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

[CEL]

If you think of our existence as a 10,000 year cycle - how many comparable cycles are possible (& how long have permissable conditions existed somewhere in the Universe)?

From where did you get the idea of a 10,000 year cycle? Homo sapiens is here for around 150 kyears, civilization has 12 000 years and technological civilization around 100 years.

 

[WhoWee]

From where did you get the idea of a 10,000 year cycle? Homo sapiens is here for around 150 kyears, civilization has 12 000 years and technological civilization around 100 years.

No problem, consider a 150,000 year cycle. How many potential cycles have there been SOMEWHERE?

 

[VooDooX]

No problem, consider a 150,000 year cycle. How many potential cycles have there been SOMEWHERE?

the point is probability aside there's a chance even if ever so small that we are the first.. there has to be a first and maybe just maybe we are it however unlikely it also has to be considered

 

[CEL]

No problem, consider a 150,000 year cycle. How many potential cycles have there been SOMEWHERE?

If humanity is wiped out, 150 kyears is not enough for evolution to work out another intelligent species on Earth.
If only civilization is completely destroyed (we are doing well for that!) 10 000 years would be enough to reconstruct it. The problem is that we have no evidence of civilizations preceding our own.
If you are saying that ours is the first civilization on Earth and others will succeed and be destroyed in intervals of 10 000 years, this is only a speculation.

 

[WhoWee]

If humanity is wiped out, 150 kyears is not enough for evolution to work out another intelligent species on Earth.
If only civilization is completely destroyed (we are doing well for that!) 10 000 years would be enough to reconstruct it. The problem is that we have no evidence of civilizations preceding our own.
If you are saying that ours is the first civilization on Earth and others will succeed and be destroyed in intervals of 10 000 years, this is only a speculation.

Unless ALL life was wiped out on Earth, I don't know why 150,000 years wouldn't be enough time.

However, my question is how many potential cycles of 150,000 years have been possible - that is conditions may have been conducive to sustaining life somewhere/anywhere in the Universe. Given the time since BB, has it been 2 billion years, 1 billion, or 570 million (the time before our dinosaurs - Cambrian) years - what is the estimate for when conditions SOMEWHERE would have first been suitable?

 

[DaveC426913]

Unless ALL life was wiped out on Earth, I don't know why 150,000 years wouldn't be enough time.

150K years is how long it took for H.sapiens to develop high intelligence from the already existing intelligent (societal) humanoids walking the Earth.

There are no creatures anywhere near the intelligence of H. habilis et al from which to develop high intelligence - unless you look to the apes (which would be simply repeating the same steps). And even that is several million years.

 

[DaveC426913]

Given the time since BB, has it been 2 billion years, 1 billion, or 570 million (the time before our dinosaurs - Cambrian) years - what is the estimate for when conditions SOMEWHERE would have first been suitable?

Surely not before the creation of Population I high-metallicity stars. That puts the first potential for life fairly recent in the universe's life.

 

[CEL]

150K years is how long it took for H.sapiens to develop high intelligence from the already existing intelligent (societal) humanoids walking the Earth.

There are no creatures anywhere near the intelligence of H. habilis et al from which to develop high intelligence - unless you look to the apes (which would be simply repeating the same steps). And even that is several million years.

I agree. The common ancestor between H. Sapiens and apes is thought to have existed 5 million years ago. Apes have evolved from that ancestor and have not developed intelligence after those million years. Even if humanity disapeared, it is not sure that some ape could evolve to an intelligent being.

 

[N468989]

Could it be possible that some being greatly more advanced than us evolve in a few days on any other place in the universe and completely wipe us out? It's like what we are to insect's and animals. So much more power. Just to imagine that the rate of evolution of life in another place could be unimaginable. One day of our life could mean millions of years of evolution for another life form in another time-space dimension.

Tomorrow we could have life visiting Earth that was created yesterday... with power much greater than ours.

In our understanding of things, we are still yet to be created, we know nothing.

The question to the thread would be: Is there, can there be, has there ever been, other life in the universe.

 

[DaveC426913]

...imagine that the rate of evolution of life in another place could be unimaginable. One day of our life could mean millions of years of evolution for another life form...

The universe is made of the same 92+ elements. By and large, the chemistry everywhere in the universe is constrained by this.

