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

[pinestone]

Well up to a point, I'd prefer if people would at least make a logical argument based on real world science or at least some sort of viable prediction, than just speculate. Otherwise we might as well just say God did it, there's only one life form in the Universe, prove me wrong.

I'll admit that I was reaching a little too far on my last comment just for the sake of argument. Yes, by all means let the discussion continue based on real world science and not solely on conjecture.

 

[pinestone]

No, what was said was not true to a point. It was completely wrong.

If it were known that existence and all of the laws of physics are fundamentally observer dependent, that would be one thing, but that is a wildly unsupportable extropolation of ideas from QM and not an appropriate discussion for this forum.

I thought 'anything goes' here in the lounge, but obviously that's not the case. In the future, I'll keep unsupportable ideas away from this forum. And, thanks for clarifying the issue of time for me. It was just a wild thought...

 

[Ivan Seeking]

No problem, but it is certainly not true that anything goes here.
https://www.physicsforums.com/showthread.php?t=5929

 

[RetardedBastard]

"There is a non-zero probability that advanced, intelligent lifeforms inhabit the cosmos. However, the likelihood that such 2 lifeforms have come across each other is incredibly remote, given the vast distances that separate them."

I guess most scientists would respond with something along this manner?

 

[Ivan Seeking]

"There is a non-zero probability that advanced, intelligent lifeforms inhabit the cosmos. However, the likelihood that such 2 lifeforms have come across each other is incredibly remote, given the vast distances that separate them."

I guess most scientists would respond with something along this manner?

I think most would say that it is a near certainty that there is intelligent life out there...if we consider the entire cosmos. Remember that the Drake eqn only applies to our galaxy.

My question is this: How can we talk about the odds of two advanced races crossing paths when we can't calculate the odds that interstellar drive technologies are possible or practical?

 

[Schrodinger's Dog]

No, what was said was not true to a point. It was completely wrong.

If it were known that existence and all of the laws of physics are fundamentally observer dependent, that would be one thing, but that is a wildly unsupportable extropolation of ideas from QM and not an appropriate discussion for this forum.

No I meant up to a point about speculation. As you'd already answered the other point I was talking about that only.

 

[Pythagorean]

My question is this: How can we talk about the odds of two advanced races crossing paths when we can't calculate the odds that interstellar drive technologies are possible or practical?

I'd always heard that interstellar travel would cost too much energy for us to be able to do it with Earth's resources. We might imagine a planet that would have the resources, but would such a planet be conducive to life? I don't know the details well enough to make an educated guess, but my gut is that such a probability is so low that it would harm the odds of advanced races ever crossing paths

But then, how do you want to define "crossing paths"? Would it not be enough to establish a long-distance communication with another race? Wouldn't that definition allow for a significant increase in the probability of two advances races crossing paths?

 

[CEL]

I'd always heard that interstellar travel would cost too much energy for us to be able to do it with Earth's resources. We might imagine a planet that would have the resources, but would such a planet be conducive to life? I don't know the details well enough to make an educated guess, but my gut is that such a probability is so low that it would harm the odds of advanced races ever crossing paths

But then, how do you want to define "crossing paths"? Would it not be enough to establish a long-distance communication with another race? Wouldn't that definition allow for a significant increase in the probability of two advances races crossing paths?

Of course we could not take with us the fuel for a two way trip until the nearest star. But when we master controlled hydrogen fusion, we could gather the fuel during the trip. It is estimated that there exists on average one hydrogen per cubic centimeter in interstellar space.
The ship should have a sustained environment, with plants providing oxygen and food and using waste to replace minerals.

 

[pinestone]

...Would it not be enough to establish a long-distance communication with another race? Wouldn't that definition allow for a significant increase in the probability of two advances races crossing paths?

My thoughts exactly. The SETI project: http://setiathome.berkeley.edu/ currently has over 3 million people sharing their resources in an effort to detect some sort of signal(s) from other life-forms. 'Receiving' seems like a good place to start- transmitting can come next...

 

[DaveC426913]

'Receiving' seems like a good place to start- transmitting can come next...

Yes. And the people at SETI realized that this logic would hold for all other races too, resulting in everyone listening and no one sending. Which leads logically to the conclusion that we've got to do both.

 

[Schrodinger's Dog]

Yes. And the people at SETI realized that this logic would hold for all other races too, resulting in everyone listening and no one sending. Which leads logically to the conclusion that we've got to do both.

