Skip to main content

The fastest Mozart you will ever hear

Large prisms used in a tunnelling experiment
In theory, science is very flexible. It is the absolute opposite of a rigid, fundamentalist religion, because there are no absolute truths in science. Theories are just as good as the evidence available - and it's entirely possible that evidence will come out tomorrow that make a widely supported theory untenable.

However, scientists are also human, and have a tendency to cling on to favourite theories beyond their sell-by date. It's not that they go into fundamentalist mode and ignore the evidence - they are more flexible than that. But they will change and patch up a favoured theory so that it matches the latest data. A good example is the big bang theory, which has been patched several times as new data emerged. (And may need patching again if it turns out that inflation wasn't really the way we used to think.) This is not surprising, though it can be arbitrary in the short term. The great British astrophysicist Fred Hoyle, for instance, pointed out to his death bed that the steady state theory he championed, an alternative to big bang, which was ruled out by new evidence, could just as easily have been patched up to match the conflicting data.

Just how flexible scientists are liable to be can depend on solid the theory is considered. Biologists, for instance, are always happy to hang bells and whistles on evolution, but it is hard to see it ever going away. Similarly, physicists are remarkably fond of the second law of thermodynamics. The astrophysicist Arthur Eddington famously said:
If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations - then so much the worse for Maxwell's equations. If it is found to be contradicted by observation - well these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.
Amusingly, the comparison Eddington gives, Maxwell's equations is probably now another example of a 'difficult to counter' theory. And so is the implication from Einstein's special relativity that nothing - and particularly no information - can travel faster than light.

This is why some experiments, mostly undertaken towards the end of the twentieth century, are particularly interesting. These 'superluminal' experiments sent quantum particles - typically photons - faster than light. (I will cover these experiments in more detail in another post.)

They did this by making use of an oddity of quantum physics. Left to its own devices, a quantum particle ceases to have a definite location and exists as a three dimensional array of probabilities. It is only when it interacts with something that its location is pinned down, according to those probabilities, which evolve over time as predicted by Schrödinger's equation. One implication of this is that particles can tunnel through a barrier and appear the other side without passing through the space in between. There is good experimental evidence that tunnelling time is zero for quantum tunnelling.

Now think of a quantum particle, specifically a photon of light, travelling from A to B. Along the way it passes through a barrier with zero tunnelling time (such as the gap between the prisms in the illustration above). This means that the photon covers the distance from A to B in less time than it should. It travels faster than light. There are many arguments between different physicists over whether or not this is truly 'superluminal' or whether it is an effect of a change in the shape of a wavefront or other obscure possibilities. But one thing is certain. When one experimenter, Raymond Chiao, said that it didn't matter if it was superluminal because you could never send a signal this way,  only random photons, he was wrong. To demonstrate this graphically, another physicist, Günter Nimtz sent a recording of Mozart's 40th symphony over four times light speed. And for your entertainment you can listen to that superluminal Mozart here. There's a lot of hiss, but it's hard to deny there's a signal.





Comments

Popular posts from this blog

Why I hate opera

If I'm honest, the title of this post is an exaggeration to make a point. I don't really hate opera. There are a couple of operas - notably Monteverdi's Incoranazione di Poppea and Purcell's Dido & Aeneas - that I quite like. But what I do find truly sickening is the reverence with which opera is treated, as if it were some particularly great art form. Nowhere was this more obvious than in ITV's recent gut-wrenchingly awful series Pop Star to Opera Star , where the likes of Alan Tichmarsh treated the real opera singers as if they were fragile pieces on Antiques Roadshow, and the music as if it were a gift of the gods. In my opinion - and I know not everyone agrees - opera is: Mediocre music Melodramatic plots Amateurishly hammy acting A forced and unpleasant singing style Ridiculously over-supported by public funds I won't even bother to go into any detail on the plots and the acting - this is just self-evident. But the other aspects need some ex

Is 5x3 the same as 3x5?

The Internet has gone mildly bonkers over a child in America who was marked down in a test because when asked to work out 5x3 by repeated addition he/she used 5+5+5 instead of 3+3+3+3+3. Those who support the teacher say that 5x3 means 'five lots of 3' where the complainants say that 'times' is commutative (reversible) so the distinction is meaningless as 5x3 and 3x5 are indistinguishable. It's certainly true that not all mathematical operations are commutative. I think we are all comfortable that 5-3 is not the same as 3-5.  However. This not true of multiplication (of numbers). And so if there is to be any distinction, it has to be in the use of English to interpret the 'x' sign. Unfortunately, even here there is no logical way of coming up with a definitive answer. I suspect most primary school teachers would expands 'times' as 'lots of' as mentioned above. So we get 5 x 3 as '5 lots of 3'. Unfortunately that only wor

Which idiot came up with percentage-based gradient signs

Rant warning: the contents of this post could sound like something produced by UKIP. I wish to make it clear that I do not in any way support or endorse that political party. In fact it gives me the creeps. Once upon a time, the signs for a steep hill on British roads displayed the gradient in a simple, easy-to-understand form. If the hill went up, say, one yard for every three yards forward it said '1 in 3'. Then some bureaucrat came along and decided that it would be a good idea to state the slope as a percentage. So now the sign for (say) a 1 in 10 slope says 10% (I think). That 'I think' is because the percentage-based slope is so unnatural. There are two ways we conventionally measure slopes. Either on X/Y coordiates (as in 1 in 4) or using degrees - say at a 15° angle. We don't measure them in percentages. It's easy to visualize a 1 in 3 slope, or a 30 degree angle. Much less obvious what a 33.333 recurring percent slope is. And what's a 100% slope