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My understanding: that is what makes the silence deafening. If it's probable that the universe is filled with other intelligent life, and we see no evidence of

My understanding: that is what makes the silence deafening. If it's probable that the universe is filled with other intelligent life, and we see no evidence of it, that means that these civilizations are all ending before they can get radio or long range space flight. Or shortly after. Does not bode well for us.

krschultz 16y ago
I might be underestimating the sensitivity of our instruments, but if we're just now being able to detect planets based on their gravitional signatures on stars, how can we be sure we haven't peered through a telescope at intelligent life already? Our species was pretty damn interesting 300 years ago, but if the aliens were looking for was radio signals we didn't "exist" to them until about 1920. And our radio waves haven't even gone that far yet, 100 light years is nowhere. Maybe in a 1,000 years when they get somewhere and aliens notice, they'll dispatch their ship and another 1,000 years later land here. I wouldn't expect to get found in the woods a millisecond after I lit the signal fire, and thats where we are today in universe terms.
- khafra 16y ago
  That's where we are--but the universe is 14 billion years old, and there are many, many planets out there much older than ours; some several times older. It should only take a few millenia for any truly successful life in our galaxy to colonize the whole thing: less than a cosmic eyeblink.
  - chc 16y ago
    It took us millions of years to get all around the globe, when it "should" (in the same sense as above) only have taken a couple hundred. I don't think we should assume that life will necessarily take the most efficient path to any particular goal.
  - krschultz 16y ago
    Yea but that point, you are getting around faster than the speed of light. If you can move faster than the speed of light, why would you use radio waves for anything? What if their entire communication/transportation happens in some manner we can't comprehend. Imagine trying to show an iPad videochatting someone else to Da Vinci. It would be black magic with so many layers of technology that he couldn't comprehend - and he was a smart guy. So in a few hundred years we've blown everything we thought we knew away. Who knows what physics and technology we will have in a few thousand years?
- acgourley 16y ago
  I'm not usually the type that debates this topic in forums and probably don't know what I'm talking about. However, my understanding is that the worry comes from not seeing artificial radio signals from other parts of the galaxy.
lukeschlather 16y ago
Look at a few numbers that we will assume to at least be in the ballpark, and roughly correspond with scientific consensus: 1. The Universe is assumed to be 13.7 billion years old. 2. Nothing can move faster than c, so light years are an effective measure of the maximum distance anything can travel since its inception. 3. Our Sun is about 4.6 billion years old. 4. The universe is 13.7 billion light-years across. Now, from these, I'm going to make a few propositions, given the lack of obvious extraterrestrial intelligence: 1. Stars stable enough to create life didn't appear until fairly late in the game, around the 9 billion year mark. 2. 5 billion years is a better-than-average time for a star system to stabilize and evolve life. 3. Stars stable enough to create life are still fairly sparse, as life in this universe is still fairly young. 4. Assuming 7 billion years as a bare minimum for the starting point for this process, and assuming the Earth is fairly quick, a reasonable upper bound for the distance that a civilization must be from us to have contacted us is 2 billion light-years. Of course, there are a lot of variables here, and it's highly probable that maximum reasonable speed for a life-form to travel is as low as .1c, which means that even a civilization that sprung into existence at 6 billion years (assuming a star system stabilized very early in the game and then also evolved life in the better-than-average time of 5 billion years) would only be able to travel 1 billion light years, cutting off a fair amount of the universe from contact. While the numbers involved in the time since the big bang are large, the distances a hypothetical civilization would have to travel are probably larger, especially given that evolving life, in our solar system's case, took well over a third of the time since the big bang, and that's not counting the circumstances that brought about the formation of our solar system, which took the remaining 2/3rds.
- acgourley 16y ago
  What about their radio signals? That travels at c. Although I don't know our maximum range on getting clear radio signals from a given point.
jeangenie 16y ago
that's a lonely way of looking at things; there's probably nothing quite like us. i've said before but should reiterate, we perceive and experience a tiny portion of what makes the universe alive.

krschultz 16y ago

I might be underestimating the sensitivity of our instruments, but if we're just now being able to detect planets based on their gravitional signatures on stars, how can we be sure we haven't peered through a telescope at intelligent life already? Our species was pretty damn interesting 300 years ago, but if the aliens were looking for was radio signals we didn't "exist" to them until about 1920. And our radio waves haven't even gone that far yet, 100 light years is nowhere. Maybe in a 1,000 years when they get somewhere and aliens notice, they'll dispatch their ship and another 1,000 years later land here. I wouldn't expect to get found in the woods a millisecond after I lit the signal fire, and thats where we are today in universe terms.

khafra 16y ago
That's where we are--but the universe is 14 billion years old, and there are many, many planets out there much older than ours; some several times older. It should only take a few millenia for any truly successful life in our galaxy to colonize the whole thing: less than a cosmic eyeblink.
- chc 16y ago
  It took us millions of years to get all around the globe, when it "should" (in the same sense as above) only have taken a couple hundred. I don't think we should assume that life will necessarily take the most efficient path to any particular goal.
- krschultz 16y ago
  Yea but that point, you are getting around faster than the speed of light. If you can move faster than the speed of light, why would you use radio waves for anything? What if their entire communication/transportation happens in some manner we can't comprehend. Imagine trying to show an iPad videochatting someone else to Da Vinci. It would be black magic with so many layers of technology that he couldn't comprehend - and he was a smart guy. So in a few hundred years we've blown everything we thought we knew away. Who knows what physics and technology we will have in a few thousand years?
acgourley 16y ago
I'm not usually the type that debates this topic in forums and probably don't know what I'm talking about. However, my understanding is that the worry comes from not seeing artificial radio signals from other parts of the galaxy.

lukeschlather 16y ago

Look at a few numbers that we will assume to at least be in the ballpark, and roughly correspond with scientific consensus: 1. The Universe is assumed to be 13.7 billion years old. 2. Nothing can move faster than c, so light years are an effective measure of the maximum distance anything can travel since its inception. 3. Our Sun is about 4.6 billion years old. 4. The universe is 13.7 billion light-years across. Now, from these, I'm going to make a few propositions, given the lack of obvious extraterrestrial intelligence: 1. Stars stable enough to create life didn't appear until fairly late in the game, around the 9 billion year mark. 2. 5 billion years is a better-than-average time for a star system to stabilize and evolve life. 3. Stars stable enough to create life are still fairly sparse, as life in this universe is still fairly young. 4. Assuming 7 billion years as a bare minimum for the starting point for this process, and assuming the Earth is fairly quick, a reasonable upper bound for the distance that a civilization must be from us to have contacted us is 2 billion light-years. Of course, there are a lot of variables here, and it's highly probable that maximum reasonable speed for a life-form to travel is as low as .1c, which means that even a civilization that sprung into existence at 6 billion years (assuming a star system stabilized very early in the game and then also evolved life in the better-than-average time of 5 billion years) would only be able to travel 1 billion light years, cutting off a fair amount of the universe from contact. While the numbers involved in the time since the big bang are large, the distances a hypothetical civilization would have to travel are probably larger, especially given that evolving life, in our solar system's case, took well over a third of the time since the big bang, and that's not counting the circumstances that brought about the formation of our solar system, which took the remaining 2/3rds.

acgourley 16y ago
What about their radio signals? That travels at c. Although I don't know our maximum range on getting clear radio signals from a given point.

jeangenie 16y ago

that's a lonely way of looking at things; there's probably nothing quite like us. i've said before but should reiterate, we perceive and experience a tiny portion of what makes the universe alive.