Lecture 2: The motion of the Earth and Moon

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Lecture 2 The motion of the Earth and Moon
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Why do we have day/night?
(diurnal motion)
Kitt Peak Arizona
Earth rotates W to E so sky appears to rotate E
to W
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constellations
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Some coordinates
zenith
horizon
meridian
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Siding Spring mountain Australia
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Motion of the Moon
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Phases (29 ½ days)
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About half of the moons orbit is visible from
Earth at any time
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The dark side of the Moon?
Synchronous rotation
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An astronaut lands on the moon how long will be
the day there?
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Sinodic month 29 ½ days
Sidereal month 27.32 days
(on average)
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Eclipses
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Lunar eclipse
Moon passes through Earth shadow
(Moon looks dimmer)
Solar eclipse
(only on a new moon)
Why so infrequent?
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Planning your next vacation?
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ANGLES
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1 degree60 arcminutes3600 arcseconds
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The small angle formula
Linear size object
distance
Angle (radn)
360 deg
How many arcsec is 1 radn ?
In arcsec!
Q units of D?
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Distances
1 astronomical unit (AU) average distance
between Earth and Sun
1AU
1 light year (ly)
1 parsec (pc) from 1 pc 1AU subtends 1
arcsec
1pc
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Powers of 10 notation
nano- (n) ?
micro- (
) ?
milli- (m) ?
)
(
centi- (c ) ?
Kilo- (K) ?
Mega- (M) ?
Giga- (G) ?
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Assignment Read pp 20 - 39 in The Universe