Why is there only one planet in each orbit around the sun?
Such a configuration would not be stable. All the planets are slightly perturbed by the other planets and so their orbits change slightly over time. So even if two planets orbited exactly opposite one another they would end up with slightly different orbits. Eventually the two planets would come close enough to interact one another through gravity, which would most likely result in a collision.
A Planet has to be three things; - Approximately spherical, so it has to be massive enough to `pull` itself into a spherical shape. - It has to orbit the sun directly (unlike a moon that is in orbit around a planet, which is then in turn in orbit around the sun). - It has to be the main object at that orbital distance from the sun, it has to be the dominant body at…
The 2006 (re)definition of a planet includes three criteria - 1) it is in orbit around the Sun, 2) it's achieved hydrostatic equilibrium (characterized by sufficient mass to have a rounded shape), 3) it has cleared the area around it orbit. Under this last criteria, Pluto, formerly considered a planet, is now classified as a dwarf planet as it has only cleared a tiny fraction of its orbit.
What are the 2 factors that newton realized that keep the earth in orbit around the sun and the moon in orbit around the earth?
Neptune (the eighth and outermost planet) was discovered on September 23, 1846. It takes 164.79 Earth years to complete one orbit and will therefore only complete its first orbit since its discovery in 2011. It is also worth noting that while Pluto is not longer regarded as a planet (it is now a minor planet) it was discovered in 1930 and takes 248.09 Earth years to complete an orbit.
Centrifugal force doesn't exist, and there is no outward force acting on planets. The only force on them is the 'centripetal' one ... the gravitational force between each planet and the sun, that attracts the planet in the direction toward the sun. That's the only force required to keep a planet in orbit ... which is lucky, because it's the only force there is.
None do. If the forces on a planet were balanced, then it would take off in a straight line at constant speed, not remain in orbit. The only force acting on a planet is the gravitational one, that attracts the planet toward the sun. Fortunately, that's the only force required to keep the planet in orbit.