Intelligent Life

Well, yes, it would be interesting to find it here first….

But this calculation isn\’t as bleak as you might think:

The chances of finding intelligent alien beings on other Earth-like planets are tiny new research has concluded.

The likelihood were are not alone and intelligent life has evolved is just 0.01 per cent on each suitable planet according to calculations by one scientist.

Assume that his calculations are correct: does that mean the possibility of intelligent life out there is low? It really rather depends upon how many planets there are out there….and with billions of stars, I\’d say that the probability is really rather close to unity.

That is, the probability on any one planet is low, but the presumed number of planets makes it almost a certainty. After all, we\’re here, so we know that it can happen, don\’t we?


12 thoughts on “Intelligent Life”

  1. The Drake equation to assess this has been around since the ’60s. The biggest uncertainty is the lifetime of a civilization capable of communicating: if there is intelligent life, we can miss it in time rather than space.

  2. This pseudo-science comes from the School of Environmental Sciences at University of East Anglia.
    Yes our tax money pays for this.

  3. He’s basically contending that the product of f-sub-l and f-sub-i (which becomes the probability of intelligent life ever evolving on a planet that can support it) is 10^-4.
    Ignoring timescales (L (lifetime of civilization) and N* (rate of star formation) to see number of civilizations that have ever existed in this Galaxy, and ignoring ability to communicate (f-sub-c, as we’re just seeing how many exist/existed, not how many we can/could talk to), plugging in estimates of 0.5 for f-sub-p (fraction of stars with planets) and 2 for n-sub-e (number of planets per planetary system in the biozone), we get:

    3 (+/-1) x 10^11 x 0.5 x 2 x 10^-4
    = 30 million intelligent races in the Mily Way’s history.

    As Kay Tie points out, the key variable is the lifetime of the civilization. If an intelligent race lasts for about 1 million years (as an intelligent race), then you can divide that by about 15,000 to get the number of intelligent races alive today. So about 2000.
    This takes into account rate of star formation, R* (which is number of stars divided by lifetime of galaxy) and Lifetime of intelligent race (a way of approaching L.

    The remaining parameter is f-sub-c: The fraction of intelligent races that are civilized and can communicate at any given point in time. Which can be any figure you like, dependant on how long you reckon we’ll last in that parameter and how representative we are.

  4. “The remaining parameter is f-sub-c: The fraction of intelligent races that are civilized and can communicate at any given point in time. ”

    If you just take us as representative, and forecast our imminent demise, then you get close to zero simultaneous others in our own galaxy.

    But a long time ago in a galaxy far far away..

  5. The chances of winning the lottery are much lower – yet someone does that every week.

    However, maybe their civilization isn’t interested in knowing anything about their stellar neighbours – that would spoil a good research grant, wouldn’t it?!

  6. It’s meaningless, really. It’s a colossally large known figure (age of universe) times a colossally large unknown figure (habitable planets) times an infinitessimaly small figure (chances of intelligent life evolving). Any estimate of probability would have to be caveatted ‘plus/minus ten billion percent’.

  7. “a colossally large unknown figure (habitable planets) ”

    When the equation was first drawn up it had to be filled with guesses. Since then we’ve got a much better handle on planetary formation, not to mention observing extra-solar planets. It’s not a meaningless equation – and the numbers we put to terms are getting better.

  8. The ones we have absolutely no idea on is the probability of a planet amenable to life actually generating life, and the probability that life will evolve towards intelligence. In either case, the value lies between zero and one, and that’s about as good as we can get. We can make the observation that both are possible, since both occurred on our planet, but we have, at present, no way of ascertaining the degree of contingency that that entailed. If this East Anglian muppet thinks he does then he’s raving. It could be that both are low, but not vanishingly low probability events, in which case the universe (a trillion galaxies or so in the visible universe times a few hundred billion stars each times 13 billion years) should have given rise to a vast number of intelligent lifeforms. Or we could be unique. We just do now know.

    Michael Crichton did a splendid job demolishing the silly Drake equation. This farrago is even sillier.

  9. To be honest, we’re in the position of the Ancient Greeks, with plenty of theory and very little experimental evidence.

    Until we take a sufficient sample of stellar systems to get good figures for f-sub-p, n-sub-e, etc, we’ll always be handwaving.

    Looking at the Telegraph article, there’s plenty of questions I’d like answered (I’ll have to get hold of a copy of the paper). For example – the timescales are mentioned, so it would be logical that he’ll have found a way of estimating the probability of step 1 (single-celled bacteria) per x million years. It does seem that this step happened pretty quickly on our planet (prokaryotes go back to circa 4 billion years ago). In fact, it could have happened multiple times – primordial Earth, under repeated meteorite bombardment with an unstable crust, was a very hostile place. Early life seems to have kicked in pretty much as soon as it was survivable.

    Given step 1, probability of step 2 per unit time has to be derived (this is the biggy – eukaryotes only appeared on the scene about 2 bn years ago). Then given step 2, probability of step 3 per unit time – etc.

    With a sample of 1 (Earth), it’s hard to see exactly how he could derive numbers that were in any rigorous sense at all. There would be dependencies between them (over 4.6 billion years, the chance of step 1 (which happened in a very short time in our history) would have to be pretty much certain – the question is when it would happen and how long would be left for the next steps.

    If, for example, Step one had a probability of 1% per 60 mn yrs, Step 2: 1% per 200 mn yrs, Step 3: 1% per 100 mn yrs, Step 4: 1% per 100 mn yrs, then we’d have 10% in 600 mn – assuming that, 10% over the next 2 bn yrs – given that, 10% over the next 1 bn yrs – given that 10% over the next 1 bn yrs … and, yes this becomes 0.01% over 4.6 bn yrs.

    But what about a hypothetical world where prokaryotes took 1.2 bn years to turn up, the eukaryotes were far quicker (1.2 bn yrs) and the final two stages took 1.1 bn years each :

    20%; 6%, 11%, 11% : 0.015% (50% more likely). And we have to take this scenario into account as well.

    Or 3 bn yrs, 1bn yrs, 0.4 bn yrs and 0.2 bn years: 50%; 5%; 4%; 4% : 0.002% (a fifth as probable)

    And so on …
    We’d have to have a probability density function that was dependent on all four of those conditional probabilities. And how rigorous are his original “x%-per-unit-time” calculations? What if each step was twice as likely per unit time – the product becomes 16 times as likely. Assuming that he does have those calculations made and it’s not just “pretty unlikely to the fourth power”.

    What’s the effect of higher/lower energy input on the planet? Higher/lower evolutionary pressures? Probability of these variables – well – varying?

    Come to think of it, the probabilities-per-unit-time of each step might vary over time. If Step 2 hasn’t yet happened after Step 1 at a given time, it may be because there are plenty of evolutionary niches to fill without a major change being required – so evolutionary pressure to make that change would be low. As the niches fill up, that pressure would increase, chance of making that step increases for any given time period.

    This calculation will be a nightmare of interlocking varying conditional probabilities – I’d be interested at how he arrived at his final figure.

    At the moment, it does look pretty much of the style “there are four steps, each one’s pretty unlikely, all four consecutively are pretty-unlikely-to-the-fourth-power”

  10. Having seen broadcasts by both daytime tv and the parliamentary channel I think it is rash to assume that intelligent life exists on earth. Which rather puts your hypothesis at risk.

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