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

[out of whack]

I'm just jumping to this last page after reading the first post, no time to read all of it. I cannot vote on this twofold question by lack of an option for "yes there is life elsewhere; no idea if they have visited us or not".

 

[StuMyers]

Jumping to the end as well to chime in "I seriously doubt it".

I've always kind of thought that since the Earth itself is on the order of 1/3 the age of the universe as a whole, and also since it took a "couple" of billion years for intelligent life to evolve here, it seems likely that we're amongst the first. The facts seem to bear this out as well, since AFAIK the universe doesn't yet appear to be teeming with life (though it's probably just a matter of time).

 

[Ivan Seeking]

The facts seem to bear this out as well, since AFAIK the universe doesn't yet appear to be teeming with life

How did you arrive at that conclusion?

 

[StuMyers]

How did you arrive at that conclusion?

Looking around.

Seriously though, if the universe were quite a bit older, I might start to expect seeing ancient extraterrestrial spores in old asteroids, life adapted to survive in vacuum, and whatnot. I'm just not seeing any.

Plus, AFAIK, the local part of the galaxy appears to be fairly quiet in the radio, relative to us. I doubt intelligent life would ever stop using radio.

 

[Ivan Seeking]

Spores in asteroids?

With the advent of the internet and directed microwaves, we are already on our way to going radio silent.

Also, I have to wonder why you would simply ignore the extra eight billion years or so... esp considering that we only took a little over four to get where we are today.

The universe may or may not be teeming with life. At this point we have no way to know. In fact, we can't even rule out the possibility of other higher life forms in our own solar system yet. Who knows what we might find in the oceans of Europa?

 

[StuMyers]

Spores in asteroids?

With the advent of the internet and directed microwaves, we are already on our way to going radio silent.

I doubt that. We're louder than ever. Radio is cheap and effective. Hard to beat.

Also, I have to wonder why you would simply ignore the extra eight billion years or so... esp considering that we only took a little over four to get where we are today.

The point was an exercise in orders of magnitude. If the universe were trillions of years old, it becomes much more likely that life will have had time to spread. 3xEarth age doesn't seem like all that long to me. In the grand scheme of things, it's reasonable to guess that we're one of the first, no?

The universe may or may not be teeming with life. At this point we have no way to know. In fact, we can't even rule out the possibility of other higher life forms in our own solar system yet. Who knows what we might find in the oceans of Europa?

So far, no evidence in support of any of that. So far, the universe appears barren of life. The default position when considering some phenomena with no supporting data... is false.

 

[SGT]

Also, I have to wonder why you would simply ignore the extra eight billion years or so... esp considering that we only took a little over four to get where we are today.

Are you saying that first generation stars could have developed life?

 

[SGT]

Plus, AFAIK, the local part of the galaxy appears to be fairly quiet in the radio, relative to us. I doubt intelligent life would ever stop using radio.

I agree with you that the probability of intelligent life in our vicinity is unlikely, but radio is only important for beings that communicate via sounds.
On Earth, ants communicate via smell, so it is possible that somewhere in the Galaxy smell communicating beings could develop a civilization for which radio would be useless.

 

[StuMyers]

I agree with you that the probability of intelligent life in our vicinity is unlikely, but radio is only important for beings that communicate via sounds.
On Earth, ants communicate via smell, so it is possible that somewhere in the Galaxy smell communicating beings could develop a civilization for which radio would be useless.

From what I recall from my undergrad astro, O and B type stars blow themselves up in a fairly small fraction of a billion years (something like 200my?). So yes, the number of heavy metallic starsystems should be increasing over time, probably exponentially increasing the probability of life over time.

Maybe you're right about smell/radio. I've only been thinking about this for like 5 minutes. But doesn't it seem likely that intelligent beings would want to communicate at lightspeed across their own planet at a very low cost? Might they not figure out a way to modulate radio to reproduce smell, just as we modulate radio to reproduce sound?

 

[SGT]

From what I recall from my undergrad astro, O and B type stars blow themselves up in a fairly small fraction of a billion years (something like 200my?). So yes, the number of heavy metallic starsystems should be increasing over time, probably exponentially increasing the probability of life over time.

