Have aliens visited earth?

[jason_t]

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Hi, we're talking about complex, intelligent life here. Good luck.

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Hi, universe is gigantor and we've likely got life on 2 planets in this solar system and some people think more.

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Hi, and evolution needs to happen just so for complex life forms to develop. It's a parlay, and a pretty crazy one.

[Leaky Eye]

For all we know it could always happen given the right conditions.

[jason_t]

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For all we know it could always happen given the right conditions.

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Evolution is random.

[TimM]

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For all we know it could always happen given the right conditions.

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Evolution is random.

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Mutations are random, yes, but if you do something randomly for a long enough time, you eventually cover a lot of the possibilities.

[jason_t]

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For all we know it could always happen given the right conditions.

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Evolution is random.

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Mutations are random, yes, but if you do something randomly for a long enough time, you eventually cover a lot of the possibilities.

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Not when the search space is as large as it is. There is an insane number of DNA combinations. Most of them are junk. Hitting upon ones that lead to complex life is rare.

[wacki]

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Not when the search space is as large as it is. There is an insane number of DNA combinations. Most of them are junk. Hitting upon ones that lead to complex life is rare.

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I used to think this. Then I started doing radiation work in a wetlab. Given the right conditions, evolution occurs with amazing speed.

Ugh... been through this a dozen times before. If it was anyone but you I wouldn't be posting at all.

[Alobar]

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For all we know it could always happen given the right conditions.

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Evolution is random.

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Mutations are random, yes, but if you do something randomly for a long enough time, you eventually cover a lot of the possibilities.

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Not when the search space is as large as it is. There is an insane number of DNA combinations. Most of them are junk. Hitting upon ones that lead to complex life is rare.

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Its like the monkeys pounding on the typewriter thing. If you have enough monkeys randomly punching keys on a typewriter, eventually one of them will punch out the complete works of william shakespear. So even if intelligent life is "OMG so super super rare" The universe is just so big that its going to happen, and more than oce. There are more stars in the universe than there are grains of sand on our ENTIRE planet, thats a whole hell of a lot of chances for life to evolve into intelligence

[jason_t]

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Its like the monkeys pounding on the typewriter thing. If you have enough monkeys randomly punching keys on a typewriter, eventually one of them will punch out the complete works of william shakespear. So even if intelligent life is "OMG so super super rare" The universe is just so big that its going to happen, and more than oce. There are more stars in the universe than there are grains of sand on our ENTIRE planet, thats a whole hell of a lot of chances for life to evolve into intelligence

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I don't think you realize how vast the search space is.

Let's take a Shakespearian sonnet.

as an unperfect actor on the stage
who with his fear is put besides his part
or some fierce thing replete with too much rage
whose strengths abundance weakens his own heart
so I for fear of trust forget to say
the perfect ceremony of loves rite
and in mine own loves strength seem to decay
oercharged with burden of mine own loves might
o let my books be then the eloquence
and dumb presagers of my speaking breast
who plead for love and look for recompense
more than that tongue that more hath more expressd
o learn to read what silent love hath writ
to hear with eyes belongs to loves fine wit

Ignoring punctuation and capitalization, there are 596 characters in that sonnet. Assume our typewriters have 28 keys---26 letters, one space and one line feed/carriage return.

Let's take a monkey and make him hit 596 keys and stop. If it's the above sonnet he gets a banana otherwise we continue starving the poor bastard and he has to keep typing. The number of 596 character-long blocks of text is 28^596. Let's estimate

28^596 ~ 27^596 = (3^3)^596 = 3^1788 = (3^2)^894 ~ 10^894.

So there are 10^894 blocks of text. Let's assume our little monkey can crank out 100 characters in one minute. So approximately every 6 minutes he'll crank out a 596 character block and thus approximately 10 every hour, 240 every day and 87600 in a year. Let's just say 87600 ~ 10^5 so that the approximate number of years for the monkey to produce the above sonnet is 10^889. There are only 10^80 electrons in the universe so at most 10^80 monkeys. With this many monkeys we're producting approximately 10^86 character blocks of length 596 in one year and the approximate number of years until the Shakespeare sonnet is produced is 10^808. The sun will have expanded and swallowed the Earth long before that.

[TimM]

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Its like the monkeys pounding on the typewriter thing. If you have enough monkeys randomly punching keys on a typewriter, eventually one of them will punch out the complete works of william shakespear. So even if intelligent life is "OMG so super super rare" The universe is just so big that its going to happen, and more than oce. There are more stars in the universe than there are grains of sand on our ENTIRE planet, thats a whole hell of a lot of chances for life to evolve into intelligence

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This is a bad analogy really.

We are not trying to produce a specific text, just a good enough one.

And we are not working purely randomly.

Just as an example, we know things like eyes evolved independently in many different lineages. So you can't say something like "If that one mutation that led to the eye did not happen, we wouldn't be here" because obviously there are many ways to get to eyes.

So we are not just blundering about the search space hoping to come across the right answer. Evolution is a feedback mechanism that is attracted to good things (like eyes).

[Leaky Eye]

Evolution is not random, it is precisely guided by the environment. Mutation is what is random.