The Drake Equation and the probability of contact with intelligent extraterrestrial life.

Greetings, all. This is just a thought I had today that I require some feedback and input on. As I have stated many times elsewhere on ATS, I have a learning disability when it comes to mathematics which I've dealt with all my life, and which tends to make me unsure about any sort of numerical conclusions I might draw in most situations. So I would like you to tell me if I'm misunderstanding something here or not. It is likely, in my experience, that I am. Your input and corrections are appreciated.

That said...

I was looking at the Drake Equation today, using this website: SETI: The Drake Equation (scroll to the bottom of the page.) I did a quick google search for current estimates of several of the factors (those which I hoped there was better data on than simply guessing,) and made highly optimistic guesses for the rest, and came up with this:

N* = The number of stars in the Milky Way galaxy is currently estimated to be between 200 billion and 400 billion. I said 400 billion to be optimistic.

fp = The fraction of stars with planets orbiting them isn't known, but the lowest estimate appears to be 5% and the highest around 90%. I wanted to be optimistic though, so I said 50%.

ne = The number of planets per star ecologically able to sustain life I hope, in our solar system, will turn out to be three. (I am hoping we find life or evidence of past life on Mars and in Europa's seas.) So I said 3 for this element of the equation.

fl = I am hoping that we will discover that in all likelihood, where life can evolve, it does evolve. So for the fraction of those planets where life actually evolves, I entered 100%.

fi = In our solar system, at least as far as we know currently, only one planet (ours) has developed intelligent life. So I rounded up from 33% (1/3 of the three planets I hope we will discover life as formed on here) to 40% for the fraction of fl that evolves intelligent life.

fc = The fraction of fi that communicates (us,) at least in our solar system, is 100%.

fL = And lastly, for the fraction of the planet's life during which the communicating civilizations survives (which I take to mean "how long the civilization continues to exist after it gains the ability to communicate," and not, "how long the civilization exists in total," since the latter would seem irrelevant to SETI,) I was generous and said 100,000 years. (We've only had the technology to attempt extraterrestrial communication for around 100 years or so, so that seems like a very optimistic time frame given that anatomically modern humans, as far as we know, have only been here for 200,000 years or so, and anything at any time could happen to wipe us out.)

So with this in my opinion very optimistic set of figures, the calculator linked to above says that there would be an estimated 2,400,000 (two million four hundred thousand) intelligent, communicating civilizations in our galaxy. I thought that sounded like a lot, but then I started thinking about the size of our galaxy.

The stellar disk of the Milky Way Galaxy is approximately 100,000 light-years (9×1017 km) (6×1017 mi) in diameter, and is considered to be, on average, about 1,000 ly (9×1015 km) thick.

Source: en.wikipedia.org...

So, I multiplied 100,000 ly by 1,000 ly, which is 100,000,000 (one hundred million) light years. Then I divided that by the number of estimated intelligent, communicating civilizations in my optimistic scenario. The result alarmed me, which is why I'm hoping (and assuming) that I'm wrong.

Apparently there would be, even under such a favorable scenario, only one intelligent civilization per every (roughly) 41 light years. If that were true, given the speed of light (and assuming no FTL communication or travel,) it would take around 40 years for communication to reach us, assuming it was even aimed at us, and vice-versa. It seems as though we should be hearing a lot more than we have thus far (although there are the Wow! Signal and one other I can't for the life of me recall which appear at least tantalizing, if not conclusive,) but that's if we're as optimistic as I was here.

If we take a more conservative approach (which for all we know may more accurately reflect the reality,) by, for example, assuming fp = 5%, ne = 2, and f1 = 30% (and many would argue that even that is optimistic,) then we end up with only 120,000 intelligent, communicating civilizations, which means that now we would have only one per every 833 light years. At this point, communication would take 800+ years at the speed of light, and we (or they) would need to travel significantly faster than light to make physical contact with us in our lifetimes.

If we're even more conservative (ne = 1, and fc = 50%,) then we end up with 15,000 civilizations in the galaxy (and that's still being optimistic, arguably, with respect to the duration of their survival post-communication capabilities.) That would mean we only get one ever 6,000+ light years or so.

