Is there life in the universe, and if so has it visited Earth?

[Ivan Seeking]

On advanced life, I tend to side with the reasonable mainstream scientists.

And what would that opinion be?

 

[nicky nichols]

There is no peer-reviewed evidence that we have ever been visited by advanced aliens.

 

[hotcommodity]

It's interesting how so many people voted no. I had no idea that so many people on PF have been around since the creation of the Earth.

 

[GleefulNihilism]

It's interesting how so many people voted no. I had no idea that so many people on PF have been around since the creation of the Earth.

It's a matter of probability. What are the odds of being found by an alien race, even if it is capable at moving at faster-then-light speeds? Almost nil.

 

[Ivan Seeking]

It's a matter of probability. What are the odds of being found by an alien race, even if it is capable at moving at faster-then-light speeds? Almost nil.

We don't know that. Given a sufficiently advanced race [and tinkering with the assumptions], it could be that contact is a near certainty.

Already we on the planet of the apes are figuring out how to detect earth-like planets.

 

[jcs]

We are not alone

Consider this...of all the planets, of all the starsystems in our wide infinite , uncharted universe...of all the millions of worlds that exists or existed before us...why are we the only one little mud ball in this plane of existence that can support life? I don't buy it. If this is the case...what a waste of space.

 

[jcs]

I agree. With all the untold planets , stars and galaxies,why is our own little mud ball the only planet in the infinate , uncharted universe the only one that can sustain life? I don't buy it...If so, then it is n huge waste of space.

 

[jcs]

It's interesting how so many people voted no. I had no idea that so many people on PF have been around since the creation of the Earth.

That's a good one. Well said

 

[hotcommodity]

It's a matter of probability. What are the odds of being found by an alien race, even if it is capable at moving at faster-then-light speeds? Almost nil.

"Probably no" wasn't one of the options. Additionally, your post assumes that there may be other life in the Universe, but that they wouldn't have the technology to reach us. I find this to be an even greater assumption than the assumption that alien life has never visited our planet. If there are indeed other races, you would have no idea what type of technology they've acquired. The human race remains primitive and crude on many levels, it wouldn't surprise me if they visited us and decided to turn right back around.

 

[GleefulNihilism]

"Probably no" wasn't one of the options. Additionally, your post assumes that there may be other life in the Universe, but that they wouldn't have the technology to reach us. I find this to be an even greater assumption than the assumption that alien life has never visited our planet. If there are indeed other races, you would have no idea what type of technology they've acquired. The human race remains primitive and crude on many levels, it wouldn't surprise me if they visited us and decided to turn right back around.

You seem unable to wrap your head around the distances and timing involved. It would be like someone from Seattle, WA walking all the way to the African Savannahs to find a single blue ant. Even if that ant figured out how to click it's mandibles together rather loudly recently it still would only be a few fractions of a second ago and so far would not have done any good.

That's what the distances and duration of the universe turn the hunt for extraterrestial life into, we're the ant, the aliens would be the seattle resident, and the clicking would be our EM broadcast technology. Sure the odds of a more advanced lifeform existing somewhere are amazingly good but the sheer size and timescales involved make us finding each other amazingly bad.

 

[Ivan Seeking]

You seem unable to wrap your head around the distances and timing involved. It would be like someone from Seattle, WA walking all the way to the African Savannahs to find a single blue ant. Even if that ant figured out how to click it's mandibles together rather loudly recently it still would only be a few fractions of a second ago and so far would not have done any good.

That's what the distances and duration of the universe turn the hunt for extraterrestial life into, we're the ant, the aliens would be the seattle resident, and the clicking would be our EM broadcast technology. Sure the odds of a more advanced lifeform existing somewhere are amazingly good but the sheer size and timescales involved make us finding each other amazingly bad.

How can one impose these limits on a race that we assume can travel the distances required in the time required? As I said, already we are figuring out how to identify other earth-like planets. What might we be able to do in a million years?

 

[CEL]

How can one impose these limits on a race that we assume can travel the distances required in the time required? As I said, already we are figuring out how to identify other earth-like planets. What might we be able to do in a million years?

Will we still be here in a million years? Nobody knows. It is clear that if we had the technology for interstellar travel, in a few million years we would be able to colonize the Galaxy, provided that we would last that long.
In that case, a civilization with our actual level of technology would probably be able to detect us in their vicinity. After decades of search we found zilch.
Is it probable that at this instant there exist other civilizations in our galaxy? In my opinion the answer is yes. Have they visited us? I don't think so.

 

[andrewj]

http://video.google.com/videoplay?docid=-5594744703753734741

Bearing in mind this post by Ivan in the UFO stickied thread.

10,000,000,000,000,000,000,000 stars in the universe, a very conservative estimate but let's assume it's correct.

