Basics of the 21cm Hyperfine transition

[@hsclouds]

Excellent simplistic explanation, keep up the GOOD work !

[@anonymous203020]

Beautiful explanation. Thank you so much!

[@imagine.o.universo]

So, in average, it took 10 million years to a hydrogen atom emmits a photon, with 21cm wavelength... Is that correct?

[@FrostDirt]

I think that's the idea.

[@azzip-x]

6:19 Nu is frequency of what?

[@mudfossiluniversity]

Does the hydrogen extend out 21 centimeters when excited? Is that what you say?

[@neutch1991]

no. When the electron passes from up to down, it emits a photon with a wave length of 21 cm.

[@mudfossiluniversity]

@@neutch1991 Thank you. I feel one wave length is the distance to the franhaufer line and that is 21cm for hydrogen. kzbin.info/www/bejne/fpOboamYpK94j9E

[@jacobvandijk6525]

@ 4:32 So its probability is very, very, very small.

[@oguzaltnbas3108]

It has long time to decay, but we have lots of these HI clouds in the Galaxy. Therefore we could detect HI-21 cm emission line although the spontaneous decay is very long.

[@bigdividends5487]

could you explain how you got the energy diffenece?

[@Vashtanerada477]

Okay this is way late and I’m not a physicist, but I would imagine that the parallel spin is axiomatically larger than the anti-parallel purely because energy values are additive. Pos + pos > pos + neg

[@Alienrookie]

Really nice explanation!

[@kateorman]

Thank you so much! I've been looking for a clear explanation for my lay person's brain. :)

[@javas16]

Thank you!

[@nictaylor7699]

This helps alot! Thank you!!