Maybe you're right about smell/radio. I've only been thinking about this for like 5 minutes. But doesn't it seem likely that intelligent beings would want to communicate at lightspeed across their own planet at a very low cost? Might they not figure out a way to modulate radio to reproduce smell, just as we modulate radio to reproduce sound?

I really don´t believe that smell communicating beings could probably build a civilization. I only mentioned the possibility in order to dismiss the need for radio.
As an EE I don´t see how anyone could use smell to modulate EM waves.

 

[StuMyers]

Digital encoding?

 

[Aether]

I really don´t believe that smell communicating beings could probably build a civilization. I only mentioned the possibility in order to dismiss the need for radio. As an EE I don´t see how anyone could use smell to modulate EM waves.

None of our senses, including smell, could function at all without modulating EM waves within our brains. Less directly, if it was important to us, we could communicate smells by Morse code; for example: ... is "the letter H" in Morse code, but this could be alternately interpreted as "fishy smell" using a rudimentary smell-a-phone protocol/language.

I present two fully medicated Parkinsonian patients with long standing history of olfactory dysfunction in whom recovery of smell occurred during therapeutic transcranial application of AC pulsed electromagnetic fields (EMFs) in the picotesla flux density...Interestingly, in both patients enhancement of smell perception occurred only during administration of EMFs of 7 Hz frequency...

Sandyk, R. (1999) Treatment with AC pulsed electromagnetic fields improves olfactory function in Parkinson's disease. Int. J. Neurosci., 97,225 -233. http://chemse.oxfordjournals.org/cgi/external_ref?access_num=000080491600006&link_type=ISI

 

[DaveC426913]

How did you arrive at that conclusion?

Looking around.

You must have better eyes than the rest of us. So far, we can't even resolve planets around the nearest stars, let alone life on them.

 

[StuMyers]

See the smiley? It was a half-joke, meaning that if the universe is teeming with life, its not doing so such that it's obvious.

 

[JasonRox]

If intelligent life ever visited us, we wouldn't know, since it is not likely that it would be interested in us at all.

Let's hope when they do visit us they don't do what humans would do when visiting other civilizations. Kill them all. Or else we certainly would know if they visited us!

 

[Ivan Seeking]

Are you saying that first generation stars could have developed life?

I am saying that we are something like forth or fifth generation stardust.

 

[StuMyers]

Really? Cool. How is that determined?

 

[SGT]

I am saying that we are something like forth or fifth generation stardust.

To my knowledge there were no fourth or fifth generation stars 8 billion years prior to the birth of the solar system.

 

[Aether]

Really? Cool. How is that determined?

In the big bang, only the three lightest elements were made: hydrogen, helium, and lithium. First generation stars then formed by gravitational forces acting on these light elements. There was no iron, oxygen, or any other heavy element in existence in the universe before this time.

http://www.nature.com/nature/journal/v440/n7088/abs/nature04807.html

 

[StuMyers]

In the big bang, only the three lightest elements were made: hydrogen, helium, and lithium. First generation stars then formed by gravitational forces acting on these light elements. There was no iron, oxygen, or any other heavy element in existence in the universe before this time.

http://www.nature.com/nature/journal/v440/n7088/abs/nature04807.html

Well yes, I understand that. I don't know how it was determined to be fourth or fifth generation.

 

[Aether]

Well yes, I understand that. I don't know how it was determined to be fourth or fifth generation.

Well, I don't know about that part either.

 

[Ivan Seeking]

To my knowledge there were no fourth or fifth generation stars 8 billion years prior to the birth of the solar system.

Sure, there is some limit. The most extreme suggestions that I have heard are a billion years or so. I don't know if this limit is an absolute limit or more of a safe guess. However, it is also possible that we took much longer than needed. AFAIK, there is no evidence to show that we evolved in the least amount of time possible. And we have many known setbacks, such as mass extinctions - including a major bottleneck in the human population in recent history. I think it was supposed to have been around ten thousand years ago.

