"Are We Alone" was a famous book written decades again about the question of whether humanity is alone in the Universe. Countless sci-fi movies and TV series have occupied our thoughts and imaginations about whether other intelligent life in the Universe exists.
The Search for Extraterrestrial Intelligence (SETI) is being carried out world-wide but SETI.org and NASA are front runners in the search for life elsewhere in the Universe.
NASA's "Nexus for Exoplanet System Science" or NExSS may be our best bet. NExSS will be a multi-disciplinary approach to study the Universe for signs of life other than ours on Earth. Every applicable science discipline and spacecraft, instrument and telescope will be applied to this search.
For me personally I have publicly commented that "life always finds a way" and that I believe the Universe is full of life. But that life still has to operate within the laws of physics as we know it and therefore it is VERY difficult to get around between the planets and stars let alone galaxies.
Our 1st electromagnetic signal was transmitted when Marconi sent his radio message across the Atlantic on Dec. 12, 1901. That message has barely travelled over 114 light years into the Cosmos. Within that sphere of 114 light years from Earth (the speed of light and how far Marconi's radio signal has gone) there are only dozens of star systems.
Even if his signal was intercepted (it was a single letter "s" in Morse Code) by a civilization at this distance of 114 light years and a reply sent, we would not receive it until 2129. Now you get an idea of how hard communication across the Cosmos can be!
I think we will find life in the form of multi-cellular organisms within our solar system in the near future. I base this on the fact that water is EVERYWHERE in our solar system and there are places on Mars and the big moons of Jupiter and Saturn that could provide havens for life as we know it - carbon and water based - to exist.
I can think of no other discovery that would cause a re-evaluation of humanity and our place in the Universe than the discovery of life, let alone intelligent life, in the Universe. Stay tuned as the Universe always surprises us.
Sky Guy in VA