have they found anything?

[JoeTheJuggler]

How far away we can detect a signal is more a function of the transmitter than the receiver. If some distant civilization was working to make themselves known, they could arrange a single we couldn't miss.

Even so, the amount of searching we've done is infinitesimally small. If they're 150 plus light years away, it would take 150 years for their signal to reach us. When you get further away than that, obviously, the transit time takes even longer. We've only been able to produce radio signals ourselves for about 100 years.

For it to be likely that we'd receive signals from another civilization would mean they'd have to have been transmitting for at least the amount of time it takes a signal to reach us (or at least that long ago--we could get signals from a civilization that no longer exists).

I think the question is, are there other intelligences like us. So, we'd have to assume that their ability (and willingness) to transmit a signal is about the same as ours. How far away could our civilization be detected? And for how long?

It's a needle in the haystack.

ETA: Or even thousands or tens of thousands of needles in a really gigantic haystack. And some of the needles appear and disappear in relatively short periods of time--or possibly in periods of times shorter than the time it takes light from the needles to reach our eyes. OK, the analogy sucks. . . .

 

[shadron]

The NOVA program on Mars exploration has been released for public viewing here: http://www.pbs.org/wgbh/nova/mars/program.html . It is a good overview of Mars exploration, down through the findings of the Phoenix mission that just recently terminated. Unfortunately there is something in the first segment that has rights restrictions placed on it, so you have to skip the description of the Viking findings and start with the Opportunity/Spirit missions.

The program discusses a catastrophistic theory of Mars dessication that is a bit controversial, but which certainly has not been debunked; others see a simple freezing of the planet's core, caused by it's small size and its incapacity to retain heat, as the culprit, but the encountering of a large meteor (a billion years later than Earth may have encountered its moon creation event) does contain an explanation of Mars weird north/south topography.

 

[davefoc]

@davefoc

Mostly agreed, but why 1000 light years?

And I'm not sure about setting up a beacon that would make us unmissable (given enough time) is beyond anything being contemplated by any civilization. A small show at such a project was actual done for a few minutes at Arecibo. I would think that if someone put their mind to it a beacon project would fall in the range of private funding (ala SETI).

1000 years was the range suggested by the optical SETI guys. It is also in the ballpark of the 722 lightyears that the people who created the table I posted earlier for the largest transmitter that they analyzed. This transmitter seems wildly more powerful than something likely to be built but it's not completely out of the plausibility range. Much less than the 22 TW's listed for it actually need to be supplied. That number doesn't take in to account the gain of the antenna or the fact that the beam can be pulsed. Still I don't think anybody's going to be building one of those things in my life.

1000 light years also seems to include enough stars so that we'd have a reasonable chance of detecting a sentient civilization. My gut feel is that 100,000 stars is in the range of the minimum number to have a significant chance of finding a sentient civilization. The 100 stars or so that lie within 100 light years just seems like too small a number to me to have a reasonable chance of finding fellow sentients.

If the signal is pulsed, what is the minimum way to pulse it so that the receiving entity would be sure it is a purposefully created signal? It might be enough to randomly vary the time between the pulses a bit or maybe the pulse length. Theorectically you could transmit information in the signal. What should the message be? I don't know the answer to any of this I was just musing.

 

[JoeTheJuggler]

Theorectically you could transmit information in the signal. What should the message be? I don't know the answer to any of this I was just musing.

I always thought the idea of transmitting a list of prime numbers would be an easy way of saying "We're here, and here's the way we think." It would also be different enough from any natural source of radiation to leave little doubt that it's an artificial or intentional signal.

 

[amb]

First, in a universe with hundreds billions of galaxies and a galaxy with roughly 100 billion stars, why on Earth (so to speak) would you suspect that this constellation (so to speak) of conditions is unique? On what do you base that assumption?

Second, most of the items you list are not at all required for life to arise. Some of them aren't even required for our kind of life to have arisen. Number 10, for example. Since life arose on Earth "our kind of atmosphere" has changed dramatically. Related to that, number 13. First oxygen is an element and "evolved" in the hearts of stars going nova and creating heavier elements. Oxygen gas is O2, again not something that "evolved"--it's just chemistry. What do you mean by too much or too little? I suggest you read up on ecology. O2 is highly reactive and poisonous to many (probably most) forms of life on Earth. Organisms that rely on it evolved to be fittest in an atmosphere with O2 in it. There was no "coincidence" about it.

I find particularly troubling your point number 7. For this wild speculation (that life on Earth was seeded from life on Mars) to be true, you'd need to accept that there are 2 planets in our solar system capable of sustaining life. And you somehow use that point to argue that life on Earth is unique? Sorry, that's just illogical; that is, it's a contradiction. Also, was life on Mars seeded from somewhere else? Seems to me if you start speculating that life can be seeded from one planet to another, you're again arguing that life is relatively common and not at all unique to Earth.