 

[Ivan Seeking]

In the Jan edition of Scientific American

Looking for Life in the Multiverse
Universes with different physical laws might still be habitable

 

[VooDooX]

apparently scientists announced today they are really rethinking that meteor that had the thing the looked like microscopic bacteria from Mars basically saying the only option is its a biological property and if thsi rock was on Earth they would have no problem classifying it as such


ALH84001 is this meteor I am sure everyone remembers it

http://www.physorg.com/news180264793.html"

“For many years, the presence of the specific kind of nanomagnetite formed by magnetotactic bacteria on Earth have been completely accepted as a biosignature when found in any Earth sediment or rock,” Thomas-Keprta said, noting that these magnetite have very specific properties.

“When we first documented these specific properties in the ALH84001 carbonates, the only alternate non-biologic hypothesis that was commonly accepted as viable was the thermal decomposition of iron-bearing carbonate,” she said. “Now that we have completely falsified this hypothesis with this latest paper, we are still left with the specific properties of the ALH84001 magnetite that, if found on Earth, would be a robust biosignature indicating production by bacteria.

“We also point to the many discoveries since our original paper showing supporting evidence such as an early strong magnetic field on Mars (necessary for the development of magnetotactic bacteria); the presence of near surface water at many locations on current-day Mars; the presence of possible oceans, major drainage channels, and other features associated with an early wet Mars; and the recent evidence for variable releases of methane into the Martian atmosphere. . . . We do not believe it is too incautious to restate our original hypothesis that such magnetites constitute strong evidence of early life on Mars.”

ALSO on the moon?!
http://spacefellowship.com/2009/12/16/signs-of-life-detected-on-the-moon/"

Surendra Pal, associate director of the Indian Space Research Organization (ISRO) Satellite Centre says that Chandrayaan-1 picked up signatures of organic matter on parts of the Moon’s surface. “The findings are being analyzed and scrutinized for validation by ISRO scientists and peer reviewers,” Pal said.

At a press conference Tuesday at the American Geophysical Union fall conference, scientists from NASA’s Lunar Reconnaissance Orbiter also hinted at possible organics locked away in the lunar regolith. When asked directly about the Chandrayaan-1 claim of finding life on the Moon, NASA’s chief lunar scientist, Mike Wargo, certainly did not dismiss the idea but said, “It is an intriguing suggestion, and we are certainly very interested in learning more of their results.”

Life seems to be pretty common indeed if 3 objets in our solar-system alone have it
what you guys think?

 

[Schrodinger's Dog]

In the Jan edition of Scientific American

I love this thread, I started it ages ago thinking it'd run maybe a few weeks at best and here we are two and a half years later and people are still posting fascinating stuff.

Ivan must be pleased with this zombie thread.

^ I heard about that on the news, interesting stuff.

Keep it up folks, gj.

 

[DaveC426913]

Welcome back, SchroDog.

 

[DaveC426913]

ALSO on the moon?!
http://spacefellowship.com/2009/12/16/signs-of-life-detected-on-the-moon/"



Life seems to be pretty common indeed if 3 objets in our solar-system alone have it
what you guys think?

Well, there's a fairly big gap between organic compounds and life. But cool nonetheless.

 

[VooDooX]

well mainly the Mars thing excites me as they have no other pluasible explanation left other then life so if that's true the answer to this thread is .. yes but fossilized :)

 

[Schrodinger's Dog]

Welcome back, SchroDog.

Thanks I been wondering and wandering around the forum deserts swatting up on me philosophising and physics and stuff. But figured it was time to come back to the oasis.

Well, there's a fairly big gap between organic compounds and life. But cool nonetheless.

Dave you're a star in this thread thanks for posting too many other MVPs to mention but props to Ivan too.

 

[HarryDaniels]

UFOs

What is the oppinion on UFOs and aliens visiting earth. I stand very on the side of against them coming here for a number of reasons, but it would be interesting to see what everyone elses take on it is. My reasons are:

Speed vs energy
Assuming that aliens could travel a very high speed, such as light speed, the amount of energy needed to raise something the size of a form of space travel to that speed for 4 years, assuming that there is a planet populated that orbits proximus centuri, would be infinate. You would also then need more energy to sustain it at this speed.

Time
As we know, time slows down for those going at a higher speed. Now, again assuming that these aliens can travel at the speed of light, they would be going far slower in time. Perhaps many millions of years behind us if hey were far away. And the likelyhood of them existing suggests that they are very far away.

Distance
Assuming again that the aliens could get to us and could travel at light speed, they could be far even for light, perhaps on the other side of the galaxy. In which case, it would take them, even at light speed, 100,000 years (give or take). I highly doubt that they would live that long and also, if theey are, they have to supply the energy and have an energy store, high enough to sustain light speed for 100,000 years.

