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If there are or were aliens, why have we not heard them? Forget visits, why haven't we heard a peep? From anywhere? The universe is 13.77 billion years old. I

by dicroce 13y ago

If there are or were aliens, why have we not heard them? Forget visits, why haven't we heard a peep? From anywhere? The universe is 13.77 billion years old. It took planet earth 4.54 billion years to evolve a species capable of emitting significant electromagnetic radiation. I'm starting to be pretty convinced that we are the first advanced species, and perhaps life is a lot more rare than we imagine.

rosser 13y ago
Because we've been listening, rather half-assedly, for less than 100 years to a thing that is orders of magnitude larger than that (in light years) and haven't heard anything ... there must be nothing there?! That's pretty much like knocking on the door of a house with all the lights on, and when it isn't answered three milliseconds later, concluding no-one is home.
codex 13y ago
Because space-time is expanding at an extraordinary rate, such that vast portions of the universe are forever inaccessible? "For example there are stars which may be expanding away from us (or each other) faster than the speed of light, and this is true for any object that is more than approximately 4.5 gigaparsecs away from us." [1] That said, 4.5 gigaparsecs is 10^10 light years, which is still pretty damn big. [1] https://en.wikipedia.org/wiki/Metric_expansion_of_space https://en.wikipedia.org/wiki/Metric_expansion_of_space
- baddox 13y ago
  Isn't the expansion of the universe way out of scope of this article and discussion? Obviously, if there are aliens that far away, they by definition cannot reach us.
  - codex 13y ago
    It could explain why we haven't encountered aliens despite the advanced age of the Earth. The Earth has been around for roughly 1/3rd the age of the universe, but because space time is expanding exponentially, only a fraction of the universe (roughly 20%) is theoretically reachable, even when travelling at the speed of light. A planet like Earth that formed around the same time, or earlier, even relatively close to the Earth, may now be in the unreachable zone. By the same token, the longer it takes for an intelligent species to evolve, the less likely it is that they will ever be able to contact us.
clavalle 13y ago
Perhaps we are being shielded. Perhaps aliens don't indiscriminately broadcast signals. Perhaps they do but they are too weak to penetrate the noise by the time they get to us. Perhaps they are encoded to match background radiation to all but those with the right cipher. Perhaps there is some sort of sub-space that messages can be transmitted on that we have yet to discover.
biot 13y ago
Perhaps pulsars are interstellar beacons placed by advanced civilizations to signal a rendezvous point for any species capable of reaching it. (Anyone know if this is the basis for a sci-fi story?) As an aside, I find it somewhat amusing when people lay out a statistical basis for how life is so incredibly rare to the point where it's unlikely that we even exist.
- drakeandrews 13y ago
  Contact is close, in that (spoilers, in case anyone hasn't read the book) the signal being broadcast contains instructions on a device to send its occupants via a wormhole network to a rendezvous point.
mynameishere 13y ago
This is why: http://en.wikipedia.org/wiki/Inverse-square_law http://en.wikipedia.org/wiki/Inverse-square_law Anyway, if you actually wanted to seek other planets, you would need a HAL-style computer, sperm and eggs on ice, and an artificial womb. Then, life could realistically spend thousands and thousands of years traveling in space. If this is even possible then I suspect one or another lifeform would have done it by now. Since they apparently haven't, I doubt there's much out there. Fermi's paradox really.

by dicroce 13y ago

rosser 13y ago

Because we've been listening, rather half-assedly, for less than 100 years to a thing that is orders of magnitude larger than that (in light years) and haven't heard anything ... there must be nothing there?! That's pretty much like knocking on the door of a house with all the lights on, and when it isn't answered three milliseconds later, concluding no-one is home.

codex 13y ago

Because space-time is expanding at an extraordinary rate, such that vast portions of the universe are forever inaccessible? "For example there are stars which may be expanding away from us (or each other) faster than the speed of light, and this is true for any object that is more than approximately 4.5 gigaparsecs away from us." [1] That said, 4.5 gigaparsecs is 10^10 light years, which is still pretty damn big. [1] https://en.wikipedia.org/wiki/Metric_expansion_of_space https://en.wikipedia.org/wiki/Metric_expansion_of_space

baddox 13y ago
Isn't the expansion of the universe way out of scope of this article and discussion? Obviously, if there are aliens that far away, they by definition cannot reach us.
- codex 13y ago
  It could explain why we haven't encountered aliens despite the advanced age of the Earth. The Earth has been around for roughly 1/3rd the age of the universe, but because space time is expanding exponentially, only a fraction of the universe (roughly 20%) is theoretically reachable, even when travelling at the speed of light. A planet like Earth that formed around the same time, or earlier, even relatively close to the Earth, may now be in the unreachable zone. By the same token, the longer it takes for an intelligent species to evolve, the less likely it is that they will ever be able to contact us.

clavalle 13y ago

Perhaps we are being shielded. Perhaps aliens don't indiscriminately broadcast signals. Perhaps they do but they are too weak to penetrate the noise by the time they get to us. Perhaps they are encoded to match background radiation to all but those with the right cipher. Perhaps there is some sort of sub-space that messages can be transmitted on that we have yet to discover.

biot 13y ago

Perhaps pulsars are interstellar beacons placed by advanced civilizations to signal a rendezvous point for any species capable of reaching it. (Anyone know if this is the basis for a sci-fi story?) As an aside, I find it somewhat amusing when people lay out a statistical basis for how life is so incredibly rare to the point where it's unlikely that we even exist.

drakeandrews 13y ago
Contact is close, in that (spoilers, in case anyone hasn't read the book) the signal being broadcast contains instructions on a device to send its occupants via a wormhole network to a rendezvous point.

mynameishere 13y ago

This is why: http://en.wikipedia.org/wiki/Inverse-square_law http://en.wikipedia.org/wiki/Inverse-square_law Anyway, if you actually wanted to seek other planets, you would need a HAL-style computer, sperm and eggs on ice, and an artificial womb. Then, life could realistically spend thousands and thousands of years traveling in space. If this is even possible then I suspect one or another lifeform would have done it by now. Since they apparently haven't, I doubt there's much out there. Fermi's paradox really.