The two planet theory goes something like this. Because of the constant bombardment of the planets by huge asteroids sterilizing a planet for millions of years, dividing this sterilasation between the two planets gives it a window of opportunity for life to evolve on one planet or the other.
Tectonic plates is what makes life possible on planet Earth, which requires a molten core which the Earth posses, and Mars doesn't, so even if microbial life originated on Mars, it would have died out had it not migrated to Earth in meteorites that were sent to Earth by asteroid collisions on Mars.
All this will one day be proven if we find microbial life underground on the planet, or on one of it's moons. Our moon has proved to be sterile unless we find microbial life deep underground on our satellite.

 

[Beerina]

Stars less massive than the sun, the habitual zones are located farther inward. but all gas planets so far discovered are roughly orbiting their star in this habitual zone. Which means the rocky planets may be too far form their sun to make animal life possible.

Not necessarily. Remember that the first realizable method to detect planets around other stars was by the star's "wobble" when a giant, nearby planet caused it to do so, barely perceptibly.

So it's not coincidence the most planets we've detected so far...have been giant planets close in to their stars.

 

[Beerina]

Even so, the amount of searching we've done is infinitesimally small. If they're 150 plus light years away, it would take 150 years for their signal to reach us. When you get further away than that, obviously, the transit time takes even longer. We've only been able to produce radio signals ourselves for about 100 years.

Unless, of course, they develop something else that lets them communicate faster, in which case, the universe would be abuzz but appear empty to the handful of 20th-century-ish civilizations scattered here and there.

 

[amb]

The speed of light is the limit. Nothing can travel faster than that. If civilizations are common in the universe, surely some must be say, a million years ahead of us technology wise, and make Fermi's statement of, if they're there, why aren't they here applies.

 

[arthwollipot]

That assumes that in a million years a civilsation will have technology to supercede the lightspeed limit (it's not just a good idea, it's the law!). This is by no means assured, and in fact by our current understanding it seems to be pretty much impossible in principle.

 

[amb]

We surely would have received at least a glimpse, or clue of any other life in the vicinity of our solar system had it been there. After all, we have had radio for close on to 200 years. The speed of light limit would not impede a civilization a million years ahead of us.

 

[shadron]

The two planet theory goes something like this. Because of the constant bombardment of the planets by huge asteroids sterilizing a planet for millions of years, dividing this sterilasation between the two planets gives it a window of opportunity for life to evolve on one planet or the other.
Tectonic plates is what makes life possible on planet Earth, which requires a molten core which the Earth posses, and Mars doesn't, so even if microbial life originated on Mars, it would have died out had it not migrated to Earth in meteorites that were sent to Earth by asteroid collisions on Mars.
All this will one day be proven if we find microbial life underground on the planet, or on one of it's moons. Our moon has proved to be sterile unless we find microbial life deep underground on our satellite.

NOVA just released a program on Mars exploration where at least two life science types think the possibility of life still on Mars ranges from poor to possible, and a couple of others think there may well have once been life there 3 billion plus years ago.

 

[JoeTheJuggler]

That assumes that in a million years a civilsation will have technology to supercede the lightspeed limit (it's not just a good idea, it's the law!). This is by no means assured, and in fact by our current understanding it seems to be pretty much impossible in principle.

Yes. Besides that, I'm pretty sure the SETI question is about a search for a civilization like ours--that is one that uses radio communication.

ETA: If the Q Continuum exists, he'll have to make himself known to us!

We surely would have received at least a glimpse, or clue of any other life in the vicinity of our solar system had it been there. After all, we have had radio for close on to 200 years. The speed of light limit would not impede a civilization a million years ahead of us.

Well not "any other life"--surely you mean any other radio-using civilization that started using radio in time for us to have received a signal in the past 30 years.

Yes, I agree that there is probably no radio-using civilization in our immediate neighborhood within the last 30 years. Since we've only been using radio communication for a teeny tiny fraction of the time life has existed on Earth, I'd point out that our SETI results so far is a very small dataset. There's no way you can jump from that to "the Earth is unique in the universe" or even "the Earth is unique in our galaxy".

NOVA just released a program on Mars exploration where at least two life science types think the possibility of life still on Mars ranges from poor to possible, and a couple of others think there may well have once been life there 3 billion plus years ago.

I saw that. It's very exciting.

I don't get how amb can use the possibility that 2 planets in our solar system can sustain life somehow argues that the Earth is unique. It seems to me that it means life arises darn near everywhere it is possible. (And what if we someday find something in the possible under-ice water oceans on Europa?)

 

[amb]

What is meant by the two planet theory is that if one or the other somehow evolved life
it could have migrated from one to the other by meteorites from mars to earth.
Perhaps life originated on mars and was transported here by an asteroid hitting mars and a chunk of rock could have been blown off the surface by the impact and seeded earth while sterilising Mars.
The chances of two relatively close rocky planets at approximately the habitual range for life to survive gives the solar system a better chance of life surviving a catastrophe.

 

[JoeTheJuggler]

What is meant by the two planet theory is that if one or the other somehow evolved life
it could have migrated from one to the other by meteorites from mars to earth.
Perhaps life originated on mars and was transported here by an asteroid hitting mars and a chunk of rock could have been blown off the surface by the impact and seeded earth while sterilising Mars.
The chances of two relatively close rocky planets at approximately the habitual range for life to survive gives the solar system a better chance of life surviving a catastrophe.

