This artist's concept shows a very young star encircled by a disk of gas and dust, the raw materials from which rocky planets such as Earth are thought to form. CREDIT: NASA/JPL-Caltech
There seem to be an almost infinite number of variables that allow life to exist as we understand it. Every time someone adds a variable, we see a smaller percent of that potential hundred bazillion planets where anyone will discover ETs.
Didn’t the Star Trek movies refer to this as “terraforming”?
I think far too many assumptions are made about habitability. Humans exist in a fairly narrow band of habitable conditions but some life could be very tolerant.
Its entirely possible that life could exist on the earth if it were as close to the sun as venus or as distant as mars. It wouldn’t be exactly the same as us.
There are innumerable variables that could be taken into account and virtually all of them are possible. Maybe a planet orbits a star in a cluster where the other stars provide enough cumulative heat for earth similar life.
I hate the word "many" in any scientific description. Wikipedia says "As of February 2011, NASA's Kepler mission had identified 1,235 unconfirmed planetary candidates associated with 997 host stars". Is "many" ten of them? One hundred? One thousand of the 1235?
Politics has the same issue. Declare that "many" people have a problem (even if it is a dozen in the whole country) and create a multi-billion dollar program to fix that problem.