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Life in Space: Are we a coincidence?

Hi guys! While I was scrolling along the courses on EdX, I came across a series of courses entitled ‘Astrophysics’ by the Australian National University. I really found it interesting and useful. So, along with all of my posts, I will include an additional post describing what I learnt in simple and easy terms.


When we talk about life in space, astronomers often come to the Drake Equation. This equation seeks to quantify the number of intelligent species that exist on this planet. Today, I will be going through this equation step-by-step:-

N-life = N-stars...

N-stars means the number of stars in the universe. We know that the universe is damn big… actually, it is HUGE. In the observable universe, there are about 10 to the power of 23 stars! That is 10 with 23 zeroes after it! That brings us to our first thought: If the universe is so big, why aren’t there more intelligent species? Or at least, intelligent species that can contact us?

N-life = N-stars * P...

Note:- "*" is equal to multiplication

P stands for the number of planets per star. In the observable universe, this stands for about 5 planets per star…

N-life = N-stars * P * H

H stands for the number of planets that suit the criteria for habitability (such as temperature). This does narrow our options quite a bit, but not as much as the next part…

N-life = N-stars * P * H * L

L stands for the fraction of habitable planets on which life gets started. You might think that this would be small, perhaps a bit smaller than H… but you would be MASSIVELY WRONG!! To put this in perspective, imagine you are writing a book, and you just close your eyes and pick 10,000 letters, punctuated by some spaces, to write it. Would you expect a perfectly written book? I doubt it. Now imagine that you have to write about 4 MILLION of these books. Do you think you will get a perfect series? OF COURSE NOT! Life getting started is so complicated. You can actually do the calculation, let us say you have got all these amino acids, and you have to arrange them in just the right sequence to make all of them fold up and become all the right proteins and enzymes and everything else, ribosomes that we need to allow a cell to reproduce itself…

I am NOT getting into that, but it is safe to say that starting life is really just a fluke. Scientists have done this calculation, and the results were that 1 out of every 10400 HABITABLE planets will produce life. THAT IS CRAZY. 10 with 400 zeroes after it is an absolutely staggering amount. This brings me to our contradiction to the first thought: How could we have ever existed? How could we have beaten those odds? 1023 is one thing, but 10400 is a whole new level… how are we even alive?

N-life = N-stars * P * H * L * I

I stands for the probability of life getting intelligence. This surprisingly, is not really that limiting, more like H. Life, no matter how, will always eventually become intelligent at some point. The only limiting factor is time. If intelligence starts billions of years after the beginning of life, it will not last long, because billions of years happen to be the lifespan of stars.

N-life = N-stars * P * H * L * I * T

The final part of our equation. T stands for the amount of time an intelligent species stays around for. Too little, and the species will die out before anything major could happen. It does happen eventually (yes, that means that some billion years later, humans will literally be dumb).

So, there you have it. A simplistic equation that extrapolates the chance of life getting started. Honestly, unless there is something out there that scientists haven’t discovered, we are probably a fluke. I mean, 1 in 10 with 400 zeroes is a huge number, so how did we ever exist? Is there something… more to it? Maybe we’ll never know…

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