• Question: Do you believe there is life on other planets?

    Asked by rachelmcclelland to Cathal, Ciara, Emma, Michael, Sive on 14 Nov 2013.
    • Photo: Michael Nolan

      Michael Nolan answered on 14 Nov 2013:

      Hi Rachel,

      20 years ago we had no way to find extra-solar planets (that is outside our solar system), now with Kepler in particular we have made great leaps forward.
      We think we know what conditions are needed for a planet to be favourable to life like our own carbon based life and now we can go hunting for such planets.
      Of course, even if we find something like earth there are other possibilities
      (1) life has yet to start on that planet
      (2) life did start, but has remained single celled
      (3) there was life but it was rendered extinct
      (4) there was life, but it destroyed itself

      Also, there could be other ways of generating life, based on say, liquid metals (who knows!).

      Given that there are around 1000000000000000000000000 stars in the Universe (answer to another question), then if even only one-billionth of them have habitable planets, that still means 100000000000000 planets with life – life could be everywhere, but separated by vast distances.

      If you are asking about life in general, then the answer is yes most definitely and we will find evidence for that on Mars. It may be that 99.99% of it is single celled, but its still life
      If you mean intelligent, conscious life like us, then it is hard to be definite, but I would say yes and we have simply not encountered them yet and the distance to be travlled to the nearest system with life could be immense, so we are, day-to-day, alone in the universe.

      This does make my head spin when I think about it!!

      M

    • Photo: Sive Finlay

      Sive Finlay answered on 18 Nov 2013:

      Hi Rachel,
      Yes! As Michael explains really nicely the universe is so massive that there’s a high chance that life did not just evolve on our planet.
      As for what type of life exists no one can be sure and it might have very different characteristics to our own living system.
      Even if there was another planet with exactly the same environmental conditions and history as Earth, there’s debate about whether life would evolve in the same way again. Stephen J. Gould, a famous palaeontologist from Harvard, wrote about the repeatability of evolution. He argued that if you could wind back the tape of the history of life then species would not evolve in the same way again because there’s so much chance involved. However, other people argue that, under the same environmental conditions, life would evolve in the same way again. Richard Lenski’s lab have been running some long-term experiments using bacteria with short generation times so we can observe their evolution. Different bacterial populations have evolved in similar ways so the evolution of life might be repeatable after all.
      So yes I think there is life out there, although I don’t know what form it might take or, if it’s from an Earth-like planet, whether it will be anything like us.
      Although I don’t think we have to worry about rolling out the welcome mat for any little green visitors anytime soon.
      Sive

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