The Drake Equation - Illustrated and Clarified (INFOGRAPHIC)

The Drake Equation is often referred to on ATS. Many times it is used and misused to support different ideas about life in the universe. Often a counterpoint to that is someone who says that the equation is not very useful since they think it is all speculation

But what do we know about the Drake Equation?

We know what it is not: It is not an equation which Drake designed to have a definitive answer in 1961. It was not a proof. It was a tool or a guide.

And despite the fact that we've filled in some of the variables with proven numbers (something I'll get to in the infographic), it still is not something which at this point in time can provide a definitive answer as there are still plenty of unknowns.

However, that may change at some point within the next 30 years.

But before we go to the future let's look back to the past when the Drake Equation was first written down...



When was the Drake Equation created?

The Drake Equation was penned by radio astronomer and founder of modern SETI, Frank Drake in 1961 at a meeting at the Green Bank Radio Telescope facility where Drake conducted his first SETI experiments.

Why was the Drake Equation created?

The Drake Equation was originally created to answer the question of how near the next communicating extraterrestrial civilization might be. This was important because the scientists at the meeting were trying to determine if their current equipment would be capable of detecting such a civilization at interstellar distances within our Milky Way Galaxy.

In short if they could get an idea of how common technological civilizations were in our galaxy then they would know how sensitive their equipment would need to be to detect them.

So to answer this question Drake broke this question down into other smaller fundamental questions which could potentially be answered with the right observations or experiments.

In 1961 these fundamental questions, represented in the equation were:

1. What is the rate of star formation in our galaxy?

2. How many of those stars have planets?

3. How many of those stars have Earthlike planets?

4. How many of those planets have life?

5. How many of those planets with life produce intelligence and civilizations?

6. How many of those civilizations build technology which can be detected?

7. How long do such civilizations exist?

Why is the Drake Equation misunderstood?

One common misconception of the Drake Equation is that it is all guesswork, that it is simply a thought experiment. This is due to the fact that many people are more familiar with equations used as proof but not as tools.

The criticism that it is simply a guessing game was valid based on the equation's origins because that's exactly what it was at the time.

In 1961 no one knew the rate of star formation or how many stars in our galaxy had planets the size of the Earth orbiting at a safe distance, they didn't even know of one planet outside our solar system. It would be another 34 years before the first planet was discovered orbiting another Sunlike star in 1995 and it would be 19 years after that that the first Earth "cousin" was discovered in 2014.

In 1961 the Drake Equation was not an equation with solid numbers but instead a tool with which to break down the large question of life in the galaxy into smaller ones which could be answered in the future.

That future has begun to take shape.

Where are we now?


In 2014, 41 years later we have actual numbers for the first 3 variables of the Drake Equation..

1. Astronomers now strongly believe that every star in the galaxy has a planet. Planets are the byproduct of star formation. Wherever we look for stars we end up finding planets including ones in bizarre orbits and those which orbit one or multiple stars in binary star systems.
   
2. 40 percent of stars have planets which are in favorable orbits, the so-called "Goldilocks Zone" planets.
   
3. One fifth of stars like our Sun have a planet which might harbor life.
   

How do we know this?

I've added to this infographic so you can see what we know, how we learned what we know, what we don't know and what we plan to build and use to learn more.

Below each variable are also pictures of the instruments we've used or plan to use to chip away at the variable they are under.

Click infographic for full resolution

There will probably be a good answer to all the factors except L the length of time a technological civilization exists if we keep doing what we've been doing: plugging away at learning each individual variable through observation and experiment.

The question of whether there is other life in the Universe is not a philosophical question anymore, it's a scientific problem which can be addressed with current and future technology.

We've come a long way since 1961 but have a ways to go.



This is one of the reasons there was much excitement at NASA last month: There is a growing realization that we are likely less than 30 years away from uncovering the next fraction in the Drake Equation: (fl) the fraction of planets which produce life.




