Radio-astronomy

Radio astronomy used the new technology developed during the war (for other purposes ...), and really flourished. Roto-vibrational^3.1 transitions in molecules have low excitation levels, which are ideally suited to probe the low temperatures in interstellar clouds. Because the wavelengths of these transitions are long, one can build very large dishes to observe them, and also it is more straightforward to build interferometers.^3.2

Today, one regularly combines data from radio-observatories across the earth to get Very Long Baseline Interferometry, which gives superb angular resolution ( $10^{-6}{\hbox{\rm arcsec}}$!). Another great advantage of radio over optical observations, is that radio waves are not absorbed by dust. (By now you know why: it's because the wavelengths are much larger than the size of the dust grains.) And so, yo can use radio-waves to probe into very dense regions, for example where star formation occurs. One of the bigger problems facing radio-astronomy today, is mobile phones ...