Intelegent life in the Universe, how common is it?

[The Andy-Man]

Firstly, who says these aliens have the same life span as us? Perhaps living to the ripe old age of 163,857 earth years is expected?

Secondly, there are so many stars in so many galaxies, that some forms o life MUST be somewhere.

Thirdly, Given that human life on this planet is reletivly young, and even life on this planet is fairly recent, many probes may well have passed and missed us.

Forthly, we are all working on the presumption that the mand us can observe eachother. Maybe they exist only in a 2 dimentional world, or a 7 dimensional world etc, and so their phyical laws and ours are incopatible,

[smacksim]

Originally posted by The Andy-Man
...
Secondly, there are so many stars in so many galaxies, that some forms o life MUST be somewhere. ...

While this generally applies to finding a parking space, it isn't really a sound way to do science.

[The Andy-Man]

Originally posted by smacksim


While this generally applies to finding a parking space, it isn't really a sound way to do science.

I beg to differ, as it is a robability thing. At sometime, someplace, there must have been life that was not Earth related. 400billion stars in billions of galaxies gives alot of room for probability.

And don't they currently theorise that the bacterial origins of life on this planet came from out there?

[pg]

don't know if this has been mentioned but i thought i read something about supernovae continuely wiping clean many light years of space before life could really get going. isn't there something stronger than supernovae also?

[Whaleboy]

Hypernovae, when a massive star collapses internally, a singularity is created within, lots of high pressure **** builds up inside and the thing explodes. Shouldn't be massively worried about that, compared to supernovae which are more frequent. If the Earth passes through one of the galaxies arms, it stands a 50/50 chance of being irradiated by a supernova. It is highly unlike that would eradicate life, especially with distances greater than 10 LY, but the radiation would cause a lot of mutation, putting the ****s up evolution. There is a school of thought that says that genetic diversity of life on Earth is fuelled by such radiation.

[Urban Ranger]

The energy of radiation from such an explosion decreases exponentially (1/r²).

1 ly = 9.4605284 × 10¹⁵m

That will take some motherly explosion out there for us to feel anything.

[Ramo]

More precisely, the energy is diffused proportionally to the distance squared.

The mean free path of particles in the universe is actually pretty damn mind-boggling (given that we can still see the microwave background radiation).

[Whoha]

Are we talking intelligent as in dolphins frolicking in the sea or intelligent as in humans building New York and selling Big Macs?

We're talking big macs.

[Joseph]

Originally posted by General Ludd
Who cares? We'll never know it if there are other "intelligent" life forms out there.

Area 51 knows. And from what a very few people who have work there say from time to time you would be amaze at what they have there.

[Odin]

Firstly, who says these aliens have the same life span as us? Perhaps living to the ripe old age of 163,857 earth years is expected?

Good point. But I don't think would live for quite THAT long.

Secondly, there are so many stars in so many galaxies, that some forms o life MUST be somewhere.

Other galaxies are irrelavent, they are to distant to contact. Also, most planetary systems are uninhabitable to everything besides the equivalent of bacteria and protozoa.

Thirdly, Given that human life on this planet is reletivly young, and even life on this planet is fairly recent, many probes may well have passed and missed us.

I think the same thing, Civilizations don't pop up at the same time.

[Odin]

Oh, and why do people think aliens look like humanoids with big heads? other sentient beings will look totally different from us, or from any living thing on earth for that matter.

(BTW: that is why I think the Roswell thing had nothig to do with aliens, me thinks those were test dummies on a ballon the US Army was testing out.)

[Last Conformist]

Originally posted by The Andy-Man

Secondly, there are so many stars in so many galaxies, that some forms o life MUST be somewhere.

Well, only if the chances of life arising on a planet are high enough. From our present knowledge it seems unlikely, but it's for all we know possible that the origin of terrestrial life was a freak occurence, with a probability of say one in 10^80 (10^80 happens to be the approximate number of electrons in the observable universe).

Thirdly, Given that human life on this planet is reletivly young, and even life on this planet is fairly recent, many probes may well have passed and missed us.

I don't know if terran life can be said to be "fairly recent"; it's been around for closer to 4 billion years, which is an appreciable amount of time even on a galactic time scale. During that time, for instance, the average metallicity has risen enough to affect planet formation.

[Darkstar]

Originally posted by Boris Godunov
Um, but we have experts in in physics. They're called physicists. Might want to read something from them sometime.

The economics are certainly considerable, but that's nothing compared to the physical possibility. Again, talk to the physicists. If, as DanS mentioned, the theoretical max speed of an unmanned object is 1/10 c., then at that speed, things will take a long time to get anywhere and longer still to relay information back.

I do on occasion, Boris. You might want to consider it yourself sometime. Can be very interesting.

First off, 1/10 c is not the max speed of an unmanned object. If people want to go do some digging on published studies of cost and feasibility that have been done for NASA, we can get closer to c then just 0.1. 1/10th is just an economical limit for current practicality.

Second, we can at anytime have an actual breakthrough in several different fields that have hinted at FTL. Maybe that will happen, maybe it won't. But it was "impossible" for man to fly until the right mixture of knowledge and can-do came along back in 1903.

[Darkstar]

Originally posted by Boris Godunov
But stars are not spaced average 1 light day apart, they're spaced many, many light years apart.

That depends on what part of the galaxy you are talking about. Stars are more distant between neighbors out at the fringes where we are versus the interior of the galaxy. And if you are talking spanning the whole galaxy (as some are), then the average distance between stars is less then a light year.

[:) Smiley]

Darkstar, do you work in aerospace down at Huntsville?