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Distance of a Galaxy - from redshift and bubbles constant watch

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    I've been given a question and I've tried finding formulae online (as they aren't in my notes) and have come up with nothing that's actually a realistic answer:

    "A spectral line of hydrogen (wavelength 21.1cm in the lab) emitted by a galaxy is oversee to have a wavelength of 21.4cm. If Hubble constant has a value of 0.06 metres per second per parsec, how far is this galaxy from Earth (in parsecs)? Given c=3x10^8."

    Can anyone provide an insight into how to go about doing this question?



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    (Original post by ThatTallGuy)
    I've been given a question and I've tried finding formulae online (as they aren't in my notes) and have come up with nothing that's actually a realistic answer:

    "A spectral line of hydrogen (wavelength 21.1cm in the lab) emitted by a galaxy is oversee to have a wavelength of 21.4cm. If Hubble constant has a value of 0.06 metres per second per parsec, how far is this galaxy from Earth (in parsecs)? Given c=3x10^8."

    Can anyone provide an insight into how to go about doing this question?



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    Do you know the doppler shift equation? You can use it to calculute the recessional velocity of the galaxy from the change in wavelength and hence the distance.
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    I believe it's (measured wavelength - true wavelength) / true wavelength = v/c. I don't see how you get the distance from that without a time?
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    I also came across a formula which gives velocity = hubbles constant x distance but I got 7.11E7 when I used both of these and not certain whether that's a realistic value (or if that distance is actually in parsecs)
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    Still need help with this if anyone will?


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