Which fortunately we do anyway without even trying, some of those waves escape the Earth. Now all we have to do is assume that the aliens aren't all broadcasting on subspace links and moved from radio to any other tech in the same way, so that we can be sure we're sending a signal in a broadcast range/spectrum someone can pick up. No point in rrecieving just radio if aliens are communicating ladio.

 

[pinestone]

Which fortunately we do anyway without even trying, some of those waves escape the Earth. Now all we have to do is assume that the aliens aren't all broadcasting on subspace links and moved from radio to any other tech in the same way, so that we can be sure we're sending a signal in a broadcast range/spectrum someone can pick up. No point in rrecieving just radio if aliens are communicating ladio.

We assume aliens would be 'listening' to our communications on RF frequencies, but if they are indeed a higher and more evolved civilization, who's to say they wouldn't be using light, x-rays or gamma rays for communication frequencies? Shorter wavelengths can travel greater distances than conventional RF without significant attenuation.

 

[Schrodinger's Dog]

The good thing about photons is, radios pick up all sorts of wavelengths, so if you're talking about a range it's not too bad, of course gamma and x-ray would be well beyond the scope of any but radio telescpopes, luckily we have them too. I think it's not beyond the realms of possibility that they are using something completely alien and undetectable by normal means though. But as you say I'm sure they would have gone through the less tech heavy options first, occam's razor would suggest that, assuming they applied that sort of methodology to their tech.

I don't think they'd use light as it suffers too much from attenuation, but who knows it's a viable communication means between planets if the signal is powerful enough? And quantum communication is not sci fi any more.

 

[Ivan Seeking]

I'd always heard that interstellar travel would cost too much energy for us to be able to do it with Earth's resources.

This is based on the physics that we know. How can we assign the odds that there might be technologies possible through a physics that we can't or don't yet understand? Either such technologies are possible or not. There are no odds. We can make assumptions based on what we know, but considering that we don't have a TOE [physicists don't even agree on whether there can be a TOE, or if M-Theory is physics or philosophy], it seems premature to assume that physics is complete enough for us to set limits on highly advanced beings who could have as much as a billion year head start on us.

 

[Schrodinger's Dog]

Also assumes that Earth's resources are all we have. And even then Earth's resources are a hell of a lot of energy we can't yet tap, if you catch my drift.

 

[baywax]

Consider this:

Origin on Earth or Arrival from Space

The idea that life on Earth had an extra-terrestrial origin may be traced back to the ancient Greek philospher Anaxagoras, who lived in the fifth century B.C. Anaxagoras claimed that the universe is made of an infinite number of spermata (seeds). These give rise to life forms on reaching the earth. Anaxagoras coined the term Panspermia, meaning literally 'seeds everywhere', for his proposal.

http://www.simsoup.info/Origin_Issues_Earth_Or_Space.html

 

[drankin]

There's nothing out there. Makes for good movies though.

This post was temporarily deleted by mistake.
Sorry about that.
Ivan

 

[Ivan Seeking]

Study dampens hopes of finding E.T.

... Watson estimates the overall probability that intelligent life will evolve as the product of the probabilities of each of the necessary steps. In his model, the probability of each evolutionary step occurring in any given epoch is 10 percent or less, so the total probability that intelligent life will emerge is quite low (less than 0.01 percent over 4 billion years). Even if intelligent life eventually emerges, the model suggests its persistence will be relatively short by comparison to the lifespan of the planet on which it developed. [continued]

http://www.msnbc.msn.com/id/24051247/

 

[Schrodinger's Dog]

Watson estimates the overall probability that intelligent life will evolve as the product of the probabilities of each of the necessary steps. In his model, the probability of each evolutionary step occurring in any given epoch is 10 percent or less, so the total probability that intelligent life will emerge is quite low (less than 0.01 percent over 4 billion years). Even if intelligent life eventually emerges, the model suggests its persistence will be relatively short by comparison to the lifespan of the planet on which it developed.

I'm not sure how he justifies this comment, since from our perspective there hass only been one "intelligent" life form and no one knows how long it's going to last, 1 billion years seems an awfully long time to me.

I know there have been a series of extinction events that lead or even made intelligent life possible, but why so gloomy about the lifespan of intelligent life?

Obviously it's speculation, anyway, but it's a tad pessimistic I think.

 

[baywax]

http://www.msnbc.msn.com/id/24051247/

So there's a 100 percent chance that I exist yet before that happened the probability was well below 0.01 percent that I would happen.(?)

 

[Schrodinger's Dog]

So there's a 100 percent chance that I exist yet before that happened the probability was well below 0.01 percent that I would happen.(?)

