I just want to know for my own curiousity.
It took me a while to figure out what you were saying (summer camp teams?). But, I assume that you are asking whether we think that Earth like planets are rare.
Certainly, there is no reason to think that terrestrial rocky planets are rare. And, water does not appear to be a terribly scare thing either. Of course, the big distinguishing factor of Earth's atmosphere is that its existence is made possible with biological interactions. Short of that, Earth-like planets should be quite common, and I find it hard to believe that even some manner of life is really all that rare.
There are billions and billions of start systems with many times that many planets. I think that Earth-like planets are fairly common within them.
I found Ward and Brownlee's arguments pretty convincing even though some ideas were proposed by a devout christian creationist astronomer (although neither one knew it at the time) if I recall correctly. Life is probably pretty common in the universe but complex "animals" are probably vanishingly rare. I remember being kind of depressed after I read the book, thinking that we could very easily be the only technological civilization in our local group, let alone galaxy. It certainly would seem to answer Fermi's paradox.
I'm not in the rare earth camp. The universe is too vast. But what do I know? To me, there is a probability that life as evolved as ours has happened sometime in the past or is on target to happen in the future, it won't be exactly the same, as we are the result of a number of freak accidents, that, I cannot deny.
No rare earth camper either. Extrasolar planets are no longer speculation. We have already found over a hundred. And these are just the big fellows. It seems reasonable to assume rocky, earthlike planets are as common as gas giants - at least within an OOM. It also seems reasonable to assume a few percent of them occupy hospitable orbits. And the probability of at least primitive life arising under such conditions also appears to be favorable. I too am troubled by the Fermi paradox. It may imply that technologically advanced civilizations tend to self destruct shortly after acquiring the ability to do so.
I'm in the 'there's no way to tell, yet' camp!
Ward and Brownlee have written a very interesting book, but as they themselves freely admit, all they have done is show that complex life on planets 'like' the Earth could be quite rare; they have little to say (because they are scientists, and are fully aware of just how little data there is to work from, in terms of their line of reasoning) about the possibility on planets not quite 'like' the Earth.
Even for planets 'like' the Earth, they have been careful to state just how uncertain many of the factors which lead them to their conclusion are.
What if the alien civilizations are just spread too much apart, even if there were 50-100 in the galaxy, they still could be spread so far apart that they havent made contact yet.
Or other alien civilizations have had contact with each other but we still havent...yet.
This is a very good point. And to keep things in perspective, even though we have been transmitting in RF for 100 years or so, that mishmash of EM waves might not even be detectable much beyond our sun's near neighborhood. Also, we have not developed a sufficiently advanced technology to enable us to put humans in interplanetary space and safely shield them from the Sun's periodic tantrums. Until there are some real breakthroughs in propulsion, shielding, etc, we're pretty much stuck to this rock. Unfortunately, the Bush administration cut funding for NASA's breakthrough propulsion project even before Bush started crowing about sending men to Mars. I guess there are no physicists advising him or his handlers.
Separate names with a comma.