### Getting in a twist about time travel

I've read a couple of things lately about time travel that just don't make any sense to me. Specifically, both said that it wasn't possible to travel into the future. One was Time Travel by James Gleick, which commented that what special relativity offers is 'just time dilation' not real travel at all, the other being Richard Muller's The Physics of Time, which I am yet to read, but according to this article suggests that you can't travel into the future as it doesn't exist 'yet.' Both of these appear to entirely miss the point.

Unlike the TARDIS in Dr Who, real time machines find travel forward in time much easier than backwards, which may be theoretically possible but is practically implausible. And the approach taken to reach the future is totally different from a time machine that disappears from 'now' and reappears at another time - but it is ridiculous sophistry to suggest that a time machine based on the special theory of relativity doesn't allow us to travel into the future. There is well established science, demonstrated in many experiments: it's possible to travel as far as you like into the future - you just have to set off in a spaceship and come back to Earth. When you arrive, you will have moved into the future. The faster you go, the further you will travel into the future.

If you move fast enough, you could end up hundreds of years into the future. Everyone you knew - including a twin if you have one - will be dead. The date will be the future date you reach. Of course, it's not an instantaneous leap into the future - but who says time travel has to be instantaneous? No other form of travel is.

The fun thing about all this is that the mathematics to work out just how far you travel into the future requires nothing more than GCSE maths - in fact, in my new book The Reality Frame I even show how to calculate it (though I admit I put it in an appendix for those who are averse to a few equations). There is no doubt about this - this is real time travel into the future, and those who say it's impossible make science seem far less interesting than it really is.

### 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