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    What radio wave broadcasts at 21 centimeters?

    Question #1693. Asked by abba. (Apr 20 00 9:23 PM)


    Thiv

    		Background radiation

    Apr 21 00, 5:24 AM
    sequoianoir

    		THE 21cm INTERSTELLAR HYDROGEN LINE

    Hydrogen is by far the most abundant atom in the universe. The hydrogen atom itself is a source of radio emission, due to the hyperfine splitting of its ground state: there is a small difference in energy (5.9 x 10-6 eV) for a neutral H atom in its ground state depending on whether the proton and electron spins are aligned or not. When the atom changes from one state to another a radio photon with l = 0.21m is produced.
    http://www.egglescliffe.org.uk/physics/astronomy/radio/radio.html

    Feb 22 04, 8:54 AM
    Nephrite

    		1427.583133 MHz in UHF Band

    According to FCC these frequencies are used here:
    1400.000 - 1427.000 Radio Astronomy
    1427.000 - 1429.000 Land Mobile - Police, Fire, Forestry, R/R

    It is also the natural resonance frequency for matter and energy in the universe, which is why it has been reserved for astronomy.

    Oct 31 06, 12:25 PM

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