Archive for April, 2010

Ice in the Antarctic

April 14, 2010
Before and After Pictures of the Larsen B Ice Shelf in Antarctica

Before and After Pictures of the Larsen B Ice Shelf in Antarctica

Two stories crossed my path this week both concerning ice in the antarctic, and taken together they form an interesting commentary on the drama, the challenges, and the context – of climate science.


The first story was a regular update from NASA’s Earth Observatory on the disappearance of the Larsen B ice shelf in 2002. I have made a composite picture (above) of the ice shelf before its collapse, and its absence after its collapse. There are articles describing:

The cause of the collapse? Well it was probably the melt ponds (visible in the left-hand satellite picture above as blue streaks) caused by an anomalously warm summer. The theory is outlined here. Taken together they form an interesting commentary on the drama of events in the antarctic.

The Register

The Register also had a story about scientists extracting Ice Cores in this area to see if there was anything anomalous about the Ice Shelf collapse. The Register story is simply a re-hash of a press release from Eureka – the press agency of the American Association for the Advancement of Science. I find it interesting to see just how little the author has bothered to change. I also note that he has failed to quote his primary source. At face value, it is an interesting commentary on the challenegs facing scientists trying to understand events in the antarctic – the work is just hard and everything breaks when it gets cold!

The context

Now The Register is not so much climate sceptical as climate cynical in a typical juvenile manner. And so they have to get in a few jibes about how really scientists don’t understand what is happening and how the Larsen Ice Shelf Collapse is anomalous. However, it is not actually that uncommon according to the NASA articles. And they have to throw in a confusing ‘factoid’ to make it seem that really there is no evidence for anthropogenic climate effects. In this case they throw in the fact that while Arctic sea ice cover is declining at 4% per decade, Antarctic sea ice cover is increasing at approximately 1% per decade. These facts arte presented like they are some way ‘equivalent’ and so cancel each other out on some kind of climate ‘factoid’ debate.

You can read about the facts here. Its a great page, full of information not amenable to soundbites. But the summary graph of the arctic and antarctic sea ice extent is given here:

Arctic and Antarctic Sea Ice Extent 1979 2009, Courtesy of the National Snow and Ice Data Center, University of Colorado, Boulder

Arctic and Antarctic Sea Ice Extent 1979 2009, Courtesy of the National Snow and Ice Data Center, University of Colorado, Boulder

Now I have analysed a few graphs in my time and the red line looks to me to be barely above statistical significance. I have written asking for the data so I can establish an uncertainty on that slope.

Taken together these, different aspects of the ‘story’ illustrate concisely the challenging context in which scientists trying to understand events in the Antarctic have to work.


April 9, 2010

I came across an intriguing story on the BBC today about the use of inhaled Xenon as a therapy for babies born with brain trauma injuries. Children inhaled the gas while being cooled just a little below normal body temperature, and somehow, they just got better! It is an intriguing story and I read it twice searching for some hint of how the Xenon had any therapeutic effect. There was nothing! Not even a hint. Of course the article is really a collection of press releases and is not the product of any journalist prepared to put their name to it, so I should not really be surprised.

There was a link to Sparks, the charity that funded the research and that had a little bit more:

“Xenon is a very rare and chemically inert anaesthetic gas found in tiny quantities in the air that we breathe. Over the past eight years, we have shown in the laboratory that xenon doubles the protective effect of cooling on the brain; however we faced the challenge of how to safely and effectively deliver this rare and extremely expensive gas to newborn babies.”

Dr Dingley has been developing equipment in Swansea for xenon anaesthesia in adults for over 10 years and has invented a machine to successfully deliver the gas to babies. His machine takes the exhaled gas, removes any waste products from it and re-circulates it to be breathed again without any loss at all to the outside air. Some types of specialist military diving equipment work in this way but it is very unusual to build a system small enough to work reliably in newborn babies.

“A key design feature of this machine is that it is very efficient, using less than 200ml of xenon per hour – less than the volume of a soft drinks can. Xenon is a precious and finite resource and difficult to extract so it can cost up to £30 per litre. As ventilated newborns breathe many litres of air per minute, any xenon based treatment would be impossibly expensive without an economical delivery method.”

He continued: “Despite these challenges, the lack of side-effects and brain protecting properties of xenon make it uniquely attractive as a potential treatment to apply alongside cooling in these babies.

