Section 1 d) Summary

Our Planet, the Earth, is located as the third planet from the Sun in the Solar System, one of billions of stars in the Milky way galaxy, which is one of billions of galaxies in the Universe.

Gravity, a force exerted by all bodies of mass, keeps celestial bodies in orbit around each other. It pulls bodies of mass back towards others and preventing them from moving far away, creating an orbit.

An orbit is a balance between the forwards motion of the object and the force pulling it inwards. Planets have almost circular orbits, whereas comets have elongated elliptical orbits. Moons and artificial satellites orbit planets in circular patterns.
Geostationary satellites have an orbit of 1 day, keeping it stationary over one area of land, and are useful for communications.

Stronger forces of attraction occur closer to the centre of a body of mass; because of this, planets closer to the Sun move faster, and comets move more quickly when they're closer to the Sun.

Orbital speed can be worked out through the following equation:

v= (2 x π x r ) / T