Yeah, given the expanse of the universe and not one galaxy that figure obviously rises dramatically, believe it or not it's not a contradiction. It's just a bit overly pessimistic IMO.

And our galaxy is $\sim$12 billion years old

 

[baywax]

Yeah, given the expanse of the universe and not one galaxy that figure obviously rises dramatically, believe it or not it's not a contradiction. It's just a bit overly pessimistic IMO.

And our galaxy is $\sim$12 billion years old

A nice way out of discussing age with people is to remind them we are all the same age as the universe... looking around 13.5 billion years old... very wrinkly! But you're right, with the shear amount of time and space we have been handed, the 0.01 percent probably comes down to about 15 million equivalents to Rome being built over that time and space. And that's being pessimistic.

 

[himynameismar]

There has to be!

 

[CEL]

A nice way out of discussing age with people is to remind them we are all the same age as the universe... looking around 13.5 billion years old... very wrinkly! But you're right, with the shear amount of time and space we have been handed, the 0.01 percent probably comes down to about 15 million equivalents to Rome being built over that time and space. And that's being pessimistic.

Not quite! At the beginning of the universe only hydrogen and helium existed. Elements until oxygen were and are produced from nuclear reactions in the stars. Heavier elements are produced only at the explosion of supernovas, so the calcium, iron and other heavy elements that constitute our bodies have a more recent origin.
But we can say that we are as old as the solar system (around 4.5 billion years).

 

[Gigacore]

If aliens have really visited our planet, then why do they visit US most ? Do they like US People ;) ?

 

[baywax]

Not quite! At the beginning of the universe only hydrogen and helium existed. Elements until oxygen were and are produced from nuclear reactions in the stars. Heavier elements are produced only at the explosion of supernovas, so the calcium, iron and other heavy elements that constitute our bodies have a more recent origin.
But we can say that we are as old as the solar system (around 4.5 billion years).

That depends on how you determine age. Some people say they're as old as the span of time between their conception and the present. Some people say they're as old as the span of time between birth and the present.

All the elements and events that conspired to bring about an organism such as myself, are what I consider my origin and everyone else's.

Here is the (theretical) version of events that took place in the first few seconds of the universe.

Approximately 10−35 seconds into the expansion, a phase transition caused a cosmic inflation, during which the universe grew exponentially. After inflation stopped, the universe consisted of a quark-gluon plasma, as well as all other elementary particles. Temperatures were so high that the random motions of particles were at relativistic speeds, and particle-antiparticle pairs of all kinds were being continuously created and destroyed in collisions. At some point an unknown reaction called baryogenesis violated the conservation of baryon number, leading to a very small excess of quarks and leptons over antiquarks and anti-leptons—of the order of 1 part in 30 million. This resulted in the predominance of matter over antimatter in the present universe.

A rather heated conception by the sounds of it.

http://en.wikipedia.org/wiki/Big_Bang#Timeline_of_the_Big_Bang

 

[CEL]

That depends on how you determine age. Some people say they're as old as the span of time between their conception and the present. Some people say they're as old as the span of time between birth and the present.

All the elements and events that conspired to bring about an organism such as myself, are what I consider my origin and everyone else's.

Here is the (theretical) version of events that took place in the first few seconds of the universe.



A rather heated conception by the sounds of it.

http://en.wikipedia.org/wiki/Big_Bang#Timeline_of_the_Big_Bang

If you count your age by the age of the quarks and leptons that form the elements in your body, maybe you are right. But the neutrons that combine with the protons to build elements above hydrogen are short lived (half life of 10.3 minutes in its free form) and heavy elements were formed billions of years after the Big Bang.

 

[baywax]

If you count your age by the age of the quarks and leptons that form the elements in your body, maybe you are right. But the neutrons that combine with the protons to build elements above hydrogen are short lived (half life of 10.3 minutes in its free form) and heavy elements were formed billions of years after the Big Bang.

Most conceptions are pretty short lived too, from what I hear. But the results are the results.

*************

The longest a civilization has lasted on Earth has been around what, 3000 years? Taking Egypt as an example you can see the ups and downs of their technological prowess. At some point between 4000 and 10,000 years ago they were building pyramids by a method no one has yet figured out today. Yet the Egyptians of today would be hard pressed to erect one of those let alone one of the incredible obelisks that are left in the neighbourhood.

So what are the odds of a civilization lasting long enough to master intergalactic or interstellar travel? Could they keep from killing each other or corporate competitions long enough to put this kind of travel together?

 

[H.M. Murdock]

There are even high hopes of finding microscopic life in one moon of Jupiter and in other places in the solar system. and that is only in our solar system.
In the universe there are more solar systems than grains of sand in the whole earth.
So I guess the question should be whether there is another sorts of inteligent life in our galaxy, rather than in the whole universe.