Yes, I understand this speculation. (It's not very parsimonious to suppose that abiogenesis happened on Mars but not on Earth.)

However, if both Mars and Earth can sustain life, it hardly makes a strong argument that life is rare or that what we've got on Earth is unique in the universe when it isn't even unique in our tiny little solar system.

Instead, it broadens considerably the "sweet spot" orbit.

 

[amb]

Aren't we discussing animal life? I've stated that microbial life is more than likely widespread throughout the universe. In fact I'm sure that one day life [microbial, or very primitive] will be found on Europa which has been observed to have frozen oceans on the surface but liquid under the ice mantle.
Also, the 'sweet spot' is what this discussion is all about. How common are rocky planets orbiting their star at the sweet spot for animal life to evolve? And it has to do so for at least since the age of the Earth's origin.

 

[JoeTheJuggler]

Aren't we discussing animal life? I've stated that microbial life is more than likely widespread throughout the universe. In fact I'm sure that one day life [microbial, or very primitive] will be found on Europa which has been observed to have frozen oceans on the surface but liquid under the ice mantle.

So far, in our only known sample of life, microbial life evolved into an incredibly rich diversity of life. So the existence of life is related to the existence of higher life forms.

I'd agree that we don't know how frequently and under what conditions we higher life forms evolve. So far, we're one for one. At any rate, there's no reason whatsoever to suppose that the Earth is unique.

Also, the 'sweet spot' is what this discussion is all about.

Yes I know. That's why I pointed out that finding two planets in our solar system alone that fall in the sweet spot most definitely does not argue that the Earth is unique in the universe or even in the galaxy.

How common are rocky planets orbiting their star at the sweet spot for animal life to evolve? And it has to do so for at least since the age of the Earth's origin.

And so far, whenever we develop technology to find extrasolar planets of a certain mass (or orientation relative to their star and our eyes, or whatever) we have found them in abundance. I admit, there's plenty we don't know, but our ignorance does not in any way suggest that the Earth is unique.

In that past, everytime we thought "we" were unique somehow, it almost always turned out to be wrong.

The number of stars out there is truly astronomical. Even if some particular necessary configuration is rare, it will surely exist many times.

 

[amb]

No one is denying that fact. What I'm
saying is that Earth-like planets with just the right conditions are not common but rare. Rare means , probably millions of Earths scattered throughout the cosmos. But don't expect one next door.

 

[JoeTheJuggler]

No one is denying that fact. What I'm
saying is that Earth-like planets with just the right conditions are not common but rare. Rare means , probably millions of Earths scattered throughout the cosmos. But don't expect one next door.

I agree there's no reason to suspect on is next door (the lack of a finding from SETI), but I don't think that even makes them "rare".

As I've been saying, terms like "rare" and "common" are relative terms. 1 in a million would mean there are thousands of them in our galaxy alone.

I contend that intelligence could be relatively common yet still rare enough (spread out in space and time enough) that any one is not likely ever to encounter another.

Most importantly, though, what do you base the assertion that they're rare on? Right now, we don't know. Earlier, I linked a study of extra solar planets that estimates "superearths" (I think up to a mass of like 5 to 10 times that of the Earth) are as "common" as one per every 3 single stars.

So far, pretty much any time we've had the technology to find extrasolar planets of a given mass (and orientation relative to us), we've found them in abundance.

But you agree now that the Earth is not likely to be unique in the universe or even in the galaxy?

 

[amb]

Earth may be unique in our part of the quadrant. May be so even in the whole galaxy. When you consider the enormous number of coincidences that occurred here to produce animal life.
And of the millions of lifeforms that developed here, only one has acquired enough intelligence to even wonder about these questions.
For example. Earth has a large moon to stabilize it's orbit. Gravity is just right. The Earth has tectonic plates, a large gas world that acts like a vacuum cleaner in attracting huge asteroids that otherwise could hit the Earth a lot more frequently, thereby destroying all animal life, we are at just the right distance from our sun to keep the water in a stable liquid condition making life possible. All this and many more reasons why the Earth may indeed be very rare, as far as our galaxy is concerned.

The above is a copy of an earlier post I made using a book titled Rare Earth as a source.

 

[JoeTheJuggler]

Earth may be unique in our part of the quadrant. May be so even in the whole galaxy. When you consider the enormous number of coincidences that occurred here to produce animal life.

I think you're looking at it backwards. You're almost looking at it the same way creationists making the "finely-tuned universe" look at it. The conditions didn't produce animal life. Life evolved to adapt to conditions.

There's no reason to think the conditions on Earth are unique in the galaxy. There's also no reason to think that the very specific conditions on Earth are necessary for the evolution of beings with intelligence like ours. I'm not sure what "our part of the quadrant" means, but I do agree that there has probably been no other radio-using civilization within 30 or so light years of us in very recent years. That's a far cry from saying intelligence like ours is unique.