What is a "billion"?

Depends if you are British or American. I think in America a billion is a million million and in Britain it is one thousand million (or is the other way round?)
I don't see the point they are making - some things happened a long time ago -so what?

A billion is a lot .

The progression, where '^' means 'to the power of', 'is: 10^1 = 10, 10^2 = 100, 10^3 =1000, 10^6 = 1,000,000, 10^9 = 1,000,000,000 (billion)

So a billion usually means a thousand million nowadays.

But, yes, it used to be 10^12 = 1,000,000,000,000

It used to be the case that our billion was a million million but we later adopted the American thousand million.

The point of the list of billions in the OP is to give some context to this very large number that is otherwise difficult to grasp.

Grannybags All the examples you give are either out-of-date, open to debate or estimates. Perhaps that's why politicians, bankers and news media talk so much in billions.

PS: Why are some people's names in black [e.g. absentgrana above] and others in blue [e.g. annodomini above]?

Frankel, those of us in blue have made our profiles public.

Frankel I don't think the examples are meant to be accurate!

Frankel The examples – and I remember something similar in the Royal Society Christmas lectures – are intended to give some kind of idea of the sheer enormity of the number not to be a precise description.

Frankel You really don't want to see my profile or even me full face.

Thanks for the info regarding black and blue names. My comment about billions wasn't meant to be taken seriously either but, reading it back, I can see why it got the remarks it did. It is quite hard to be ironical. Back to the drawing board.

So, is a trillion three thousand million?

I think a trillion usually means "the cube of ten thousand", i.e. 10^12

It used to mean, in Britain, 10^18, or "the cube of a million".

Aha, I think that makes sense. Thanks Bags. I didn't do maths at secondary school. Girls did business arithmetic.