1. The archetype terrestrial planet
Earth
The archetype terrestrial planet

2. Size, Shape and Mass Radius: 6,378 km (about 4000 miles)
A slightly flattened sphere, because of Earth’s spin.
about 21 km greater at the equator than at the poles.
Mass: 5.97 x 10^24 kg
Density: 5.52 g/cm³
(Water has a density of 1 g/cm³)
Surface Gravity: 9.8 m/s²

3. Orbit Radius: 1 AU ( 149.6 million km or 93 million miles)
Period: Earth days
Rotation
Period: 23 hours 56 min. (Sidereal day) The sidereal day is the time it takes to rotate once
Solar Day: 24 hours (Noon to Noon)
These are different because the Earth moves on its orbit changing the direction of the Sun
Axial Tilt: 23° 27”

4. Earth’s Composition The Earth takes the form of a solid ball of rock,
composed of…
Oxygen %
Silicon %
Aluminum %
Iron %
Calcium %
Magnesium, Sodium & Potassium about 2% each
Others %

5. The interior of Earth is hotter than its Surface, Two Reasons Why
The Earth was born hot.
Impacts of smaller bodies colliding heated the forming Earth
The Earth is cooling, but due to its size not quickly enough to cool completely yet
Radioactive decay heats the interior.
As radioactive elements decay they give off energy
This heats the Earth’s interior