Archive April 2011

the misc-ience word cloud (apparently) aimee whitcroft Apr 27


So, I have been playing with datavis applications.  As one does.

Wordle: misc-ience[make clickings to enlarge]

Today’s little graphic is courtesy of Wordle, which generates word clouds from RSS feeds or, alternatively, from delicious user names.

Given that I stopped using delicious* when there was that little bruhaha this year, the word cloud generated therefrom is not, I feel, entirely accurate.

Then again, the word cloud generated from this here blog was, well, interesting.  And it’s that which I present…  Enjoy!


* I use Diigo now.  And gotta say, I really, really love it.  It has truly insanely awesome features :)

Pushing stuff with light: how Crookes radiometers work aimee whitcroft Apr 26


Yesterday, I bought a Crookes radiometer.  And proceeded to play with it.

crookes radiometer

This post has come out of people asking me ‘how does that work?’

A Crookes radiometer is a simple little device, generally now produced as a novelty item.  It allows the quantitative (i.e. wif all numbers in) measurement of the intensity of electromagnetic radiation: heat, light, etc.

It’s made of a glass bulb containing a partial vacuum, a low-friction spindle and some lightweight metal vanes, spaced evenly and with one side reflective/white, and the other side dark.  The partial vacuum is because some small amount of air is necessary to allow the currents which push the vanes, but lots means there’s too much for the vanes to push against.

And, when you put it in sunlight, bounce frikkin’ laser beams off it, point IR at it or even put it near a heat source, those vanes spin (black side trailing/moving away from light).  How fast they spin is due to the intensity of the radiation.  Also, they spin backwards if you cool the radiometer, which is kinda neat :)  And makes me want to put things in freezers.

Now, to answer the question of how it works:

There are two forces involved – one shown by a German, and one an Irishman

First, the German.  Einstein, in fact. It had been proposed that the warmer dark side of the vanes warmed up gas molecules coming into contact with them slightly more than the light side.  This then increased the speed at which the molecules bounced off the vanes, in turn exerting a tiny net ‘push’ on the dark side.

However, these faster gas molecules would also impede other such beasties from coming into contact with the darker side of the vanes; in theory, therefore, the two forces would cancel each other out.  It took Einstein to show that this was not, in fact, the case at the edges of the vanes because of the temperature difference there.

BUT.  This didn’t quite explain the speeds seen – more was needed.

And it was provided by one Osborne Reynolds*, who was a big man in fluid dynamics**.  He found that if a porous (i.e. wif all holes in) plate was kept hotter on one side than the other, gas molecules would flow through the holes, from the cooler side to the hotter side***.  Kinda like people flowing from a couch onto a dancefloor.  Maybe.

ANYWAY, while the vanes in a Crookes radiometer aren’t porous, the space around their edges behaves like pores, with gas flowing from the cooler (light) to the warmer (dark) side.  This causes a pressure difference****, pushing the vanes forward.

Anything else that you may read in booklets/museums/anywhere else is incorrect.  It’s NOT light pressure pushing on the vanes; nor is it the dark sides outgassing.

So, both of these forces are in play, although apparently, we’re not sure which (if either) has the greater effect.

And that, dear friends, is how it works.  Hooray for science :)

End note: a friend of mine also has one, but on his,  each vane has a single, large black dot on the light side. Apparently there is still debate as to which design is better.

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* However, the research was actually published by one of my favourite Scots of all time: James Clerk Maxwell.  Not only is he a pivotal figure in electromagnetism as well as a bunch of other stuff, he also liked to write rather clever (but still silly) poetry.

From a Tennysonian parody, the first stanza:

The lamp-light falls on blackened walls, And streams through narrow perforations,
The long beam trails o’er pasteboard scales,
With slow-decaying oscillations.
Flow, current, flow, set the quick light-spot flying, Flow current, answer light-spot, flashing, quivering, dying,

The poem’s called Lectures to Women on Physical Science (not quite sure I agree with some of the sentiment expressed here, but yes :P)

More of his poetry here – some of it’s rather beautiful

** Posts of mine involving fluids: oscillating animals and teapots.  And that’s _not_ counting the ones about alcohol…

*** Remember, kids – temperature is simply a measurement of how fast particles are moving.

**** Ahem.  To be more accurate – this happens when the pressure ratio is less than the square root of the absolute temperature ratio.

Why did you choose to study science? aimee whitcroft Apr 15


For me, reading Virtual Organisms in high school nailed it (although it may always have been something of a fait accompli).

science: good for making toast (awesomeness taken from Invader Zim)

science: good for making toast (awesomeness taken from Invader Zim)

It’s certainly an interesting question, though, both for those of us who are still gainfully employed in science, and for those of us who now use our science superpowers for other purposes.

Dr Colin Hanbury, who is with the Graduate School of Education at the University of Western Australia, is trying to figure out why increasing numbers of Aussie high school kids aren’t choosing to study science.

In order to help him do so, he’s designed a questionnaire, open to people from any country, asking them, well, why they did choose to study science.

