It would be increasingly strange, at the moment, not to comment here on what's been happening. There's a lot to be said, but some of it shouldn't be said in this setting. Some of it is much bigger than DACE.
Anyway I've been enjoying bike runs at the weekends. I believe I'm not a very fast cyclist but I enjoy cycling on a fast bike. I love those weekend sensations: of setting off from the house on my road bike and thinking, "wow, this is fast even just rolling downhill"; of shooting uphill in high gears; of having been out for a long time and feeling you can just keep going and going. I've begun to pore over descriptions of more expensive bikes, wondering if they would actually feel faster, if I might travel less pathetically slow on one. I've learned that so-called cro-mo steel alloys have excellent strength to weight ratio and are preferred for bike parts for this reason. "Cro-mo" is steel alloyed with chromium and molybdenum.
Molybdenum, what a strange name. Element number 42 - nice number, six times nine. Where does it come from? Actually we know the answer to that question. It is produced in the interiors of red giant stars in the so-called s-process, and behind the blast wave that travels outward through a star in the explosive events of a supernova, in the r-process. "s" stands for "slow" and "r" for "rapid". Both involve the absorption of neutrons by nuclei, and radioactive decay of resulting, unstable nuclei. Immediately after the supernova explosion there are lots more neutrons flying around than normal, even for the interior of a star; hence the "r".
There is enough molybdenum now, in the Earth's crust, for us to be able to use it in cro-mo alloys and work towards those sensations of speed, because the universe is 13.7 billion years old and there has been enough time for lots of generations of massive stars, becoming red giants, spawning supernovae, and enriching the abundances of such heavier elements in the Milky Way as a whole.
If I ever get one of those nice bikes with the cro-mo parts and enjoy sensationally fast feeling bike rides in the myriad tiny, sunlit roads south of Glasgow, my thoughts will doubtless turn occasionally to the Sun's far future, to a time when it has swollen and engulfed the Earth and molybdenum is getting manufactured with many other rare substances in its deep interior, when DACE and universities and human beings are part of history, possibly lost from all conscious thought. I'll relish that sense of speed and think about the age and far future of the Universe.
(Supernova 1987a image: NASA, ESA, K France, P Challis, R Kirshner)
