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February 2009 Archives

We have a new addition to the household furniture this week - a year-old black and white cat which we acquired second-hand from the SPCA. Amongst other things, he's taken to sitting on the couch looking just like a cushion.

Getting a pre-loved (or, dare I say it, pre-abused) animal from the SPCA is a bit of a gamble - you don't quite know what you're going to end up with. And certainly we are still finding out about this guy's nature. Things like having to experiment with what food he will and won't eat (tentative conclusion - he has expensive tastes - need to change this).

In many ways, finding out about the cat's nature (NB he is still nameless - can anyone think of a good name for a black cat with four white socks?) is rather like doing science. You have to try things out and see what the result is.

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Associated with the heating and cooling of contracting and expanding air, is the hot north-west wind that hits the east coast areas of New Zealand, particularly Canterbury.  This 'Foehn' wind occurs when a moisture-laden wind comes from across the Tasman Sea (i.e. from the north-west) and over the southern alps. As it does so, a number of effects happen.

First, the moist air hits the wall that is the West Coast. Anyone who has flown from Auckland to Queenstown along the West Coast on a clear day (clear day? yeah, right) will have seen just how sharply the mountains rise up as you go back from the coast. The only place the air can go is upwards, and as it goes upwards, it cools. Cool air can hold less moisture than warm air, so it dumps it as rain. That pretty well explains why the west coast is so wet.

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I was reminded while driving in to work this morning that we're getting into hot air ballooning season in Hamilton - with a balloon hanging nicely over the road to district drivers like myself.  Flight with hot air balloons isn't exactly rocket science - quite simply hot air is less dense than cold air, so hot air rises. Encase it in a balloon, and up goes the balloon.

Those of you who live in a house with more than one storey might have noticed during the recent high temperatures that the upper storeys are rather warmer than the lower ones - same effect going on. But, if that's the case, have you thought about why it is that mountains are colder at the top. If hot air rises, shouldn't it be warm at the top of Mt Cook?

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I read a very short news snippet in Tuesday's NZ Herald that said that a British nuclear submarine had collided with a French counterpart. Admittedly, the source quoted is 'The Sun' newspaper in the UK - which is not best known for its accuracy in reporting - but leaving that issue aside, you have got to ask the question as to how two submarines, with well-trained crew and possibly carrying rather precious loads (nuclear weapons) are able to come into contact.

 

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In the magazine Physics World (on-line version here), produced by the UK Institute of Physics, I recently read a neat little article about physicists visiting primary schools. The essence was that young children can ask some pretty insightful questions, but also that they can see science in a different way to adults.  For example, the writer (Pete Edwards) frequently gets asked 'What's your favourite planet?'

That got me thinking. What's my favourite planet?  I had to admit that I don't actually have one. I tried thinking back to when I was five, but that didn't help me. (Of course, there were more planets to choose from back in those days...)

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The what?  No, the analemma isn't some strange pet that Hagrid keeps well-chained in his hut, rather it's something that many of us are familiar with, especially if you, like me, have trouble getting out of bed in the morning.

It's nearly two months since the longest day (21 December), but you may have noticed that the evenings are not all that much darker than they were back at Christmas. The same cannot, however, be said of the mornings. No more being woken by the birds at quarter to five - it is now noticably darker in the mornings, and, as we know, is destined to get a lot darker still.

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You may have seen a snippet in the papers and on the internet a few days ago about two satellites having a mid-air (should that be mid-vacuum?) collision. What is surprising is that this doesn't happen more often. 

As Edwin Cartlidge reported recently, it is only 51 years since Sputnik was launched, and in that time we have gone from one piece of space-junk to about one hundred thousand pieces (counting bits 1 cm in size as a separate item). These things include the obvious such as expired satellites and spent rocket stages, but also contain the more bizarre, like an astronaut's glove (what, did he just drop it while out on a space walk or something?) and a toothbrush (!!!) About fifteen thousand items are being actively tracked by the US Department of Defense. Just what they propose to do about potential collisions, I'm not quite sure, but it is worth noting that despite all this floating rubbish there is only one confirmed case of someone being hit by a piece of space-junk returning to earth (and she escaped uninjured).

This picture is a nice illustration of just what the Earth's backyard looks like.  Just what would a visiting martian think of us?

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The Baked Alaska is an experiment that is certainly worth doing at home. The idea is that you place a block of icecream on a sponge base, and then smother it in meringue (for those who have only ever bought a pavlova, that means well beaten (stiff) egg white, with sugar folded in, about 50 grammes per egg-white). Stuff the whole thing into a hot oven (about 230 degrees, I think) for about 3 minutes or so, and, if all goes to plan, you should have a nice meringue crust with a soft, cold, ice-cream centre.

