Primo Levi's Calculation: Human Mass on Earth's Surface

[Markolie]

Primo Levi: "Human Surface"

Homework Statement

http://answers.yahoo.com/question/index?qid=20101205082200AAZCums

What calculation did Primo Levi use to get the following conclusion:
According to Primo Levi's book, if the human mass of 250 million metric ton would be spread over the surface of earth, the thickness of the "human surface" is 16000st of a millimeter.
The density of a human body in this case would be 1000kg/m3. Surface Earth = 510 million km2

Homework Equations

None

The Attempt at a Solution

I wouldn't have the slightest idea to solve this.

Thanks in advance!

 

[tiny-tim]

Did you make this up? What book is this?

 

[Markolie]

I'm totally confused myself too. None of my friends could solve it either. I'm sorry if it isn't fully understandable because I'm Dutch :).

Book: "Il sistema periodico ("The Periodic Table") p.168 (Primo Levi) I think...