1. How do the planets stay in orbit around the sun?
The solar system was formed from a rotating cloud of gas and dust which spun around a newly forming star, our sun, at its center. The planets all formed from this spinning disk-shaped cloud, and continued this rotating course around the sun after they were formed. The gravity of the sun keeps the planets in their orbits. They stay in their orbits because there is no other force in the solar system which can stop them.

2. How does gravity affect a planets orbit?
Kepler wondered why some planets closest to the sun move faster than the planets that are farther away.
Newton put the answers together with his own law of universal gravitation.
Due to the force of gravity, the attraction between the Earth and the other planets are attracted to each other. Attraction depends on the masses of the objects and the distance between the objects (planets).

3. Gravity
Planet on Which You Would Feel the Heaviest: Jupiter: A 100-pound person would weigh 254 pounds on Jupiter. Planet on Which You Would Feel the Lightest: Pluto. A 100-pound person would weigh only 9 pounds on the dwarf planet Pluto. On Mercury and Mars, a 100-pound person would weigh only 38 pounds.

4. Revolve
When an object moves in orbit around another object, it revolves around it.
The Moon revolves around the Earth. The Earth revolves around the Sun

5. Rotation
Earths spinning on its axis. The Earth rotates towards the east
The time it takes for the Earth to rotate completely around once is what we call a day. That is what gives us night and day.
As the Earth rotates only one half of the Earth faces the sun at any given time.

6. Revolution Revolution is the movement of one object around another.
The revolution of the Earth around the Sun takes one year.