References:

1. Drake, Frank, SETI Institute Website - Biography and CV

2. NASA Goddard Website, Milky Way Churns Out Seven New Stars Per Year, Scientists Say

3. Diehl, Roland, Nature Radioactive 26Al from massive stars in the Galaxy

4. Leconte, Jérémy, Forget, Francois, Charnay, Benjamin, Wordsworth, Robin & Pottier, Alizée 2013, Nature Increased insolation threshold for runaway greenhouse processes on Earth-like planets

5. Kasting, James F., Kopparapu, Ravi, Ramirez, Ramses R., & Harman, Chester 2013, ArXiv e-prints Remote Life Detection Criteria, Habitable Zone Boundaries, and the Frequency of Earthlike Planets around M and Late-K Stars

6. Kopparapu, Ravi Kumar 2013, The Astrophysical Journal A Revised Estimate of the Occurrence Rate of Terrestrial Planets in the Habitable Zones around Kepler M-dwarfs

7. Petigura, Erik A., Howard, Andrew W., & Marcy, Geoffrey W. 2013, ArXiv e-prints Prevalence of Earth-size planets orbiting Sun-like stars

8. University of Puerto Rico Planetary Habitability Laboratory Website, The Habitable Universe

a reply to: JadeStar

yup - the drake equation takes a lot of flak doesn't it

my best argument in its defence is :

what evidence for zero ?

its simple - unless you apply ZERO as a variable - drakes equation predicts at least 2 civilizations - us - and a minimum of one other - in the universe

so why zero ???? peoples common criticism of drake is " its guess work "

but claiming zero isn't a guess - its statement of fact [ all be it alledged ]

I have never heard a rational explaination for zero in the drake equation

I am very cautiously optimistic and excited about what my grandkids will learn in school. It'll be the same stuff we envisioned while sitting around a campfire listening to Phish...

a reply to: JadeStar

Thanks for an excellent thread, S&F.

Personally I think a more accurate equation should have way more variables and the final total would be miniscule.

Mind boggling none the less and that's what counts.

originally posted by: ignorant_ape
a reply to: JadeStar

yup - the drake equation takes a lot of flak doesn't it

my best argument in its defence is :

what evidence for zero ?

its simple - unless you apply ZERO as a variable - drakes equation predicts at least 2 civilizations - us - and a minimum of one other - in the universe

so why zero ???? peoples common criticism of drake is " its guess work "

but claiming zero isn't a guess - its statement of fact [ all be it alledged ]

I have never heard a rational explaination for zero in the drake equation

I agree, Zero is the only rational argument against the Drake equation, though the actual argument of Zero itself is irrational, because there will obviously be at least 1 other just in our galaxy, based on statistical probability.

From our experience, life exists in even the most extreme environs on our planet. Thus life can exist in many varied, both to the extreme and the mild, environments, relative to our experience.

I think we will find at least simple life basically everywhere. Advanced, space capable life though.....probably more like 1 in billions or trillions of life supporting planets.

originally posted by: ignorant_ape
a reply to: JadeStar

yup - the drake equation takes a lot of flak doesn't it

my best argument in its defence is :

what evidence for zero ?

its simple - unless you apply ZERO as a variable - drakes equation predicts at least 2 civilizations - us - and a minimum of one other - in the universe

so why zero ???? peoples common criticism of drake is " its guess work "

but claiming zero isn't a guess - its statement of fact [ all be it alledged ]

I have never heard a rational explaination for zero in the drake equation

Well it is supposed to work out the number of possible civilisations that WE can communicate with so we can't include us in the answer.

Parts of the equation ARE and most likely always will be guess work others will be guesstimated from statistics from observation now as we can NEVER get data for every system the result could always be wrong.

N= first 3 factors from statistics next 4 guesswork

So could zero be a possibility

a reply to: ignorant_ape
I wouldn't even consider using the Drake equation at first. I would look to how our civilization started which is indeed very "shady". On earth there are accounts of many other known extraterrestrial and advanced civilizations but much evidence is lost forever. The hardest accounts to decipher is religion. On top of that is the fact that in many places on earth people are taught to believe linear evolution when really nobody knows anything about the past. Half the times carbon dating doesnt even work on old artifacts and structures because they've obviously been reconstructed and refurbished as time goes on so our entire sense of time is off for one. People don't even know what the facts in religion are and what the fiction in it is.
That leaves one sentence on finding other civilizations ourselves: We're screwed.

a reply to: JadeStar

Brilliant infographic/information!

