Earthquake!!

If the entire population of China jumped off of a 1 foot step
ladder at the exact same moment, an earthquake of 10 on the
Richter scale would be felt in the United States of America.

But, since the population of China is three times that of the
US, if the entire population of the USA jumped off of a
three-foot step ladder at the same time, at the exact right
moment, that earthquake would be sent back to China.