I guess my point is that changing a few variables in the Drake Equation appears (if I'm not completely wrong, which as I said I would not be surprised to find that I am) to drastically alter - for better or worse - the ostensible probability of not only intelligent, communicating life in our galaxy, but more importantly to us (or to me at least,) the probability that we would ever be lucky enough to establish communication - let alone contact - with them.

Personally, I keep an open mind. I am completely open to accounts of alien visitation (barring proof to the contrary that is irrefutable,) but I'm equally open to the possibility, based on the above, that maybe - just maybe - it's a really, really long shot.

Your reasoning looks sound to me. And I'm very good at math. When things are multiplied together as they are in the Drake equation, increasing several of them at once can drastically alter the product.

It is a very long shot.

The Drake Equation allows us to guess at the average time a communicating civilization might last, but not when they existed ...

So say such a civilization can last 10,000 years. If they are a 100,000 light years away, we may both be gone before we hear each other's signals.

And if they came and went 200 million years ago, their signals reached our planet long before we were here.

It's not just where are they or how many of them are out there ... but WHEN are they. This narrows down the possibility quite a lot.

One factor that isn't included in the Drake equation that maybe should be is the very big step of moving from very simple, single-celled life (or maybe some non-cellular analogue elsewhere?) to multicellular lifeforms. The first single-celled life forms - the first life - seems to have appeared on this planet almost 4 billion years ago (little more than half a billion years after the planet, itself, formed). But it took about another 3 billion years before the first multicellular lifeforms appeared, so the life on Earth, so far as we know, was single-celled for the first 3/4 of the planet's history.

That's a pretty significant stretch of time and a very big factor in the development of a world from just being able to support life to being able to produce a technological civilization. If the time this change took on Earth is the norm, then it likely probably greatly reduces the likelihood of us finding other civilizations.

Now include the fact that humans are making so many assumptions (based on OUR world) about where life exists and what it looks like, and your Drake Equation suddenly is completely useless, and actually worse than just plain guessing.

Some other things about it.... only human frequency included (our "dimension"), only human visible light range included, assumption that time travel is not possible, assumption that other species would use extremely slow radio waves to communicate, assumption that travel above light speed is impossible, assumption that nobody would use worm holes, assumption that this 3D world and its physical laws is all there is. And so on.

You can make equations for stuff such as measuring the distance from A to B where all the things in the equation are unlikely to ever change. In Drakes case, ALL FACTORS in his equation are EXTREMELY LIKELY TO CHANGE as our public knowledge grows.

The result from ancient math equations is still accurate because the foundations for those have not changed in thousands of years. The foundations for those are not guesses, therefore they will always be valid. Drakes Equation, on the other hand, is ONLY guesses.

Its ridiculous to even make a equation for this in my opinion. We could as well make a equation for the amount of people in love in America at this point in time and it would have a much, much larger chance of being correct since the factors involved are somehow predictable and known to us. Unlike Drakes...



[edit on 1-8-2010 by Copernicus]

reply to post by Copernicus


I agree 100%, and have taken a great deal of heat for saying as much in the past. Basically every variable in the equation is a completely unknown factor, or an educated guess.

It's an interesting experiment, the first time around. But quite useless. You know what's useful? SETI, R&D into novel propulsion technology, and all other means of taking a hands-on approach to get out there. We'll find it when we find it, and then we'll know.

Armchair guessing about about variables that will stay unknown until we directly experience them is a waste of time.

I may be wrong and don't mean to be the negative poster but if I remember correctly and for what I could tell reading your OP (haven't slept in a day so I'm a bit groggy) the drake equation hypothesizes how many intelligent civilazations are in the milky way galaxy. Well the milky way galaxy is 100,000 light years across. So using your numbers below, the 120,000 possible communicating civilizations, they could be closer than you think if spaced out evenly. Closer than 1 light year even.

"If we take a more conservative approach (which for all we know may more accurately reflect the reality,) by, for example, assuming fp = 5%, ne = 2, and f1 = 30% (and many would argue that even that is optimistic,) then we end up with only 120,000 intelligent, communicating civilizations, which means that now we would have only one per every 833 light years. At this point, communication would take 800+ years at the speed of light, and we (or they) would need to travel significantly faster than light to make physical contact with us in our lifetimes."

