The "Great Andromeda Nebula", which is no nebula at all but a galaxy like our own Milky Way, drifts across November nights. It is the most distant object we can see with the naked eye; more than two million light years away. That's very, very far away. So far away in fact, it takes its light more than two million years to reach us. And that is a long time ago. A very, very long time ago.
For those who aren't familiar with such things, a light year is the distance light travels in a year, which in itself is a little weird. The distance lights travels in a year? What's that? Who cares about that?
Astronomers care, and it's the sort of thing that can really set a person's mind to wandering. It's more than a measure of distance ... mind-bogglingly huge distance ... it's a flight of fancy; it's a bit of poetry; it's an F-sharp minor chord with an open E strummed on a guitar; it's a thing for reordering priorities; it gives one a sense of place in the cosmic pecking order. Or it's something you just don't care about it. In that case; tsk, tsk.
It seems a little peculiar perhaps, using what is essentially a unit of time, in this case a year, to describe how far away something is. How far away is that? Why, it's how far it takes light to travel in 365 days. What? Something kind of like Abbott and Costello in that kind of thinking.
So, how far does light travel in a year? Well, it travels at a nearly impossible to comprehend 186,000 miles per second. That's right; you turn on a light and it has traveled 186,000 miles in a single second. That means light travels 11,160,000 miles per minute! That's 669,600,000 miles per hour!!!
If we carry on with the math, we find that light travels nearly 6,000,000,000,000 miles in a year. I don't even know what that number is! And the "Great Andromeda Nebula" - that galaxy much like ours, filled with star systems and planets and comets and meteoric particles and who know knows how many types of life forms fighting how many pointless wars - is two million times 6,000,000,000,000 miles away from us, and when we look at it, we are seeing it as it appeared two million years ago. Wow. I need an aspirin.
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