
Wolfram Alpha's take on the Drake Equation - cosgroveb
http://www.wolframalpha.com/input/?i=drake+equation
======
DanielBMarkham
One of the things I love so much about the Drake equation is how it's all so
much bullshit.

Before you downvote me, I think it's a great equation and I don't have
problems with folks using it. As long as you know what you are doing. really,
think about it, all it actually says is that there is this list of things that
we feel have to happen in order to determine communicating civilizations, and
given any random set of probabilities for a list of things, you multiply them
together to get an aggregate answer. It doesn't address whether the list is
complete, or overly complex, or mis-stated. The numbers provided are juts best
guesses. It's just "multiply a bunch of numbers together and get a new number"

I love it. It's definitely not science -- yet it has this cool-looking formula
involved. It also has a powerful impact on folks who use it.

Drake is really cool in that it gets people thinking about how likely ET is.
For that, it's a wonderful tool. But at its heart there's really not much
there. At least yet. Perhaps in the future we'll have some solid survey
results to put in, especially with Kepler online. Can't wait to start seeing
those results coming in.

~~~
dantheman
I really dislike the drake equation because it's the epitome of bad science --
when someone enters value for the variables they have no idea what is
reasonable, absolutely no idea -- is it 0.1 or
0.0000000000000000000000000000001 we have no way of knowing.

Though I do like how it gets people to realize how small and insignificant we
are in the grand scale that is the solar system, the reasoning we take to get
there is fundamentally flawed. We use numbers that have everyday meaning to
us, and of course it spits out nice results; this is flawed reasoning since we
have no basis to think those numbers are even remotely correct. In general, I
just think it's sloppy thinking that takes advantage of deficiencies in human
thinking -- it's a magic trick.

~~~
DanielBMarkham
I really tried to be even-handed with my comment -- I didn't want to sound
like a troll -- but you are completely correct.

In fact, the Drake Equation is a religious statement. That is, it is a
creative speculation using commonly understood symbols to that which are
completely unknown to us. It's the same as a couple of cavemen sitting on a
hill talking about thunder as being large rocks falling from a cliff in a
faraway valley. It makes sense, it fits in with what we know, but it's really
just a bunch of guesses connected with symbols that, based on context, we feel
social approval towards. It's a mind-hack. And a very nicely executed one at
that.

The reason I didn't use the "R" word, religion, is that folks see that word
and stop thinking. They give you an instinctual answer. No way! I'm not
religious! etc.

The Drake equation basically says what anybody who has looked up at the night
sky knows intuitively: there are a lot of stars out there, and it's extremely
unlikely that we're all by ourselves. It just does it in a way that makes us
feel like we're receiving some sort of imparted scientific wisdom, instead of
what it really is: creative speculation. In that sense the formula itself may
be total bullshit scientifically, but what it tells us about how science and
religion play with each other is very important. People look at it and just
_feel_ that there is some truth there, and there is, but it's not the same
kind of truth as f=ma, although both statements are expressed mathematically
and have the same air of seriousness around them.

~~~
jerf
"The Drake equation basically says what anybody who has looked up at the night
sky knows intuitively: there are a lot of stars out there, and it's extremely
unlikely that we're all by ourselves."

Further reinforcing your core point, it can also tell you that we are. You
don't have to be _that_ painfully conservative with the numbers to come with
one or fewer per galaxy. For instance, 50% of stars having planets may be a
brutal overestimate, a lot of stars are in multi-star systems or other
situations in which there are no stable orbits, resulting in any initial
planets getting ejected very quickly if they form at all. 2 Earth-like planets
per star is a bold statement, depending on the exact definition of "Earth-
like", we only have one in our system and if you read past the propaganda in
the planet finding press releases they aren't coming up with all _that_ many
other "Earth like" planets yet. Yes, that's because they still can't see them,
but the press releases convey a false sense of how the search is going when
they do things like call a planet with a surface gravity of 3 or 4 G and a
surface temperature beyond rock's liquification point a "Super-Earth". 10000
years is a bold estimate for how long a civ will be around and communicating,
certainly. I actually am against the self-loathing that some circles find
fashionable but 10,000 years is a long time. I consider these numbers generous
and it _still_ only comes up with 10.

It's missing some terms, too. Irregular galaxies [1], approximately 25% of the
galaxies out there, are thought to be entirely unable to support complex life
because basically all the stars in such galaxies will take a system through a
region of the galaxy with too much radiation and sterilize the planets every
few tens of millions of years. I mean this only as an example, you can go on
naming more fairly reasonable criteria that eliminate half or more stars from
contention for quite a while (star types, star galactic orbits, other galaxy
attributes, even before we get to planets we can eliminate a lot).

To brutally abuse notation, the night sky is O(n^3) in size, if the
probabilities of developing civilization are O(2^n)-type it doesn't matter how
large the sky is. Big numbers fall fast when you multiply independent
probabilities together, and it's not sophistication to just give up and
declare there must be a lot of other civilizations out there; it's still a
mathematical copout. We don't know.

[1]: <http://en.wikipedia.org/wiki/Irregular_galaxy>

~~~
bad_user
I agree with your poing, but Mars is earth-like and it could have carried life
...

