Earth

Earth images
Mass (Earth=1)1.00
Equatorial diameter (km)12,800
Period (years)1.00
Mean distance from Sun, 106 km150
Density (water=1)5.52
Surface gravity m/s29.78

Earth is the only planet with liquid water on its surface. In fact, 70% of the Earth is covered by water. Our oceans and air were formed by gases seeping from the Earth as it cooled after formation. Fossils indicate that life began on Earth at least 3.5 billion years ago.

Planetary data
Earth's seasons
Earth's Moon
Index

Earth Concepts

Solar System Illustration

Solar System Concepts
 
HyperPhysics********** Astrophysics R Nave
Go Back





Earth's Moon

Moon images
Mass (Earth=1)0.0123
Equatorial diameter (km)3480
Period (days)27.3
Mean distance from Earth, 106 m384
Density (water=1)3.34
Surface gravity m/s21.67

The Moon is our nearest neighbor, but it has evolved very differently from the Earth because it's gravity is too weak to hold an atmosphere. With no air, the lifeless Moon has no surface erosion from wind, rain, or snow, and thus lunar craters and even astronaut footprints last for millions of years.

Man first set foot on the Moon on July 20, 1969 when the landing craft from the Apollo 11 mission touched down on the Moon.

The temperature extremes on the Moon are from about 107°C down to -153°C.

The moon's average orbital speed is 5700 km/hr. It's orbit is inclined at 5.2° to the ecliptic, so you don't get a lunar eclipse or solar eclipse every time the Moon and Sun are aligned with the Earth. The eccentricity of the Moon's orbit is about 5% so the Moon's apparent size changes. This affects solar eclipses: when the Moon's angular size is near a minimum, it doesn't completely cover the Sun's disc and you get an annular eclipse.

Phases of the Moon
Index

Moon Concepts

Solar System Illustration

Solar System Concepts
 
HyperPhysics********** Astrophysics R Nave
Go Back