Module P7Observing the Universe

Module P1,2,3 16.5%

Coursework 33%

Module P4,5,6 16.5%

Module P7 33%

Starter: some deep questions(in the form of some stupid jokes)

How many astronomers does it take to change a light bulb?

How many cosmologists does it take to change a light bulb?

How many radio astronomers does it take to change a light bulb?

How many General Relativitists does it take to change a light bulb?

Seven – one to change it, the other six to complain about light pollution.

Only one – but it takes fifteen billion years.

None – they can’t be bothered with that shortwave rubbish.

Two – one to hold the bulb, the other to turn the Universe.

Sidereal DayMeasured relative to a star, the Earth takes 23 hours 56 minutes to rotate.

Solar day: One 360º rotation of the Earth measured according to the Sun

Sidereal day: One 360º rotation of the Earth measured according to a star.

Solar DayAfter 23 hours 56 minutes, the Earth has turned through 360 degrees.

However, the Sun is not directly overhead because the Earth has moved along in its orbit.

It takes an extra 4 minutes for the Earth to rotate so that the Sun appears directly overhead.

Phases of the Moon

Lunar Eclipse Montage

Lunar Eclipse

Solar Eclipse

Solar Eclipse

To think about

The Moon orbits the Earth once every 28 days.

Why don’t we get lunar and solar eclipses once each month?

Lunar Eclipses – why so rare?PLAN VIEW

SIDE VIEW

The tilt of the Moon’s orbit carries it just beneath the Earth’s shadow – except once or twice every two years

Plane of Earth’s orbit

Plane of Moon’s orbit

Solar Eclipses – why so rare?PLAN VIEW

SIDE VIEW

The tilt of the Moon’s orbit means that its shadow touches the Earth quite rarely – roughly once every hundred years for a given location

Plane of Earth’s orbit

Plane of Moon’s orbit

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