And the Drake equation is possible given the criteria and confirms there must be intelligent life: maybe in the galaxy, but definitely in the universe by the laws of probability.

http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html

And apply this to the universe, in a sort of what if way assuming this is fairly typical.

My question is two fold, we're fairly certain that probability indicates there must be life elsewhere in the universe, and assuming evolution works in simiilar if not the same ways elsewhere: it's fair to claim that their is intelligent life, so we accept life is out there? Yes/no?

Now given the conclusion is yes, do you think the intelligent life has visited Earth?

c\onspiracy theorists would have you believe that were inundated with the feckers . but don't you really think intelligent beings would try and make contact
not just with the cia but with the populus

 

[Ivan Seeking]

This is not about conspiracy theories. It might be [if such things are possible] that we have been visited and the CIA is as clueless as everyone else.

 

[Ivan Seeking]

In that case, a civilization with our actual level of technology would probably be able to detect us in their vicinity. After decades of search we found zilch.

We may not be looking for the right thing. Either way, after thinking about this problem for about twenty years, I realized that we can't say that the odds of contact are astronomically small, as most people do. This is like saying saying that we know the odds that interstellar travel [IST] is possible. Well, either the laws of physics allow it or they don't. There really are no odds. If IST is not generally possible, then the odds of contact may be small or zero. But if IST is possible, contact could be a near certainty. There is simply no way to know. We can only guess at the odds of the odds. Based on our current understanding of physics, contact seems to be unlikely, and in most cases, impossible.

 

[DaveC426913]

We may not be looking for the right thing. Either way, after thinking about this problem for about twenty years, I realized that we can't say that the odds of contact are astronomically small, as most people do. This is like saying saying that we know the odds that interstellar travel [IST] is possible. Well, either the laws of physics allow it or they don't. There really are no odds. If IST is not generally possible, then the odds of contact may be small or zero. But if IST is possible, contact could be a near certainty. There is simply no way to know. We can only guess at the odds of the odds. Based on our current understanding of physics, contact seems to be unlikely, and in most cases, impossible.

IST is definitely possible. Now, it may not be practical, but it is achievable.

Thing about judging whether it's practical is that it then becomes a guess as to the motivation of the the minds doing the judging - and then we're back to guessing how aliens think.

Who knows, maybe they evolved on a planet that's 95% water, and generation ships or suspended animation are as natural to them as in-flight movies.

 

[Ivan Seeking]

IST is definitely possible. Now, it may not be practical, but it is achievable.

Sure, at this point we can only imagine it being possible for a few local stars, but that's where the "unlikely" chance of contact comes in - leaving the door cracked open just a bit. Even if we are ultimately bound by the technical limits that we understand now, there is always a chance that someone else lives in the immediate neighborhood.

 

[PlasmaSphere]

This seems relevant. Top 10: Controversial pieces of evidence for extraterrestrial life.

http://space.newscientist.com/article/dn9943

1. 1976, The Viking Mars landers detect chemical signatures indicative of life

2. 1977, The unexplained extraterrestrial "Wow!" signal is detected by an Ohio State University radio telescope

3. 1996, Martian "fossils" are discovered in meteorite ALH80041 from Antarctica

4. 2001, A more rigorous estimate of the "Drake equation" suggests that our galaxy may contain hundreds of thousands of life-bearing planets

5. 2001, The red tinge of Jupiter's moon Europa proposed to be due to frozen bits of bacteria, which also helps explain the mysterious infrared signal it gives off

6. 2002, Russian scientists argue that a mysterious radiation-proof microbe may have evolved on Mars

7. 2002, Chemical hints of life are found in old data from Venus probes and landers. Could microbes exist in Venusian clouds?

8. 2003, Sulphur traces on Jupiter's moon Europa may be the waste products of underground bacterial colonies

9. 2004, Methane in the Martian atmosphere hints at microbial metabolism

10. 2004, A mysterious radio signal is received by the SETI project on three occasions - from the same region of space

Also i remember the Red rain in Kerala incident where red rain sporadically fell on the southern Indian state of Kerala. I think most scientists now think it was likely terrestrial, but the possibility is still there.
http://en.wikipedia.org/wiki/Red_rain_in_Kerala

 

[Ivan Seeking]

Warp Drive: A New Approach
http://xxx.lanl.gov/PS_cache/arxiv/pdf/0712/0712.1649v2.pdf

To be published in JBIS in early 08, and co-authored by PF member robousy.
https://www.physicsforums.com/showthread.php?t=204637

 

[hubertg]

I think the odds for life are out there. However, the universe is incomprehensibly large. It would seem to me that distance and time would be a prohibitive factor that any given life form could possibly find us, let alone get here...it would be like some one looking for one particular grain of sand on/in all the beaches and oceans of earth. Beam me up scotty !..hg

 

[Pippo]

...it would be like some one looking for one particular grain of sand on/in all the beaches and oceans of earth....hg

I fully agree, it's impossible to find one particular grain of sand, but let me say that the grain of sand is surely there, it's in somewhere.

