Loss of Material From Earth

## Question:

I understand the difficulty of trying to answer questions from someone not taking your course, but if you find yourself intrigued by the question thanks. If no, thanks anyway. I'm trying the impossible at age fifty three, to write a book. I want what I write to be believable to everyone including someone of your learning. my question is. If the earth suddenly loss a mass of weight, say solid granite rock, an area of 30 ft by 40 ft by four miles, would there be any effect on the earth, especially if the process was repeated at random? I'm not saying displaced rock, I'm saying gone, or a science fiction term disintegrated. (This has nothing to do with recent reports that scientist now say the earth weighs less than we thought). thanks in advance.
## Answer:

Here are some thoughts.
First, people age 53 still seem like kids to some of us old guys. You could wait to see if you get younger but I recommend getting on with it. Best of luck with your book.

Regarding the sudden loss of rock, let's assume for now that the density of the lost material is the same as the average density of the earth. It is apt to be lighter since the crust is floating on the mantle which floats on the core but we can adjust for that later if we need to. The volume in cubic miles of the lost material is 30/5280*40/5280*4=0.000172 cubic miles. Now compare that to the volume of the entire earth in cubic miles. The formula for the volume of a sphere is 4/3*pi*r^3. For the earth that is 4/3*3.14*4000^3=268000000000 cubic miles. The lost material then is 0.0000000000000642% of the total volume of the earth and the same percentage of its mass if we assume uniform density. Adjusting for a more realistic density will only reduce this percentage. Such a tiny loss of mass, while it would cause considerable disturbance locally, would have a negligible short term effect on either the rotation of the earth or its orbit about the sun. In fact the earth gains mass through the accumulation of meteoric dust and meteorites. I wonder how many years accumulation would be a mass equivalent to your loss. You might try searching for "mass of earth" at http://www.google.com for that sort of information. If you need further explanation of this or have other science type questions, don't hesitate to ask.

This information is brought to you by M. Casco Associates, a company dedicated to helping humankind reach the stars through understanding how the universe works. My name is James D. Jones. If I can be of more help, please let me know.

JDJ