Question: are we alone in the universe

Matt Bilton answered on 17 Nov 2014:

This is a quote from the Hitchikers Guide to the Galaxy:

“Space,” it says, “is big. Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space, listen…”

I think that the chances of there being some sort of life elsewhere in the universe, given the size of the universe…is pretty high. We know it is possible for life to arise at least once in the universe after all, because we are the proof.

If once – why not more times?

Much research into the beginnings of life is based on the repeating the sorts of conditions that may have been present on Earth, before life. Chemical reactions that can produce molecules important for life, like nucleic acids (that form RNA and DNA), amino acids (that form proteins) and fatty acids (that form fats – important for cell membranes) are not that hard to imagine happening elsewhere, maybe on a distant planet that looks like earth. And these sorts of molecules could very possibly lead to bacterial-type life on other planets in the universe.

But what about more complex life?

The ‘eukaryotic’ cells that make up our bodies actually contain an interesting organelle within them. In the distant distant past this organelle may very well have lived independently – as separate bacteria. These bacteria-like cells, within our cells, are called mitochondria.

Mitochondria are like little batteries that provide energy to our large and complex cells. And perhaps these batteries are what have allowed complex life to exist in the first place.

Almost all eukaryotic cells have these batteries – mitochondria – and they are much more complex than bacteria. All multi-celled organisms are made from eukaryotic cells.

So, maybe complex life requires two things. 1) the right chemistry to take place to make single cells, and 2) the chance event of the right cells meeting – so that one can become a battery for the other. Maybe this sort of chance event is less likely.

This idea was discussed by Nick Lane – a biochemist – in the book ‘Power, Sex, Suicide – Mitochondria and the Meaning of Life’. If you are interested in the origins of life, then I would recommend reading this book!

On the other hand, perhaps it is possible for complex life to arise in one or many other ways. It really is very hard to say. If anything is possible though, the universe is so large there is a very good possibly that somewhere it has happened!

To summarise, I don’t know whether we’re alone in the universe either. It seems very unlikely that there are no single celled organisms out there. Complex life though? Hard to say! But I like to think so :).