I am old enough to remember way back when we did not have the technology to detect planets around other stars. Most scientists believed that planets were extremely rare.
A few of us, who believed in conservation of angular momentum, felt that planets were fairly common, but we just didn’t have the technology to see them.
Now that we have the technology to see planets, but not earth-like ones, we have started to believe that planets are common, but earth-like planets are rare.
In a few more years we will be able to detect earth-like planets, and will discover that there are a lot more of them than anyone suspected...
Bingo.
Though around what type of star? Ours is a G2V. There's one nearby, but it's part of a trinary system. The next one is hundreds of light years distant.
Conditions for technological life might well be a lot rarer than we once thought.
The biggest surprise in finding extra-solar planets are the large number of “hot Jupiters” (giant planets in close to the sun). Granted we should be finding these most given the techniques being used, but statistics have shown that the sampling bias does not account for this large number unless such formation is more typical than our formation.
We are also seeing systems with much more eliptical orbits than we experience in our Solar System. Both hot Jupiters and elliptical orbits would be an issue for life to develop in the same fashion as it did in our Solar System.
These factors make scientists conclude that our type of Solar System (rocky interior planets with large screening gas giants to the outside) is rare.
I think most scientists believe that simple life can readily take form, but multi-cellular organisms will be extremely rare (not to mention the additional improbability of developing intelligence capable of technology). It took 3 Billion years to go from single cell to multi-cell organisms on Earth according to the fossil record.
It should also be remembered that a generation of star formation and death had to occur before the formation of our Solar System.
Our moon which plays an important part in our life cycles is very unique when compared to the other moons in the Solar System.
The gas giants (in particular Jupiter) screens us somewhat from asteroid and comet impacts (another unique feature).
I think we understand enough physics to appreciate how unlikely faster than light travel and communication are. If that is the case I suspect we live in a very lonely corner of a galaxy with few if any other technologically advanced species in it. No Federation or Galactic Empire for us.
“In a few more years we will be able to detect earth-like planets, and will discover that there are a lot more of them than anyone suspected...”
I’d venture a guess that the number of Earth-like rocks vs. non, is the same as the number of humans vs. non-human life, on Earth.
Mars and Venus are Earth-like. Why would we think they are rare?