So xenon is an anaesthetic! I was gobsmacked. Finding out that xenon has any biological activity is like finding out that a maiden aunt is a pole dancer in here spare time. The defining feature of xenon and its noble gas brothers and sisters – helium, neon, argon, and krypton –  is that they don’t react with things. So how could they have any biological activity, especially something so profound as anaesthesia? So to the web! And now with two mysteries to solve: Firstly, how does xenon perform this trick in the absence of any specific chemical interactions, and secondly: how does anaesthesia work anyway!


Wikipedia – always my first port of call when I have no idea at all about a topic – actually had an article about therapeutic uses of Xenon (which already included a link to the BBC story that appeared earlier today!). And there are actually a plethora of articles (e.g. 1 , 2, 3) about the use of Xenon to induce ‘medical sleep’ in a relatively safe (if expensive) manner. All the articles state that xenon has this effect, but none of them state how! Now xenon is a big fat atom – and it is highly polarizable (i.e. electric fields distort its electron cloud easily) and so it can be stuck electrostaticaly to a wide variety of charged molecules. But there isn’t anything specific about its general fatness that would cause it to stick one biological site rather than another. So this one remains a mystery!

So how does anaesthesia work anyway?

At its briefest, I was astonished to discover that ‘nobody knows’! Wow! Paul H Ting has a helpful summary, and there are several other articles hither and thither, but at the bottom of it all, we just don’t know. Searching for some deeper insight, I called upon my subscription to the archive of the Scientific American. There I read a long article which clarified some of the components of the anaesthetised state. Specifically it mentioned:

  • Sedation: Reduced arousability, as evidenced by longer response times, slurred speech  and decreased movement. Neuronal activity across brain cortical areas drops.
  • Unconsciousness (also called hypnosis): Impaired perception of, and response to, stimuli. Cortical depression is deeper than in sedation. Activity in the thalamus, an area important for integrating brain processes, also falls significantly.
  • Immobility: Lack of movement in response to stimulation such as shaking or heat. Suppression of spinal cord neuronal activity is the main cause of this temporary paralysis, although the cerebellum, a motor control area, may also contribute.
  • Amnesia: Lack of recall for the anesthetized period. Many brain structures involved in memory formation, including the hippocampus, amygdala, prefrontal cortex and sensory and motor areas, exhibit anesthetic-induced changes.
  • Others: Muscle relaxation and lack of pain (analgesia) are sometimes included in definitions of the anesthetized state and are largely attributed to depression  of spinal cord activity.
But despite the extensive discussion, the article concluded that although people had some clues, at the moment they just didn’t know how it all worked.
So today I learned two things: Xenon is a near perfect anaesthetic – but nobody knows why. Wow!

Transport Fuel Consumption

April 8, 2010
BBC 'graphic' on fuel prices - notice the misplaced zero on the 'y' axis.

BBC 'graphic' on fuel prices - notice the misplaced zero on the 'y' axis.

I have read various reports today about increases in petrol prices and an apparent consequential decrease in fuel consumption. It seems set to become an issue at the election. My own views on this are simple – petrol is nowhere near expensive enough. Such a view will make me popular with no one (aside from my secret circle of ‘Green’ friends) and that is why I am (among other reasons) not a politician. But I contend that I am right and I can back up my view with real data. I can also say what I mean by ‘expensive enough’.

What is ‘expensive’?

If transport fuel (diesel and petrol) was really ‘expensive’ in some absolute sense, then changes in price would be reflected in changes in consumption. Perusing the UK data on this I find very little evidence that even quite dramatic price changes have caused even a minor tremor in consumption. Let’s look at the UK data on prices and consumption available from the UK’s statistics hub.

The data on prices is downloadable from the Department for Energy and Climate Change in an Excel spreadsheet with weekly data from 2003. The data looks something like this:

Weekly UK Fuel Prices 2003 to 2010

Weekly UK Fuel Prices 2003 to 2010

The price data shows a general trend rise of about 8% per annum since 2003  and a significant peak in 2008. Did this affect fuel consumption? This data is available form Her Majesty’s Customs and Excise who keenly count each litre of fuel dispensed. The data for the last 10 years looks like this:

Transport Fuel Consumption 2000 to 2010

Transport Fuel Consumption 2000 to 2010

The data are annualised and so do not show any detailed response to the weekly data on fuel price. However it is clear that the above inflation trend rise in fuel prices has not caused a trend decrease in fuel consumption. Notice in particular the absence of any decline in consuption in 2008 when fuel prices peaked. There is evidence of a fall in fuel consumption in the last year or two, but this is not because of fuel prices – this is (presumably) because of the recession.