I’ve been in touch with Colin, and he said he’s particularly interested in comparing New Zealand and Australia.  Also, he’ll give me a shout when the results are ready, so stay tuned :)

In the meantime: go forth!  Fill out forms*!  Let’s get some pretty data to play with.

Also, if anyone happens to have to hand information on student enrollments in NZ, by subject, I’d be most keen to have a look…


* It’s a quick and painless procedure

Peacock spiders FTW aimee whitcroft Apr 14


Cutest.  Spider.  Ever.

Think he's cute now?  Just _wait_ until you see his party trick.

Think he's cute now? Just _wait_ until you see his party trick.

Well, possibly.  Not being familiar with all the spiders on this or any other world(s), I realise I cannot definitely make such a statement.

However, the peacock spider (Maratus volans) is one seriously, seriously cute little critter.

For those with short attention spans, the action really starts getting going at about the 3 minute mark.

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(Video by Jurgen Otto, who may well be the first person to manage to do so.  Nicely done, Jurgen!)

I found the final line rather amusing :)


HT: @hectocotyli and the always-fantastic Myrmecos blog

Introducing a new blog: Just So Science aimee whitcroft Apr 12

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This could not have been better timed.

just so science 2

Rather than making any jokes (I know, I know), we’re simply going to get straight to the point, and introduce Elf Elfridge, our newest blogger.

Elf is the proud and, dare I say it, starry-eyed* owner of Just So Science, which will be looking at things which are very far away, and things which are very small.  But not necessarily simultaneously.

In fact, Just So Science will cover the fields of astronomy and nanotechnology, for the most part.  Both of which are exceedingly interesting, and come with the added benefit of excellent imagery.

Welcome, Elf!  Glad to have you on board :)


*Apparently, I couldn’t help myself.  More coffee, please.

Global premier: First Orbit aimee whitcroft Apr 11


Now, ordinarily I don’t use my blog to push events*.

Yuri Gagarin in Sweden

Yuri Gagarin in Sweden

However, and having said that, sometimes something comes along which looks to be particularly fascinating.  And tomorrow, just such as  thing is to take place.

Sadly, the Auckland event is booked out * sniff *, but Wellingtonian’s have the opportunity to watch the global premier of First Orbit, a documentary specially made for the 50th anniversary of Yuri Gagarin’s epic trip.

For those whose memories temporary elude them, Yuri Gagarin was the first man in space.  This was in 1961, when people were still using the (far cooler, methinks) term ‘cosmonaut’.  This was also the point in the space race in which the Soviet Union was very firmly kicking buttski. Those interested may also enjoy this infographic, which breaks down the Vostok’s history-making trip.  And, of course, the interwebs are fairly awash with further information.

Other treats on offer tomorrow at the Carter include the preview of a brand new planetariuam show, “Dawn of the Space Age”, as well as a speech by the Russian ambassador.

Also, I’m told there may be free wine.

So come!  But it may be a good idea to call the Carter and book a seat or five.  Just saying :)


First Orbit is absolutely stunning.  Also, I would not suggest wearing mascara while watching it.  Just saying.

And it can be downloaded here, or watched on the YouTubes here.


* Ahem.  While I’m at it, in that case: shameless self-plug.  Next monday (18th april) is the 5th nerdnite wellington.  Topics will include antennae/satellites, open hardware, narrative and scrabble.  And it’s still free :)  And you should come.

The best view yet of earth’s gravity aimee whitcroft Apr 01

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As a general rule of thumb, I find that anything science-related which makes me shout ‘squeee’ may be something about which I should consider posting.

Credit: ESA

Credit: ESA (Go to the website. The geoid _spins_)

And so, today, I thought I’d share just such a thing.

The European Space Agency (ESA) has just released our best map yet of the earth’s gravity, in the form of a ‘geoid’*: what the surface of our ocean might look like under the influence solely of gravity, without the influence of pesky tides and currents.

The data used to generate this geoid has been collected over the past  two years by the GOCE satellite**, which orbits at about 250km high (this is considered veeery low) in order to get the strongest gravity signal it can from the earth.

And yup, that geoid most certainly ain’t spherical.  What you’re seeing there are areas of higher and lower gravity, quite literally.  I notice that NZ is sitting in a reddish zone, there :)  Apparently, much of this difference in gravity has to do with a number of factors, including the earth’s shape, centripetal and centrifugal forces,  forces, latitude, altitude, topology, geography and so forth.  Lots, in other words.  And no doubt our Google overlords can provide further details on the subject :)

Apparently, such models are extremely useful, for example for better understanding ocean dynamics such as sea level change, ocean circulation and ice changes.

It could also be used to improve our understanding of the causes of earthquakes (think March 11, Tohoku, if you’re wondering why this is important).


* Nope, the literal translation is not ‘spinning sphere of joy’.  Although one might be tempted to think so.

** Which, awesomely, uses an ion thruster.  Phwoar.

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