Monthly Archives: January 2020

In January we walked around Bristol

Clifton suspension bridge crosses the Avon Gorge, a tidal river linking Bristol Harbour to the sea. They had a competition in 1831 to build a bridge that 3-masters could get under, It was judged by Thomas Telford who was good at bridges, he had just built the one across to Anglesey. He rejected all entries (which included four from Brunel) and then pulled one of his own out of his back pocket which he said was much better.

So they asked Telford to build it but then realised they could not afford it. Brunel had a quiet word with the judges and pulled a new design out of his back pocket that was £10000 under Telfords. Then the people of Bristol decided to riot and suddenly nobody wanted to go there any more and work stopped. Brunel took the ironwork to build his Royal Albert bridge at Saltash, the splendid one you see when you go to Plymouth. Then he died.

It was only when they dismantled Hungerford suspension bridge in 1860 in London that the remaining needed links in the suspension chain were obtained second-hand at a knock-down price and building could restart. It was supposed to be Egyptian with stone sphinxes on the towers but they couldn’t afford those either.

Its a splendid bridge built before they had invented wire to make these kinds of things. Its made out of real Meccano. If you take a very large spanner set with you as you walk across you can undo it.

Here is something not many people know. William Butterfield, the arch emperor of Victorian Gothic and architect of my old Oxford college, Keble, sent in a design to the competition when he was 15. Isn’t it splendid? What a pity they did not take him seriously.

Photograph of an exhibit in the excellent new Bridge Visitor Centre

Humpty science

What Alice did not find out when Humpty disintegrated was why all the kings men couldn’t do anything about him.

Maybe it never occurred to her to ask the question. It is, after all, in the nature of Humptys to break. Just as, before Newton asked his question, heavy things fell because it was in their nature to fall.

Humpty broke because, over time, left to themselves, complex things change to more simple things. That is how we sense time; it is how we know that time is not running backwards. And putting Humpty together again requires energy; so much that even all the Kings men didn’t have enough between them.

This is the Second Law of Thermodynamics. Complex ordered things left to themselves become simple random things. Look in your sock drawer. Entropy is the word given to the degree of complexity; or more correctly, absence of complexity. Entropy naturally increases; order naturally changes to disorder.

Life is complex. It is highly ordered. It has low entropy. When NASA asked James Lovelock (of the Ghia hypothesis) how they might detect life on another planet his answer was simple; make a device for measuring entropy. And he quickly knocked one together for them.

What does low entropy look like? It looks like Humpty Dumpty; a collection of small bits put together in an ordered fashion likely to fall at any moment. It is the presence together of complex molecules that would naturally react to form much simpler less ordered, more random, ones. Like the highly ordered particles in cellulose (wood) in an atmosphere of oxygen. When they change to their high entropy state–when Humpty breaks–they burn together to become carbon dioxide particles flying around randomly.

Our atmosphere is 22% oxygen in the presence of lots of plants made of complex carbon-containing molecules, but with only 0.04% carbon dioxide. Low entropy. Mars’ atmosphere is 95% carbon dioxide and only 0.1% oxygen and no plants. High entropy. The difference between the two is life. And making life on earth has been a long, difficult, massively energy consuming process.

Life on Earth is a massive Humpty waiting to fall.

10th January and its 10 degrees outside.

My thermometer says It’s not been below zero at all this winter here bottom left.  Down the allotment my leeks are growing their flowering shoots three months early and nobody else seems to have noticed what is going on.

And yet I’m now force fed climate drivel that is at best flakey and at worst flagrant hypocrisy.  So I’m going to write about the science; I dont expect anyone to read but it will do me good and help bring down my blood pressure.

So here is a bit about a man called Fourier.  He was, of course French and about 200 years ago he laid modern physics’ biggest foundation stone. And nobody has ever heard of him.

This bit is not about his day job though.  In his spare time he discovered global warming.

Half a century ago I had a wonderful time reading original science papers in their first edition from library shelves they had occupied since publication.  And I was even paid to do it.  I never thought it would happen again but it has. But now without the shelves.

Here is one,  It is volume 27 of Annales de Chemie.   And here on page 236 Monsieur Fourier begins a general remark that we are hotter than we should be.
He was thinking on a little experiment done by a Genevan meteorologist and mountaineer, Horace de Saussure, who took an earthenware pot, lined it with insulating unreflecting black cork and created isolated layers within it using horizontally sealed sheets of glass. In each cavity was a thermometer.

When he let the midday sun shine down into this stack of layers, the lower ones heated faster than the upper ones and all became hotter than the outside air.   And he noted that the heat energy was not the shiny stuff that came from the sun; it was different; it came from the warmed sides of the jar. The green house effect was born (but not yet christened).

It was not until almost 100 years later that a Swede, Svante Arrhenius, explained what was really going on.  He’s best known for explaining brilliantly the mathematics of dissolving things, for which he awarded himself the Nobel in 1903.

He it was who first realised that it was carbon dioxide (he called it carbonic acid), everywhere in the air, that absorbed the heat.  Not only that, he did the maths:

If the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression.

Translating, this says that the carbon dioxide will increase steadily for quite a while without us noticing much but then it will suddenly take us by surprise.

My leeks are surprised.  But the people take no notice.