These evidence, to me, proove that aliens haven't visited us. However, I am not an expert on the subject and would like to know what others think. Please share with me, or us, your thoughts on space travel.

 

[mgb_phys]

What is the oppinion on UFOs and aliens visiting earth.

Why would they visit us in person?
You build 1000 space probes, shoot them off toward nearby G type stars.
When one arrives it builds a bunch of planetary probes to examine any habitable planets.
It then builds 1000 copies of itself and sends them off to a further set of G type stars.

Even if takes the probe a 1000 years to reach the next star and a year to build each copy of itself within a few million years you have a probe in orbit around every habitable planet in the galaxy

(search for Von Neumann machines)

 

[Ivan Seeking]

Why would they visit us in person?
You build 1000 space probes, shoot them off toward nearby G type stars.
When one arrives it builds a bunch of planetary probes to examine any habitable planets.
It then builds 1000 copies of itself and sends them off to a further set of G type stars.

Even if takes the probe a 1000 years to reach the next star and a year to build each copy of itself within a few million years you have a probe in orbit around every habitable planet in the galaxy

(search for Von Neumann machines)

This paper [published in the JBIS], makes the point that it makes the most sense to look for probes, not ET.
http://www.ufoskeptic.org/JBIS.pdf

The last two posts were merged with this thread.

 

[mikelepore]

Why would they visit us in person?

Since they're another species, we have no reason to expect them to have behaviors that seem to demonstrate "reasons" or "motives" to us, just as it makes no sense to us that salmon migrate the way they do, or mosquitos fly into flames. For example, perhaps the extraterrestrials have only one emotion and it is: "If you can possibly leave the world, then leave" -- and that has motivated everything else -- eat and reproduce in order to survive so that we can later leave -- invent tools and go through industrial development so that we can later leave. It doesn't have to make any sense to us. Our own set of reasons for doing things (scientific curiosity, aesthetic appreciation, sensation of comfort, sex drive, etc.) could be accidental and found only on earth. Space travelers anywhere in the universe only need to have evolved due to any reason whatsoever for becoming tool-makers with dexterous limbs and powers of abstraction. Their "why" might be incomprehensible to us.

I offer the same answer to those who ask, "If E.T. came here, why didn't it land at the United Nations and announce itself?" or "What would be the point of making a kaleidoscopic pattern in a cornfield?" The inquirer is projecting human motivations onto something that is not known to be remotely similar to human life. I give the same answer to Neil deGrasse Tyson, who doubts the existence of interstellar explorers who travel for many generations, because, he said, "Scientifically, we have a rule: you want to be alive at the end of your experiment, not dead." Yes, humans do, but we don't know that other intelligent beings think like us.

I don't assert that any of these things have actually happened. I'm only citing these examples to caution that the imputation of human motives to alien life would not be justified.

 

[shredder666]

I think its highly probable that aliens exist, but probably really far away.

Probability of alien life form existing in the universe would be, imho, irrelevant, because what are the chances of them developing means interstellar travel?

But if, in some science fictions... they travel on motherships, then I guess it would only be a matter of time before they enslave us..

 

[Ivan Seeking]

Probability of alien life form existing in the universe would be, imho, irrelevant, because what are the chances of them developing means interstellar travel?

That is an interesting question. Do we know?

If interstellar travel is possible but we just haven't discovered the required physics, it may be a near certainty that we have been or will be visited many times. On the other hand, it may be that we already recognize the limits of travel and the chance of visitations is zero. We can't really talk about the odds of a visitation unless we can calculate the odds that future discoveries will or could be made. So it seems to me that we can't know the odds [probability]; the range is 0 to 1.

 

[HarryDaniels]

On the subject of motives, assuming they would send a probe so many light years away from them, why? If we took this to a human motive for this, you could say it was for an energy source. If they could travel at the speed of light they would have to have a huge amount of to sustain the speed of light for four years or more. This would be impossible. The same rule would apply for an unmanned (or unaliened ;)) probe, they would still need a huge amount of energy.

Also, there are so many stars in the sky with so many planets orbiting them. How could the aliens find us, probe or not. I am not debating that aliens exist, if we looked at the figures, it is very likely for life to exist just in our galaxy, let alone the hundreds of millions of other galaxies. Though the likelihood of them reaching here is almost zero, and breaks many laws of physics as well as time. As I said in my last post, if they traveled at light speed for four years at the least, imagine how slow they would be going in time, if they decided to visit us when we were just becoming human, they may take four years in there perception, but they would take perhaps the human races lifetime to get here in our time. Its very unlikely.

