What percentage chance would we have to notice, if a trillion broadcast stations exist in the universe, each one broadcasts for an average of ten thousand years? About 0.00000296%
One in a million ain’t even close.
Tris
Tris, that link didn’t work.
Think how frustrating it would be if another sentient, “intelligent” race was constantly receiving our signals but they are oblivious because they’re in an earlier stage of development (similar to our Roman era). Of course, neither them nor us could ever confirm that.
Here it is again, since the link should work, but doesn’t
Suppose a trillion civilizations, in the universe have each been expanding for an average of ten thousand years. Suppose these civilizations expand at the speed of light. Suppose further that this state of affairs is more or less constant, with new civilizations replacing fallen ones over the fifteen billion years of universal history. So, where are they?
Well, given that:
(1.5 x 10[sup]10[/sup])[sup]3[/sup], x 4/3 pi = 1.413 x 10[sup]31[/sup] cubic light years in the universal neighborhood.
And these trillion civilizations occupy
4.189 x 10[sup]24[/sup] cubic light years,
the percentage of space occupied by those civilizations is
0.00000296%
Originally from Brain Glutton
This would have to be the most unscientific equation ever devised.
You are free to put anything you like into it and you will, inevitably, get whatever nonsense you want out of it.
The simplest fact is, life forms exist down to at least 3000 ft into the Earth, including the hottest conditions. Ditto the ocean deeps.
Is it so unreasonable to suppose that the development of life, within a fairly wide range of conditions, is as inevitable as a chemical reaction anywhere (within reason) in the universe?
(click off your damn signature tune)
I agree with Cervaise. I think one place to start is with a definition of life. So far, attempts to define it have eluded biologists.
The value of the equation to science is that it gives mathematical form to the question of whether life exists and how common it is. As we learn more about other star systems with things like the space interferometer (planned for ~2015 or so) and even current techniques using stellar doppler shift to locate planets we can fill in more of the variables in the equation. This allows us to set upper bounds on the possibilty of life in the universe.
The above quote in my post was from AOB, not Brain Glutton, as it might seem due to my formatting error.
Says who? Here’s a gooddefinition:
The reason we haven’t yet found any traces of alien life might not be merely the distance to other worlds or that nearby aliens are not sentient or or are pretechnological, but that they simply don’t exist.
So far, astronomers have discovered at least 111 planets (cite) in other solar systems, but they are all gas giants at distances from their suns that preclude the evolution of life as we understand it (yes, there might be life as we don’t understand it, but since we don’t know what that might be, we will pass that over. For our purposes, “life” means carbon/oxygen critters). There may well be terrestrial planets in some of those systems, but the conditions in most of those systems make the formation of terrestrial planets in stable orbits unlikely.
When you think about it, we are extraordinarily lucky in that our home is situated in a corner of the galaxy that’s free of excessive radiation or nearby supernovas that would fry us, and we are not in a binary system. Our sun is stable and at just the right size to maintain our world in a habitable zone long enough for life to develop. Even so, our world has undergone enormous catastrophes that have driven life here nearly to the edge of extinction several times.
It might be that life is a rare and precious commodity in the universe.
For futher reading:
Snowball Earth : The Story of the Great Global Catastrophe That Spawned Life as We Know It, Gabrielle Walker
Rare Earth: Why Complex Life is Uncommon in the Universe, Peter Douglas Ward and Donald Brownlee
When Life Nearly Died: The Greatest Mass Extinction of All Time, Michael Benton
One nitpick, I would replace two with “two or more” in (5). I don’t see why multiple sexes might not be possible.
Keep in mind that the primary detection method uses the very small doppler shift in the star’s spectra caused by the star’s wobble about the gravitational center of the star-planet system. This means the detection method will have a much easier time of finding very massive planets that orbit very close to the parent star. An earthlike world orbiting where we are might be missed entirely.
I beleive I mentioned that. But as I understand it, if a giant planet is orbiting it s sun that closely, it has likely cast out terrestrial planets from the habitable zone. There may well be terrestrial planets orbiting further away from their sun, but they won’t be life-bearing.
Says lots of people.
Inoshiro said:
Nah, I’m with Alan Owen Bess on this one. The ‘Drake Equation’ gives the illusion of mathematical precision, but each of the terms of the equation are so wide-ranging and vague that it’s pretty meaningless.
Here’s another ‘scientific’ equation. I call it the ‘Sam Stone’ equation. It improves upon the Drake equation by making it simpler:
L = N(t) * P
Where L = the number of star systems that have life, N(t) is the total number of star systems in the universe, and P is the probability that any given star system developed life.
