π in the Sky

Maybe it's because the climatologists daren't stick their heads above the parapet until things warm up a bit, but the world seems to have exploded with a series of macho scientific posturing.  First we have the French Scientist who has calculated Pi (π) to 7.2 trillion places.  Which begs the question - why?  What has he achieved?  What can he do with it now he's got it?  And who's checked his workings?  And who is he hoping to impress?  If it's girls, then unless he bumps into Kate Bush he's not going to get too far, I reckon.  Or maybe he's wanting to impress other Pi-calculating scientists?  You can imagine them, in the pub, after a long day's π-calculating, comparing 2.8billionth digits over a cider and black.
Then we have the American scientists who tell us that a star 3,600 Light Years away could explode as a supernova, killing us all. Being in a scientific mood I'd like to carry out a little test on these scientists.  It's a simple test.  Are they still paying into their pensions?  Oh, they are?  That's OK then.  But again it's a headline-grabbing story.  I quote from Robin Scagell, vice-president of the UK's Society for Popular Astronomy: 

"The star may certainly became a supernova soon – but soon could still be a long way off so don't have nightmares."

 The words "certainly" and "may" have never lived in such inappropriate propinquity.  And Mr Scagell's pronouncement - indeed his very existence - gives me other things to worry about.  If he represents the "Society for Popular Astronomy", why have I never heard of it?  And if he is the vice-president, who is the president?  And was he so busy popularising astronomy that he wasn't available to give a quote himself?  Or is the "Society for Popular Astronomy" an association like the National Secular Society, only having two members who therefore get to elect themselves to all the important jobs?  Why don't they merge?  Form a "National Society for Popular Secular Astronomy"?  After all, we wouldn't want nasty Religious Astronomy - people explaining the start of the Universe with technical diagrams of God throwing stars about... And then at least there would be four people in the organisation - albeit the sharing out of the jobs would become more sensitive.  I guess you'd need a President, Vice-President, Chairman and Chief Exec.  But you could bet there'd be no danger of a sudden shortage of anoraks.
I have other concerns over the death-by-supernova theory.  So I got Burton to do the maths for me.  Now, a missed factor of 10 could be the difference between life and total devastation for the solar system here, I realise.  So I hope someone can check my working...


The Supernova is forecast to go off with a force equivalent to 20 billion, billion, billion megatons of TNT.  That makes 2x10³⁷ kilograms of TNT.
The star is 3260 Light years away.  Or  3x10¹⁹m.
A sphere with that radius has a surface area of  about 1x10⁴⁰m.  Based on the surface area being 4πr³. Ooh look - that's π again.  See how all things come together?
Which I make an impact, all things being equal, of about the equivalent of 0.17g of TNT per square metre.
1g of TNT releases 4,180J of energy.  So we're looking at 700 J/m².  Which sounds quite a lot.  Indeed, it's roughly three times the amount of energy that the earth receives per square metre every second from the sun.

So my only real worry is that these numbers were actually all a bit large for Burton's pocket calculator.  It took him ages to key in all 7.2 trillion and 1 digits of π.  If anyone can show the figures are wrong, I'll start panicking again.