Also, making physical contact with a species may not be as tough as people beleive. I'm not math wiz or physicist, but one of the few people if not the only UFOlogist I even care to listen to is Stanton Friedman. He's stated before that if we were able to accelerate a craft at 1G (9.8 meters per second) constantly that we could reach the speed of light in 1 year. Pretty neat. Theoretically, it may be possible for a nuclear fusion reactor
of some sort to have the energy to do that. Also, if you were able to travel 99.9% of light it would take the occupants on board a craft only 20 months to go 37 light years. Remember that Einstein said time was relative, and those that travel close to
the speed of light expierience almost no time. Now those not in the craft expierience regular time. So, let's say 5 earthlings left to make contact light years away, theoretically they could do it, but the people on earth would be long gone. The 20 months on the craft would be more like 100,000+ years on earth.

Here's a 12 page paper where Mr. Friedman explains the math and physics behind it better than I can.

www.scribd.com...

Sorry if that was a little incoheret. I love the drake equation. Any thread that discusses it, I have to read. Don't normally comment but I would just like to say that:

A) if there is life in our galaxy it may be closer than we think
B) space travel over distances measured in light years may not be as daunting of a task as we think

thanks guys

reply to post by Copernicus


This is why I acknowledged that the Drake Equation requires a lot of assumptions, and why I said I am completely open to the possibility of alien visitation. My only point was to raise the opposite possibility - that such contact might in actuality be very unlikely for all we know.

Originally posted by GeechQuestInfo
I may be wrong and don't mean to be the negative poster but if I remember correctly and for what I could tell reading your OP (haven't slept in a day so I'm a bit groggy) the drake equation hypothesizes how many intelligent civilazations are in the milky way galaxy. Well the milky way galaxy is 100,000 light years across. So using your numbers below, the 120,000 possible communicating civilizations, they could be closer than you think if spaced out evenly. Closer than 1 light year even.

Well, it's believed to be 100,000 light years across, and 1,000 light years thick on average. So to get a very rough estimate of the total area in which intelligent civilizations might exist in our galaxy, don't we have to multiply 100,000 by 1,000 before dividing it by the number of possible communicating civilizations?

I'm not math wiz or physicist, but one of the few people if not the only UFOlogist I even care to listen to is Stanton Friedman. He's stated before that if we were able to accelerate a craft at 1G (9.8 meters per second) constantly that we could reach the speed of light in 1 year. Pretty neat. Theoretically, it may be possible for a nuclear fusion reactor
of some sort to have the energy to do that. Also, if you were able to travel 99.9% of light it would take the occupants on board a craft only 20 months to go 37 light years.

I completely forgot about time dilation to be honest. Provided I understand it at all, you are correct. We should be able (and so should any other alien entities trying to reach us) to travel great distances within our lifetimes, provided we had the necessary technology (which "they" might, even if we do not currently) even though it would still take many, many years in the most conservative scenarios.

How about this:

Total Nr of Galaxies
Total Nr of stars in each
Total Nr of planets orbiting each star

And the sumeries to the extent to Total nr of civ´s to reach technology
to travel Intergalactic using NO TIME..

I tried..

Came up to 4000 civ´s in the UNIVERSE that "COULD" have the
KNOWHOW and ability to reach us..And be alive today..

[edit on 1-8-2010 by Miccey]

I don't believe the Drake equation was meant to show how many species could exist. I feel like it is simply a thought exercise that has no real answer.
You could ask the following question,
If after 10 years, you discovered that the hospital had switched your son at birth, would you want your biological son back?
This question is one of hundreds asked in The Book of Questions. The book was written by a psychologist and the questions have no definitive answers. Your answer is based on your personal feelings and experiences.
What the Drake equation did is force scientists who thought that man was the only intelligent species to admit that there may be others. The equation proves that there must be others somewhere no matter how low you estimate it.

Originally posted by ChicUFO
I feel like it is simply a thought exercise that has no real answer.

I agree, and was going to make the same exact point. Perhaps in the future, as science learns more we can actually start filling more of the variables with real data. But for the foreseeable future, it's almost all just guess work and an interesting thing to play with to help one better consider the possibilities.

