From Stars to Stalagmites

The following sections are included:

• Contents

• Acknowledgements

• Introduction

The age or agelessness of the Earth has been discussed in philosophy and religion from antiquity. Modern scientific estimates emerged through the nineteenth century with the development of geology, leading to our present estimates based on radioactive dating, developed in the early 20th century. These great ages seemed to be in conflict with the principles of thermodynamics. It was thought that the Sun's energy could only have been enough to shine for some 20 million years, but Rutherford estimated the age of Cambrian rocks at over 500 million years.

Such an age can be reconciled with the laws of physics only if we take into account the effects of radioactive decay generating heat in the Earth's crust, and of the fusion of hydrogen to helium in the Sun.

Our best current estimates are somewhat over 4 billion years for the oldest surviving rock grains on Earth, and 4.57 billion years for the Solar System. The geological cycles of erosion and uplift are driven by plate tectonics, which in turn is a result of the outward flow of heat generated from radioactivity. The Sun itself will run out of hydrogen some 4 billion years from now.

Really important ideas in science are not the work of a single individual or even a single generation. The idea of an atom, for instance, was developed by ancient Greek philosophers, revived by eighteenth century chemists to make sense of their discoveries about the composition of matter, and used by nineteenth century physicists to explain the effect of temperature and pressure on gases. Our modern idea of molecules, formed with definite shapes by joining atoms together according to definite rules, was developed by chemists studying naturally occurring substances in the late nineteenth century. In the early twentieth century, the structure of the atom itself was explained in terms of more fundamental particles, while the last half century has seen advances that make it possible for us to directly sense, and even move, individual atoms.

If we had to name one person who, more than any other, turned physics into the kind of science that we can still recognise today, that person would have to be Isaac Newton. If we had to do the same for chemistry, we would choose Antoine Lavoisier. Newton, the first scientist ever to receive a knighthood, became president of the Royal Society, Member of Parliament, and died in his bed at age 84. Lavoisier became a senior tax official and financier (with special responsibility for tobacco), director of the Gunpowder Administration, spokesman for the Academy of Sciences, and at age 50 was guillotined for his services.

Lavoisier, to whom we owe our modern concept of an element, sought the limelight, promoted his own reputation, rose from bourgeois origins to wealth and prominence, was at the centre of Parisian public affairs, and was executed for political reasons when he was still at the height of his powers. John Dalton, to whom we owe our modern concept of an atom, affected an almost excessive modesty, spent most of his adult life as a provincial school teacher, rarely visited London, paid scant attention to the honours it had to offer him, died of natural causes at age 78, and was buried with full honours. Lavoisier was a victim of the French Revolution. Dalton was part of the community of innovators and thinkers who gave birth to the Industrial Revolution. Lavoisier gave as clear a definition of an element as was possible at the time. Dalton's concept of an atom contained built-in errors that would hamper chemistry for a generation, until science was ready to accept an idea that Dalton himself had rejected, but was later articulated by a neglected (one might even say justly neglected) Italian contemporary.¹

Sun-stuff, new, lazy, hidden, strange, gas-from-radium; helium, neon, argon, krypton, xenon, radon. These noble (meaning unreactive) gases are not on the whole particularly rare substances. Helium, in fact, is the second most common element in the Universe, after hydrogen, while the air in an average sitting room contains about a kilogram of argon. The first real evidence for these elements dates back to the eighteenth century, when the very concept of a chemical element was in its infancy, but it took a hundred years for this evidence to be properly appreciated. The noble gases seemed at first to violate all the known rules of chemistry, but came to play a central role in our understanding of the chemical forces that bind all substances together. The really interesting fact about them, scientifically speaking, is their almost total lack of chemical properties.

Tragedy is a word that is much misused. It should be reserved for disaster that overtakes a hero as a result of his greatness, as well as his failingsx. Hamlet is a tragedy, not just because our hero ends up dead, taking half a dozen people with him, but because his own reflective intelligence is instrumental in his fate. By this strict definition, the story of Fritz Haber, indicted war criminal, Nobel laureate, patriot and miserable exile, is indeed a tragedy. He sought to serve his country, and helped destroy it. The moral dilemmas of Haber's career will not go away, and the ironies of unintended consequences are timeless.

A crime has been committed, and there are three suspects. The first is a wellknown repeat offender, but will turn out – on this occasion at least – to be working for the authorities. The second is an apparently innocuous and highly valued citizen, with friends in high places. The third has a strong alibi, but faces politically motivated prosecution, based on circumstantial evidence. The mystery is finally solved using spy technology, and the whistle-blowers richly rewarded.

Sunlight and rainfall, the collapse of three great dynasties, and a grave warning about the future; all these inscribed in the detailed chemistry of a hands breadth height of stalagmite from a cave in China.

The word "metal" comes to us from the Greek metallon, mine pit. This in turn is related to metallao, "I enquire", a word perhaps ultimately derived from meta alla. Meta as in metaphysics, alla as in allergy or allotrope or allele, other; in search of other things.¹ Let us dig more deeply into the subject.

"We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes."

So wrote the French astronomer and mathematician, Pierre-Simon, Marquis de Laplace, in 1814. Happily, he was wrong from beginning to end.

All these 50 years of conscious brooding have brought me no nearer to an answer to the question "What are light quanta?" Nowadays every Tom, Dick and Harry thinks he knows it, but he is mistaken.

Albert Einstein, correspondence with M. Besso, 1951 I think I can safely say that nobody understands quantum mechanics.

Richard Feynman, in The Character of Physical Law (1965) Ch. 6.

If everything is made of atoms, and molecules are made of atoms stuck together, what are the rules that govern how many of each kind stick to each other, and how they arrange themselves in three-dimensional space when they do so?

John Donne, admirable poet but deplorable philosopher, subscribed to the doctrines of Intelligent Design, and faith through ignorance. Can we do better, as we approach the four hundred and second anniversary?

We can answer Donne's question at levels that he himself could not even have imagined. Why do things absorb light? Why do green leaves absorb the particular light they do, and what do they do with it once they've got it? How come this light is available to them? Why does this look green to our eyes? How would it look to John Dalton's eyes, or to the eyes of a chimp, a monkey, a bee, a deer? And finally, a question that happened to be the subject of one of my own first research papers,¹ why is the colour of blood so different?

Liquid water is one of the most common, most important, and most strangely behaved substances on the surface of this planet.

Something very disturbing is going on when a distinguished candidate for the most important job in the world has to apologise for agreeing with the overwhelming scientific evidence on these matters. And I would rather he had spoken of "accepting" the fact of evolution, rather than "believing" in it; evolution has been part of any reality-based worldview for almost a century, but that is another story. Hopefully, in the unlikely event that Jon Huntsman ever reads this chapter, he will emerge with his understanding of the reality of global warming based on something more than trust.

We ourselves are part of the natural world that we study. Every carbon atom in our body has been captured by photosynthesis from the atmosphere, every carbon atom on our planet was fashioned in some long-exploded star.

The following sections are included:

• Endnotes

• Glossary

• Index