Why time travel is just fine

Those of us who enjoy science fiction - and all the indications are that a good proportion of those who are interested in science do enjoy it - might have felt a little depressed at the recent announcement that the discovery of a new shape for an atomic nucleus could 'ruin our hopes of time travel.'

According to Science Alert (an outfit, I must admit I hadn't heard of), 'Physicists have confirmed the existence of a new form of atomic nuclei'. Now, putting aside that unwanted plural, they reference the BBC, which also makes the claim that this discovery 'may [..] end hopes of time travel.'

What the discovery actually shows is a nucleus with an unusual symmetry, and a Dr Scheck of the University of the West of Scotland says that this Radium-224 nucleus 'violates the theory of mirror symmetry and relates to the violation shown in the distribution of matter and antimatter in our universe.'

Now that's interesting and important stuff (if verified), but Dr Scheck goes on to say 'We've found these nuclei literally point towards a direction in space. This relates to a direction in time, proving there's a well-defined direction in time and we will always travel from past to present.' From which the BBC deduces 'So time travel would appear to be a non-starter.'

No need to give up hope, though, time travel lovers, as I don't know where to start on what's wrong with this, and I hope that the last part of the quote is BBC interpretation, rather than Dr Scheck's thought on the matter. First, I'm not sure that Dr Scheck's assertion that this proves that 'there's a well-defined direction in time and we will always travel from past to present' is even true. This seems a huge leap to make from this discovery.

However, more to the point, the practical implications for time travel rely on a total misunderstanding of the nature of the beast. Firstly, travel into the past and future are not symmetrical. It's much easier to get into the future than the past. Hang on a second. We just moved into the future. Okay, that's not very impressive, but with a touch of applied special relativity, anyone moving quickly through space can travel into the future of the place he or she is moving quickly with respect to. The Voyager 1 probe has moved around 1.1 seconds into the future. It works, we know it works - there's no questioning it. There is time travel - and it's a bizarre assumption that it has to be into the past.

When it comes to travelling into the past, it certainly is impractical for the foreseeable future, apart from small scale effects such as those experienced by GPS satellites (which effectively drift a tiny amount into our future, so on returning to Earth, if they ever did, would move into their past). But even more dramatic backward shifts are not impossible, whether or not what Dr Scheck asserts is true. This is because the sensible approaches to travel into the past, making use of general relativity, don't involve travelling backwards in time per se - they involve finding or making somewhere that time runs slowly (easily done thanks to special relativity) and finding a mechanism to get into that place (that's the hard bit - but as the GPS example shows, you don't need time to 'run backwards' to do so).

Sadly, then, this is a case of looking for a dramatic media hook for a science story and forcing one to fit, even if it means distorting the science far away from its real, and still very interesting, implications and possibilities.

There's far more on time machines and time travel in my book Build Your Own Time Machine (UK)/How to Build a Time Machine (US).

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 2010 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 exp...

Murder by Candlelight - Ed. Cecily Gayford ***

Nothing seems to suit Christmas reading better than either ghost stories or Christmas-set novels. For some this means a fluffy romance in the snow, but for those of us with darker preferences, it's hard to beat a good Christmas murder. An annual event for me over the last few years has been getting the excellent series of classic murderous Christmas short stories pulled together by Cecily Gayford, starting with the 2016 Murder under the Christmas Tree . This featured seasonal output from the likes of Margery Allingham, Arthur Conan Doyle, Ellis Peters and Dorothy L. Sayers, laced with a few more modern authors such as Ian Rankin and Val McDermid, in some shiny Christmassy twisty tales. I actually thought while purchasing this year's addition 'Surely she is going to run out of classic stories soon' - and sadly, to a degree, Gayford has. The first half of Murder by Candlelight is up to the usual standard with some good seasonal tales from the likes of Catherine Aird, Car...

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...

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