There is evidence that Mars once carried liquid water on its surface, it's
formed out of the same materials (carbon, hydrogen, water) and had all the
elements needed for life. Mars lost its liquid water because (contrary to
earth) it lost its atmosphere because it also lacks active plate tectonics
(also, contrary to earth).

So our solar system has 2 earth-like planets ... with one that became a desert
and died, but that was once very much like Earth, with some people still
hoping to find microscopic life at the poles.

That's not too shabby. Basically it is considered that if a planet holds
liquid water, then it can carry life (liquid water implies other things, like
the presence of an atmosphere). Bigger solar systems may contain even more
earth-like planets, but I agree: an average of 2 is way too high.

EDIT:

Also, one other thing: if Mars wouldn't have lost its atmosphere, then oxygen
would have spread faster than on earth, because the planet is smaller, which
means the transition from microscopic life to macro would have been faster.

~~~
jerf
That's what I meant by "it depends on your definition of Earth-like". Mars and
Venus are at least debatable, many of the planets being reported as "Earths"
in the media aren't. (Yet. I freely acknowledge this will change, and soon. I
have no doubt that we will find rocky planets of the approximate right size in
the approximate right orbit in the near future. Getting a bead on their
chemistry and such is going to be a lot harder for a while, though, but we'll
crack that too, eventually.) I tend to favor "actually capable of supporting
life" but the equation doesn't seem to actually require that.

Mars has the strike against it that it is arguably on the frozen side of the
zone of life. Earth is actually already on the somewhat cold side and has
spent a fairly large portion of its life as an ice planet; some have
speculated that our frequent ice ages have contributed to our diversity of
life by moderately predictable periodic mass extinctions, but of course this
is just a theory in all the bad senses of that phrase. Venus is possibly too
far on the hot side but I have an easier time envisioning life on a relatively
hot planet than a relatively cold one. We have extremophiles here on Earth and
who knows what they'd be able to evolve into if they weren't in such a small
niche? Whereas cold really puts a stopper on life; a critter can evolve that
can survive being frozen and possibly even carry on simple life functions but
only at a very slow rate, and for all we talk about how fast and robust life
is it does not take very much slowdown of life before you can't get an
intelligent civilization evolved before the sun ceases to support life. Life
is thought to be ~3.5 billion years old here, and it's hard to pin down
exactly how long the sun could sustain non-intelligent life but it could be as
little as ~1 billion years. Cold life has a real challenge getting to
intelligence in time. (Also why I don't spend any time wondering about life in
nebulas; they may be a science-fiction staple but at the rate they could live
they don't have enough time to evolve into anything interesting before the
heat death of the universe.)

------
geuis
Its interesting that Alpha has the equation baked in. What would be more
interesting would be to see a regularly updated version of this with the
latest cosmological data coming in from telescopes like Kepler. Over the next
3-5 years, Kepler is going to be finding Earth-size planets that exist in
their star's habitable zones.

For those not familiar with how Kepler is finding planets, I'll explain.
Basically, Kepler looks for planets transiting in front of their stars. The
telescope watches for dips in the star's light. If the planet has an
atmosphere, in some cases it can even get an idea of some of the gases from
the light.

The reason that astronomers aren't expecting to find Earth-size worlds in the
habitable zones is that they have to wait for several transits to know for
sure they've seen a planet. The reason that most of the planets found to date
have been gas giants orbiting very close to their stars is that it only takes
a few weeks or months for them to transit the star several times. Astronomers
can see one transit, but have to wait for a 2nd to hypothesize a planet is
found, and have to see a 3rd or more transit to verify the planet is real.

So Kepler has likely already detected suspected Earth-size planets in
habitable zones around at least a few stars. However, the telescope has to
watch for several years to confirm the transits. Imagine an astronomer in
another solar system that has seen Earth transit the Sun. They would have to
wait 3-4 years to see Earth transit the Sun several times to confirm our
existence.

Edit: Meant to include this earlier. There are multiple ways to detect
exoplanets, including the transit method.
[http://en.wikipedia.org/wiki/Methods_of_detecting_extrasolar...](http://en.wikipedia.org/wiki/Methods_of_detecting_extrasolar_planets#Transit_method)

~~~
RomP
This is something I have hard time understanding. Most of the stars are having
star flares most of the time. If they're like our Sol, they have periods of
high and low flares activity, but within the periods the pattern is random
(i.e. noise). Presumably, the change in luminosity caused by a random flare is
bigger than by a planet transit (remember transit of Venus?). So how are they
filtering the noise out?

~~~
jerf
There's no quick answer to that question, unfortunately, because if you want
something other than handwaving the answer is to go learn about the basics of
signal processing. But in short, the signature of a set of random flares and a
regular crossing of a planet are sufficiently different that they are easily
separated by the correct tools, the frequencies are totally different.

~~~
gloob
Are there any resources you could recommend for learning about signal
processing?

~~~
eru
You could try reading (and working through) "Structure and Interpretation of
Signals and Systems".

------
thebooktocome
If I had a buck for every distinct interpretation of values for the Drake
Equation, I wouldn't need to grade homework for a living.

Whether this is a comment on the Drake Equation or my salary is an exercise
left to the reader :)

------
Adrock
What's really depressing is if you assume the number of communicating
civilizations is 1 and make average lifetime of communicating civilizations be
the free variable.

