Newton's Estimates of Object Masses & Distances

[exmarine]

How did Newton estimate or know the masses of various objects, like the earth, moon, sun, etc., in order to check his equations? And how about the distances, say to the moon, and sun?

Thanks.

 

[fresh_42]

Niklas Koppernigk 1473 - 1543
Johannes Kepler 1571 - 1630
Issac Newton 1643 -1727

Bernard of Chartres (around 1100) used to say that "we [the Moderns] are like dwarfs perched on the shoulders of giants [the Ancients], and thus we are able to see more and farther than the latter."

Science never takes place in a vacuum. There have been scientists before and there will be after. In this special case, e.g. Kepler's laws have already been know.

 

[phyzguy]

How did Newton estimate or know the masses of various objects, like the earth, moon, sun, etc., in order to check his equations? And how about the distances, say to the moon, and sun?
Thanks.

He didn't know the masses. Nobody knew these values until Henry Cavendish performed the Cavendish Experiment and measured the value of G in about 1797, more than 50 years after Newton died. Before that, only the product GM was known. This is why the Cavendish Experiment is sometimes referred to as "weighing the Earth". The distances were known, at least approximately. Even the ancient Greeks had a decent estimate of the size of the Earth and the distances to the Sun and Moon.

 

[John Park]

How did Newton estimate or know the masses of various objects, like the earth, moon, sun, etc., in order to check his equations? And how about the distances, say to the moon, and sun?

As long as the orbiting body is much less massive than the central body (e.g. the Moon about the Earth to a fair approximation; any planet about the sun) the size and shape of the orbit don't depend on how massive the lighter body is.