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Cosmology: Doppler EffectIf you watched season 1 of Big Bang Theory, Sheldon clearly shows
the doppler effect in a halloween party to some confused girls.
That is literally the doppler effect in real life but what even is
it?
The doppler effect is the compression/spreading out of waves that
are emitted or reflected by a moving source. As the source is
moving, the wavelength in front of it are compressed and the
wavelengths behind are spread out.
The Doppler effect causes the line spectra of distant objects to
be shifted either towards the blue end of the visible spectrum
when they move towards the Earth or towards the red end of the
spectrum when they move away from the Earth.
Red shift is used as evidence for the expanding universe, as
distant objects are red-shifted. The more distant the object, the
greater its red-shift.
Z = v/c = difference in frequency/frequency = -difference
wavelength/wavelength
The Doppler effect can be used to identify binary star systems,
where two stars are orbiting a common centre of mass. As the stars
eclipse each other, they are travelling perpendicular to the line
of sight from the observer. This causes each spectral line to be
split into two, where one is blue-shifted and the other is red-
shifted. Quasars are objects which have very large red shifts
which means they are so far away and they are bright, you go
blind.
Cosmology: Hubble’s Law
Hubble’s law states that a galaxy’s recessional velocity is
directly proportional to its distance from the Earth. It
essentially states that the universe is expanding from a common
starting point.
V = Hd
H = 65
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