The Earth is our home planet. It is the third planet from the Sun and orbits
the Sun at an average distance of approximately 93 million miles (149 million
The Earth rotates on its axis, completing one revolution every 24 hours
with respect to the Sun (23 hrs 56 min with respect to the stars). The
axis of the Earth is tilted at 23 degees and 27 minutes relative to its
orbital plane about the Sun. This produces seasons on the surface of the Earth.
The Earth completes one orbital revolution around the Sun in 365 days 5 hrs.
The Earth has a liquid core and a solid crust which is broken into several
plates which slowly move along the surface of the planet. The surface is
covered approximately 70% by liquid water.
The mass of the Earth is approximately 6.5 x 10^21 tons (5.98 x 10^24 kg)
and the mean diameter of the Earth is 7,926 miles (12,753 km). The resulting
acceleration (ge) is given by:
ge = 32.2 ft/sec^2 = 9.8 m/sec^2
The Earth has an
composed of 78% nitrogen, 21% oxygen, and traces of other gases including
carbon dioxide and water vapor. The atmosphere provides the medium for
the important water cycle and life cycles that occur on the planet. The
upper regions of the atmosphere provides sheilding from radiation from
the Sun. The atmosphere also moderates the temperature extremes on the planet.
Average properties of the atmosphere are
on another page. The atmosphere is the source of
on a rocket going into orbit around the Earth, and provides a
means for slowing spacecraft as they return from orbit. The
of the atmosphere all decrease with
above the Earth's surface. The thickness of the atmosphere is approximately
62 miles (100 km).
The Earth has a magnetic field which protects the surface from radiation
from the Sun and provides a convenient way for navigating on the surface.
A single satellite, the
orbits the Earth.
Our Neighbors in Space:
Circular Orbit Calculator:
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