Category Archives: the Universe …

What are the odds that you exist? The fallacy of your specialness.

What are the chances that you exist? That is, you personally.
I’ve heard this question posited many times.
I think Richard Dawkins mentioned it in one of his books, or maybe in an interview, and I’ve recently seen it on the back cover of the new book by Dr Alice Roberts titled “The Incredible Unlikeliness of Being“, (the book that gets my prize for the wittiest book title of the year, being based, in case you don’t know, on the book title “The Unbearable Lightness of Being” by Milan Kundera).

The question is usually asked in something along the lines of: what are the chances that your mother and father would meet? Maybe your mother turned left instead of right at a street corner and bumped into the man who was later to become your father. What are the chances of that?
And what are the chances that your grandparents met, and that their parents met, and that their parents met before them?
The chances are surely vanishingly minute.
Yes they are.
Your existence is statistically almost infinitely unlikely.
(Hence the title of Alice Robert’s book, The Incredible Unlikeliness of Being.)

However, as incredibly unlikely statistically your own personal existence is, it isn’t actually incredible in the sense of being beyond credibility.

As far as I can work out, the statistic concerning the likelihood of one’s own existence is a trivial or mundane statistic – in that it may be true but it has little significance.

Here’s an analogy to show what I mean.

I’m going to type a list of thirty random numbers.


There it is.
Now, what are the chances of that row of numbers being those particular digits in that particular order?

The chances are one in 1,000,000,000,000,000,000,000,000,000,000.

(A simpler example of the same principal is that the chances of writing any specific list of digits that’s only two digits long is one in a hundred – the combinations being from 00 to 99, or in other words a hundred possible combinations.)

You probably don’t think that it’s incredible that I’ve just written down a list of numbers that has only a one in a million million million (etc) chance of existing. I had to write down a list of thirty digits after all, and every list of thirty digits has the same incredibly low chance of being written. But one of them is inevitably going to be written.

It’s the same with people.
The chances of you existing may be almost vanishingly unlikely, but if it wasn’t you who existed it’d be someone else, in the same way that if it wasn’t that list of thirty digits it’d be a different one. (Your mother may have turned right at the street corner instead of left and bumped into a different man who would father a child who wasn’t you, while your father (who now wasn’t bumped into) continued on his journey to a work appointment at which he would meet his future wife).
We’ve got to end up with someone rather than no-one. It just doesn’t have to be you.
Or if it doesn’t have to be someone it has to be something. Maybe a descendant of the dinosaurs (because the asteroid missed), or more likely something that we can’t even envisage because there are just so many possibilities – just as there are so many possibilities when it comes to writing random thirty digit lists of numbers.
We haven’t even considered random million digit lists of numbers yet. Let’s not bother – just because something’s vanishingly unlikely doesn’t make it special.


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Are we alone in the galaxy? Brian Cox thinks so.

Is there anyone out there?
Are there other stars than the Sun in the galaxy that are orbited by planets that support intelligent life?
Brian Cox doesn’t think so.
In his BBC tv series on the human race’s place in the universe – Human Universe – he gives his reasons.
I’m not sure that I agree with him, but here’s his thinking.
In the 1940s Hungarian/American mathematician John von Neumann came up with the concept of self replicating machines (which he called universal constructors) – machines that could reproduce themselves. (Having just stated that von Neumann came up with the concept I’d like to qualify that statement with the observation that most concepts are thought up independently by several people, it’s just that only one of them usually gets the credit).
If such machines were to be launched into space they could land on asteroids, planets etc and mine the mineral resources there, using the minerals to construct replicants of themselves. By a process of asteroid/planet hopping they could thus multiply and spread out through the galaxy. It’s estimated that by such a process the whole galaxy could be colonised in ten million years.
If an intelligent alien race had at some point over ten million years ago (that is, for most of the history of the galaxy) decided to create such machines they’d have spread throughout the galaxy by now and we’d be able to see evidence of their existence.
But we can’t, so they didn’t.
This, according to Brian Cox, is the clincher when it comes to deciding whether advanced, space-going civilisations have existed before. He thinks that because the concept of self-replicating galaxy-colonising machines constructed by advanced alien civilisations is possible in principle we have to construct an argument for why we don’t see them – and he can’t think of any such argument.
He concludes that therefore it’s probable that there never have been advanced space-going civilisations in the galaxy up until now – until we came along.
Personally, I’m slightly uncomfortable with the reasoning here. The lack of evidence of self-replicating alien technology in our vicinity seems like a rather tenuous reason to dismiss the concept of intelligent alien life-forms.

In the tv programme Brian Cox stated that he couldn’t think of any reasons why where wouldn’t be evidence of alien self-replicating machinery, so I assume that he’s weighed up the arguments and has dismissed the ones that give reasons why advanced civilisation may exist and yet may not send out self-replicating machines. Unfortunately he didn’t give us any examples, which is a shame.
I can think of a few off the top of my head. They’re probably all flawed, but here are three of them.
Reason one: advanced alien intelligences have existed that are capable of making self-replicating galaxy-colonising machines, but they decided not to. They may have realised that a galaxy that was full of their machines, self-replicating endlessly – long after the civilisation itself had died out – was not a good idea. They’d probably have tried prototype self-replicating machines on their home planet first, with either inconvenient or dire consequences.
Reason two: the advanced alien lifeforms just weren’t interested in galactic colonisation, for either psychological or practical reasons.
Reason three: self-replicating machines have indeed spread throughout the galaxy, but the machines are hidden from our perception so that they don’t disturb us.

The whole television programme was about the possibility of life elsewhere in the universe (and was actually subtitled “Are We Alone?”), culminating in a discussion about intelligent alien life, so to dismiss the possibility of alien intelligent life on the basis of ‘no self-replicating machines’ without giving his reasons seems a bit lax.
Maybe he thought that the audience for such a programme wouldn’t be interested in arguments that were made in order to be dismissed, or maybe he just ran out of time (Time that could have been found, may I suggest, by cutting the silly sequence in which school children lined up with coloured lanterns to depict, very badly, the Hertzsprung-Russell diagram perhaps. Anyone who could make sense of that sequence probably already knew what the Hertzsprung-Russell diagram was).


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