Also considering the fact that we are extremely unique I don't see why another inteligent being wouldn't be interested in us as a developing species. so it is problably that they may have been interested in a place like earth.

 

[Ivan Seeking]

Astronomers have sighted the smallest extrasolar planet yet orbiting a normal star - a distant world just three times the size of our own.

...The planet orbits a star which is itself of such low mass it may in fact be a "failed star", or brown dwarf.

Astronomers found the new world using a technique called gravitational microlensing. This takes advantage of the fact that light is bent as the rays pass close to a massive object, like a star.

The planet, called MOA-2007-BLG-192Lb, is about 3.3 times the size of Earth. Some researchers have suggested the planet could have a thick atmosphere and have even speculated there could be a liquid ocean on its surface. [continued]

http://news.bbc.co.uk/2/hi/science/nature/7432114.stm

 

[Ivan Seeking]

...The scientists, from Europe and the USA, say that their research, published in the journal Earth and Planetary Science Letters, provides evidence that life's raw materials came from sources beyond the Earth.

The materials they have found include the molecules uracil and xanthine, which are precursors to the molecules that make up DNA and RNA, and are known as nucleobases.

...The analysis shows that the nucleobases contain a heavy form of carbon which could only have been formed in space. Materials formed on Earth consist of a lighter variety of carbon. [continued]

http://www.physorg.com/news132577096.html
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-4S3G406-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=d14b77a37b5fdfa2f307a1b73badb63e

 

[Ivan Seeking]

A trio of "super-Earths" have been found near a sun-like star, a team of European astronomers announced today.

...The part of the sky being studied contains 45 potential planets that are smaller than 30 times the mass of Earth, the astronomers said. Most of them orbit HD 40307 quickly—every 50 days or less.

"We are convinced that there are plenty of planets everywhere," said Didier Queloz, a member of the research team from the Observatoire de Genève in Switzerland.

The discovery is creating a buzz throughout the astronomy community.[continued]

http://news.nationalgeographic.com/news/2008/06/080616-super-Earth's.html

 

[B. Elliott]

I saw that article a couple of day ago on Science Daily. The size of the planet instantly made me think of this article...

Others have speculated that the heat pulse due to the Lunar-originating impact was the trigger to start plate tectonics but we show that this is a minor effect of timing. Instead, the enabling factor is the removal of ~70% of the primordial crust of the Earth to a position in orbit 400,000 km overhead. If that crust were returned and replaced on Earth it would fill the ocean basins with wall-to-wall continent. This would choke plate tectonics, as on Venus, and displace the oceans to flood the land to a depth of several km.

Without plate tectonics, new mountain belts could not form. Earth would be a Waterworld with occasional shield volcanoes emerging briefly above the waves. If regular catastrophic convective overturn occurred, as on Venus, life would have a precarious foothold indeed. There may be many habitable worlds, but they are likely to be Waterworlds where swimming or flying creatures might evolve significant intelligence, but would be unlikely to progress to discover fire, electricity, computers, radio, and rockets.

http://www.spacedaily.com/news/life-01x1.htmlI wonder if we're currently able to detect moons around any of these planets?

 

[CEL]

I saw that article a couple of day ago on Science Daily. The size of the planet instantly made me think of this article...



http://www.spacedaily.com/news/life-01x1.html


I wonder if we're currently able to detect moons around any of these planets?

There is another theory that requires a moon for the appearance of life:

The chemicals of life are dissolved in the oceans in concentrations too small to combine and originate complex molecules.
Some biologists believe that life originated in clay. Tides carried the primeval soup into puddles, where water evaporated leaving the chemicals embedded in the clay. There the concentration was big enough for the formation of complex molecules.
Although the Sun causes tides, they are too small in comparison with lunar tides. So, it is possible that the existence of a big moon in a close orbit is essential to the origin of life.

 

[DaveC426913]

There is another theory that requires a moon for the appearance of life:

The chemicals of life are dissolved in the oceans in concentrations too small to combine and originate complex molecules.
Some biologists believe that life originated in clay. Tides carried the primeval soup into puddles, where water evaporated leaving the chemicals embedded in the clay. There the concentration was big enough for the formation of complex molecules.
Although the Sun causes tides, they are too small in comparison with lunar tides. So, it is possible that the existence of a big moon in a close orbit is essential to the origin of life.

Well, clay aside, there is a popular theory that ascribes the origin of life to the existence of tidepools.