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

[Pythagorean]

However, it is a perplexing question to ask where and when did life first begin to emerge in the universe. And its not so far off the topic of this thread to ask this because, one would have to know these things in order to know when and how life "has visited Earth".

We can consider the time period we have to work with... 14 billion years... and the amount of material available to form life with... 10 to the power of 9... we still have to come up with the period during which life could form in the universe with proper conditions and relative stability for continued evolution etc...

I'm not the best at statistics and modeling but PF is probably the right place to ask this question..."what is the earliest period in the universe's development that life could begin to develop and where would that have been?"

This brings up another question that has always swam around when considering abiogenesis, too. Did life necessarily have to start in a single place?

Could there have been a period in a universe that was very conducive to the formation of life somewhat independent of space? Of course, there would still be a distribution of regions where it was more or less probable, but why is the question always asked from the standpoint that there's only one place of origin?

ADDENDUM:

Of course this doesn't mean that all these 'origin zones' were conducive to long-term development and evolution of their host life forms. Apparently (at least in the carbon-based model) we need something like Earth for that, where volcanoes and earthquakes serve to distribute nutrients about the surface of the planet.

 

[BoomBoom]

Very massive stars, exactly the ones who turn supernovae, are short lived. An extremely huge star can go supernova in a few hundred million years. So, the building blocks of life were possibly present in the first billion years of the universe.

Thanks Cel.
So, now how long would it take for those heavier elements to condense into new solar systems and the planets to cool to the point where abiogenesis could begin?

Then we can tack on a few billion years on top of that for life to evolve...

I'm just trying to get a sense of what the earliest possible point at which life could have evolved in the age of the universe.

 

[baywax]

Then we can tack on a few billion years on top of that for life to evolve...

Actually, with Earth being around 4.4 billion years old and the stromatolites that are thought to have been formed by some form of algae at around 3.5 billion years... it looks as though life only requires about a billion years to get to a point where it is mobile and constructive. This would mean that by about 500 million years into Earth's development there could have been a rudimentary form of life developed and evolving on earth.

In other words, with the proper conditions, you don't need "billions" of years for life to develop. This would dramatically push back the date of the first "emergences" of life in t he universe's "habitable zones".

(The plurals are for Pythagorean)

 

[BoomBoom]

This brings up another question that has always swam around when considering abiogenesis, too. Did life necessarily have to start in a single place?

If we really believe (well, many of us) that life forms so easily given the proper elements and conditions, then why is it that many assume it only happened once and all life on Earth came from a single source? If this is the case, then it should be happening all the time here on Earth IMO.

Craig Ventor is doing his ocean sequencing project where he is taking random samples from waters all around the world and sequencing the DNA recovered and I heard they are discovering incredible amounts of new genes not found in any other species (I can hunt down a link if required). Much of the microbial life of Earth could have come about more recently.

If this is not the case, and all life on Earth did come about by some freak accident, then I'd be much more skeptical about it existing elsewhere.


Ok, here's one article http://www.genomenewsnetwork.org/articles/2004/03/04/sargasso.php"

In the Sargasso Sea, they found 1800 species of microbes, including 150 new species of bacteria, and over 1.2 million new genes. Although they don’t know what most of these genes do, the research is a first step to understanding more about life in the Sargasso Sea and the larger ocean.

 

[BoomBoom]

This would mean that by about 500 million years into Earth's development there could have been a rudimentary form of life developed and evolving on earth.

In other words, with the proper conditions, you don't need "billions" of years for life to develop.

True, but I was putting this in the context and frame of reference of the original poll question, "...and if so, has it visited earth?".

For a life form to develope far enough to engage in space travel and travel to distant solar systems, I think it would be safe to assume that would take billions of years. In other words, how soon in the age of the universe could "intelligent" life have emerged?

 

[baywax]

For a life form to develope far enough to engage in space travel and travel to distant solar systems, I think it would be safe to assume that would take billions of years. In other words, how soon in the age of the universe could "intelligent" life have emerged?

For a virus, which can withstand the extremities of space, it would take as long as a virsus takes to develop... probably not billions but millions of years.

Intelligent life is not too far behind the development of rudimentary life forms. But you're right in that it would be around 3 billion years. However, if we look at whales as intelligent or primates with the ability to sign and recognize symbols etc... we can knock about 25 million years off the 2-3 billion.

So, we still need to know at what period during the development of the universe there were areas of stability and materials and conditions that would support life's origins.

 

[DaveC426913]

Intelligent life is not too far behind the development of rudimentary life forms. But you're right in that it would be around 3 billion years.

Which means they've could have been around for 10 billion years. Which poses the rather famous question:

So where are they?

