-
Asked by balaclava to Alan, Caspar, Diana, Murray, Sarah on 25 Mar 2011 in Categories: General.
Question: How likely is it that there are other life forms like us?
- Keywords:
-
Alan Winfield answered on 14 Mar 2011:
Very, very unlikely in my opinion.
However, I think it is likely that there is life elsewhere in the Universe. I think the vast number of galaxies, the vast number of stars in galaxies, and the number of stars that have planets – as astronomers are now discovering – means that the likelihood of life elsewhere in the Universe is high. However, I think that most of that life will probably be rather simple – perhaps the alien equivalent of single celled organisms. I’m sure that more complex forms of alien life – like multi-celled organisms on Earth – will have evolved elsewhere in the Universe. But the likelihood that they are like us is I think impossibly small.
If you are interested in finding out how likely intelligent life is you should look at Drake’s equation, which tries to work out the likely number of civilisations in our galaxy with which we might be able to communicate. Here’s the Wiki article:
http://en.wikipedia.org/wiki/Drake_equationYou will see that the Wiki article gives an answer of 10. Quite a few – but this number relies on so many estimates – like how many planets per star capable of supporting life, what percentage of these will develop life, what percentage will be intelligent life, and so on, that it’s really only just a guess.
But even if the number given by Drake’s equation is correct (which I very much doubt) I don’t think any of those intelligent aliens will look at all like us. The science fiction idea that most aliens are humanoid with two arms, two legs, a head-like thing where our heads are is I think a myth. If we met one of these aliens we would probably have a hard time even figuring out which bit was it’s head. However, even though they might not look like us at all, I think some of their behaviour might be similar. That’s because to evolve intelligence – I would argue – you need to be a social animal (or alien) thus I think that these aliens would probably (sometimes) care for each other, (sometimes) fight each other, and so on – just like humans.
-
Caspar Addyman answered on 14 Mar 2011:
In my opinion, there will definitely be life on other planets. (Although probably not on any of the planets in our solar system) Some of those distant planets will almost certainly have complex multicellular life.. but how closely will it resemble us? I doubt we will ever really know. It would be cool to meet aliens but the energy required to travel interstellar distances seem so large and the time it would take so long that i doubt any aliens would make the trip. They might send out robots or we might even just overhear their television signals. But the best bet is that they might send a radio signal. That is what the SETI project is looking/listening for.
-
Sarah Thomas answered on 14 Mar 2011:
Well it seems likely to me that there must be some kind of other life forms? I mean, we have an entire universe with more stars and planets in it than we can possibly imagine, surely there can’t just be one planet in the whole of existence that is teeming with forms of life? We have fish that live in the extreme depths of the sea, bacteria that can give in boiling hot springs, people that live in the Artic!
It seems to me that bacteria are the best example of lifeforms that live in extreme conditions so maybe it is most likely that there are lifeforms like bacteria living on other planets.
But then I was thinking, if life evolved on another planet, would they evolve to be like us? I mean like walking around on two legs? And I guess it depends on their environment but if it’s about survival of the fittest, and of all the creatures on our planet, it is humans that have advanced furthest, then I suppose aliens probably would evolve to be similar to us.
But then it seems that technologically advanced civilisations are pretty good at destroying themselves and others so maybe there have been other lifeforms but know they are all gone…
Good question though!
-
Diana Drennan answered on 14 Mar 2011:
Well, given the size of the universe, and the sheer numbers of stars, I think it very likely that there is life somewhere out there. Would they be like us ? I think probably not. I really enjoy reading Science Fiction, and one of the themes often explored is what else could life look like. We used to think that it would have to be like us, but we keep finding all these examples of how “weird” life can actually be. Here on earth there is life that doesn’t need oxygen or is even incapable of growing in oxygen, there is life beneath the ice at the polar caps, there is life in the boiling water near hydrothermal vents. There is even life that can use arsenic instead of phosphorus in it’s DNA ! There are, however, broad concepts that I think define what’s alive – for instance, living things grow, respond to stimuli, reproduce and evolve – so in these ways, they’ll be like us. Will they find us ? I don’t know – the universe is a really big place. Why would they look here ? and how would they get here ?
-
Murray Collins answered on 25 Mar 2011:
I really don’t nkow. There is so much still to discover about other planets that might support life. The moons of jupiter may support life, but definitely not like us!
There is a lot of path-depenendency in the development of species. This means that what species develop in the future depends to a certain amount on what nature has to work with now. This may may make it more unlikely that there are things that are like us at all.
Finding life somewhere else in the universe at all would be very exciting!
Comments
Caspar commented on :
Alan – I’ve often wondered one could come up with a set of “Star-Trek” equations to go with the Drake equation.. Basically it would give you some probability estimates on how closely intelligent life-forms would resemble us. I think it’s a good bet that any aliens we meet will have bilateral symmetry. I think they would have an organ we’d recognise as a brain and that any sense organs they have will mostly be situated at one end probably quite close to their brains. so I think that yes they’d also have “heads”.. then they’d need something resembling arms, tentacles or a trunk to be successful at tool use.
there’s probably also a very good chance that their biology would be based on carbon chemistry and possibly even feature DNA, RNA, etc.
however, estimating the odds for any of these features is a lot more messy and biological than the Drake equation.
Of course, even then it seems unlikely that all these aliens would speak perfect English like they usually seem to in the movies!
Alan commented on :
Caspar – great idea – you’ve really got me thinking! But I’m not sure I agree with all your assumptions about alien morphology. Re bilateral symmetry – while it’s true that most animals on this planet have bilateral symmetry I’m not sure why aliens should necessarily have the same. I suspect that the predominance of bilateral symmetry on this planet may have something to do with the physics of swimming – in other words you need to apply equal force on both sides to propel yourself forward through the water. But let’s not forget axial or radial symmetries – star fish, sea urchins and jellyfish – all reasonably successful forms otherwise they wouldn’t be around today. I’m a big fan of Stephen J Gould who pointed out the massive contingency in evolution. If the tiny fish-like thing called pikaia hadn’t survived the Cambrian vertebrates may not have been the top (in terms of complexity, intelligence etc) sea and land animals now – and that brings me to brains. I wonder if backbones don’t lead – as a by-product – to nervous systems where alot of the thinking is lumped together in brains. I’m not sure I can think of an especially good reason thinking shouldn’t be distributed throughout bodies – and of course invertebrates don’t have single major neural organs but a number of smaller clumps. It’s interesting to speculate on whether – if insects had evolved to be really smart individually (instead of going down the swarm intelligence route) – they would have ended up with single large brains. Sense organs are interesting too and it makes sense to have them at the front if you mainly move forward, so I think having key sense organs clumped together at the front is probably a side-effect of bilateral symmetry. Jellyfish are very interesting in having eyes all the way round (especially the box jellyfish with several different kinds of eyes). So I think alot follows from the kind of symmetry.
But you’re right – estimating probabilities is going to be virtually impossible!