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In this post we are going to take a detailed look at the Famous Drake Equation. I consider it to be the second most widely known equation amongst non Physicists after E=MC2.
Devised in 1961 by the late American Astrophysicist and Astrobiologist Frank Drake, it addresses one of the biggest questions we have as a civilisation.
Are we alone in the Universe?
It has certainly received plenty of criticism through the years. Whilst considered more of an approximation than a serious attempt to determine a precise result, the aforementioned criticism was levelled at some of the highly conjectural terms it contains and the fact the combined multiplicative effect raises such uncertainty with any derived value it couldn’t be used to draw firm conclusions.
With all that said, it still remains a very interesting piece of work and something that the average person can understand relatively well.
The nuts and bolts
First of all we need to take a detailed look at the terms of the equation and understand them. It may appear a little daunting at first but work through it and try to understand what Drake was trying to estimate with each term.
Remember that each full stop (or period) means ‘multiplied by’, so the maths of this equation is actually quite simple. Its just a big multiplication sum.
N: The number of civilisations in the Galaxy with which communication may be possible.
R*: The average rate of galactic star formation, or how many new stars are born each year.
Fp: The fraction of those stars that have orbiting planets
Ne: The average number of planets orbiting those stars that can support life as we understand it
Fl: The fraction of those planets that could actually develop life at some point
Fi: The fraction of those life bearing planets where intelligent life (or civilisations) may develop
Fc: The fraction of those that develop technology which releases detectable signals into space
L: The length of time those signals remain detectable
As you can see, some of the terms are very speculative. The advancement of science and technology has made certain terms such as R* or Fp much more accurate, however some of the later terms are wide open to conjecture.
What this means is we are going to get a variable result from this equation. A ‘best and worst case’ scenario.
I think the real beauty of this is that you don’t need to be a Physicist to hold a worthwhile opinion on its output.
What is realistic?
Realistic values in the Drake Equation are a matter of hotly contested opinion. A good starting point would be to look at what Frank Drake himself cited in his original 1961 work.
Drake postulated that 10 new stars are born each year per galaxy. 50% of those will have orbiting planets and 2 per solar system would be habitable, the latter presumably based on Earth and Mars in our own solar system.
He then stated a contentious number, 100% of habitable planets would develop life. Should we find life, or even evidence of it having previously been present on Mars this number would be considered far more realistic.
From those planets developing life he stated that 1% would develop intelligent life and of those only 1% would develop the ability to communicate.
The final input is again a challenging number to buy into, but it was his belief that a civilisation would maintain the ability to communicate for an average of 10,000 years. This is probably the most argued input value in the original work.
So, the results of these inputs give us an approximation of the number of intelligent civilisations in the Milky Way Galaxy.
That figure is ten.
Ten intelligent, communicative civilisations in our own neighbourhood. Extrapolating that to the wider Universe the number reaches a staggering 1500 billion.
One for the skeptics
What if we input extremely low values? What if we are so skeptical we put numbers into the Drake Equation that suggest the chance of intelligent life is really very low indeed. Try these:
R*: Only 7 new stars are born each year.
Fp: Only 22% have orbiting planets.
Ne: Just 0.01% of those are habitable.
Fl: Of those only 0.1% develop life.
Fi: Of those only 0.1% develop intelligent life.
Fc: Of those just 1% gain the ability to communicate into space
L: Those signals remain detectable for only 1,000 years.
The result here is that each galaxy has 0.000000154 intelligent civilisations. Pretty low.
However if we extrapolate that across the wider Universe, which is so unthinkably vast, the estimation is 23,100 intelligent civilisations.
This really is sobering food for thought, even given the highly conjectural nature of some of the terms in the equation in excess of 23,000 galactic civilisations is mind blowing.
The numbers here are suggesting that being the only intelligent inhabitants of our Universe is pretty unlikely.
One final tweak
I couldn’t resist one final tweak of these numbers. Something very topical and relevant to our current science.
What if we find life on Mars?
Should that be the case then 100% of the habitable planets in our solar system would have developed life. Lets put that into our skeptical number set above and see what effect it has.
We need to tweak the Fl term in order to do this. We currently estimated it at 0.1% and our own observations may well show that it is actually 100%.
Lets dial it up, but remain cautious. I’m going to set it at 5%.
The effect of this is that we no longer have a potential 23,000 intelligent civilisations in our Universe.
We have over 1.1 million.
An easier visualisation
When writing this piece I came across a wonderful visualisation researched and designed by David McCandless and coded by Fabio Bergamaschi where you can tweak the input values really easily and see the differing effects. I thoroughly enjoyed putting various scenarios into this tool and experimenting with the results.
They have even included an additional term representing the number of times a civilisation could potentially re-evolve (important given the average age of planets) and a more up-to-date equation developed by Prof Sara Seager which focuses on the detection of biosignatures to determine the presence of intelligent life.
Experiment with the tool yourself and see what conclusions you draw from it.
https://www.informationisbeautiful.net/visualizations/the-drake-equation/
The post How To Understand The Famous Drake Equation. Are We All Alone In The Universe? appeared first on The Average Scientist.