When transport fuel prices cause people to change habits and use less, then fuel will be in some objective sense be ‘expensive’. We are not yet close. Personally I think fuel prices will need to practically double before people will change their habits. It is important to understand that the ‘habits’ are not vices. People have made rational choices about how far to live from their place of work based on the cost of houses and the price of fuel. When this balance changes then people will make different decisions. Similarly business have made decisions about locations of factories and warehouses based on similar considerations. I cannot stress enough that despite the fact that I do want fuel prices to rise, I sympathise with the people who will pay the price. They are not paying the price for their own poor choices, but for their own rational responses to a market that has been left to its own devices.

Cryosat 2:Isn’t precise measurement cool:-)

April 8, 2010
How Cryosat Works

How Cryosat Works

Precision Measurement 🙂

The BBC had a heartwarming story today about an ‘Ice Explorer’ satellite. The story was meant to be heartwarming because poor Professor Duncan Wingham had already built the satellite once and seen it blown up at launch.  Now he watched the rebuilt version lifted to orbit in a mere 16 minutes. However my heart was warmed not by his triumph over adversity – a typical media take an any endeavour – but by the mission’s reliance on precise electromagnetic measurement. Something my own team are getting quite good at.

As far as I can tell, the Cryosat 2 measures sea ice thickness by measuring the time delay between radar pulses reflected from the top surface of sea ice, and the surface of the sea detected in between patches of floating ice. All this while traveling at thousands of kilometres per hour 700 kilometres above the Earth’s surface. The heart of this measurement is the ability to detect a time delay corresponding to radar waves traveling an additional 50 centimetres or so. In order to resolve this extra distance with a resolution of a centimetre or so, the satellite must be able to make timing discrimination of just 30 picoseconds. WOW! At a height of 700 km, a centimetre represents just one part in 70 million of the travel time. Very clever.

The NPL Boltzmann Team with 'Cranberry 2' cavity reson

The NPL Boltzmann Team with 'Cranberry 2' cavity reson

Very clever, but actually we have done something not too dissimilar. As part of our efforts to determine an accurate value for the Boltzmann constant we have recently worked out the diameter of a 120 mm diameter spherical resonator with an uncertainty of just ±10 namometres. This is a measurement uncertainty of roughly 1 part in 10 million. This is not quite as good as Cryosat, but this is an absolute measurement – something Cryosat doesn’t need to do. We can detect changes at level around 10 times better than this!

Our latest triumph, has been to detect the effects of the antennae we use to make our measurements! This is quite a trick. To measure the diameter we insert two small antennae (just tiny straight pieces of wire) into our sphere which send and receive microwave signals. We send out different frequencies of microwaves and work out the diameter from the frequencies at which the microwaves bounce backwards and forwards most strongly within our sphere. However all kinds of tiny defects have a small effect on the result. We can measure these, but how do we detect the effect of the probes we are using to measure with? If we remove the probes, then we can’t measure anything! The trick for achieving this is subtle and depends on a profound understanding of what is happening inside the sphere. We have been able to determine that our probes change our estimate for the radius by around 2 parts in a million – this is way more than anyone else had ever assumed. In other words, the probes we use to measure the diameter change our estimate of the diameter by around 240 nanometres. We are able to detect this and correct for it with an uncertainty of only around 10 nanometres.

So What?

I would bet money that some of NPL’s advanced metrology is somewhere inside Cryosat 2. I don’t know how or where. But I would also bet money that some of the metrology my team and I are developing in our project will also be inside something equally cool and clever in 10 years time. But at the moment I just don’t know what!

The Michael de Podesta Theme

April 5, 2010
Michael de Podesta

Michael de Podesta

Life is strange. And it only gets stranger. Recently I became 50 and amongst the most curious of presents was a gift from a neighbour, John Rhys Marlow, of a composition based on my name. And this week he recorded it for me.

