Transcript Evidence for general relativity

Relativity
H8: Evidence for general relativity
1
Bending of light
 General Relativity predicts that a light ray passing near
the Sun should be deflected by the curved space-time
created by the Sun’s mass
 The prediction was confirmed by astronomers during a
total solar eclipse, by Eddington in 1919
2
Bending of light
 Bending of light can have an affect of
acting like a lens
 We call this gravitational lensing
3
Gravitational lensing
4
Gravitational lensing
5
Gravitational red-shift
 When a source moves and it emits a
wave, the wavelength will change
 If the source is moving away from us
then the wavelength will be longer, this is
called red-shift
 If the source is moving towards us then
the wavelength will be shorter, this is call
blue-shift
6
Gravitational red-shift
 This is often used to calculate the speed
of distant star is Astronomy
 The faster the source is moving the
greater the wavelength change
 It has been found that all sources are
moving away from us (red-shift)
 Therefore the Universe is expanding
7
Pound-Rebka experiment
 Two scientists fired an EM wave through
a 22 m tower
 In theory the wavelength will change as it
is in the Earth’s gravitational field
 It showed the wavelength had shifted
 Therefore confirming Doppler effect due
to general relativity
8