[edit on 8/1/2010 by LifeInDeath]

In my opinion, if a species has been around long enough and advanced steadily in that time, there has to be a certain point at which the species has the technology to ensure their existence is permanent (i.e, infinite).

Just as we are beginning to have the technology to replicate at the DNA level, and shoot down NEO's if one ever came too close, a highly advanced and old species should have the technology to terraform or take off for the stars, permanently.

S&F though.

[edit on 1-8-2010 by SaosinEngaged]

I agree that with our limited knowledge the Drake Equation is by no means an accurate means of estimating the probability of encountering intelligent life in our galaxy. However, just as it was originally intended to - as has been pointed out - force science to consider the possibility of advanced extraterrestrial life, I feel that the reverse can also be true. It forces us to consider the possibility that contact may be unlikely.

I guess I should explain that despite being a skeptical person, I always just felt that on the basis of common sense alone, the magnitude of the galaxy (let alone the universe,) etc. contact - if we survive long enough as a species - was all but ensured in some respect. It never occurred to me before that there was any strong chance at all of us going, say, a million years from now without encountering other intelligences (this is presuming we haven't already, which I don't know for certain - I'm open to the possibility that we have.) But this has forced me to consider the possibility that we may never make contact even in such a long span of time.

It was just a sobering thought for me.

Originally posted by area6
It is a very long shot.

The Drake Equation allows us to guess at the average time a communicating civilization might last, but not when they existed ...

So say such a civilization can last 10,000 years. If they are a 100,000 light years away, we may both be gone before we hear each other's signals.

And if they came and went 200 million years ago, their signals reached our planet long before we were here.

It's not just where are they or how many of them are out there ... but WHEN are they. This narrows down the possibility quite a lot.

I think this is taken roughly into account already in the Drake Equation:

fL is fraction of the planet's life during which the communicating civilizations live

Originally posted by oniongrass

Originally posted by area6
It is a very long shot.

The Drake Equation allows us to guess at the average time a communicating civilization might last, but not when they existed ...

I think this is taken roughly into account already in the Drake Equation:

fL is fraction of the planet's life during which the communicating civilizations live

oniongrass is right, Fl does take the when into account, sort of. The equation doesn't need to account for the exact distance and signal travel time for each civilization because it's dealing in statistics that factor that in.

And the Fl is critical.

In this episode of Cosmos, Carl Sagan comes up with only 10 civilizations in the Milky Way with his first Fl estimate.

www.hulu.com...

Then, he increases his estimate for Fl, and comes up with a bigger number. But if there are only 10 civilizations in the Milky way, that might explain the Fermi paradox, they would be so far from us it might be difficult to make contact with them.

Something else to consider that the Drake Equation does not factor in is the theory that as a species grows more technologically advanced it grows more "quiet."

Guardian UK Article from Jan 2010

reply to post by PW229


Very interesting point! Things like that, in combination with the other factors, really do make me wonder how likely it really is that contact will ever be made. At times it almost feels like it would have to be a once in several hundred million shot. Then at other times it seems almost inevitable depending on my perspective.

I'm always open to the possibility, though. (And hoping for it. At times, desperately.)

Originally posted by ChicUFO

What the Drake equation did is force scientists who thought that man was the only intelligent species to admit that there may be others. The equation proves that there must be others somewhere no matter how low you estimate it.

This is exactly what I thought it was supposed to be, though?

even upon lowering the 'guessed variables' won't it always show there to be other life out there? I guess it's just a matter of the distances, in the end...

If you'd like to fiddle with the numbers without doing the calculations there is an excellent "online" version of the equation available where you can mess around:

PBS, Drake Equation Online Tool

Edit: You can use L in a different manner than intended. Instead of thinking about the average lifespan think of it in terms of how long a civilisation may be detectable. This will result in the number of civilisations that we (or they) may be able to detect at this time. I estimated using the data available on Earth that the average time a civilisation may be detectable is around 200 years. Of course there is a flaw! As our own technology advances we may find a time in the future where we could detect a fly farting at the other side of the galaxy! So the equation must be looked at in the sense of, "what could WE detect given the variables!"

[edit on 3-8-2010 by PW229]