Sound science

This week, I finally managed to carry out a little experiment I've been planning for some time. The delay was because I needed access to a military jet-fighter.

You must have noticed how, when a jet-fighter flies past, the noise it makes appears to come from behind the aircraft. When I was a kid, I mistakenly believed that this was because the jet was flying faster than the speed of sound. The real reason is that the light arriving at your eyes from the jet is travelling at approximately 300,000,000 metres per second, whereas the sound arriving at your ears from the jet is travelling at around 330 metres per second—roughly a million times slower. This means that the light arrives at your eyes pretty much instantaneously, whereas the sound arrives at your ears slightly later, depending on the distance of the jet. By the time the sound arrives, the jet has moved several fusilage lengths further along its flightpath, meaning that you are seeing the jet where it is now, but you are hearing the jet where it was a short while ago.

We are able to judge the direction from which a sound is coming because we have two ears. When the sound is coming from the right, say, it arrives at our right ear a split second before it arrives at our left. It is also, thanks to the inverse-square law of acoustic waves, and to the fact that our ears point in opposite directions, louder in our right ear than our left. Our brains use these differences and other subtle cues to calculate the direction of the sound. Amazing, or what?

I finally got to perform my experiment on Monday evening. I was in the garden watering my tomatoes when I spotted a jet-fighter travelling down the valley towards me, low and fast. Its flightpath would take it about 100 metres in front of where I was standing. So I dropped the watering can and hurried to a location on the patio with a better view.

As the jet flew past, the sound appeared to be coming from a few plane-lengths behind the aircraft. Then I took out my other piece of vital experimental apparatus—my right index finger—and inserted it firmly into my right ear. As if by magic, the sound from the jet suddenly appeared to be coming directly from the aircraft. Unable to detect the direction of the sound with data from only one ear, my brain quite sensibly deduced that it must be coming from the plane.

For the remaining few seconds that the jet was in view, I repeatedly removed from and inserted into my ear my index finger, causing the direction of the sound to move repeatedly back and forth.

Give it a go some time. You don't really need a jet-fighter; any noisy, fast-moving aircraft will do.

Previous experiments:

Calling a spade a spade

Observer: The Dawkins delusion: science good, the rest bad

Thanks to Richard Dawkins I [Neil 'I Lie for a Living' Spencer] have just acquired a new title. It's official: I am an 'Enemy of Reason', a wily opponent of rationalism interviewed (in my capacity as The Observer magazine's astrologer) by Dawkins for a new two-part TV documentary.

Dawkins is right, and you, Neil 'Shite Merchant' Spencer, are, without doubt, a charlatan, enemy of reason, opponent of rationalism, and complete and utter tosser. You're a fucking astrologer, for Pete's sake!

Why in the name of Holy Bollocks does The Observer—an otherwise sensible newspaper—feel the need to have a sodding astrologer on its staff? Answer me that!

Neil Spencer claims he can predict people's futures based on the time of their birth and the arrangements of the planets. You'll notice I say claims and not believes. He sells his specious prognostications to dupes who either do genuinely believe in such bullshit, or wrongly think it's just a bit of harmless fun. Either way, that makes Spencer an Enemy of Reason, and he knows it.

Vector

BBC: Outbreak source 'linked to lab'

There is a "strong probability" the foot-and-mouth outbreak began at a research site, inspectors have said…

The Health and Safety Executive found there was a "negligible" risk it had been spread by the wind or flooding. But its report said the disease could have been the result of human movement.

Apparently, local badgers are demanding a cull.

Responsible journalism

From the front page of today's Sunday Times:

Slaughtered cows
Environment department officials check some of the cattle culled yesterday in response to the outbreak of foot and mouth disease at Wanborough in Surrey.

Good to see responsible journalists flying helicopters over quarantined areas infected with airborne viruses. It's all in the public interest, you see.

We know what dead cows look like, thank you. There really is no need to put any more living ones at risk for the sake of a few snaps.

Vocation

Carolyn's elder daughter (10) to me (42) on Tuesday:

When I grow up, I want to be a teacher… You can shout at children all day, and you get to eat free toast.

She went on to explain that the free toast is funded from the takings of school fairs.

Before you dismiss this as wild conspiracy theory, I should point out that Carolyn's daughter appears to have inside knowledge: her mum manages the accounts for her school's fair.

This is how it started for Woodward and Bernstein.

Putting the Dick in Dictionary

From a telephone conversation with Carolyn this lunchtime.

C: Oh, before you go, Richard… I've been telling my children that you once read a dictionary. Is that right?
R: Which dictionary?
C: Any dictionary.
R: No, it's not right. Why on earth would I want to read a dictionary?
C: I don't know. It just seemed like the sort of thing you would have done.

So it's official: even friends who have known me for 42 years seem to think I need to get a life.

Seeing Reds

RAF Red Arrows Team News: Display Programme 25 to 29 July

This weekend sees the Team (Reds and Blues) criss-crossing the United Kingdom. Our planned timings are: […]

28 July
1500 Reds depart Edinburgh Airport
1556 Reds arrive RAF Brize Norton

And what is on a direct line between Edinburgh Airport and RAF Brize Norton? That's right: my house! The following should have been included on the above itinerary:

1527 Reds appear out of nowhere, flying in low, tight diamond formation, and startle the crap out of Richard as he is trying to rewire his phone connections

Damn impressive, though. Wish I'd had my camera to hand.

What the hell is that?!!

HOLY CRAP!! I just went outside and the sky was this freakish blue colour. And bang in the middle of it was this blindingly bright round object that appeared to be emanating heat.

I have heard tales of such phenomena, but have, until now, put them down to the ramblings of the deranged and feeble-minded.

It's the dawn of a new era.