It's all in our mind, or to be more specific most of us are walking around with rocks in our heads.
What is the mass of these "missing rocks"?
There are roughly 7.5 billion people on the planet and the average human head is 5kg. Most heads aren't solid rock, so I'm going to have to guess on this next part. I'll guess that our heads are about 2/3 rock, but this is not evenly distributed throughout the population. There are some with small pebbles and there are others who are solid granite.
So, roughly 37.5 billion kilograms worth of heads with 2/3 being rocky = 25 billion kilograms or 25 million metric tons of rock (~55.1 billion pounds, ~27.6 million US tons).
How much volume does that take up? Well, I guess it depends on how dense we are and the rocks in some people's heads are so very, very dense. Another site says 13 cubic feet per ton. I guess they mean US ton, since they're using cubic feet.
An Olympic swimming pool is 50 meters by 25 meters by 2 meters, so 2500 cubic meters.
Therefore, we humans are walking around with enough rocks in our heads to fill over 4000 Olympic size swimming pools!
In case that doesn't help, it would take up 5,096,750 square meters if there were no space at all between them.
On the other hand, this is only about 1260 acres. That's about 50% larger than Central Park or about 0.6% of the land area of Fort Hood in Texas or about 4 times the size of the National Mall in Washington DC.
There are no missing rocks (Score:3)
It's all in our mind, or to be more specific most of us are walking around with rocks in our heads.
What is the mass of these "missing rocks"?
There are roughly 7.5 billion people on the planet and the average human head is 5kg. Most heads aren't solid rock, so I'm going to have to guess on this next part. I'll guess that our heads are about 2/3 rock, but this is not evenly distributed throughout the population. There are some with small pebbles and there are others who are solid granite.
So, roughly 37.5 billion kilograms worth of heads with 2/3 being rocky = 25 billion kilograms or 25 million metric tons of rock (~55.1 billion pounds, ~27.6 million US tons).
How much volume does that take up? Well, I guess it depends on how dense we are and the rocks in some people's heads are so very, very dense. Another site says 13 cubic feet per ton. I guess they mean US ton, since they're using cubic feet.
So to put into terms we can all understand
13 cubic feet = 0.37 cubic meters.
27,550,000 * 0.37 = 10193500 cubic meters
An Olympic swimming pool is 50 meters by 25 meters by 2 meters, so 2500 cubic meters.
Therefore, we humans are walking around with enough rocks in our heads to fill over 4000 Olympic size swimming pools!
In case that doesn't help, it would take up 5,096,750 square meters if there were no space at all between them.
On the other hand, this is only about 1260 acres. That's about 50% larger than Central Park or about 0.6% of the land area of Fort Hood in Texas or about 4 times the size of the National Mall in Washington DC.