SpaceFollow

And to be fair, this is how most people view the equation. But Drake himself was attempting to justify SETI funding, so he's specifically talking about the odds of actually communicating with (or receiving communications from) an extraterrestrial life form. While just thinking about the odds of intelligent life developing somewhere somewhen other than our own planet is interesting and perhaps makes one feel better about the universe itself, it's not terribly useful. If we can never actually interact in any way with that life, there's no real reason to spend any effort beyond the self affirming "we're sure there's other life somewhere".

Spending time and money attempting to pick up communications from alien civilizations should be based on the odds of us ever doing so. And given the methodology (scanning for light speed limited RF), it's absolutely critical to include time into the equation. Think of it this way: Our Galaxy is about 120,000 light years across at its widest point. It's a bit over 13 Billion years old. Graph that in four dimensions and you're talking about an object that is 100,000 times longer on the time axis than it is "wide" on the space axis.

Imagine a pencil that's about a quarter of an inch in diameter and about half a mile in length. The Drake equation is the equivalent of attempting to calculate the number of dark spots in the wood of a pencil in a single short cross section (all of human existence is only about 1/20th of an inch in length), but is really calculating the total number that exist at any point along the whole length of the pencil. That's why I say that time is a huge factor. It's the factor IMO. It's far far far far far far (enough fars?) bigger than the distance in space.



I suppose it depends how you calculate "L" though. If it's lifetime of a communicating species divided by the total years of the galaxy's lifespan, then it is going to take that into account. But I've never seen anyone use this as something that reduces the value, but only increases it. So we assume that all species that ever will exist all exist at the same time, and the longer they exist, the more likely that their communication will bridge the distance between them and someone else. That's the assumption. And IMO it's wrong.




Correct. As a thought experiment, we can do what we want with it. My issue is with how it is commonly used to convince people that the odds of there being alien life right now that we might just hear any day now is much much much higher than it really should be. Hell, I'm as big a fan of space and science and alien life as the next guy, but we ought not to lie to ourselves along the way. The odds of ever picking up a signal from aliens via the methods used by SETI are about as close to zero as you can ever get. And if we continue listening for a thousand years, they will still be virtually as close to zero. If we listen for a million years, it'll still be quite low (and if we haven't come up with better methods by then, we've probably been wiped out anyway). Because the odds that any species evolved and communicated at any point within a range we could pick up signals at the correct distance and time for us to pick said signal up during that time period is very close to zero. Even if we assume that 1,000 intelligent species will evolve in our galaxy, when we divide that by just the current lifespan (and it's probably less than halfway through its total), that gives us one species in the galaxy per 13 million years. Increase that to 10,000 species during that time period and we're about 50/50 in terms of being able to find evidence of them after a million years of looking.


Time is the factor, not space. It's entirely possible (quite probable in fact) that we could develop FTL capability tomorrow and explore every planet in the galaxy over the next thousand years and still not find any intelligent life, not because it's too far away but because there simply isn't any that happens to be alive at the same time and in the same galaxy as us. Now maybe most species who develop far enough never die out (or rarely do). In which case there might be hundreds of species that are millions or even billions of years old floating about. In which case, when we advance far enough, they'll probably contact us and until then they'll likely want nothing to do with us. Tons of possibilities I suppose, but I just personally find the approach SETI used to be overly optimistic and extremely unlikely to yield any results.


Never know though!

Noone posted this yet?

Amazing stuff.

That last video on beauty would've been awesome if he hadn't been talking throughout the whole thing. It was interesting what he said, but that accent, man.

Nerd.

I read it as the Space Personality Sphere.

*insert politically correct feminist rant here*

In ToS I believe it is "no man". I think they changed it to "no one" for TNG.

Very naive of you.

http://www.youtube.com/watch?feature=player_embedded&v=EgKXcQ9PLuc

o-mazing in hd