h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The recent launch of a space telescope to search for earth-size planets prompts the question. Will there be any life on these planets and what form might it take?

siliphone based.

If the conditions on these planets are similar to ours then the life will most likely be similar to what we get here. If conditions are different but still support life... speculation is useless, we'd have no way of knowing.

If conditions were reasonably similar we might expect dinosaurs but if no comet struck the planet and wiped them out would they ever get brainy? Life would I suppose emerge from the sea as on Earth?

Speculation is useless whatever the conditions.

If you re-ran evolution on Earth all over from scratch you'd get a very different outcome. Natural selection is not a random process, but two other hugely influencial processes in evolution - mutation and genetic drift - are both stochastic in nature.

Short answer: we don't know.

Ste

To answer the "will there be life" part...

Once you get any conditions where self-replicators can emerge from non-replicating predecessors, you get life. I think those conditions are rare, but the universe is big enough to make life common. How common highly complex life is (such as what we find here on Earth) is unknown.

See the famous Drake Equation: http://en.wikipedia.org/wiki/Drake_equation

Also, a good book about the emergence of life from non-life is by Robert Hazen, entitled "Genesis": http://www.amazon.com/Gen-e-sis-Scientific-Quest-Lifes-Origins/dp/0309094321


Ste

See the famous Drake Equation here instead A11049347

...and also A17498514 (currently in Peer Review) has some pretty good links

Galaxy Babe, That A17498514 is really good!
Those noisy numbers increasing 6,15,27,31 and then falling away suddenly 20,5 and gone could be a signal from a UFO zipping through the sky between the Pleidaes and the Earth. That would explain why they couldn't find it again wouldn't it? Are they sure it wasn't from an aircraft? Perhaps one of those stealth jets or whatever it is that they have up there nowadys. Or even a passing taxi driver or pizza delivery boy? But all those other things apart from the UFO would be on other frequencies wouldn't they?

That's also interesting about the Drake Equation.
The Llareggub Equation goes like this:

We know one solar system intimately. Let's assume it's a typical system. It currently has intelligent life.

How many typical solar sytems are there? Billions, if not trillions.
Therefore there must be billions or trillions of systems with/had/will have intelligent life.

The chance of there being no other intelligent life is therfore zero.

If only 10% of intelligent life can/will/has survived then it still leaves millions of intelligent species out there.

Drake's famous equation with it's answer of 75 is rather pessimistic I feel.

We must now assume that we are of average universal intelligence. There must be solar systems with buffoons out there but on the other hand there must be sytems where even an Einstein or, dare I say it, a pessimist like Drake would be considered a dunce.

Maybe some of their travellers are nearer to us than we think when I think of the Wow! clue. And there's no need to suppose that those at home are watching the French Revolution on their television sets for who knows what methods they have of gathering information.

We, sitting in the middle, have a long to go. As far as from Stone Age to Space Age into the future. It's impossible to imagine where civilisations that are say 35,000 years more advanced (think of the time of the appearance of Cro-magnon Man) are up to now. They may safely observe us undetected. I think we can be sure of that.

That Llaregub Equation doesn´t seem to hold up. Why should we assume our solar system is typical. Looking out into the universe most solar systems seem to be binary. It is believed planetary formation might not be possible in binary star systems. And the planets we have found so far are all Jupiter style planets, although that might just be because they are easier to find. And looking at the history of earth, even if life on other planets arises, it may well never get past unicellular life. Look how long that took on Earth.

As for what aliens are actually like, well I do think we can say something about that. For one thing looking at evolution on earth I´d wager they are likely to have eyes. Less likely to have wheels.

Xanatic,
Think about Mars. Running water is there in abundance they tell us now. So what's living underground there? Cannabilistic fish? Moss or fungus eating snails? Snakes? Spiders? Sponges? Green Men?

Of course giant gas planets may have life on their numerous moons that the attract if not on the giant gas planet itself. I don't think the fact that life took a long time to colonise Earth is a factor. There are billions of solar systems older than ours.

Hmmm, they are saying water may be there in small amounts. But nothing definite yet.

Yes, there could be life on the gas planets in other solar systems. But then wether our system is typical is irrelevant anyway. And as for life on earth, it seems to have arisen very quickly after Earth stopped being molten. That makes it seem likely it happens easily with the right conditions. But the fact that it took 3 billion years to go from unicellular to multicellular life makes it seem that is a rather hard step. So even if there is life on a lot of planets out there, 99% of them might never get beyond some slimy covering on rocks.

"Running water is there in abundance they tell us now."

No this is absolutely wrong.

There maybe bacteria on mars, or other single celled organisms. At best.

I thought the's shown us pictures of Amazonian sized waterfalls that moved huge rock boulders . You mean to tell me they were only dribbles? Size does matter then!

There is a theory that life went from single cell to multicellular very quickly, but that it was completely wiped out, back to the unicellular level again by a runaway cold spell which froze the entire earth for about 200 million years. If the theory is true, this may have happened many times.

You refer to the Snowball Earth theory right?

Where did you see those waterfalls? NASA recently published some pictures which showed what could be ravines caused by running water within the last 7 years. But it could also be caused by a few other things.

I'm presuming Mars once held an atmosphere which has now evaporated into space and underground (as water) when I say there's probably life there. In other words there was a dense atmosphere millions of years ago and life eveolved and when the atmosphere was lost life adapted to survive, went into caves into pools of water. Probably the creatures have lost their eyesight but that's no big deal, I've seen a species of blind fish living in the pitch dark deep in a cave in Slovenia; small and pink they were.

Xantic - same pics probably - there was no scale on the one I saw in the local paper unfortunately. It depends on the scale. It looked like scree slope where a waterfall or a spring had emerged and they said this had happened in the last 10 years or something like that.

Well, the reason why Mars has so little atmosphere is because of the low gravity. I don´t think there is any reason to believe it once had a thick one, which then disappeared. Or that there was life during that time. That is just plain speculation.