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RelativityRelativity

H8: Evidence for general relativityH8: Evidence for general relativity

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Bending of lightBending of light

General Relativity predicts that a light ray passing near General Relativity predicts that a light ray passing near the Sun should be deflected by the curved space-time the Sun should be deflected by the curved space-time created by the Sun’s masscreated by the Sun’s mass

The prediction was confirmed by astronomers during a The prediction was confirmed by astronomers during a total solar eclipse, by Eddington in 1919total solar eclipse, by Eddington in 1919

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Bending of lightBending of light

Bending of light can have an affect of Bending of light can have an affect of acting like a lensacting like a lens

We call this gravitational lensingWe call this gravitational lensing

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Gravitational lensingGravitational lensing

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Gravitational lensingGravitational lensing

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Gravitational red-shiftGravitational red-shift

When a source moves and it emits a When a source moves and it emits a wave, the wavelength will changewave, the wavelength will change

If the source is moving away from us If the source is moving away from us then the wavelength will be longer, this is then the wavelength will be longer, this is called red-shiftcalled red-shift

If the source is moving towards us then If the source is moving towards us then the wavelength will be shorter, this is call the wavelength will be shorter, this is call blue-shiftblue-shift

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Gravitational red-shiftGravitational red-shift

This is often used to calculate the speed This is often used to calculate the speed of distant star is Astronomyof distant star is Astronomy

The faster the source is moving the The faster the source is moving the greater the wavelength changegreater the wavelength change

It has been found that all sources are It has been found that all sources are moving away from us (red-shift)moving away from us (red-shift)

Therefore the Universe is expandingTherefore the Universe is expanding

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Pound-Rebka experimentPound-Rebka experiment

Two scientists fired an EM wave through Two scientists fired an EM wave through a 22 m towera 22 m tower

In theory the wavelength will change as it In theory the wavelength will change as it is in the Earth’s gravitational fieldis in the Earth’s gravitational field

It showed the wavelength had shifted It showed the wavelength had shifted Therefore confirming Doppler effect due Therefore confirming Doppler effect due

to general relativityto general relativity