The alien hypothesis?

[Blake Stacey]

Quoting jbor at bigpond.com:

> Actually, "Science" does seem to spend an awful lot of time (and 
> money)  investigating whether Mars could support, or has supported, 
> organic  life and so forth. I'd imagine that the probability of the 
> existence of  "life" elsewhere in the universe could be calculated 
> scientiffically,  i.e. via some sort of equation where the expanse of 
> the known universe  is moderated against the likelihood of 
> environmental and chemical  conditions needed to generate and sustain 
> "life" manifesting  spontaneously. I suspect that the odds would be 
> quite good.  Hypothetically-speaking, that is.
>

Been done.  We have the "Drake Equation", named not for any Celtic dragon but
for astronomer Frank Drake, which takes the big question "Is there anybody out
there?" and divides up our uncertainty.  Each factor in the Drake Equation can
be estimated (or guesstimated) based on a different set of scientific 
findings.
The first number, R*, is the rate of star formation in the galaxy, 
which we can
figure out by looking through telescopes.  Other parameters, like f_L -- the
fraction of possibly life-bearing planets which in fact go on to develop life
-- must be estimated using biochemistry, molecular biology and geology.  While
all of these variables have considerable "plus or minus" as regards their
values, the most contentious is probably the last, the number Drake 
called L. The variable L represents the average lifetime a civilization 
stays "alive". Drake estimated L at 10 years; Michael Shermer puts it 
at 420.  (Pass the bong,
dude.)

http://en.wikipedia.org/wiki/Drake_equation

http://en.wikipedia.org/wiki/420_(drug_culture)

In Timothy Ferris's book **The Mind's Sky**, he quotes a poem which apparently
floated through the SETI community:

> Of all the sad tales
> That SETI might tell
> The saddest would be
> A small value for L.

Freeman Dyson pointed out, some years ago, that the Drake Equation 
should really
be called the "Drake Inequality".  According to Dyson, the equation needs one
more factor, a parameter to represent how many "daughter" civilizations are
colonized by each intelligent species.  The Drake Equation as it was 
originally
stated gives the **minimum** number of civilizations in the galaxy, but if
civilizations achieve interstellar spaceflight, the actual number would be
higher, possibly much higer.  At present, the only way to estimate this number
is to take an average over the values proposed in science-fiction novels.

> As to "intelligent life" or UFOs, well, that'd be a separate 
> equation.  Or a derivative of the first. But the concept of 
> "intelligent life" is  problematic in that it's another one of those 
> self-defining systems or  semantic constructs. And, coming at it from 
> another perspective, it's a  little but egotistical, if not downright 
> solipsistic, to assume for  oneself the mantle of supreme being in 
> all of existence.
>

Don't wanna go there.  Murky waters.  Let me just say that the SETI 
people have
worked very hard to imagine what sort of communication might be possible with
species as different from humanity as scientists can imagine.  (As different,
that is, while still being consistent with known physical law.  Beings 
from the
Q Continuum need not apply.)

Blake