> They would have been there the whole time, they didn't just pop into existence because it got observed. Unless they are quantum beings. But more seriously,

> They would have been there the whole time, they didn't just pop into existence because it got observed. Unless they are quantum beings. But more seriously, at cosmic scales it is possible we observe something/some civilization in our present that actually no longer exists. There should be something like the Drake Equation to determine the likelihood of a civilization we observe actually currently existing based on the observed distance. To your point the oldest radio broadcasts are just over 100 years old, since they travel at the speed of light they will need 100,000 years to travel the length of the Milky Way, so if a civilization as advanced as ours were on the other side of the galaxy in the future to receive them, what are the odds humans will still be around? Assuming we are around, then it would be about another 100,000 years for them to send a directed communication at the speed of light, so I think you are correct it’s not worth the effort to worry.