We often hear about climate change, unknown epidemics, or the threat of nuclear war. Just by browsing the newspapers or social media, we feel like the world may not have much longer to live! The talk of global destruction seems much more real now than it did a few years ago. But while scientists or environmentalists are worried about melting glaciers or the depletion of the ozone layer, a group of mathematicians is calculating human extinction from a completely different perspective. Their calculation is not based on any fossils or temperatures, but rather on statistics and probability.
A strange conclusion has emerged from that mathematical calculation – humanity will survive on this earth for a maximum of 17,100 years! This mathematical calculation or prediction has a 95 percent chance of being correct. Did you frown upon hearing that number? Let’s not worry too much and try to understand this interesting yet terrifying mathematical theory in a simple way. Let’s try to find out how mathematicians calculated this number with such certainty. The theory I’ve talked about so far is called the Doomsday Argument. This idea was born in 1983 by astrophysicist Brandon Carter. Its main basis is the Copernican Principle. What is this again?
A strange conclusion has emerged from mathematical calculations – humanity will survive on this earth for a maximum of 17,100 years! This mathematical calculation has a 95 percent chance of being correct. In the 16th century, Nicolaus Copernicus first proved that the Earth is not the center of the universe. We have no special place in the vastness of the universe. The same argument is used in the Doomsday argument. Our current position as humans in the vast timeline of time is nothing special at all, but rather completely random. Suppose that all the people who will ever be born on this earth, from the past to the future, are lined up in a straight line. Where exactly are you or I on that line? Since we are not special, we have an equal chance of being in the middle of this line or anywhere else.
I understand, the calculation still seems a bit complicated! Let’s try to understand with the help of a simple example. Suppose you have two identical boxes in front of you. One box contains 10 ping-pong balls numbered from 1 to 10. The other box contains 100,000 balls numbered from 1 to 100,000. But you don’t know how many balls are in which box. Now you are asked to pick a ball from any box without looking. You pick up the ball and see that it has the word ‘4’ written on it. Now, using a little common sense, tell me which box the ball is most likely to come from?
Suppose you have two identical boxes in front of you. One box contains 10 ping-pong balls numbered from 1 to 10. The other box contains 100,000 balls numbered from 1 to 100,000. Surely you would say, from the one with 10 balls! Because the probability of getting a ‘4’ from a small box is 1 in 10. And the probability of getting a ‘4’ from a box with 100,000 balls is 1 in 100,000, which is almost impossible! The number is exactly the same for our human race. About 117 billion people have been born on earth so far. That is, you or I are the 117 billion number ball (read human) on this earth. Now, if humanity spreads throughout the entire galaxy in the future and gives birth to trillions of trillions of people (the box with the million ball), then the chances of our number falling so early are very small.
On the contrary, if humanity becomes extinct in a few thousand years (the small box), then the chances of our number being 117 billion are the highest! Mathematicians say, that straight line I mentioned, suppose we do not fall into the top 5 percent of the total human population. The probability of this is 95 percent. If we do the math using this logic, we see that 20 times fewer people will be born in the future than the total number of people born on earth so far (117 billion). That is, the maximum number of people born on Earth from the past to the future could be 20 times 117 billion. That is, 2.34 trillion! It is mathematically almost impossible for more people to come to Earth.
The maximum number of people born on Earth from the past to the future could be 20 times 117 billion. That is 2.34 trillion! It is mathematically almost impossible for more people to come to Earth. Now let’s compare the numbers with the present. For the past 40 years, an average of about 130 million children have been born in the world every year. Although the birth rate is decreasing, the total population is increasing. If we assume that this 130 million birth rate will remain the same in the coming days, then it will take humanity only 17,100 years to reach that maximum limit (2.34 trillion)! This number may fluctuate a little if the birth rate decreases or increases, but the basic calculation will remain around that 17,000. So will everything really end after 17,000 years? In fact, science is a game of logic and argument. That is why many scientists have directly rejected this calculation of the Doomsday argument.
Their argument is that if we do not just think about humans but consider all living things together, starting from the first bacteria born on Earth, then this calculation will be completely reversed and the destruction of the world will be postponed by billions of years. Another group of scientists claims that humans have only just become intelligent enough to calculate this extinction! Perhaps we have only just begun to think because we have crossed this boundary of intelligence. That means we may be at the very beginning of human civilization. If so, then the Copernican Principle does not apply here and our future is still very long! None of us, at least those of us reading this article, will be able to see for sure whether the Earth will actually survive after 17,000 years. But these mathematical statistics at least tell us how small and fleeting our existence is in the vast canvas of time!