It's been a while since I've had a look at the Drake Equation. I wasn't aware just how much progress we have made in terms of pinpointing realistic values for some of those variables.

Some things I'm not clear about however. Why is the rate of star formation factored but not the current amount of observable stars?

Shouldn't the equation(s) follow the form of:

X(t) = (Y multiplied by De)(t)

X(t+t') = (Y multiplied by De)(t) + (R* multiplied by De)(t')

Does that make sense?

Where (De) represents the variables of the Drake Equation excluding R* (rate of new star formation per year).

Where Y is the amount of observable stars in the universe, or the speculated amount of stars to exist up to the current time, (t).

And where X is the number of possible advanced civilisations for time (t) along the universe's timeline, with the addition of the (R*) scaled function for time (t') into the future.

Otherwise, the equation only looks at the potential of any future star to harbour communicative and intelligent life, and how long it would take for communication.

Unless, that's all it's meant to do? Am I being stupid lol? It's late.

Also, surely the equation only takes an accurate form after MULTIPLE contacts with advanced life. So, in essence it's use as a detection tool or statistical analysis for future contact is sort of illogical in a way. Unless we use our own variables as humans.

The last 3 factors of the equation - Fi, Fc and L - will drastically change with each newly discovered intelligent intergalactic species. It could have a huge variance. We'd have to plug in our values for the first iteration.

But if we're doing that... Our best bet is to instead completely focus our search, or should I say continue to focus our search, for Earth-like planets. We have to stick with what we know can create intelligent life.

If we can at least get a ratio of Earth-like to non-Earth-like planets for different types of galaxies, we can extrapolate that to the universe and get an actual value for the number of Earth-like planets to exist for time (t), and that will exist for time (t').

Then, we apply the numbers we know for a 'fact' regarding our own development on Earth and apply it to the number we get above. This is the most accurate answer I believe we can calculate for now.

But, we have to be careful with what we define as Earth-like in the above equation.

I don't think we have a great idea of how much of a tolerance exists regarding these crucial life factors, and furthermore how big of a compromise can be made between them - for our own Earth conditions that is.

Still, if we strictly use true Earth-like planets only, we can take a really decent guess.

The problem with this approach is always the Fermi Paradox. All logic then says that an Earth-like planet in the past, covering the whole of time (t), would have done this same procedure and in turn found OUR planet in their search for Earth-like bodies.

So, where are they? But, seriously, I do agree that in 30 or so years time these sort of things will be A LOT clearer for humanity. Hopefully, that's a good thing lol.

originally posted by: JadeStar

I actually tried to pronounce that as a word.

Rfpne-feficl.



Personally, I don't attach that much importance to Drake's equation. For me, it's more important that there are billions upon billions of star systems out there, and that our own system is in no way unique.

Drake equation

Coupled with fermi paradox

Taken with infinity

And you have the reason I am agnostic

originally posted by: wildespace

Personally, I don't attach that much importance to Drake's equation. For me, it's more important that there are billions upon billions of star systems out there, and that our own system is in no way unique.

I agree that it is almost a certainty that other intelligent life is out there, considering that there are hundreds of billions of stars in the galaxy -- heck, there are hundreds of billions of galaxies. The one thing that the Drake equation (when the variables are filled in) attempts to tell us is how common that life may be.

Is there a good chance that there is intelligent life relatively close to us whom we may someday meet, or are they so uncommon that we are just some anonymous star lost among a sea of hundreds of billions of other star to them. One could argue that the may have the technology to detect that Earth's atmosphere indicates life processes, but then again, we may be just one of hundreds of thousands of other planets that show life processes. They may be so far from us that we may not really stand out in a crowd to them.

What happens if a completed Drake equation tells us that life is really uncommon? For example, only one technological civilization in a galaxy every One Million years or so. The closest intelligent life in the universe that coexists in time with us may be so far away that our entire galaxy is just a faint speck in their sky.

So while I believe that -- even ignoring the Drake Equation -- there is other intelligent life in the universe, the Drake Equation (with variables) could tell us that life may be so rare that we for all intents and purposes should consider ourselves to be "alone", just like a person on a deserted island may be "alone", even though civilization does exist far across the ocean.

Visit the ATS Live Forum for more information. Look for Out of the Box SE5 EP3.