I know I haven’t posted for ages, but I am kind of past the point of caring now.
You may remember a while ago I reblogged a post about the Doomsday Theory.
Afterwards, I completely forgot about it.
But I have been thinking.
And I have found a gaping hole in the argument.
I’m sorry if you don’t like maths, but I do and this is my blog.
So here is a maths-based post about why we are probably not going to die today.
I hope you have read the other post, because I shall assume you know what I’m talking about from hereonin. I love weird words like that.
First of all, Bayes’ Law:
Also known as Bayes Theorem, or conditional probability.
Do not ask Wikipedia about it.
I hate Wikipedia.
They are stupid.
Anyway, Bayes Theorem states that:
p(A|B)=p(B|A) X p(A) / p(B)
Where p(A|B) means “the probability that event A will happen, given that event B has happened”
It has many applications in everyday life, but I am not here to talk to you about them.
The point of this post is WE ARE NOT GOING TO DIE.
The aforementioned gaping hole in the argument: 10 billion and a 1 trillion are not the only possible numbers for a population to stop at.
Because I am lazy, and couldn’t be bothered to come up with a general algorithm, I chose to imagine that it could stop at any integer from 10 to 19 inclusive.
Then we apply Bayes Law.
Event A is now “the probability that civilisation ends when world population reaches 10 billion”
Event B is “the probability that world population is currently 7 billion”
Using the analogy of picking billiard balls out of pots, p(B|A) is 1/10, or 0.1
Maybe it isn’t, if we use real billiard balls. I am woefully ignorant of the rules of billiards.
Do the balls get numbered as high as 19?
How about bingo balls, then?
Yes, that would be better.
Because I used ten possible pots (10, 11, 12, 13, 14, 15, 16, 17, 18 and 19), p(A) is 1/10, or 0.1
That much is easy
Using a calculator, a piece of paper, and a pencil, I worked out that the overall probability of picking a 7 is 167,324,635/232,792,560.
Which comes to 0.7187714. Or thereabouts.
p(A|B)=0.1 X 0.1 / 0.7187714
Which comes to: 0.01391263.
So there you go.
The probability that we all die when world population reaches 10 billion is just over 1%
ALthough, actually, the calculations shouldn’t stop at 19, but extend into infinity.
At this point, physical reality impinges on such things.
There is not room on the earth for an infinite number of people.
Even if we work out space colonisation, that will not be enough.
And BESIDES any of that, there are completely different rules governing supply-and-demand of resources we depend on, birth and death rates, and other STUFF like that.
Population studies mostly agree that it will oscillate, then stabilise, at what depends on somebody-or-others constant.
I can’t remember what any of those rules are.
But, in an overly-simplistic fashion, we are not going do to die simply because we have survived thus far.
That is not how the world works.
PS for my further thoughts on probability, see this.