Just for kicks, in the following Real Player video clip, Dr. Richard Henry - Professor of astrophysics at Johns Hopkins University - suggests it to be most likely that we exist along with civilizations that are tens, or hundreds of millions of years ahead of us, and a very small chance that we would coexist with populations of approximately the same age.
http://play.rbn.com/?url=usanet/usanet/g2demand/scifi/freedomofinfo/richard-henry256k.rm&proto=rtsp
from
http://www.freedomofinfo.org/science.html

 

[SGT]

Sure, there is some limit. The most extreme suggestions that I have heard are a billion years or so.

What does that mean? 4th and 5th generation stars were formed 1 billion years after the Big Bang?

I don't know if this limit is an absolute limit or more of a safe guess. However, it is also possible that we took much longer than needed. AFAIK, there is no evidence to show that we evolved in the least amount of time possible. And we have many known setbacks, such as mass extinctions - including a major bottleneck in the human population in recent history. I think it was supposed to have been around ten thousand years ago.

Well, I think that 4 billion years is a very reasonable amount of time to create an intelligent species.
The mass extinctions were beneficial to our appearance. Without them the great predators would survive, with no chance for smaller predators like the vertebrates initially and mammals hundreds of million years later to flourish.
Big predators don´t need intelligence. They survive and reproduce very well without it.

Just for kicks, in the following Real Player video clip, Dr. Richard Henry - Professor of astrophysics at Johns Hopkins University - suggests it to be most likely that we exist along with civilizations that are tens, or hundreds of millions of years ahead of us, and a very small chance that we would coexist with populations of approximately the same age.
http://play.rbn.com/?url=usanet/usanet/g2demand/scifi/freedomofinfo/richard-henry256k.rm&proto=rtsp
from
http://www.freedomofinfo.org/science.html

I agree with that opinion, provided that technological civilizations don´t extinguish themselves and can last for tens or hundreds of million years.

 

[StuMyers]

I would guess that an intelligent species should last indefinitely. Why only 'tens' of millions of years?

I would also imagine that intelligence or no, life will wind up spreading itself all over the place, adapting to who knows what environment (why not vacuum?), given enough time for it to drift.

I'm sort of puzzled though as to why the universe doesn't look like Times Square, if you get my drift.

 

[Pythagorean]

maybe/maybe not. Never had an encounter, not holding my breath.

 

[Ivan Seeking]

What does that mean? 4th and 5th generation stars were formed 1 billion years after the Big Bang?

No, I mean that ETs could have up to a billion years head start on us.

Well, I think that 4 billion years is a very reasonable amount of time to create an intelligent species.

"I think" is hardly a good argument. Again, is there any evidence to show that we evolved in a minimum of time?

The mass extinctions were beneficial to our appearance. Without them the great predators would survive, with no chance for smaller predators like the vertebrates initially and mammals hundreds of million years later to flourish. Big predators don´t need intelligence. They survive and reproduce very well without it.

That all depends on the stressors encountered. There is no way to know what might have evolved in the absense of mass extinctions.

 

[SGT]

I would guess that an intelligent species should last indefinitely. Why only 'tens' of millions of years?

I would also imagine that intelligence or no, life will wind up spreading itself all over the place, adapting to who knows what environment (why not vacuum?), given enough time for it to drift.

I'm sort of puzzled though as to why the universe doesn't look like Times Square, if you get my drift.

A technological civilization has many means of self destruction. War with high destructive power weapons, pollution caused by technology are two examples. Other causes could be found.
We have barely escaped a nuclear war and pollution is a great concern.

 

[SGT]

No, I mean that ETs could have up to a billion years head start on us.

Agreed, if their civilization lasted that long.

"I think" is hardly a good argument. Again, is there any evidence to show that we evolved in a minimum of time?

Is there any evidence that this time is not a minimum?

That all depends on the stressors encountered. There is no way to know what might have evolved in the absense of mass extinctions.

Yes, if the Cambrian extinction had not happened maybe we could now have intelligent Anomalocaris.

 

[StuMyers]

A technological civilization has many means of self destruction. War with high destructive power weapons, pollution caused by technology are two examples. Other causes could be found.
We have barely escaped a nuclear war and pollution is a great concern.

I would guess that once an intelligent species managed to spread itself off of it's planet of origin, it would become very difficult to completely extinguish. I can't really image that not happening for us within a few hundred years. In the grand scheme of things then, humans will have taken about 200 000 years to more or less establish themselves permenantly.

