet, the latest galaxies to be discovered at the edge of the observable universe are calculated to be nearly eleven billion light years away! The universe extends far beyond that to at least 13.7 billion light years! We cannot yet see beyond this remote part of the universe, because the light from there hasn’t yet reached us across the vastness of space. A big place indeed…
And it is getting bigger! In 1929, Edwin Hubble discovered that faraway galaxies were retreating outwards, and the further away they were from us the faster they retreated. Scientists now see the universe as a kind of vast balloon, expanding in all directions. More recent evidence suggests this expansion is accelerating. This theory, if true, forces acceptance of two startling consequences: that the universe has an outer edge and that it must have had a beginning. In other words, the universe began in an explosion of unimaginable force that is not yet finished! This latest theory of the universe’s origin is now widely accepted by experts worldwide and is known, appropriately, as the ‘Big Bang’. The experts are now refining the theory to try to explain some of the mysteries of the universe, such as what the universe was like in the first moments of its existence. It is thought that at one very early point in its existence, the whole universe was contained in a space the same size as this article you’re now reading. Not only that, a little earlier still, the universe was less than the size of the full stop at the end of this sentence. Very weird, but true, according to the latest research. So perhaps squeezing the universe into a 500 word article is not such a difficult feat after all! Next club meeting is on 7th February when Dave Lillis will give a talk on observing the Moon.
03-02-2007 The Universe – in 500 words! (Article 71)
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