Michael de Podesta Theme (mp3)

I have nothing to say. It is wonderful to have such neighbours, and I feel privileged to have any piece of music named after me. I also love the sound of this piece. But as I said, life is strange, and it just gets stranger and stranger.

Protons for Breakfast 12

April 2, 2010
Protons Week 2: Looking at Light

Protons Week 2: Looking at Light

It is the evening of Good Friday 2010 and the 12th presentation of Protons for Breakfast finished on Wednesday. I am exhausted. Not so much from the course, but from the course on top of the hardest project on which I have ever worked.

The course was possibly the most successful yet, with the most attendees and the best retention rate. At the end of the course we collect feedback which is read by me and then included in a report to NPL management. I always find the feedback intriguing and this session’s is the typical. I can’t really post it all – there is too much, but I will post everything people wrote on two sections: One thing you have learned and Feedback for NPL Management. I post it here for you make of what you will. Reading this makes me want to do it better next time. And together with the team of fantastic colleagues, I will. But now I intend to enjoy a break – by which I mean devoting myself whole heartedly to my regular job!

One thing you learned…

  • What heat is?
  • Have broaden my understanding of physics from my a-level course. Also that mobile phones aren’t as harmful as I initially thought!
  • The Sun is bigger than the Earth!
  • Which way round the changes are in static electricity.
  • Not much.
  • Hard to think of just one thing – there are so many! Memorable moments; depiction of light-wave through sticks and jelly beans, heat hand-print on the wall (+ others). So the movement of light along a line of consecutive elements. And how one body affects another and for how long this lasts.
  • That mobile phone transmitters are nothing to be too worried about.
  • How atoms and particles act/react. How not to wear egg!
  • If you put an egg in a microwave and put a glass on it, leave it for a while then take it out, the egg explodes.
  • There are loads of atoms in our body.
  • That static will impact any material including wood and food stuffs.
  • That absolutely everything is electric!
  • All about infra-red and the global warming.
  • Eggs explode! Microwaves and telephones are not a problem.
  • Science is full of surprising facts.
  • Mobile phones.
  • Whatever the topic someone has written a song about it!
  • A lot.
  • Mobile phones experiments have all ended up inconclusive.
  • Where to begin – motion – that particles are in constant motion and it changes. How temperature changes the way particles move.
  • More about light spectrum.
  • That there’s atoms in everything apart from fields.
  • Duck eggs unreliable under stress.
  • Don’t put eggs in the microwave.
  • Mobile phones are not bad as I had thought.
  • There is electricity in everything.
  • Water bends!
  • About waves and mostly mobile phones. LOADS!
  • Loads about atoms.
  • How to make experiment.
  • Nuclear power.
  • How atoms and protons work.
  • I understand and can now argue about global warming. I was able to work out why a wok gets hotter than an frying pan.
  • Science is not scary! It’s all around us, from the air we breathe to the protons we drink.
  • That liquid nitrogen when poured briefly over skin will not burn or scald.
  • How make ice cream using liquid nitrogen.
  • I learnt how a mobile phone works and about infrared rays and how they ‘fry’ your brain.
  • Absorpion/emission of light emission frequencies/’jiggling’ + spectroscopy.
  • Different heats atoms move faster.
  • How to make ice cream out of liquid nitrogen.
  • That everything is electrical!
  • Atoms jiggle at different rates depending on whether it’s a solid/liquid/gas.
  • That water can hover.
  • A better understanding of how global warming is occurring.
  • I didn’t realise that every “single thing” had atoms. I was fascinated to learn about light electricity and heat.
  • We are all electric!
  • How weak the radiation from mobile phones really is.
  • How electrons and temperature work.
  • The theory behind atoms as being building blocks of our universe.
  • A lot about atom and how they’re moving when/when not being affected.
  • All that electricity everywhere!
  • Science is fun (world’s away from the dull and boring lessons I remember from school).
  • Lots about the application of science – I never thought I would understand oscillation and hertz.
  • The amount of fun with a microwave over (including Mr Egg).
  • The whole world jiggles.
  • Jelly baby waves!
  • Why energy saving light bulbs are saving!
  • That everything is made of atoms.
  • Light is a wave. Colour perception – loved Andrew’s slot in week 2.
  • That light is everywhere, and about phones! and how to spell ciao! Thanks for that ☺
  • Wave patterns – everything has electricity – that you can keep a metallic strip in the air with bursts of electricity. I wish I could remember some of the things I learned!
  • How mobile phones work. I have A level physics (1984) and so much had an air of familiarity but a fair proportion of it was new.
  • Temperature is a measure of the speed things are moving at.
  • Gherkins can conduct electricity! Different uses for electromagnetic radiation.
  • Lego men are cool …… being realistic ….. exploding eggs are cool.
  • How little I know.
  • Nuclear power ultimately stellar not solar.
  • The really neat way of describing the  relationship between electricity/heat/??? waves and atoms.
  • Too many to name!
  • That we are not running out of carbon fuels. I had thought that when the oil became scarce we would be forced to find more sustainable fuels – but oh no! Too much coal nothing to stop us overheating the planet, except ourselves.
  • How to get to the pub in 90 seconds. Many things. And especially developing understanding of how global warming occurs – and the small ????? proportion of carbon. And how mobile phones work.
  • Sausages conduct electricity.
  • Sausages conduct electricity.
  • I especially like week 1 (I sadly missed week 2 and 3) but for the first time I felt I had a skeleton framework to hang my science on.
  • Electromagnetic field, atoms and their purpose!
  • Atoms jiggle!
  • How large the sun is in relation to earth.