~~~
khafra
You might be interested in The Great Filter, although it probably won't make
you feel any better: <http://hanson.gmu.edu/greatfilter.html>

------
exit
note that the drake equation gives the number of _currently_ communicating
civilizations.

if you think there are 10 communicating civilizations now, each communicating
for 10000 years, then there should have been quite a few such civilizations in
the 13000000000 year history of our milky way galaxy.

if the parameters provided apply for 1% of the milky ways history, we would
expect 13000 communicating civilizations in total.

i would imagine any communicating civilization lasting 10000 years would also
develop self reproducing space probes, thus becoming a permanent feature.

~~~
narag
When first stars appeared they were made out of hydrogen. It seems that you
have to wait for second or third generation stars (formed from rests of
previous defunct stars) in order to have heavy elements that would form
planets and allow life.

We could be the _first_ , or one of the first civilizations in the galaxy.
Trouble with the equation is that it does make nobody happy. As we are knowing
better some factors (like how many stars have planets) it seems that life
should be everywhere.

But it's enough that one the still unknown unknowns is worse than we think, to
make the density as low as a few dozen civilizations in the galaxy. That's too
far for us to communicate in a 10.000 years scale.

BTW, I find this 10.000 number is cruft from cold war era. Some people love
the extintion idea, not sure why.

------
btilly
The best response to the Drake opinion, IMO, is Tipler's point that if even
one civilization created and sent out a von Neumann machine just a million
years ago, they'd be here by now. So the fact that we don't see them all over
suggests that they do not exist at all.

See
[http://en.wikipedia.org/wiki/Von_Neumann_probe#Implications_...](http://en.wikipedia.org/wiki/Von_Neumann_probe#Implications_for_Fermi.27s_paradox).

It should be noted that if our civilization survives another few hundred
years, we are likely to send out von Neumann machines.

~~~
Confusion
We are? I find that a rather bold assertion. The main problem of the von
Neumann machine is gathering and _transforming_ enough materials on its own.
If we need enormous amounts of ore and factories to do that, so does the
machine. It would need to be mindboggingly _huge_ , also because it needs
enough fuel to reach new sources. A tiny machine won't work, because it can't
refine it's own materials. Really, the practical problems are being hugely
underestimated.

------
PostOnce
The Drake Equation's most telling fault, for me, is the "average lifetime of
communicating civilizations".

The default is 10,000 years. That results in 10 civilizations. A 1,000 year
lifespan means there is only 1 civilization, and a 100,000 year lifespan means
there are 100 civilizations.

As if we have any idea how long a communicating alien civilization would last.
We don't even know how long we will last, and aliens would be completely
different to us.

------
iwwr
A quick thing to notice, if you fiddle a bit with the variables, you can get
the answer "1" to the number of civilisations in our galaxy. Just decrease the
probability of life or intelligent life. After all, it took 3 bn. years before
the first multicellular life developed on Earth and 1bn. years for
intelligence to develop afterwards.

------
rblion
Seems low considering Milky Way has between 200,000,000,000 and
400,000,000,000 stars.

~~~
eru
But a year is not that long, either.

------
bufo
<http://xkcd.com/384>

------
random42
Why the search of ET Intelligence is of _any_ significance for mankind (or
even science for that matter)? Even if we assume that ET life exists, in all
likelyhood, after spending billions of trillions of dollars, we may get to
know that ET exists (assuming they do), are thousands of light-years away from
us.

Apart from the curious "are we alone?", does answering this question, has any
positive/productive outcome?

~~~
jbri
I hear that "transistor" thing is pretty much a waste of time too. A
scientific curiosity at best.

It's not necessarily about the destination, the stuff we find on the journey
is valuable in its own right.

------
PixelRobot
That's some optimistic data there.

~~~
danparsonson
That's what I thought - "average number of Earth‐like planets per star with
planets: 2"... really?

~~~
deutronium
I'd like to know where that value comes from, is there any scientific basis to
it?

~~~
rflrob
When the equation was first proposed, I'd guess they assumed Sol is an
"average" solar system, and given that we have Earth, which is by definition
Earth-like, and Mars, Venus, and several of the Jovian moons, which could all
fit a suitably loose definition of "earth-like", Drake might even have thought
he was being conservative.

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leon_
2 earth like planets per star with planets? that's bold.

~~~
ceejayoz
Depends on your definition of "Earth like". Mars would fit some definitions -
rocky, atmosphere, water present.

~~~
PixelRobot
I assume "Earth like" in this context means planets that resemble the only
planet known to hold life at least enough to be capable of holding life
themselves. The problem is we don't even know what that means exactly. It's
also assuming that life can only exist in "Earth like" conditions.

Also, if Fraction of Earth‐like planets that develop life = 1 and Mars is an
"Earth like" planet, are they assuming life evolved in Mars too or something?

------
aseem
Shouldn't the answer be 42?

~~~
mooism2
That was a different question.