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With summer comes the barbeque. And with the barbeque, all too often, comes food poisoning. As far as I can see there are two reasons for this:

1. Barbeques are almost always cooked by men.  This is a phenomenon that surely needs study by sociologists. At the first glimpse of summer, the man, who hasn't set foot in the kitchen for six months, suddenly acquires a Michelin star and his own TV show, and becomes the undisputed king of cuisine. Women are banished to the outer reaches of the solar system, and the area around the barbeque becomes the domain of man.

2. (and here is where the physics lies) Barbeques, especially the traditional charcoal burning ones, are not particularly temperature controllable. This means it is easy to incinerate the outside of your chook-leg, but leave the inside almost raw.

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As I said, General Relativity in all its glory is an impenetrable wall of mathematics such that, if you ever have the misfortune to come across someone who says they understand it, your best bet is to offer a slight smile and back away carefully. Do not let anyone try to lecture you in it, and never, ever, get stuck in a lift with such a person, or you will be subjected to the following.

 

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Following from my brief comment last time about 2005 being Einstein year, I wonder if you, like me, have ever thought why it is that Einstein is so famous. I mean, just about everyone you will meet on the street will recognise a photo of Albert Einstein, but how many would recognise (say) Charles Darwin or Marie Curie (or even NZ's own Ernest Rutherford)?

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I've recently been asked to participate in a 'cafe scientifique' event looking at the relative achievements of Darwin and Galileo. For those who don't know, 2009 is the 200th anniversary of Charles Darwin's birth, and the 150th of the publication of 'Origin of the Species' (how very thoughtful it was of him to arrange that both occur together), so this year has been labelled 'Darwin Year'. You may remember that 2005 was 'Einstein' year - 100 years after Einstein sprung into prominence, in the physics circles at least (Widespread public fame came a bit later).

Generally speaking, I think these kind of debates are rather meaningless. We often get subjected to them by ineffective sports commentators filling in time - 'Would Roger Federer at his peak have beaten Pete Sampras / Bjorn Borg etc at their peaks?' . It's a non-question - we'll never know.

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Following on from the last entry, another example of symmetry breaking on the roads is the stop-start kind of traffic jam that forms in heavy traffic on a motorway. When sitting in a traffic jam caused by 'sheer weight of traffic' (affectionately known as SWOT to traffic-analysts) you might, like me, have been inclinded to think something like "if everyone gently moved forward at exactly the same time we could get the whole thing moving along". And that would happen, if everyone accelerated evenly at exactly the same time. That's a case of  'symmetric' traffic flow - everyone is doing the same thing.

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I spent the weekend (plus a couple of other days) at Lake Waikaremoana, enjoying the bush and the scorching sunshine (yes, evern in Te Urewera). There's not a lot of physics that goes on there; maybe that's why it is so relaxing, with the science focussed towards earth-science (I hope that rock doesn't fall on us) and biological-science (is that a weka? - No, don't be silly - yes, I'm sure it is). But I will pull out some physics, namely the state of the road.

State Highway 38 is hardly what you'd call a motorway, though if your definition of a road is something that you can drive a car along it fits the bill, just. One very frustrating thing on metal roads such as this one is the way it becomes corrugated - lots of equally spaced ridges - which makes it in places like driving on corrugated iron. It can't be good for the suspension. The cause of these, as far as I'm aware, is over-enthusiastic acceleration.

But why does this cause lumps? Surely, on average, car wheels going over the road will result in the level of the stones being smoothed out, not forming into regular corrugations. This is an example of a broad class of physics phenomena that can be collectively titled as 'symmetry breaking'. We might expect the natural state, to be nice and symmetrical (in the case of the road, nice and smooth) but in actual fact something happens that breaks the symmetry, and we get patterns forming (like the corrugations).

Once the corrugations start to form, the action of an accelerating car is to grow the ridges that exist, leaving less touched the grooves between them. So a weak pattern of corrugation becomes progressively stronger and stronger, and, over the course of time, the pattern will inevitably occur.

A simple model of this is trying to balance a pencil on its point. If you get it spot on, it will work (in theory), but the slightest deviation from vertical will be emphasized and it will become a large deviation, and ultimately the pencil will fall. It is utterly inevitable. Which way it will fall you can't tell until it starts moving, but fall it will. Same with corrugated roads. Once those ridges start appearing,  it's hard to stop them.

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