 

[Ivan Seeking]

A promising but labour-intensive technique to find alien worlds has netted its first multiple-planet system, a new study reveals. The technique, called microlensing, can find smaller planets than rival methods, and one day might be able to find distant counterparts to Earth. [continued]

http://space.newscientist.com/article/dn13322-first-multiple-planet-system-found-by-microlensing.html

 

[Schrodinger's Dog]

Well I'm glad this thread is still going. There are some more conventional forms of space travel, that whilst not achieving interstellar travel particularly readily might be worth while. Like Solar sails, that gradually increase speed. Also there are suggestions that if you could create a sufficient amount of gravity in front of a ship this would bend space enough to shorten the distance between two objects, which is pretty much the idea of warp drives, thus avoiding the problem of FTL.

For the moment though, conventional albeit cutting edge methods are being explored such as ion drives.

http://news.bbc.co.uk/1/hi/technology/4527696.stm

I remember a suggestion as well of them using the sun as a gravitational lens, and our solar system as a giant observatory. But this is well beyond our current means.

 

[mikelepore]

Does anyone know whether binary and triple stars are likely to have planets? Would those planets orbit one of those stars or orbit the system of stars? Would the mass distribution of those stars cause the orbits of the planets to be highly eccentric? The reason I ask is because too much eccentricity, giving anyone planet temperature swings from too hot to too cold, would strongly affect the term in the Drake equation that represents the percentage of "earth-like."

 

[CEL]

Does anyone know whether binary and triple stars are likely to have planets? Would those planets orbit one of those stars or orbit the system of stars? Would the mass distribution of those stars cause the orbits of the planets to be highly eccentric? The reason I ask is because too much eccentricity, giving anyone planet temperature swings from too hot to too cold, would strongly affect the term in the Drake equation that represents the percentage of "earth-like."

As a star collapses from a cloud of gas and dust, a quality called angular momentum causes formation of a central condensation surrounded by a thin disk of matter. At this point it seems the system then either evolves into a planetary system or a binary/multiple star.

If a planet could form, it would orbit the main star, but its orbit would be influenced by the other stars.

 

[mikelepore]

A highly eccentric orbit obeys conservation of angular momentum just as much as a circular one does. It could be rare to have a system with the planets close to being in concentric circles, which is important for making life possible in our own system. I was thinking about several ways in which too much eccentricity is bad for the probabilty of life. Temperatures may swing across hundreds of kelvins. Planets are more likely to exert tidal forces on one another, causing vulcanism or even crumbling whole worlds. Larger planets may eject smaller planets out of their orbits or collide with them. Not only is there the probability of those amino acids doing something interesting, but they also have to be left undisturbed for a long time. In the earliest posts in this topic, someone estimated the probability of a system having an "earth-like" planet to be around 1/3. That astonished me. I thinking that this one probability factor must be a very, very small.

 

[_Mayday_]

10,000,000,000,000,000,000,000 stars in the universe, a very conservative estimate but let's assume it's correct.

I know we are assuming it is correct. BUT how would someone go about making such a prediction if so much of the universe is out of our reach?

I'm going to say yes, there is life other than us, but that is just being optimistic maybe as it would be pretty cool :shy:

I don't think it has ever reached Earth though. No reason.

 

[Schrodinger's Dog]

I know we are assuming it is correct. BUT how would someone go about making such a prediction if so much of the universe is out of our reach?

I'm going to say yes, there is life other than us, but that is just being optimistic maybe as it would be pretty cool :shy:

I don't think it has ever reached Earth though. No reason.

As I said this is a speculatory thread asking you to make your own conclusions, based on your own experiences and knowledge. Of course we cannot know what is going on beyond our visible Universe. But it's not a huge jump to assume that given the sheer numbers of stars we are not alone. Even scientists admit this as a credible hypothesis, given the numbers, this is why SETI exists. Of course the whole point is to get people talking about the likelihood, even if it isn't grounded in scientific fact, it still makes an interesting topic of conversation.

Why is it optimistic though, to think given the absolutely huge expanse of the universe, and the recent knowledge that planets are far more common than we thought, why is it a jump to think life isn't out there, somewhere else?

 

[_Mayday_]

It would be nice to think there is something else out there, but I can't imagine it. Would other life live in totally different condition? If so then yes, I would agree that there is probably other life, I say this because it just means that the conditions for life are less specific so I would think there is a higher probability.

It would be very interesting to see how they differ from us though.

 

[CEL]

... In the earliest posts in this topic, someone estimated the probability of a system having an "earth-like" planet to be around 1/3. That astonished me. I thinking that this one probability factor must be a very, very small.

The only solar system we know that has an earth-like planet is ours. There is one planet out of nine with life, so a more reasonable assumption is that 10% of the planets have such property.