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

1. Jul 26, 2005

### 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....

2. Jul 26, 2005

### 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.

3. Jul 26, 2005

### HallsofIvy

Staff Emeritus
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?

4. Jul 26, 2005

### 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.

5. Jul 26, 2005

### Johnnymac

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

6. Jul 26, 2005

### 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.