And finally, no matter how incredible the ET life is, I very much doubt that it could break the laws of physics.
-Harry

 

[Ivan Seeking]

And finally, no matter how incredible the ET life is, I very much doubt that it could break the laws of physics.
-Harry

We just have to be careful when we invoke the "laws of physics". To which laws in particular do you refer?

Even with our undestanding of physics today, exotic forms of transportation, say in the form of a wormholes, for example, might be possible given enough energy. So do we mean the laws of physics or the practical limits of technology? Also, physics is not complete. We cannot state with certainty what limits do exist even within the existing framework. The recent interest in Heim's work is just one example of how quickly our perception of the possibilities can change. Suddenly we were talking about a practical hyperspace drive that could EXCEED the speed of light as viewed from our frame of reference, without violating the "laws of physics".

There are also ideas like the Alcubierre metric, or "Warp Drive".

 

[bobquantum]

Well, there are a hell of a lot of stars out there, so it is almost for sure that there is intelligent life out there. The problem is, the chance of them visiting a simple star system such as us out of a quadrillion other star systems is pretty mch close to nil.

 

[Ivan Seeking]

Well, there are a hell of a lot of stars out there, so it is almost for sure that there is intelligent life out there. The problem is, the chance of them visiting a simple star system such as us out of a quadrillion other star systems is pretty mch close to nil.

Is it? I can imagine scenarios that might motivate an alien species to investigate us. For one, perhaps life is rare. In that event, one might imagine advanced technolgies that allow alien scientists to find us. Note that in the time that I have moderated this forum, our ability to detect earth-like planets has improved dramatically. We are doing things now once thought to be impossible because scientists years ago could not imagine the electronics revolution and the resulting computing power now possible. How much better at this might we be in a million years? Also, life may be common, in which case we might expect to have neighbors [in galactic terms].

So how exactly do you calculate your odds?

 

[HarryDaniels]

Again, it is all relevant to energy and where would the energy to open a worm hole come from, assuming that they are real and can be opened. Where would this energy come from.

 

[Ivan Seeking]

Again, it is all relevant to energy and where would the energy to open a worm hole come from, assuming that they are real and can be opened. Where would this energy come from.

That is certainly a problem. That is why I pointed out that we may be talking about the limits of technology and not limits of physics. But I also look to potential cracks in the lining. Until the picture is complete [if a unified theory can ever be found], one can always argue that the door is open to discoveries that fundamentally change the game. The best example of this recently is probably the stuff related to Heims work.

I want to be clear that at best, Heim's work is under consideration, and at worst it may already be known to be hopelessly flawed. However, as the reports of his work emerged, the immediate potential ramifications of his theory were nothing short of astounding. In fact we saw NASA and two other agencies [I think the USAF was one] announce plans to test the concept. But the point is not to say Heim's work is relevant, rather that our expectations can change very quickly.

To the best of my understanding, according to one take on Heim's theory, it may be possible to shift a craft into another "space" in which the speed of light is relatively greater than in our space. Now I don't claim to understand the meaning of that, but that was the basic idea. I believe his theory provides for several higher dimensions that somehow allegedly makes this possible. It was also stated that one could artificially drive the speed of light to higher values in that space by adding energy to the engine or drive. By doing this, one could exceed the speed of light relative to our space while not exceeding the speed of light in the alternate space.

This is an example of how one might imagine a crack in the lining - a way around the problem of distance without violating the known laws of physics. The Alcubierre drive proponents seek to circumvent the speed of light limit in a somewhat similar fashion - by moving through a space that is moving through space [as near as I can recall, and whatever that means]. The point is not that any of these ideas will work, rather that we can already imagine ways that approaches like these might work.

Here is one old thread about Heim's theory. I want to stress again that I'm pretty sure that people have found problems with his work. It was believed by some serious scientists to be a unified theory.
https://www.physicsforums.com/showthread.php?t=106059

Even worse for those who do not favor this line of thought: Even with a unified theory, the possibility of future discoveries cannot be excluded.

 

[Ivan Seeking]

A correction to the statement about the alcubierre drive: The idea there is to contract space in the direction of motion while expanding space behind it, or something along those lines. Sorry, I have to be vague as I haven't reviewed this sort of thing for a long time. Here are a couple of threads about that subject.

https://www.physicsforums.com/showthread.php?t=255507
https://www.physicsforums.com/showthread.php?t=365753

I think I was describing how the warp drive operates on the Enterprise , but there are a few serious, exotic ideas, floating around.