It’s ‘scientific’, and provably true. It’s also entirely useless. The Drake equation isn’t much better, since many terms in that equation are pretty much unknown within large orders of magnitude. For instance, we may discover some fundamental reason why stars in certain areas can not have life, which we don’t understand today. Then you’ll need a new term (or you can roll the lowered probability into one of the others, a ‘feature’ of equations that have vague terms with unknown values).
Yes, but if it orbits out near Jupiter it might also be missed just as we would. It is rather negative for the prospects of life, though, to find so many giant planets so close to their stars.
Here’s another ‘scientific’ equation. I call it the ‘Sam Stone’ equation. It improves upon the Drake equation by making it simpler:
L = N(t) * P
Where L = the number of star systems that have life, N(t) is the total number of star systems in the universe, and P is the probability that any given star system developed life.
[/QUOTE]
Mathematical form != mathematical precision. The drake equation, once some of the variables that we can fill in using telescopic methods have been filled in, provides an upper bound on the probabilitty of intelligent life. This is a valuable thing to know. Your “Sam Stone” equation does not and will never be useful. The two are not analogous.
Mathematical form != mathematical precision. The drake equation, once some of the variables that we can fill in using telescopic methods have been filled in, provides an upper bound on the probabilitty of intelligent life. This is a valuable thing to know. Your “Sam Stone” equation does not and will never be useful. The two are not analogous.
– fixed formatting
Mine has an upper bound too. If P=1, then every star system has life. Since we do not, in fact, know if this is the case, I could argue that my equation is more accurate.
Sure Sam, and there might be a billion barrels of oil under my house that will make me rich. We already pretty much know that P << 1 from things like the preponderance of binary star systems (very hard to get stable planetary orbitals there) and the above mentioned super-giant planets orbiting near their suns. Why not just admit you were wrong?
I’m not wrong - my example was absurd for a purpose. My point is that an ‘equation’ that just seeks to find the product of a whole bunch of very vague, unknown terms is of very little use, and not particularly scientific. Do you believe the Drake equation has provided any insight into how much life there may be in the universe? It’s merely a list of things we don’t know - and many of them we won’t know until and if we find life around enough stars that we can put some reasonable error bars around each term. And even then, propagation of error with that many terms is still likely to leave you with a huge range. It’s just not very useful.
Here’s an example. Let’s say we want to determine how many people will be on Earth in a century. We could formulate an equation like this:
Number of people = (P(w) * y) * L(w) + n*y(Br - Dr)
P(w) = probability of war per year
y = number of years
L(w) = loss of life per war
Br - birth rate
Dr - death rate
n = number of people at current time
Or something like that. It sounds all scientific, and if we ran around and tried to quantify each term we could come up with a ‘reasonable’ number – which will bear absolutely no releationship to reality. Because for all the terms we have in that equation, we are missing far more.
I see the Drake equation the same way. It’s fun for thought games, and maybe for some people it’s a device that helps clarify their thinking. So it’s not useless. It’s just hopelessly inadequate for the purposes of coming up with a real number that we can have any confidence in. There will be no time in the future when we’ll be able to plug values into the Drake equation and come up with a number that can be said to be a reasonable, scientific estimate of the number of civilizations out there. At least, not unless you want to take each one of those terms and create a thousand new variables for each one.
For example, in just the last few years a theory has come out that for life to exist a planetary system needs a Jupiter-sized world to act as a cosmic sweeper to prevent the inner planets from being continually bombarded. There’s no term for that in the Drake equation. Sure, you can roll it into one of the others, but that just highlights how vague and useless each term is.
And what’s worse is that some of those terms are totally unknowable until we actually find life. Things like “the probability that life will form given earthlike conditions”. We have a data point of ONE. That tells us absolutely nothing. Even if life is found on Mars, we won’t know if Earth or Mars weren’t contaminated by each other due to meteor strikes. For that matter, even if we found life on planets around the nearest stars, it’s still possible that the panspermia theory is to blame (i.e. life only appeared once, but over billions of years it managed to migrate around the the local group of stars).
If we get to the point where we can describe the terms in the Drake equation with enough accuracy to have confidence in them, we’ll already have the answer.
Just my opinion.
You keep arguing against a straw man that I never had any interest in. I didn’t say you would one day be able to use it to say “there are 10,250 +/- 50 civilizations in the galaxy”, I said it let you establish an upper bound and that’s all I ever claimed for it. If you want to dislike it because it won’t tell you how many little green men there and give you their internet addresses that’s fine, but that isn’t what I (or anyone else that I know of) is claiming.