Alien Intelligence

Ryujin · Jun 28, 2015

Umbran said:
The first commercial radio station went on the air in 1920. So, that footprint is more like a bubble 95 light years across. Call it 100, just for sake of rounding the number.

We don't have an accurate measure, but by star density estimates, there's something like 10,000 to 14,000 stars in that sphere.

Our Sun is spectral type G - there are 511 stars of this type in that sphere.

About 22% of those stars probably have Earth-sized planets in their habitable zones. That makes for about 100 potential worlds to hear us, before we even start to consider anything particularly exotic.

I was going from the point of the first intelligent radio broadcasts, which would have been radio telegraphy, to give it the best possible chance. We're still talking about short odds and a rather massive time scale, with us only having been here for a relative instant.

Morrus · Jun 28, 2015

Ryujin said:
Radio waves radiate in all directions. The diameter of the sphere is twice the amount of time that we've been transmitting

Sure. The word "diameter" wasn't used though. A "300 ly bubble", to me, is one with a radius of 300 ly in all directions from the centre.

Umbran · Jun 28, 2015

Ryujin said:
I was going from the point of the first intelligent radio broadcasts, which would have been radio telegraphy, to give it the best possible chance. We're still talking about short odds and a rather massive time scale, with us only having been here for a relative instant.

Whether the odds are short is not at all clear. There are arguments that intelligent life should be rare, and other arguments that it should be pervasive, and we do not have any solid reason to take one side over the other. So, it is kind of a toss up.

It would seem to me that, should such life be pervasive, there are good reasons to take a Star Trek-ish, "don't talk to them until they are good enough to find us themselves," position. So, not having heard from them doesn't really signify, to me.

Homicidal_Squirrel · Jun 28, 2015

Ryujin said:
The first is why while I tend to believe that there must be other intelligent life in the universe, I very much doubt that it has ever visited us. You've got the limiting factors on development of intelligent life. Then consider how long such a culture might exist, without destroying itself. On again to whether or not they would develop space travel, let alone something that would make interstellar travel viable. On top of that consider that we've only created an intelligent EM "footprint" that's, at best, something less than a 300 light-year bubble.

Us, the technological level is also a limiting factor. For some reason we tend to believe that other intelligent civilizations would be far more advanced than us. It's possible, but not certain. Even if they were far more advanced, it doesn't mean they'd be advanced enough for space travel.

Ryujin · Jun 28, 2015

Homicidal_Squirrel said:
Us, the technological level is also a limiting factor. For some reason we tend to believe that other intelligent civilizations would be far more advanced than us. It's possible, but not certain. Even if they were far more advanced, it doesn't mean they'd be advanced enough for space travel.

And not only is there the range of intelligence to consider, but also its existence at all. For some reason we assume that intelligence is a sort of natural evolutionary goal, but there are plenty of very successful forms of life that we would hardly consider to be self aware. I've previously made the comment that, perhaps, intelligence is an evolutionary dead end or "mistake." It also took millions of years to get to this point. We've been here for an eye-blink. We could be gone tomorrow.

Umbran · Jun 28, 2015

Homicidal_Squirrel said:
For some reason we tend to believe that other intelligent civilizations would be far more advanced than us. It's possible, but not certain.

The odds are actually quite good, when you consider time.

The Universe is approximately 14 billion years old. Life on Earth is about 3.8 billion years old.

So, assume life starts at random times - the chances are higher that any life we encounter is *older* than our own, than it is to be younger. Easily having been intelligent, technology-using creatures for millions or billions of years longer than we have.

There are no guarantees, but it seems like a reasonable thought.

Ryujin · Jun 28, 2015

Umbran said:
The odds are actually quite good, when you consider time.

The Universe is approximately 14 billion years old. Life on Earth is about 3.8 billion years old.

So, assume life starts at random times - the chances are higher that any life we encounter is *older* than our own, than it is to be younger. Easily having been intelligent, technology-using creatures for millions or billions of years longer than we have.

There are no guarantees, but it seems like a reasonable thought.

Well, yes and no. What is the minimum length of time before intelligent, tool using life can evolve? How long does it take for that life form to develop interstellar travel technology? What is the life expectancy of such intelligent life, before it kills itself off? Is it even possible to circumvent the light barrier in a manner that permits life, or even machinery, to span the distance between solar systems? If not, will life develop that can see a benefit in creating vessels that will not reach other star systems in their own lifetimes, or even in a hundred generations?

I think that it's far more likely for us to detect an alien transmission, as evidence of intelligent life elsewhere, than it is for us to ever meet such life. Even then, you might imagine that the universe would be full of such transmissions to be detected, even today. Even if the time period in which a civilization uses radio emissions was very short, a universe in which alien life was plentiful should see a fair bit of intelligent transmission.

Morrus · Jun 28, 2015

Ryujin said:
Well, yes and no. What is the minimum length of time before intelligent, tool using life can evolve? How long does it take for that life form to develop interstellar travel technology? What is the life expectancy of such intelligent life, before it kills itself off? Is it even possible to circumvent the light barrier in a manner that permits life, or even machinery, to span the distance between solar systems? If not, will life develop that can see a benefit in creating vessels that will not reach other star systems in their own lifetimes, or even in a hundred generations?

I think that it's far more likely for us to detect an alien transmission, as evidence of intelligent life elsewhere, than it is for us to ever meet such life. Even then, you might imagine that the universe would be full of such transmissions to be detected, even today. Even if the time period in which a civilization uses radio emissions was very short, a universe in which alien life was plentiful should see a fair bit of intelligent transmission.

The inverse square law is the issue. Transmissions degrade over distance very rapidly. Given that ours aren't exactly strong to begin with, you'd have to be looking pretty darn hard with extremely sensitive detection equipment even just at a light year out.

Ryujin · Jun 28, 2015

Morrus said:
The inverse square law is the issue. Transmissions degrade over distance very rapidly. Given that ours aren't exactly strong to begin with, you'd have to be looking pretty darn hard with extremely sensitive detection equipment even just at a light year out.

No doubt, but then one would assume that at least some of these postulated "more advanced" races might want to make their presence known. Sending more powerful, or even tight beamed transmissions at some likely source of life. And if life is that plentiful, then the odds of there being someone in our range rise accordingly. There just seems to be so much working against a "plentiful life universe", from where I sit.

A short story and a book that I read, some years back, both come to mind. In the short story the Earth was the subject of an alien invasion, by a multi-species empire. They landed their ships, opened up the doors, and were cut to pieces by Earth weaponry. It seems that the trick of FTL travel was much more simple than we supposed and we had somehow missed it when they had discovered it, roughly about the same time that they discovered the use of muzzle loading gunpowder weapons.

The book was sort of the flip side. The aliens found us, somehow, from many hundreds of light years away, and sent a powerful LASER transmission that contained all of their knowledge. The aliens were never met, nor visualized. The knowledge that they sent was the sort that we could use to destroy ourselves over the course of a bad weekend but, apparently, the originating aliens could not conceive of a race that would be as stupid as we are.

Morrus · Jun 28, 2015

I was more talking about our own radio bubble and how weak it is. The TV and radio signals weren't designed for long range transmissions

Alien Intelligence

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Morrus

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Ryujin

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Morrus

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