Our universe is not only vast it is expanding in all directions. The universe almost certainly has intelligent life at various time and places. That any develop sufficiently to communicate by radio broadcasts of sufficient power within the relatively tiny area of our ~100 years or so of our being able to listen considering the time it takes for signals to reach us mean that our sampling window is just too small.
Imagine a sphere centered around earth spreading out in all directions. The outer edge represents the space where their radio could have reached us by now since we became capable of listening and even bothered carefully listening. Meaningful systematic SETI is like 1970’s and forward. So ~50 light years or so. Anything further hasn’t reached us yet. Anything closer may have already passed us. Maybe they stopped. Maybe they moved onto something past radio, or maybe they are dead.
For example, humanity has had aproximately 125 years or so of radio where someone could detect us. Not a long time. We are already breeching 7 of 9 planetary boundaries, environmental limits that once breeched work like a timebomb that risk our civilization’s collapse and possible extinction. We could nuke ourselves out of existence at any minute for the last 75 years. How long will we be broadcasting for? That expanding sphere of space where our radio has reached will hollow out if/when we stop broadcasting. So alien civilizations that want to listen to us can only be in that very thin slice of space between when we started and when we stop broadcasting. Compared to the universe, it’s nothing. Our galaxy, the milky way is 84000ly in diameter to give you some perspective.
For us to find alien life, our two civilizations both have to fall within our imagenary expanding hollow sphere of radio listening and their hollow expanding sphere of broadcasting. We’ve barely scraped the smallest corners of our own section of the unfashionable part of the spur on a minor spiral arm of our galaxy. 50ly/84000ly= 0.059% of our galaxy for anyone currently broadcasting. Our listening sphere goes back in time and out in distance a lot further, but has similar limitations. If anyone in our nearest neighbouring galaxy, Andromeda, was broadcasting, they would have had to do it ~2.5 million years ago for us to hear it now. If they did it ~2.500050 million years ago, we missed it because we weren’t listening.
Our universe is not only vast it is expanding in all directions. The universe almost certainly has intelligent life at various time and places. That any develop sufficiently to communicate by radio broadcasts of sufficient power within the relatively tiny area of our ~100 years or so of our being able to listen considering the time it takes for signals to reach us mean that our sampling window is just too small.
Imagine a sphere centered around earth spreading out in all directions. The outer edge represents the space where their radio could have reached us by now since we became capable of listening and even bothered carefully listening. Meaningful systematic SETI is like 1970’s and forward. So ~50 light years or so. Anything further hasn’t reached us yet. Anything closer may have already passed us. Maybe they stopped. Maybe they moved onto something past radio, or maybe they are dead.
For example, humanity has had aproximately 125 years or so of radio where someone could detect us. Not a long time. We are already breeching 7 of 9 planetary boundaries, environmental limits that once breeched work like a timebomb that risk our civilization’s collapse and possible extinction. We could nuke ourselves out of existence at any minute for the last 75 years. How long will we be broadcasting for? That expanding sphere of space where our radio has reached will hollow out if/when we stop broadcasting. So alien civilizations that want to listen to us can only be in that very thin slice of space between when we started and when we stop broadcasting. Compared to the universe, it’s nothing. Our galaxy, the milky way is 84000ly in diameter to give you some perspective.
For us to find alien life, our two civilizations both have to fall within our imagenary expanding hollow sphere of radio listening and their hollow expanding sphere of broadcasting. We’ve barely scraped the smallest corners of our own section of the unfashionable part of the spur on a minor spiral arm of our galaxy. 50ly/84000ly= 0.059% of our galaxy for anyone currently broadcasting. Our listening sphere goes back in time and out in distance a lot further, but has similar limitations. If anyone in our nearest neighbouring galaxy, Andromeda, was broadcasting, they would have had to do it ~2.5 million years ago for us to hear it now. If they did it ~2.500050 million years ago, we missed it because we weren’t listening.
Here is a map of stars withing 50ly of us.
Edited for clarity and something aproximating correctness. It still sucks, but I’m too hungover.