50 Years Ago

The past four months … have seen a spate of discoveries of molecules in space by their microwave radio emission. First was the detection of ammonia … then water … and now, more surprisingly, formaldehyde has been picked up at the National Radio Astronomy Observatory … A group at the Massachusetts Institute of Technology has also been using the Arecibo dish to look for signals from sulphur hydride, so far without success … All the molecular emissions which have so far been picked up come from cool regions in the galaxy, which is why the signals are more than curiosities. The cool regions are clouds of dust and gas which are thought to be in the process of contraction into stars and planetary systems … The discovery of formaldehyde is held to be significant because it is indirect evidence for the existence of methane in the cool interstellar clouds.

From Nature 5 April 1969

100 Years Ago

Curious as it may seem, the origin of the brilliant metallic and iridescent colours in birds and insects has never been satisfactorily explained, though it is generally supposed among naturalists and others that they are in some way produced by the interference of light at the surfaces of thin plates, as in the soap bubble. Nevertheless, various other explanations have been put forward, and Michelson, with the weight of his great authority, decides unequivocally that they are due to selective reflection at the surface of a very opaque film, as in the case of metals or dry films of aniline dyes. For this conclusion he relies upon the “rigorous optical test of the measurement of the phase-difference and amplitude ratios” when polarised light is reflected. This view has, however, by no means gone unchallenged by Lord Rayleigh, Mallock, and others.

From Nature 3 April 1919