World Builders™                                                                                 Session Two  --  Geology

Forming the Rocky Surface of Your Planet

After many thousands of years your planet will become a world with a solid surface.

Put text here.

Let's draw a cross section of your planet. Does it have an iron core? Probably. But how big is the core?

Checking back with Weight, Mass and Density we see that

We know from the page about Circle Math that the volume of a sphere =

If we take the radius of the earth as 1, then the volume of earth  =

4 * 3.14 * (1 * 1 *1) 3

3                           =           4.18

The density of the earth is 5.5

Mass = volume * density             in this case,   4.18 * 5.5  = mass of the earth = 229.9

Now the mass of the earth has two densities

Density of the iron core = 8

Density of the rocky mantle = 3

Let's call the unknown amount matter m

Then 3m + 8m = 229.9

11m  = 229.9                  therefore m = 229.9/11  =  20.9    Round this to 21

CHECK:     (3 * 21) * (8*21)  =  63 + 168  = 231

8/x +  3/x  =5.5

(8+3)/x = 5.5         =  11 = 5.5x     x = .5

so iron core is 4.0 and mantle is 1.5

 Earth

Diameter of earth 12,756 kilometers 7920 miles   r= 3960

inside 7016 kilometers 4359.5miles     r=2180

outside 2870 + 2870 = 5740  1783 miles    3566 miles

The density of earth is 5.5

4 * 3.14 * 1/3 = 12.56/3 = 3.14

Example One: