Lecture 2: Lecture 2: Spaceship Spaceship

EarthEarthMan is…related inextricably to all reality, known and unknowable…plankton, a shimmering phosphorescence on the sea and the spinning planets and an expanding universe, all bound together by the elastic string of time. It is advisable to look from the tide pool to the stars and then back to the tide pool again.

-- John Steinbeck

Earth’s RotationEarth’s Rotation

The Earth’s The Earth’s OrbitOrbit

The Reason for SeasonsThe Reason for Seasons

Spring Equinox

Fall Equinox

Summer Solstice

Winter Solstice

Summer Solstice at the Summer Solstice at the Arctic CircleArctic Circle

Precession of the Precession of the Earth’s AxisEarth’s Axis

Phases of the MoonPhases of the Moon

EclipsesEclipses

Solar eclipse: occurs when the Moon’s shadow falls on the Earth – occurs only at new moon.

Lunar eclipse: occurs when the Moon passes through the Earth’s shadow – occurs only at full moon.

Solar Solar EclipsesEclipses

Total

Partial

Annular

path

path

A total eclipse of the A total eclipse of the SunSun

Fixed Stars and Fixed Stars and Wandering PlanetsWandering Planets

The Sun’s Motion Through The Sun’s Motion Through the Zodiacthe Zodiac

The Mystery of The Mystery of Retrograde MotionRetrograde Motion

Jupiter, shown at onemonth intervals

Explaining Explaining RetrogradRetrograde Motione Motion

Stellar ParallaxStellar Parallax

Stellar Motions Stellar Motions in the Solar in the Solar

NeighborhoodNeighborhood

Rotation in the GalaxyRotation in the Galaxy

Hubble’s LawHubble’s Law

The The ExpandiExpandi

ng ng UniverseUniverse

Astronomical Distance Astronomical Distance UnitsUnits

Astronomical Unit (AU)

150 million kmdistances between planets

parsec (pc) 3.09E13 km distances between stars

kilo-parsec (kpc) 1000 pc sizes of galaxies

Mega-parsec (Mpc) 1.0E6 pcdistances between galaxies

1 parsec = 3.26 light years