What did newton predict using his ideas about gravity?

Answer 1

After inventing a formula to describe gravity, Newton had this nice-looking formula,

but he couldn't do much with it because he didn't know any Calculus. He asked

around to find somebody who could fill him in on Calculus, and was surprised to

discover that nobody knew what he was talking about, because Calculus didn't

exist yet. So he did the only thing he could think of . . . he invented Calculus, and

then he was all set, and had everything he needed.

He took his formula for gravity, massaged it with Calculus, kneaded it with Geometry,

and came up with a bunch of really neat but weird predictions:

-- Planets travel around the sun in elliptical orbits, with the sun at one focus of

each ellipse.

-- The radius vector (line) from the sun to each planet sweeps out equal area

in equal intervals of time, so the planet has to travel faster when it's nearer

the sun, and slower when it's farther from the sun.

-- The ratio of the square of orbital period to the cube of the semi-major-axis

of the orbit is the same number for every object that orbits the sun.

These predictions didn't go over too well with the people in Newton's neighborhood,

for a variety of reasons. First of all, most of them couldn't read. The ones who

could read were also mostly left out in the cold, because they could only read

English, whereas Newton did his writing in Latin. And finally, even the people

who could read Latin, like his rector, his Bishop, his beadle, and his sexton, had

no idea what the heck he was talking about altogether.

But finally, after Newton had almost given up in despair and nailed his article

to the front door of the church, a tourist visiting his town happened to walk by

one day. He stopped to read Newton's paper, and hadn't gotten past the first

few paragraphs before he yelled out "Eureka!" and went running down the

street to Newton's house. He had to wait a while because Newton was taking

a bath with his gold crown, but he finally scored an audience with the old man

and breathlessly gave him the news:

His three predictions of planetary motion that he made up from his gravity and

his calculus were exactly the same as three popular Polish proverbs called

"Kepler's Laws". It seems that Kepler was a guy who had spent his whole life

going through the notebooks and diaries of Tycho who was a Danish hermit

who spent his life in the woods looking at the stars every night and . . . well,

it was all very complicated, but the bottom line was that Kepler came up with

the exact same three laws by going through years and years of actual factual

measurements of the real motions of the real planets, and now here came Newton

with his calculus and his geometry and his gravity and showed why the planets

must move in the way they actually do.

And that was the best proof of gravity that anybody could ask for, so Isaac said

to the visitor "Good day to you sir", and they all lived happily ever after.

Answer 2

Newton used his ideas about gravity to predict the motion of planets and moons in our solar system. He also proposed the concept of universal gravitation, stating that every object in the universe attracts every other object with a force proportional to their masses and inversely proportional to the square of the distance between them.