 

[baywax]

Which means they've could have been around for 10 billion years. Which poses the rather famous question:

So where are they?

Actually we're trying to determine when, in the history of the universe, there were the proper conditions, materials and intervals for the first signs of life to develop in the universe.

This question will be answered partially if we know when the first supernovae were beginning to take place in the young universe.

Does anyone have the stats on that. I still haven't found any info on when the first supernovae started happening in the universe.

 

[DaveC426913]

Does anyone have the stats on that. I still haven't found any info on when the first supernovae started happening in the universe.

Look up "population III stars".

https://www.physicsforums.com/showthread.php?t=113668" that discusses at least the possibility of a Pop III star at a mere 900My after BB.

 

[BoomBoom]

Which means they've could have been around for 10 billion years. Which poses the rather famous question:

So where are they?

Intelligent life formed only 3.7B years after the BB? I think that is being VERY generous there.

We took nearly 5 billion years to arise and I would assume you could tack on a big chunk of time for the gases from the supernova we came from to condense into a new solar system...perhaps another billion or so?

As far as "where are they?":
Even giving the most optimistic assessments for the Drake equation, the nearest intelligent life could be 1,000+ LYs away. We have only been sending out signals that could be detected for 100 years or so. Chances are that an alien civilization wouldn't even be capable of detecting us for eons.

Then there is the other issue of whether or not interstellar travel is even physically possible in a reasonable span of time. So IMO the chance of aliens visiting Earth has got to be as close to 0% as you can get.

 

[baywax]

Look up "population III stars".

https://www.physicsforums.com/showthread.php?t=113668" that discusses at least the possibility of a Pop III star at a mere 900My after BB.

Thanks Dave.

This probability gives us about 13 billion years to develop life in the universe.

As we know, there are always spurts of development and evolution then catastrophes that can undo millions of years of evolution. Take for example the plight of the dinosaurids. So, with this factor in mind, we need to try to take down our expectations a fair amount to account for this phenomenon.
This is because a stable environment doesn't always stay stable.

 

[DaveC426913]

As far as "where are they?":
Even giving the most optimistic assessments for the Drake equation, the nearest intelligent life could be 1,000+ LYs away. We have only been sending out signals that could be detected for 100 years or so. Chances are that an alien civilization wouldn't even be capable of detecting us for eons.

Then there is the other issue of whether or not interstellar travel is even physically possible in a reasonable span of time. So IMO the chance of aliens visiting Earth has got to be as close to 0% as you can get.

The question though is: why have we not detected any radio or other leakage from them? They could be anywhere in the galaxy and, as long as they beat us to intelligence by a mere 100,000 years, we could detect them - if the signals were strong enough and if they weren't deliberately hiding.

 

[baywax]

The question though is: why have we not detected any radio or other leakage from them? They could be anywhere in the galaxy and, as long as they beat us to intelligence by a mere 100,000 years, we could detect them - if the signals were strong enough and if they weren't deliberately hiding.

Whether we've detected them or not may depend on the signals they're using. Could be very different technology like... micro waves or lasers or something that we either wouldn't look for or would miss completely.

 

[DaveC426913]

Whether we've detected them or not may depend on the signals they're using. Could be very different technology like... micro waves or lasers or something that we either wouldn't look for or would miss completely.

I suppose I forget just how darned big the sky is, and how big a light year is. It's not like they're going to have Christmas lights strung between the constellations.

 

[baywax]

I suppose I forget just how darned big the sky is, and how big a light year is. It's not like they're going to have Christmas lights strung between the constellations.

What are the possibilities of using laser to transmit info... and power even...?

 

[BoomBoom]

The question though is: why have we not detected any radio or other leakage from them? They could be anywhere in the galaxy and, as long as they beat us to intelligence by a mere 100,000 years, we could detect them - if the signals were strong enough and if they weren't deliberately hiding.

Good point. Although a mere billion years or so doesn't sound like much as far as the age of the universe is concerned, it is a VERY long time for a civilization to develope.

Even though the distances would probably be much to vast to send any type of signals back and forth (much less travel them), I would love to check out what they had on TV some 1000 years ago! :)

 

[Chronos]

The fact remains, there is no incontrovertable evidence 'aliens' have visited earth.

 

[CEL]

What are the possibilities of using laser to transmit info... and power even...?

The main reason laser is efficient in transmitting information is that the bean is focused in a narrow solid angle, instead of omni directionally.
If an alien civilization was deliberately trying to communicate with us, they could use a laser bean focused at our solar system, but this presuppose they know we are here and are interested in talking to us.
An omni directional transmission would spread its energy and soon become less powerful than the background noise.
Of course, if you use special codification, you can transmit and be detected with negative signal to noise (SN) ratios, but this assumes that the receiver knows the transmitted code.

