Preliminary question; Is it worth any tax investments....or private investments...to attempt to "contact" or at least listen for communications from alien extra-terrestrials (A.E.T.s)?
Second question; Have A.E.T.s ever visited earth?
My answer? No to both.
it’s not worth any investment for us or them - except if you want to communicate with them. Carl Sagan noted; “Extraordinary stories of possible UFO’s (Unidentified Flying Objects) require extraordinary evidence”.
To date there has been none.
But listening for them is another story. They might have a message for us. They might teach us something that might save us from our headlong race to extinction. Maybe they might appreciate our wisdom.
As to the second question - If any alien race would have figured out how to travel many light-years to reach us, they easily could have figured out to call, via radio and/or TV transmissions, and talk to us first. So it's almost illogical for aliens to attempt to visit us here.
But observing us via listening to our radio broadcasts is another story.
They would have learned quickly that we fight over fossil fuel and territory still - we haven’t brought our growing population under control, that we've created "religions" to answer mysteries that weren't easily explainable that ended up being very powerful, and that we haven’t figured out how to get even close to 100% pollution free energy and total recycling.
So talking to us is a lot safer -for them - than visiting.
Now, for SETI (the government sponsored educational group, Search for Extraterrestrial Intelligence) to invest in listening tools is another story. The more sensitive we can make them, the further away from earth we can detect possible radio/TV transmissions from more than 100 years ago (or 100 Light years, or LY, away).
We know radio and TV signals go the speed of light (186,000 miles per second); we also know that there’s about 10 stars with earth-like planets within a hundred years (LY) of us….so if they (within 100 LY of us) focused on our early and/or recent radio/TV signals, they know we’re doing the same - listening for them.
Assuming that OUR radio is strong enough to go light years with sufficient strength to be detectable - we’ve only started transmitting around 100 years ago - then these folks within our 100 LY circumference are the only ones who know we’ve evolved to a civilization.
But with sufficient funding - we might be able to listen beyond that 100 year circle, or sphere. In other words, even though we started sending out signals a little over 100 years ago; older civilizations may have sent out signals far longer ago than that.
All we need is the equipment sensitive enough to detect it; and that's being developed as I write this.
It makes no sense for them to come here in disguise, or pretend we can’t see or know who they are.
We know that we can barely even make sub-atomic particles last longer by getting them up to the speed of light; so getting an organism to travel close to the speed of light is a long way off.
So let’s stop talking about “aliens beings here on earth”….that’s impossible to be considered by anyone with an elementary science education.
But let's strongly support "listening" for A.E.T.'s. We might learn something from them; or we might be able to teach them something.