Science of Discworld Read Online Free Page A

very close to 1/137 (and a lot of ink was devoted to explanations of that whole number 137, at least until more accurate measurements put its value at 137.036). The advantage of the fine structure constant is that its value does not depend on the chosen units of measurement — unlike say, the speed of light, which gives a different number if you express it in miles per second or kilometres per second. The Russian physicist Alexander Shlyakhter analysed the different chemicals in the Oklo reactor's 'nuclear waste', and worked out what the value of the fine structure constant must have been two billion years ago when the reactor was running. The result was the same as today's value to within a few parts in ten million.
    In late 1998, though, a team of astronomers led by John Webb made a very accurate study of the light emitted by extremely distant, but very bright, bodies called quasars. They found subtle changes in certain features of that light, called spectral lines, which are related to the vibrations of various types of atom. In effect, what they seem to have discovered is that many billion years ago — much further back than the Oklo reactor, atoms didn't vibrate at quite the same rate as they do today. In very old gas clouds from the early universe, the fine structure constant differs from today's value by one part in 50,000. That's a  huge  amount by the standards of this particular area of physics. As far as anyone can tell, this unexpected result is not due to experimental error. A theory suggested in 1994 by Thibault Damour and Alexander Polyakov does indicate a possible variation in the fine structure constant, but only one-ten thousandth as large as that found by Webb's team.
    It's all a bit of a puzzle, and most theorists sensibly prefer to hedge their bets and wait for further research. But it could be a straw in the wind: perhaps we will soon have to accept that the laws of physics were subtly different in the distant reaches of time and space. Not turtle-shaped, perhaps, but... different.

Or at least, less radioactive. We can but hope.

He was the victim of a magical accident, which he rather enjoyed. But you know this.
     

 
    They say that every formula halves the sales of a popular science book. This is rubbish — if it was true, then The Emperor's New Mind by Roger Penrose would have sold one-eighth of a copy, whereas its actual sales were in the hundreds of thousands. However, just in case there is some truth to the myth, we have adopted this way of describing the formula to double our potential sales. You all know which formula we mean. You can find it written out in symbols on page 118 of Stephen Hawking's A Brief History of Time — so if the myth is right, he could have sold twice as many copies, which is a mindboggling thought.
     

 
    The fine structure constant is defined to be the square of the charge of an electron, divided by 2 times Planck's constant times the speed of light times the permittivity of the vacuum (as a handy lie, the last term might be thought as 'the way it reacts to an electric charge'). Thank you.
     

THREE
    I KNOW MY WIZARDS
     
    IT DID NOT TAKE LONG for the faculty to put its collective finger on the philosophical nub of the problem,  vis-à-vis  the complete destruction of everything.
    'If no one will know if it happens, then in a very real sense it wouldn't have happened,' said the Lecturer in Recent Runes. His bedroom was on one of the colder sides of the university.
    'Certainly we wouldn't get the blame,' said the Dean, 'even if it did.'
    'As a matter of fact,' Ponder went on, emboldened by the wizards' relaxed approach, 'there is some theoretical evidence to suggest that it could not possibly happen, due to the non-temporal nature of the thaumic component.'
    'Say again?' said Ridcully.
    'A malfunction would not result in an  explosion  exactly, sir,' said Ponder. 'Nor, as far as I can work out, would it result in things ceasing to exist from the present