The Earth in Space
Feb 23, 2016
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.