Has anybody ever tried to do a quantitative guess at how long it would take an exponentially growing population to spread across an entire galaxy (assuming only known feasible technology)?

 

[SGT]

I would guess that once an intelligent species managed to spread itself off of it's planet of origin, it would become very difficult to completely extinguish. I can't really image that not happening for us within a few hundred years. In the grand scheme of things then, humans will have taken about 200 000 years to more or less establish themselves permenantly.

Has anybody ever tried to do a quantitative guess at how long it would take an exponentially growing population to spread across an entire galaxy (assuming only known feasible technology)?

A civilization will have the means to extinguish itself hundreds of years before it can spread to other solar systems.
Once the spreading starts in one million years this civilization could traverse the galaxy. The lack of communicating civilizations in our neighborhood (as far as we know), seems to demonstrate that technological civilizations don´t last this long.

 

[StuMyers]

A civilization will have the means to extinguish itself hundreds of years before it can spread to other solar systems.
Once the spreading starts in one million years this civilization could traverse the galaxy. The lack of communicating civilizations in our neighborhood (as far as we know), seems to demonstrate that technological civilizations don´t last this long.

Why one million years? Just curious where that number comes from.

And a lack of communicating civs could just as easily imply that we are the first, right?

 

[SGT]

Why one million years? Just curious where that number comes from.

Our galaxy is 200000 ly across, so an advanced civilization with means to travel at 1/5 c could spread in 1 million years.
Not that the original inhabitants would travel to the other side of the galaxy, but their colonies would spread in the same way that the original Africans never reached Australia, but South Asians, descended from them did.

And a lack of communicating civs could just as easily imply that we are the first, right?

Not necessarilly first, but the only living at the present moment.
Second generation stars, containing all necessary elements for life must have formed one or two billion years after the Big Bang. So, as Ivan said, there could be civilizations billions of years ahead of ours. The fact that they are not swarming the galaxy indicates that civilizations don´t last for billions of years.

 

[StuMyers]

...or, that they are very very rare. If they were common, but short lived, might we not expect to see a universe filled with relics (possibly in the form of radio signals or longwave, or whatever)?

 

[SGT]

...or, that they are very very rare. If they were common, but short lived, might we not expect to see a universe filled with relics (possibly in the form of radio signals or longwave, or whatever)?

Since we have not being outside the solar system we cannot know if there are relics of alien civilizations anywhere. As for radio signals we are loking for them and have found nothing until now.
There are two problems with radio signals.
First, their energy drops with the third power of distance, so even a very strong signal will fall below the background noise after traveling a few light years, unless they are aimed directly on us. So we probably can only detect signals from actually existing civilizations. The signals from the dead ones is immersed in the noise.
Second, even if we detect a coherent radio signal we can´t be sure if they are of natural or artificial origin. When the first quasar was detected, the regularity of its emissions led some astronomers to speculate if they were artificial. Before being named quasar it received the name LGM (from Little Green Men).

 

[StuMyers]

I seem to remember that there was something called the 'watering hole' where the galaxy is naturally fairly quiet in radio, where you might expect it to be loud, were it teeming with intelligent radio users.

 

[Ivan Seeking]

And again, already we are going radio silent. With a window of only about one-hundred years here on earth, radio is probably a very poor signature to be used in the search for ETs. And since we don't know what will be used a million years from now, or even in another hundred years...

 

[StuMyers]

Why do you think Earth would ever go radio silent? Radio is a super cheap and super fast way to communicate around a planet. If anything, I'd guess more and more data will get crammed into louder and louder signals, as we get better at pulling them apart.

 

[Ivan Seeking]

The shortest answer: Directed microwaves... Direct TV is a good example. Also, all analog TV transmissions in the US will be banned in two years.

Soon, with "view on demand" coming along, such as with Joost, you will probably replace your television signal with the internet. Already I watch some of my favorite shows, like Meet The Press, online, and at my leisure.

 

[cshum00]

The talk is usually about intelligent species. But what would humanity do if they find species who are in the process of being intelligent?

Experiments? Slavery? Cooperation? Play the role of God?

Make your guess.

