# Chance of life on other planets

Discussion in 'Astronomy, Exobiology, & Cosmology' started by James R, Sep 4, 2010.

1. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Kieth1,( post 98) is even more wrong than TruthSeeker (post 95)or Green Destiny(post 9). 8 eggs is a more probable answer than either 10 or 11 to James' question in the OP.

Instead of just guessing, take a second look by analysis. I.e. first assume that there are 10 eggs in the original 100 boxes. You found 1 and have now 9 eggs in 99 boxes. What is the chance the next box you open will be empty? Obviously, 90/ 99 as 90 boxes are empty. Then assuming second box opened was empty as James states, then there are then 9 eggs in 98 boxes of which 89 are empty. Etc.

So here is the way to compute probability of what happed (Only one egg found in 10 boxes) assuming there are 10 eggs in the 100 boxes.
Chance box 2 found to be empty is 90/99.
Chance box 3 found to be empty is 89/98.
Chance box 4 found to be empty is 88/97.
Chance box 5 found to be empty is 87/96.
Chance box 6 found to be empty is 86/95.
Chance box 7 found to be empty is 85/94.
Chance box 8 found to be empty is 84/93.
Chance box 9 found to be empty is 83/92.
Chance box 10 found to be empty is 82/91.

So if there are 10 eggs the probability of what James told happening is the product of these nine different fractions. I get that to be less than 0.408 for the probability that you will find only 1 egg in first 10 boxes you open. To make James’s story typical it should have near a 50/50 chance of being what happened. Thus there must be less than 10 eggs initially in the 100 boxes.

Lets change the assumption to be that there were initially 9, not 10, eggs are in the 100 boxes and see how probable it is that you only find one in the first ten tries. Then after finding first egg is found there are 8 left in 99 boxes or 91 empty boxes. So expected probability of box 2 being empty is 91/99 and assuming box 2 was found to be empty, etc. the probability that box 10 was also found to be empty is 83/91. I.e. all the prior numerators are one higher than before and dominators are the same.

So probability of Jame’s event happening if there are 9 eggs initially is:
91/99 x 90/98 x 89/97 x 88/96 x 87/95 x 86/94 x 85/93 x 84/92 x 83/91 which I get to be less than 0.453

For 8 egg case, again using fact all the prior numerators are one higher than before and dominators are the same, the probability of Jame’s event happening if there are 8 eggs initially is:
92/99 x 91/98 x 90/97 x 89/96 x 88/95 x 87/94 x 86/93 x 85/92 x 84/91 for which I get 0.50187

Nice problem James. From the OP I get the impression you invented it. Intuition can often be wrong. I felt sure 10 was too many as to avoid finding even one more egg when there are nine left seemed unlikely to me, so I decided to do it correctly. Hope you appreciate my effort - it is very rare that I calculate this much at my age.

Last edited by a moderator: Sep 19, 2010

3. ### granpaRegistered Senior Member

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I would say that the 2 most probable possibilities are that 'life is virtually everywhere' and 'life is virtually nowhere'. We simply dont know enough to tell which is right though. So the a priori (bayesian) probability (not the actual probability) would be 50/50.

Its true that we have found life on one planet but due to the anthropic principle (we wouldnt be here to see it if it wasnt) we are just as likely to have found this life whether life is virtually everywhere or virtually nowhere. Until we find life in one other place the a priori (bayesian) probability doesnt change.

5. ### adoucetteCaca OccursValued Senior Member

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Where would we go?

I can see us going to other places in this solar system to explore, but not as an expansion of viable real estate.

Arthur

7. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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If the universe were to remain as it is now (not expand into a cold death with possibly even the molecules ripped apart by the growing "dark energy.") then yes intelligent live would evolve many times.

Doing so takes a very long time and if we assume that liquid H2O is required that limits the sites for development of intelligent life to tiny fraction of the planets.

It is quite possible that low level life forms had a head start, compared to Earth by a million years, but IMHO, Earth had a great advantage over all most all of them, the moon, which is unusually large in comparison to the planet it orbits.

I.e. Even to day the moon raises tides of more than 1 meter. If it orbited a much more massive planet than Earth at this same center to center separation, the tides would be much smaller. (The much greater gravity of the larger planet would keep the shape nearly free of tidal distortion.)

In the early history of Earth when early forms of life were beginning, the moon was closer and tides of greater than 100 meters happened every few hours. This means that a large part of the Earth's land surface was was never really dry. Sunlight and moisture was widely available there in addition to always available some where in the wet oceans. I think this greatly accelerated evolution* so even if it was not the first to have very simple life originate Earth with its relative large moon may have won the race to create intelligent life, at least inside the sphere we can can ever expect to communicate with. I.e. for all practical considerations Earth may now be the only planet with "intelligent" life. (Intelligent is in quotes because I doubt Earth's version is stable for even 10,000 years against self destruction.)

