Definition of "cm"

Researchers have come up with a way to glimpse the infant Universe by decoding the earliest ripples in its light.They say this can be achieved by capturing the specific radio wavelength of 21cm from the heavens.The trick is to tell the difference between 21cm waves from our galaxy and those from distant, ancient sources.

2012 June 20, Jason Palmer, “Dark matter tracks could give earliest view of Universe”, in bbc.co.uk‎ (in English), retrieved 2012-06-20