I have recently turned my reading from the earth-bound subject of natural evolution to the rather wider topic of astrophysics. Of course, I'm still reading popular science books rather than weighty tomes on the subject but there's still something spine-tingling about the sheer size of the universe and the fact that we are so insignificant in that.
It was presumed for a long time that the Earth was the centre of the solar system, and even once the Earth going around the Sun was understood, it was still supposed that the solar system was the centre of the Universe. The book I have recently read ("Death By Black Hole" - a great title, and only a mediocre book, mostly, unfortunately) talked about the argument for this being that there are the same number of visible stars in each direction and how this argument is akin to getting lost in a dense forest and proclaiming that you must be in the middle because you see the same number of trees all around you but I think he missed a larger point - one in fact he didn't touch on at all in the book, surprisingly.
Nothing in the Universe travels faster than the speed of light. Well, let's say that if things do travel faster than the speed of light then a flip-side version of the special theory of relativity means that we can never slow them down to slower than the speed of light to interact with them, so let's ignore them. The important thing is that light doesn't travel faster than the speed of light - and neither do radio waves, microwaves or gamma rays. So, if we suppose that the universe is around 14 billion years old then things in the universe only started to send out radiation of whatever form around 14 billion years ago (probably slightly less, as for the first little while, the universe didn't have lumpy things such as stars in it) so if there is anything in the universe more than 14 billion light years away from us, then the radiation from that something won't have reached us yet so we can't see it.
Now I hear you saying that even if something travelled away from the dust cloud which would become the Earth for 14 billion years at the speed of light, it would only be 14 billion light years away, so how can anything possibly be more than 14 billion years away. That assumption would be true if the universe was made of a space-time which was like the x/y graphs we used to draw at school - but it probably isn't. So for the moment, I'm happy to accept that something can get more than 14 billion light years away from us in a particular direction without having to travel at faster than the speed of light.
But the problem with this book wasn't so much that (or that fact that the author devoted an entire chapter to explain why the USA was the best nation for "discovering scientific things" in the 20th century - yes really!) but that I found the whole thing thoroughly disheartening.
Deep down, I know that the universe is just a very large collection of swirling particles and the fact that some of those particles have been joined together in the hearts of stars to form atoms and that the Earth is just a collection of those atoms which happened to have met each other along the way and stuck together for the time being. Life on Earth is indeed a wonderful thing, and it's easy to get carried away in the romance of imagining that if evolution can do this much in a couple of hundred million years, imagine what the life of the future will look like. But if there is life evolved from Earth's current flora and fauna in a few billion years time - chances are it won't be on Earth.
There are a few things over the next few billion years which are pretty much certain to wipe out life on Earth as we know it - both those creatures who rely on the Sun's energy to survive and the extremophiles, recently discovered in all manner of places living off the energy from bubbling volcanic activity deep under the sea. In around 5 billion years time, all of the hydrogen in the Sun will have been turned into helium. Game over for that particular reaction. With the energy gone, the Sun won't have enough oomph (a technical term) to start turning that helium into heavier elements and so the core of the sun will start to shrink under gravitational pressure. In doing so, it's going to heat up (eventually to the point where the helium can start fusing together to form interesting elements - including the magical carbon!) but that heating up is going to cause the gaseous layers of the sun to expand beyond the orbit of the Earth - the Earth isn't going to boil, it's going to vaporise.
And if that wasn't enough, the galaxy andromeda is heading towards the Milky Way at quite a rate. In a few billion years, the two are going to come together. Now even though a galaxy contains a few billion stars, there's very little chance of two of those stars actually hitting each other - but there is a good chance that one of them will come close enough to the solar system to compete with the Sun in terms of pulling power - ie. gravity - to play a rather impressive game of billiards with the planets and their moons.
All of this plays out in cosmological time, which makes geological time look rather short and makes the lifespan of species and life on Earth look even shorter. It is rather disheartening to think that life of Earth is but a mere flash in the cosmic pan. A brief flicker of life in an otherwise dead Universe. Of course, I am not geocentric enough in my thinking to believe that I'm a product of the only flicker there's been.
But even more disheartening is that within the flicker of life on Earth, the time during which we've been doing things which life from flickers of life elsewhere in the Universe is even smaller - around a hundred years, maybe slightly more. So there is a sphere of around one hundred light years across with the Earth at its centre within which it's possible - with the right equipment pointed in the right direction - that intelligent life could pick up the fact that we exist.
But the time during which we've been able to listen to the skies is even smaller than the time during which we've been sending radiation out into space.
It's reasonable to assume that the same is true of other flickers of life. Whilst they may well be ahead of us in terms of their intelligence and their technology, it's likely that it also took millions of years from the first spark of life to civilisation generating radio waves and sending them out into space.
It's also reasonable to assume that life dies out on planets. I don't think life on Earth will be here forever - and not just for the long-term reasons mentioned above - nor for the more immediate concerns of global warming. So chances are, if SETI ever does pick up a non-random signal from outer space, the beings who sent it are long dead and buried - who knows, we may even pick up a distress signal from a civilisation on its last sparks as the flicker of life dies away on that planet.
Of course, when talking about life on other planets, you can't ignore a few places in this solar system where there may be life lurking. We can be sure of a few things, though. Firstly, I'm pretty convinced that - despite the imagination of sci-fi writers - life from anywhere else in the solar system (and indeed the Universe) will be carbon-based and will be largely made up of carbon, hydrogen, oxygen and nitrogen atoms. I suspect that they will have internal processes and structures which rely on susbstances similar to amino acids and the proteins they form. I'm even sure that on any planet where life has come further than single-celled organisms, natural selection will have been played out similarly to how it has been played out on Earth.
By similar - I don't mean, of course, that the same species will have evolved. But I do suggest that a similar process will have taken place. If the nearest star to the planet happens have a peak of radiation somewhere other than in the visible light range, then I would expect life to have evolved some way to navigate using microwave detectors or even radio wave detectors instead of eyes as we know them. I would also expect life on another planet to be roughly the same size as life on Earth. I don't think we'll find any beings the size of a solar system nor any beings smaller than a bacterium.
It's all fascinating, and I could blindly speculate for hours about the life that undoubtedly exists somewhere else in the Universe and the life that quite possibly used to exist elsewhere in our solar system on Mars, Venus, Titan or Europa but what is sad for me is that the wonder of the Universe happens so slowly - on such large scales of time - that we only see a very small portion of it.
It is like being taken to see the most marvellous play ever written but being told that you can only listen to one of the greatest actors of the day utter a single syllable somewhere just before the interval. If you're lucky, you'll be handed a partial copy of the script and be able to read what fireworks would've taken place had you been around a little longer. Sad indeed.
But not as sad as the thought that the whole thing is being played to a - statistically speaking - completely empty theatre.