Skip to main content

Alarming logic

I am faced with a small but satisfying logical puzzle in my office at Bristol University. When I come in first thing (actually, even if I come in about 10), the alarm is often set. In fact, the first time I ever entered the building the blasted thing started beeping at me, and no one had bothered to tell me there was an alarm. So now, as I belatedly know the code, I unset it. But the puzzle is - how and when does it get set?

I certainly never set it on leaving. I wouldn't know how to, and anyway I have no way of knowing if the building is empty. It's a tall, old house - my office is on the second floor and I can often spend the entire day here without seeing another inhabitant, though I regularly hear them. The same uncertainty must surely apply to any ordinary resident. So how is it done?

In principle it could be automated. To be safe, there would have to be motion sensors in every room, which as far as I can tell there aren't. So if it is automatic, perhaps they just assume there's no one here after, say, seven pm and set it. Pity the person trying to put some serious work in. The alternative is a security person pops in and does it. But if so, would he or she really bother to ascend the four flights of stairs to my room, night after night, when there's never anyone here? I somehow doubt it.

So it looks like it's likely to be a case of set the alarm and fingers crossed. Remind me not to work late.


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