 

[DaveC426913]

The main reason laser is efficient in transmitting information is that the bean is focused in a narrow solid angle, instead of omni directionally.
If an alien civilization was deliberately trying to communicate with us, they could use a laser bean focused at our solar system, but this presuppose they know we are here and are interested in talking to us.
An omni directional transmission would spread its energy and soon become less powerful than the background noise.
Of course, if you use special codification, you can transmit and be detected with negative signal to noise (SN) ratios, but this assumes that the receiver knows the transmitted code.

Not to contradict CEL, he may be an expert Legumications Specialist for all I know, but I have never found beans to be efficient over interstellar distances.



(Once is a typo, but twice is mock-worthy )

 

[CEL]

Not to contradict CEL, he may be an expert Legumications Specialist for all I know, but I have never found beans to be efficient over interstellar distances.



(Once is a typo, but twice is mock-worthy )

I stand corrected. But it is not polite to mock a foreigner for not spelling correctly your language.
Since I cannot edit my post, I ask the moderator to do this for me. I obviously meant beams not beans. Thanks.

 

[DaveC426913]

I stand corrected. But it is not polite to mock a foreigner for not spelling correctly your language.
Since I cannot edit my post, I ask the moderator to do this for me. I obviously meant beams not beans. Thanks.

Actually, your grammar and spelling are so good I had no idea English wasn't your first language. Otherwise I wouldn't have teased you. No hard feelings.

 

[CEL]

Actually, your grammar and spelling are so good I had no idea English wasn't your first language. Otherwise I wouldn't have teased you. No hard feelings.

Apologies accepted. I trust the spell checker to correct my writings, but since bean is an existing English word, of course the mistake was not detected.
By the way, I was born and live in Brazil.

 

[baywax]

The fact remains, there is no incontrovertable evidence 'aliens' have visited earth.

None have been identified. There are, however, two suspicious bits of evidence that aliens have visited here... on earth... Zapper Z's orchids and the humanoids with pointy heads in Vatican City.

 

[CEL]

None have been identified. There are, however, two suspicious bits of evidence that aliens have visited here... on earth... Zapper Z's orchids and the humanoids with pointy heads in Vatican City.

Could you please provide links for these evidences?

 

[baywax]

Could you please provide links for these evidences?

You can find Zapper's orchids in the "How Does Your Garden Grow?" thread.

Here's one pc of photo evidence of the pointy headed aliens... not sure but this one looks like Yoda...

http://www.spurgeon.org/images/pyromaniac/TeamPyro/b16.jpg

 

[CEL]

You can find Zapper's orchids in the "How Does Your Garden Grow?" thread.

Here's one pc of photo evidence of the pointy headed aliens... not sure but this one looks like Yoda...

http://www.spurgeon.org/images/pyromaniac/TeamPyro/b16.jpg

Good evidences.

 

[baywax]

Good evidences.

Yes but of what I'm not sure. Devil worship?

 

[baywax]

I see no reason to disbelieve that life exists elsewhere in the universe. The development of life is a relatively simple process that appears to require some mud, prions and nucleotides in a hot and turbulent environment. I don't think there is a shortage of this combination in the universe.

Whether extraterrestrial life has visited Earth or not is hard to prove beyond a doubt. If we are the product of extraterrestrial viral seeding or the intervention of some intergalactic travelers remains to be proven. Proving it will be difficult since we have no way of comparing life on Earth with life in another galaxy... as of yet.

Even if we find microbes on Mars, they may appear the same as terrestrial microbes because all microbes look the same. DNA matching may or may not help to distinguish between Mars microbes and Earth microbes. However, if Earth seeded Mars or Mars seeded Earth with microbes, in what way could this be demonstrated?

 

[DaveC426913]

Even if we find microbes on Mars, they may appear the same as terrestrial microbes because all microbes look the same. DNA matching may or may not help to distinguish between Mars microbes and Earth microbes. However, if Earth seeded Mars or Mars seeded Earth with microbes, in what way could this be demonstrated?

Gene mapping can tell us how divergent the two strains are. Finding strains on Mars that indicate they diverged from Earth life a billion years earlier than Earth had cooled would be a good indicator that Mars seeded Earth.

 

[baywax]

Gene mapping can tell us how divergent the two strains are. Finding strains on Mars that indicate they diverged from Earth life a billion years earlier than Earth had cooled would be a good indicator that Mars seeded Earth.

How do you date gene divergence?