Luis Alvarez and the dinosaurs

Luis Alvarez, born on June 13th, 1911, was described by the American Journal of Physics as, "One of the most brilliant and productive experimental physicists of the twentieth century.” He received the Nobel Prize in 1968 for his work on the liquid hydrogen bubble chamber that enabled photographs of particle interactions which led to the discovery of a range of new particles. Before then he’d played a major role in aviation radar, helping to develop the Ground Controlled Approach that proved so valuable in the Berlin Airlift.

He is more famous in popular scientific culture for the paper that proposed an extra-terrestrial cause for the Cretaceous-Tertiary extinction of the dinosaurs. He’d observed a thin layer of clay exactly at the boundary, a clay later found to contain materials and minerals that could only have been formed under the shock and stress of extreme temperatures and pressures. In 1980, Alvarez and his son published a paper, jointly with Frank Asaro, and Helen Michel, proposing that an asteroid impact had caused the mass extinction. The impact point was later identified as Chicxulub, on the edge of the Yucatan Peninsula in Mexico, and this is now generally accepted as the explanation for the demise of the dinosaurs after their 200 million years of dominance.

There is some concern that it could happen again, with an asteroid or comet causing an extinction level event that could wipe out humanity after only 3 million years of dominance. Funds are now spent on cataloguing bodies whose trajectories might intersect Earth’s orbit, and in populist culture the movies “Armageddon” and “Deep Impact” have depicted attempts to thwart such a calamity.

Indeed, the calamity that threatens life on Earth has been a staple of popular literature. In the 1970s it was the notion of an impending new ice age. The geological cycle put us coming to the close of an interglacial period, about to undergo a new big freeze. Popular scientific articles depicted its likelihood and its effects. Similar, but man-made rather than geological or solar, was the fear of a nuclear winter caused by the atmospheric debris of a nuclear war obscuring the sun for years and killing first vegetation, then animals. It was hailed as a warning to insist on nuclear disarmament.

Currently the big threat is seen not as cooling, but as warming, with greenhouse gases heating up the planet and altering its eco-systems, perhaps melting its ice cover and raising ocean levels. All of these hypotheses are not seen simply as harbingers of doom, but as things that humanity can do something about. We are seen as creatures that can use the technology that has established their dominance to change their circumstances and their vulnerability to nature. We might alter the orbit of incoming extra-terrestrial incoming objects, or build vast nuclear power stations to stave off the effects of a new ice age. Or we might switch from fossil fuels to electricity generated by sources, including renewables and nuclear, that cause much less atmospheric pollution, in order to mitigate global warming.

Some biologists claim that we are hard-wired from our primitive past to detect and avoid danger, and that in consequence we are risk averse, rating dangers more prominently than opportunities. It has long been a staple of economics that we rate the avoidance of loss more importantly than the prospect of gain. It could explain why we constantly stress the dangers that might afflict us, and why we revel at a popular level in impending catastrophes. Fortunately, as Julian Simon pointed out, human creativity is the ultimate resource, one that will never run out, and one that equips us to meet any such dangers and to surmount them. We are most unlikely to meet the fate that befell the dinosaurs, the fate whose cause identified by Alvarez. We will not go quietly.