I only recently learned about GUID’s, that is Globally Unique Identifiers, usually meaning the Microsoft one. It’s a ‘number’, but made up of the digits (0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F). The computer dudes refer to this as Hex or Base16. We humans normally use Decimal or Base 10.

Anyway GUID’s are 32 Hex numbers long. It wouldn’t take that long to write one out. In fact, like this: 21EC2020-3AEA-1069-A2DD-08002B30309D. Their main purpose is to provide a unique number for things like serial numbers. For example each Ipod has one. I’m not sure if it’s a GUID but it’s similar. You can also see them inside your Windows Registry.

So how many unique ones are there?

The answer is 16 raised to the 32nd power. That is 16^{32}. Or roughly 10^{38}. That is a 1 followed by 38 zeros.

Now, on this pale blue dot of ours – planet Earth – there are about 6 billion people. Something like 10^{9}

So how many GUID’s per person? If you remember your maths it’s quite easy: 10^{38} divided by 10^{9}. That is: 10^{(38 – 9)} or 10^{29}. So we can each have a 1 followed by 29 zeros worth of GUIDs . Well beyond a billion billon billon each. Probably enough.

But that’s not enough maths for today. Oh no. We still have our own **galaxy** to think about. The milky way has about 100 billion stars. That is 10^{11} stars. If each of those stars supported a population like ours, there would be 10^{(11 + 9)} or 10^{20} beings.

So with our humble 32 hex GUIDs, we could give each being 10^{(38 – 20)} or 10^{18} GUIDs each. Hey, isn’t that a billion billion each? Nice.