When Hubble did his early work on the expanding universe, he knew nothing about
ID: 298427 • Letter: W
Question
When Hubble did his early work on the expanding universe, he knew nothing about the cosmological redshift. He used the Doppler shift equations instead, but these gave him the correct answer. Why? These two sets of equations (Doppler shift and cosmological redshift) are the same and always give the same result for all cases. Hubble was using only ordinary galaxies. If he had used galaxies with AGN's, the equations would not have worked. Hubble was fortunate enough to use only galaxies for which the gravitational redshift and the cosmological redshift nearly cancel, so the Doppler shift provided essentially the whole effect. Hubble was using only relatively nearby galaxies for which the non-relativistic cosmological redshift and the Doppler shift provide the same result.Explanation / Answer
Answer : These two sets of equations are the same and always gives same reresults for all cases.
explanation : The electromagnetic radiation of an object towards the red wave length of electromagnetic spectrum is called red shift
Change in frequency of sound with distance is called doppler shift.
Thease two shifts telles that the frequency of the electromagnetic wave decreases with increasing distance from the source i.e increase wavelength with distance i.e decrease in energy with distnce.
Expances equation derived from the two shifts v = Hd
where v is the gelaxy's radial outward velocity
H is humble constant
d is distance of gelaxy from earth
It tells that the velocity of the wave increase with distance i.e increase with wave length.
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