Two cars are parked side by side. Does each car pull on the other?
Kepler found his three laws by staring at tables of planet positions: patterns without a reason. Nearly seventy years later, Newton showed all three follow from one law about a falling apple.
You've already met Newton's law of universal gravitation: every mass attracts every other mass, with a force that follows the inverse-square law.
Newton asked which paths that one force would let an orbiting body follow.
The mathematics answers: the closed paths come out as ellipses with the attracting body at one focus. That is Kepler's first law.
The same force speeds a body up as it falls inward and slows it as it climbs away: equal areas in equal times, Kepler's second law.
And the inverse-square law reproduces the period-radius pattern Kepler found: the third law.
Which law did Newton show Kepler's three laws follow from?
Which law explains why the planets' orbits are ellipses with the Sun at one focus? The same one: each of Kepler's laws follows from the law of universal gravitation.
The law that drops an apple onto the grass is the law that steers the planets.
Newton showed the law that pulls a falling apple also governs which motion?
Astronomers see Jupiter's moons obeying the period-radius pattern. What does Newton's work say about why?
The inverse-square law of gravitation reproduces the period-radius pattern for any set of bodies orbiting one center.
Jupiter's gravity follows that same universal law.
Jupiter's moons obey the pattern because Jupiter's gravity follows the universal inverse-square law.
One rule, from your desk to Neptune. That is why the law is called universal gravitation.
Esme says the pull that drops a phone also keeps Earth orbiting the Sun. Is she correct?
Which statement about Kepler's laws and Newton's law is correct?
A telescope finds planets circling a distant star, obeying Kepler's period-radius pattern. What does that suggest?
What did Newton add to what Kepler had already done?