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. The stay in their orbits because there is no other
force in the solar system which can stop them.