Star-Craving Mad by Fred Watson

Author:Fred Watson
Language: eng
Format: epub
Tags: SCI000000, SCI004000
ISBN: 9781743433720
Publisher: Allen & Unwin
Published: 2013-01-15T16:00:00+00:00

7

HOME

TRUTHS

Digging up the ruins of our Galaxy

Home is where the heart is. So goes the old saying, and I guess it’s still true, even in this age of unprecedented mobility. But, before you decide that this is a chapter for the stay-at-homes, have a think about this. How many of the old sages who delighted in trotting out such gems as ‘Home is where the heart is’ ever stopped to think about exactly what they meant by ‘home’?

Well, it’s where you live, of course.

Yes, but doesn’t that depend on your viewpoint? For example, if you were a stray bacterium, a valiant survivor of NASA’s pre-launch sterilisation stowed away aboard the New Horizons spacecraft en route to Pluto, wouldn’t home be the Earth? From the perspective of an interplanetary traveller, for whom distance is measured in millions (or billions) of kilometres, home is definitely our planet rather than 22 Acacia Avenue or 7 Gasworks Lane. But, curiously, even this definition of home is a moveable feast. Once you start thinking about the stars, the scale changes again, and you’re into light-years. A light-year, as I’m sure you’ll remember, is the distance light travels in one year: 9.46 million million kilometres, as the crow flies. It’s a very long way. And I’ve noticed that scientists studying stars and gas clouds within a few hundred light-years of the Sun tend to think of home as the Solar System as a whole—not even our particular planet. It seems that, for astronomers, warm and fuzzy thoughts of home can equally well be about their street, their planet, their Solar System or—taking things up a notch—their Galaxy.

Of all the definitions of home that we can imagine, the Milky Way Galaxy, in which our Solar System is embedded, must surely rank as the grandest. This gigantic agglomeration of a few hundred billion stars, plus copious helpings of gas and dust, and an embarrassing amount of something whose identity is still unknown—dark matter—represents the ultimate in terms of our home in space. And I guess the reason we identify with it so strongly is that beyond our Milky Way other galaxies are ten a penny, numbering perhaps 100 billion in the observable Universe—and who knows how many beyond our reach? It does make our Galaxy seem rather special.

So there you have it. Home is where the heart is, and home is the Milky Way Galaxy, splendid in its spiral structure and replete with stars. In that respect, we’re all stay-at-homes, since there is no possibility with current technology of any of us ever leaving our Galaxy. But it doesn’t mean we’re not travellers. The Earth is moving through space as it orbits the Sun at a speed of 30 kilometres per second. And, if that’s not enough travelling for you, the entire Solar System is whizzing around the centre of our Galaxy at nearly ten times the Earth’s speed, taking about 200 million years to make a complete circuit. Now that’s travelling.

GALACTIC PORTRAIT

If home is the Milky Way

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