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

• Precession- 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

Moon Craters

Why can you not see craters as well on Earth as on other baron planets and moons?

1. Water (oceans) covers the craters.2. Water erodes the crater’s edges and obscures

them from view.3. Vegetation (forests) covers the craters from

view.4. Clouds/Atmosphere make the Earth’s surface

less visible from space.

The Barringer Crater near Winslow, Arizona. The crater is about 49,000 years old.

Lunar Motion

The same side of the moon always faces the Earth.

• distance from earth- 384,000 km (238,606 miles)

• 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.

Andromeda Galaxy