*Environmental change is the driver of evolution. Earth had great changes on most of the land ever few hours.

Last edited by a moderator: Sep 19, 2010
8. ### TruthSeekerFancy Virtual Reality MonkeyValued Senior Member

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Billy T, you just reminded me of probability. Thank you.

9. ### IamJosephBannedBanned

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Barely is right; its antithesis is making assumptions without even a 'berely'. The survey poll concerns a first hand knowledge of the known universe, which says the unknown is more likely as the known than not so. We also know for a fact no life imprints were ever seen for 15 Billion years in the known sector of a poll survey. You are saying we have to check every last boulder of the universe - that is not how science and math operates.

10. ### keith1Guest

Good to see your words again, Arthur, and good question.

Its the old "long journey starts with one step" analogy at best.

The technology for the task is barely an inception as yet, beside what Newton, the various space agencies, and the ground-based civil entrepreneurs have started...

Or the old "one would have to be there first"?
One would think an advancement limit would be reached, as to further conception, without being there. (Case in point, experiments that could only be accomplished with the International Space Station).
Space-based presence to facilitate that which would come only from trial and error of everyday living in that environment...Permanently, in numbers greater than can be accumulated overnight. In environments that are larger than can be constructed on the ground (Earth). Using the materials available from low-grav. sources (moon, asteroids).

Its that old rant still playing. Just have to go do it. Then decide what we're doing...then.

11. ### keith1Guest

This is a really good question, as it strikes at a very core issue.
What benefits would we gain for the cost outlays in technical advancement to actually note their presence?
--Seeing their city lights?
--SETI has no viable trace at the frequencies they've been monitoring. That could change with different strategies not yet developed.
--Other?

12. ### Green DestinyBannedBanned

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That's just silly... I mean, it's impossible to expect a planet to have lifeforms to evolve with the same history as ours... Not in our universe. They're maybe lifeforms which are similar to us - possible only through excepting that perhaps DNA is shared over vast distances, but to expect them to have a history similar to us... well... it's statistically impossible.

13. ### adoucetteCaca OccursValued Senior Member

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GD,
I was not suggesting that there is any statistical probablity of this actually occuring, I'm just asking how close would a civilization identical to our own have to be for us to be able to detect it? Making the civilization identical to our own is just a way of simplifing the question.

I'm just trying to get an understanding of what we can/can't yet do as far as detecting a similar intelligent life form as ourselves at a distance.

The next question would be, if we TRIED to put out a message into the universe (keep costs reasonable, don't think of this like the Manhatten Project), selecting stars within a given radius, how far away do we think we could send a message that a civilization with the same level of technology as ours, that was similarly listening as we do with SETI could detect it?

Arthur

Last edited: Sep 20, 2010
14. ### swivelSci-Fi AuthorValued Senior Member

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2,494
The premise that there's only one basket is flawed. We look at thermal vents along the ocean floor, a place no sane scientist expected to find life, and we found entire ecosystems. Same goes for lake beds with crazy salinity levels, acid baths, areas with toxic metal content.

Then we look to the cosmos and see the building blocks of life present in the vacuum of space. There are amino acids up there, like the glycine found in that comet (and other meteorites). Another telling fact is how early we find evidence of life here on Earth.

It may be that liquid water is pretty much a guarantee of finding life. Everywhere we look with liquid water, we find life. That's a pretty good percentage.

So, I feel as certain as I can about anything that life exists around other stars. I'm just not sure there's any other technological life out there. We have only one instance of that in all our baskets, which makes it a different sort of consideration. Also, our solar system has a ton of unusual features, any of which might be necessary for technological life (mass ratio of planet/moon; not a binary system; large proto-star like Jupiter to clean out impactors).

15. ### IamJosephBannedBanned

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If life forms exist, there is no way it can be rationalised as of the same status as earth: some will be older, thus more advanced, because of the time factor. When we quote impossible distances, we forget to quote great time periods in benefit to other potantial life making themselves known throughout the universe.

This says, at least some of the much older planets can/must bear life, say 11 Billion years old, and that they could have mastered a way to get a message across the universe, or large sectors of it - because the uni is expanding, and a message sent 11 Billion years ago would not be effected by the distances: the message traveling all over the universe would in fact be assited by the distances, which would act as an elevator platform, delivering the message to a new planet like earth say 5 billion years ago: it must travel with the expanding distance. But we have no imprints of life for some 5 B years on earth - and for some 15 B years in the known universe. That's the correct math!

