The Earth in Space

Physical properties of Earth• diameter (equator)-

12,756 km

• diameter (poles)- 12,714 km

• circumference (equator)- 40,075 km

• average distance from sun- 149,600,000 km

In The Past

• people thought the sun, moon, and stars orbited around the Earth

• thought the Earth was flat

Earth’s Motion and Seasons

• Earth’s tilt has fluctuated throughout geologic time from 21.5o- 24.5o.

• above the Arctic Circle receive 24 hrs. of daylight• below the Antarctic Circle 24 hrs. of darkness

• Earth’s axis wobbles in a large circle that that takes >26,000 years to complete.

Earth’s Motion

• Solstice- sun reaches its greatest distance from the equator.

• Equinox- days and nights are equal length.

• When the northern hemisphere points towards the sun we experience summer.

Solstices

• northern hemisphere- June 21st

• southern hemisphere- December 21st

Equinoxes

• northern hemisphere- March 21st

• southern hemisphere- September 21st

Earth’s Moon

• probably formed when a large object collided with Earth shortly after it formed

• moon rocks range from 3.2-4.6 billion years

• crust, mantle, and solid iron core

• craters- form when meteorites strike the moon

Lunar Motion

The same side of the moon always faces the Earth.

• distance from earth- 384,000 km

• complete orbit takes 27.3 days

Solar Eclipse

• occurs when the Earth moves into the moon’s shadow

Lunar Eclipse• occurs when the

sun, Earth, and moon line up.

• the full moon moves into Earth’s shadow.

The Moon’s Formation

1. co-formation hypothesis

2. capture hypothesis

3. collision hypothesis

Our Solar System

• composed of sun, planets, asteroids, and comets

• >99% of all the solar system’s matter is contained in the sun

PlanetsInner Planets

MercuryVenusEarthMars

Outer Planets

JupiterSaturnUranusNeptunePluto

Asteroids and Comets• asteroids are small,

rocky bodies that lie mostly in a belt between Mars an Jupiter.

• comets are made mostly of rock and ice

Origin of the Solar System

The sun and planets probably condensed from a nebula (large cloud of gas, ice, and dust) about 5 billion years ago.