Is there any message you would like to give to the NPL management team…

  • No
  • Thank you for organising such interesting lectures – more should be able as it really enriched my learning in physics! I really enjoyed it!
  • I am very glad to have attended the sessions.
  • I understand this course was given by volunteers – I hope you give them a Christmas bonus!
  • Just thank you.
  • No. Thank you!!!!
  • How big is NPL?
  • Thank you for the opportunity!
  • Thank you!
  • Well done! And thank you.
  • A huge thanks for giving up your time and making this an interesting and entertaining course for a wide age group.
  • Thank you very much your all team members.
  • More courses like this! It’s a great way to engage with the local community.
  • You are the best!!!
  • You were all great, very smart, and a true inspiration. Everything was explained simply whilst not patronising, few people can do that. Thank you very much.
  • Do you have more ways of accessing what the NPL does. It would be fascinating to know/see more.
  • Michael and helpers v. enthusiastic.
  • Your doing an excellent job and keep it up.
  • Brilliant initiative. Wish more places did similar, credit to NPL.
  • Thanks, it was good.
  • Well done! And thank you!
  • See comment under ‘anything else’. Shouldn’t there be a museum on this site possibly linked to Bushy Park, Americans in WWII. If you want to talk about this I’m on
  • Need to let more schools know about the course. Keep doing this. Excellent course.
  • Fantastic course. You should blow your own trumpet more often about what happens here.
  • Great work!
  • No.
  • You guys are great!!
  • Brilliant. Please keep the talks! You are one of the only groups that makes adult lectures suitable for kids.
  • Publicise these much more widely. Take PfB on the road?
  • Thanks for a well run course.
  • You’ve done well.
  • This has been a fantastic experience. I wish you could do more outreach work to local state secondary schools.
  • Thank you – it has been great fun. Michael is an amazing presenter – so enthusiastic.
  • Keep up the good work!
  • The course is fantastic and I never learned anything at school. They should take in on tour.
  • Brilliant course, fantastically run by truly enthusiastic people.
  • Thank you very much for the time and effort you put in to this course. It is wonderful. Thank you very much Michael.
  • I think these sessions are a great way of bringing science to life for kids and making creating some excitement about the topic. I work at BP (here as a parent) but I am involved with the BP schools link scheme. I have told my link school about this course and the BP ext affairs people.
  • No, not really! But I like your powerpoints. Very well done!
  • Keep it up.
  • This has been the most amazing course. Keep employing these wonderful people.
  • I am now truly able to share Michael’s immense passion for physics! Physics Woo!!
  • No.
  • I admire your engagement and enthusiasm.
  • Thank you for all your hard work this is a very valuable.
  • What a super way to advertise what NPL is all about,  why you exist and why science is ???
  • Thank you very much for all efforts have been done!
  • The course should be filmed and shown in schools. If every one knew about it the demand would be huge. Same about people attending in person. Michael is a star and his enthusiasm infectious. His powerpoints were brilliant. Michael is the Jeremy Clarkson of the Physics World.

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