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Yes, all those features reduce the possibility of life quite a bit. But the biggest problem is distance. All those technologically advanced life forms are unable to communicate with any others. Send a message to Andromeda, they'll discover it 2 million years from now, their answer won't get here until 4 million years in the future. We've only been around for a total of say a 150,000 years. I wouldn't bet we'll be here waiting when that I love you too gets here.

17. ### Green DestinyBannedBanned

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Since the very first prokaryote - that single-celled life came into existence, life boomed because of the abundance of water... having water though does not necesserily secure the arguement we will definately find life. It may be to your knowledge that we have tried to recreate the primordial sea from which life is expected to have sporadically appeared from, however, this has been to an amazing fail. We have not been able to recreate life in the lab.

18. ### keith1Guest

Given our (and I use the term "our" with gratitude, that I am accompanied by such wisdom as the humans who have advanced "us", with such apparent ease and rapid time period) realization of this lately plausible discussion, is there is no foreseeable impediment to our advancement that one could not extrapolate that human forefront technology will continue to advance at this same rapid pace?
Is a fully understood TOE the end of Science, or just a benchmark, where Science adjusts it's focus on the engineering and manipulation of the continuum dynamics, to further these fantastic notions, such as ease of communication throughout the distances?
I would think the days (not that long ago) of people riding horse and buggies, laughing at the insane notions of space travel and the other future possibilities, now fact, would have humbled us to further doubt of overcoming the hurdles that lay before us...

My ease of optimism seems well warranted.

Last edited by a moderator: Sep 21, 2010
19. ### keith1Guest

A complex process we may not have the lab equipment and time durations to substantiate thoroughly?
And has the aspect of primordial micro-lifeforms arriving here, dormant through the rigors of a cruel journey on the dust of interstellar winds, and seeding many environments along the way, both habitable as well as those unproductive...been conclusively ruled out?

20. ### Green DestinyBannedBanned

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Of course not. Panspermia Theory is still a mainstream fringe-theory.

And how much time does one need? If one takes into account life requires a long time to create intelligent lifeforms, how much time does that really give us when expecting the first prokaryote to come into existence?

21. ### Green DestinyBannedBanned

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We don't know how long it takes, if we have our methods right, which is really my point.

22. ### DinosaurRational SkepticValued Senior Member

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Proxima Centauri (about 4 light years away) is the closest star to our Solar System. In the next 5-10 or more years, we might develop technology to detect signs of living organisms at that distance & further, but probably not beyond a few thousand light years. Detecting evidence of intelligent life is much more difficult.

If a culture like ours was on Proxima Centauri, I do not think that any of their radio or TV broadcasts could be detected by us. I do not think they could detect our radio or TV broadcasts.

The strength of transmission signals obey an inverse square law. An inverse square law applied to transmissions designed to reach a few hundred (at most 1-2 thousand miles) would show that such transmissions would not be detectable 4 light years from the point of transmission.

A laser or other tightly focused transmission) would be detectable at a greater distance than a radio or TV transmission, but I do not know the equation for the decrease with distance.

Laser beams are reflected from mirrors left on Luna by American astronauts. They are used to accurately measure the Earth-Luna distance. I think a standard radio or TV broadcast might not be detectable at the Earth-Luna distance. Earth-Astronaut communications were accomplished by directed transmissions, while standard broadcast transmissions are not tightly focused in one direction.

I do not know if a tight laser beam would be detectable at the Earth-Centauri distance. I do not think it would be detectable beyond a few thousand light years, but would not bet real money on this POV.

At astronomical distances only extremely powerful transmissions are detectable: Quasars, millisecond pulsars (rapidly rotating neutron stars), & other stellar phenomena are detectable.

SETI is a joke.

23. ### NeverflyBannedBanned

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Even so, Proxima Centuari and its sister stars have a lot of gravitational interaction between them that we don't have here.
IF there was life there, the conditions for development should... I say should, heck I don't know... be quite different than ours.

Whatever transmissions we've sent would have been broken down to static before it reached the Kuiper Belt.
A lot of people fret about what aliens would think of our television transmissions. But the transmissions would break down over distance.

The Arecibo message, however, is a tight and focused powerful beam. It does have a good chance of reaching someone, provided anyone in that direction is listening for it.

SETI has horrible odds for success. But... it's a risk. A shot in the dark. That offhand chance that another civilization sent a powerful message of "Anyone out there?" 50,000 years ago in our (Or omni directional) direction.
Fat chance. But not impossible.
We wouldn't be able to communicate, but we'd have the ability to state to ourselves, "Well, that answered ONE question..."

Then again... the target for the Arecibo message was 25,000 light years away. That's a long wait.