# Solving the mass of the Earth using 17th and 18th Century tools

#### Johnnymac

Solving the mass of the Earth using 17th and 18th Century tools....

Good afternoon, morning, evening everyone....

I am looking for a little guidance on how to solve for the mass of the Earth utilizing only tools and theories available to people in the 17th and 18th Century.

I have Newton's and Keplar's laws available....

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#### Yegor

$$G\frac{M}{r^2}=g$$
Telescope was invented already, so r is available. g - also isn't big problem. The most difficult thing is to measure G. But there are some ways. This data is enough.

#### HallsofIvy

What does having a telescope have to do with finding r, the radius of the earth? That as calculated about a thousand years before the telescope was invented, wasn't it?

#### Yegor

Yes. It really was (if i remember correctly, even 2 thousand years before). Just when i started to think how to measure r, telescope was my first idea. If i lived in 18th century i would use it.
Sorry, i wasn't presice.

#### Johnnymac

Thank you both!!! Here's to solving!!

#### amt

Several centuries ago, the radius of the Earth was found using the angles of the Sun rays formed on Earth. To find the mass you will probably have to use g=(G.m1.m2)/r^2. This means you will need the mass of another body, like the moon.

Not sure how else you could find the Mass of the earth.

"Solving the mass of the Earth using 17th and 18th Century tools "

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