Edit: To make it more general. What would humanity do if any kind of extraterrestrial life is found? Including the intelligent and the unintelligent ones? (Besides announcing it to the public in the news)

 

[Ivan Seeking]

Here is a short blurb about a radio free earth

AM: What do you think of the idea that more advanced civilizations will be radio silent, just as we are becoming more radio silent due to satellite transmission and fiber optics and that sort of thing?

NT: That's correct. That's a scary, very realistic notion. Not only that, but our TV waves aren't escaping Earth anymore because a growing number are receiving their signals via cable. So the total broadcast universe is shrinking.

http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1425

 

[Ivan Seeking]

The talk is usually about intelligent species. But what would humanity do if they find species who are in the process of being intelligent?

Experiments? Slavery? Cooperation? Play the role of God?

Make your guess.

That is not appropriate for this discussion. You could start another thread in General Discussion if you wish to pursue this.

 

[cshum00]

That is not appropriate for this discussion. You could start another thread in General Discussion if you wish to pursue this.

Sorry. I thought i might be appropriate since it is related and i saw a few shifts too (like from life in universe visited Earth to whether there is life other than earth, then extinctions of civilizations, etc).

I just make another thread.

 

[Ivan Seeking]

No problem. It is logically connected but too far off topic for this forum.

 

[StuMyers]

Here is a short blurb about a radio free earth


http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1425

Thanks. I find that blurb pretty surprising. I still just find it hard to believe that something so useful and so cheap (radio) will ever really be abandoned. I'd be interested in seeing the total radio flux from Earth (in the interesting frequencies) over the past decade. I have to wonder if we aren't really becoming silent so much as we are seeing the dominant communication medium shift. In other words, radio keeps its purpose, increases in net, but diminishes as a fraction of the sum total of communication signals?

 

[Ivan Seeking]

I don't see how that would happen. Sure, we may have a billion cell phones transmitting, but only with a few watts of power each. The days of 50KW omnidirectional radio transmissions are likely [soon to be] a thing of the past

 

[SGT]

A practical 14 GHz antenna with a diameter of 20m will have a beamwidth of about 0.08 degrees. This means that at the distance of a medium altitude satellite (10000km) the half power beamwidth is 14 km, much larger than the satellite antenna.
So, most of the power irradiated from Earth to the satellite will be lost in space.
Of course, we could build 14 km diameter antennas on Earth in order to loose only half of the irradiated power, but think of the environmental problems created by those arrays all over the globe.

 

[Ivan Seeking]

What is the typical radiated power in this case?

The added complication here is mentioned by Tyson: As signal encryption becomes more sophisticated, the broadcasts signals will look more and more like noise.

Why would we want to build 14Km antennas?

 

[SGT]

What is the typical radiated power in this case?

I have no idea.

The added complication here is mentioned by Tyson: As signal encryption becomes more sophisticated, the broadcasts signals will look more and more like noise.

I don´t see why.

Why would we want to build 14Km antennas?

In order to keep radio silence against eavesdropping aliens. It is not my idea, it is yours.

 

[Ivan Seeking]

I have no idea.

I would expect that the radiated power is very low as compared to traditional radio.

I don´t see why.

By definition, encryption means less obvious - highly compressed digital data streams do not look like analog radio.

In order to keep radio silence against eavesdropping aliens. It is not my idea, it is yours.

I never said any such thing. I am talking about the logic in using radio for detecting other civilizations. How you came up with that is beyond me.

 

[SGT]

I would expect that the radiated power is very low as compared to traditional radio.

The overall transmitted power is lower than in broadcast transmissions, but remember that these are not truly omnidirectional. The antennas are designed to transmit in the horizontal and most of the power that would escape due to Earths sphericity is reflected back by the troposphere.
A transmission to a satellite is aimed directly out of the planet.

By definition, encryption means less obvious - highly compressed digital data streams do not look like analog radio.

It escapes me why a stream of ones and zeros would be less conspicuous than an analog signal.

I never said any such thing. I am talking about the logic in using radio for detecting other civilizations. How you came up with that is beyond me.

You said that we are leaking less radio signals toward the space. The only way to accomplish this is using huge antennas. Of course, more directional antennas would mean less power loss. I don´t think that the economy in transmitted power would compensate for the environmental problems created. So, the only reason would be to hide against eavesdropping aliens.