Drake Equation or Rare Earth?

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Exactly.

The Drake equation is simply a mathmatically fleshed out version of the common sense conclusion that in a big universe even the unlikely is certain to occur somewhere sometime. Its only a matter of degree: how rare or how common intellligent life is.

Drake-type equations are usually based on the big obvious variables of planet size and whether or not it is in the goldilocks zone.

But you're right that the Drake eguations is weak on UNcommon sense: what I call the "Kitty Kalen Theory" that little things mean alot whether we are yet aware that they mean alot or not.. Having a moon to keep the earth upright may be more vital than we think, or having a magnetic field to keep out cosmic rays, or sharing a solar system with a jupiter to absorb the space shrapnel. Little traits that might smight not seem important may be vital to keep life going and evolving and also be rare and make earth more peculiar than we think it is.

But even if you take the drake equation without the Kitty Kalen Theory it still tends to cancel itsself out. Plugging our best estimates into the equation yields numbers for alien civilizations but numbers that mean that they are probably so far between in both place and/or in time that civilization cant even detect each other, much less communicate, much less visit each other. So for practical purposes we ARE alone, even if we are not actually alone. The good news is that the universe is big. The bad news is that the universe is big. There is a big gap between saying "we are not alone" and saying "we are being visited".

oh yeah.... Some spelling mistakes can be fatal.

I agree. I bolded "sometime" because people* often talk about how big the universe is to point to the statistical likelihood of life off Earth, but don't talk about how old it is. It may not be merely gigantic distances that separate us from other life forms but also also gigantic chunks of time. Life on Earth went from unicellular to walking on the moon in a very short time, compared to how long the universe has been around. Life on Earth may end in what is also a comparitively short time. While I think it's statistically likely that life arose off Earth, I think it's also statistically likely that it happened long before the narrow little time window that would be necessary for it to accomplish interstellar travel slightly before or simultaneous to when we became able to recognize that had happened.



*I don't mean you, since you did re-iterate the largeness of time as well as space. But I often hear the largness of space argument given without the largness of time argument going along with it. I agree with your whole post.

I try to be original sometimes, that's one reason why I'm not a parakeet.

You can still edit it for the first week.

While the usefulness of the Drake equation is grossly exaggerated, I do suspect that there is probably intelligent life out there...somewhere.

The drake equation is just a framework for guessing but over time the variables should become clearer.

The new Kepler scope recently found a huge number of planetary candidates, including Earth sized ones. Every time they get a better net, they find more planets. That helps resolve part of the equation.

http://blogs.discovermagazine.com/80bea ... e-a-dozen/

That is somewhat not surprising. Our position within the Galaxy most likely lends itself towards Earth like Planets. Several of the Rare Earth criteria involve galactic position.

Sure. But it's one factor in both equations. The more rocky planets we find, the more that Drake's value for this variable improves.

I've always believed the cosmos is vibrant with life. Even if the chances of life evolving are infinitesimal, there're so many places in the universe, there must be at least another one where life started, and once it begins, is hard to stop it. Earth experienced lots of global catastrophes over it's history, and yet, here we are, discusing about life. I don't think, though, that all life must be carbon based. That's just as saying the sun revolves around the earth, IMO. Even now there's a new discovery every day, so just because we haven't seen any other kind of lifeform, doesn't mean it has to be like we imagine it.

there is amino acids in interstellar nebulae so i think life is pretty darn common, intelligent life is something completely different.

I think it's as simple as that we can't fully comprehend the infinitesimal magnitude of the chances of various parts of the Drake equation, so we erroneously overestimate them. Truth be told, we can't even come close to truly comprehending the size of the universe, but we can approximate it numerically and plug it into formulas as a kind of "OMG that's big". So when we take something we've clearly seen evidence of (and right here, no less), such as intelligent life, it's difficult for us to imagine that it might be so rare as to be within a few orders of magnitude of the inverse of the "OMG that's big".

I think we drastically overestimate the chances of finding a real earth-like planet, and also the chances of intelligent life evolving. Both of these require so many conditions to be precisely right. On the flip side, I think simple or microbial life could be relatively common in the scope of the universe or even galaxy, both because it's much easier to reach that point than intelligent life, and because (at least as far as we've observed on earth) more complex life requires a narrower set of conditions to survive, so that there could be many planets that would be capable of only supporting simple life and not an ecosystem required for more complex life.