Are we alone? This is for me one of the big questions. Probably not, but where are they? Earth is about 4.5 billion years old and life here on earth some 3.5 billion years. Intelligent life, not so long. Intelligent life that can communicate to another world out there somewhere? Radio is now maybe 130 years old, but in the early years was quite primitive so any alien out there more than 100 light years away won’t know about us. At the rate we are carrying on we are probably going to wipe ourselves out in the not to distant future. So there will be an expanding shell, 100 - 1000? years thick of our radio signals, but it will grow fainter the bigger it gets. The bigger it gets the more difficult to detect.
Now if ET had a similar life experience their “shell” is maybe past us or not here yet. We can only try to find them and SETI is doing a good job by using the power of idle computers. Please support them.