3 ms·
> Hydrogen can absorb or (suitably excited) emit light at 21cm wavelength specifically, better than all other wavelengths. Based on the article, I don't think
by ballenarosada 9y ago
> Hydrogen can absorb or (suitably excited) emit light at 21cm wavelength specifically, better than all other wavelengths.
Based on the article, I don't think this is right. http://astronomy.swin.edu.au/cosmos/S/Spin-flip+Transition http://astronomy.swin.edu.au/cosmos/S/Spin-flip+Transition, linked, describes the 21cm emission as occurring once every 10 million years for a single atom.