As usual, Burlington House in London was the place to be on the second Friday of the month, from October to May the scheduled slot for the Royal Astronomical
Society to gather. This time the theme, at least for me, was the extraordinary numerical precision that the Earth and space sciences are capable of while remaining a distinctly human activity.
Take the first speaker, Nils Olsen of the Technical University of Denmark (the world’s 137th best in the ranking system of which I am part). He’s an expert on the Earth’s magnetic field. You probably don’t appreciate just how feeble the Earth’s magnetism is. The field is about 60 microteslas strong, ie millionths of a Tesla. Your local hospital has an MRI machine with a field of 1 to 7 Tesla.
You may think, like I did, that this magnetism is caused by molten iron in the Earth’s core, which starts about 2900km below your feet. Mostly it is. But 3 per cent of it comes from magnetised rocks in the Earth’s crust, the bit we all stand on. And we even know that 2 nanotesla of the field, two billionths of a Tesla, come from water circulating in the oceans. Because seawater is salty, it conducts electricity, so its movement creates a magnetic force.
OK, how handy is this knowledge? Well, it’s useful for purposes like improving the accuracy of the GPS system. But it also allows Olsen and colleagues to model the Earth’s core and calculate that the iron in it is convecting at about 30km a year. It’s impossible even in principle to design a machine to visit the core, and yet people can find out all about it.
Or if that didn’t do it for you, what about the last speaker, Andrej Prša of Villanova University? You may know that most stars in the sky are not single objects like our Sun, but instead form pairs, or even more ambitious units of several stars. Because you can then observe them orbiting and crossing each other, multiple star systems allow ridiculously exact measurements to be made of their size, light output, mass and other characteristics. On a diagram he showed, there were no errors bars, because they would be smaller than the dots on his chart of the mass and size of the stars viewed by the US Kepler space telescope.
This precision is allowing us to take astronomy, always regarded as one of the “exact sciences,” to a new level at which we can work out, for example, that 0.12 of the mass of the Sun is the smallest size for a functioning star. But Prša himself, an enthusiast with an excessive liking for the term “awesome,” left us in no doubt that it’s human imagination that has given us this new way of getting unprecedentedly familiar with our galactic surroundings.
It’s hard to tell whether Prša was the afternoon’s highlight, or the speaker immediately ahead of him, Steve Fossey of University College London (4 in the Rankings, since you ask). He and his students have become overnight stars, as it were, for discovering a supernova in a nearby galaxy, M82. This was a purely serendipitous discovery that accidentally scooped all the big supernova finding programmes that have sprung up in recent years – including one whose optics were swamped by its sheer brightness. As a result, Fossey and his students are now famous for finding a supernova while eating pizza in North London. But be clear about one thing. Fossey may have had serendipity on his side, but his presentation left me in no doubt that in this case, as Pasteur put it, chance favoured the prepared mind. His students are exceptionally lucky to have had a billion to one chance turn up, but also to have been put in a position to grab it. If university education in the UK is worth £9000 a year, Fossey and people like him are the reason why.