-- If you go outside at the same time every night and look at
some familiar stars, you'll see each of them them move westward
at almost exactly 1 degree per night.
-- The reason for that apparent motion is the real motion of the
Earth in its orbit around the sun, at almost exactly 1 degree in
every 24 hours.
(average during a whole year is 0.9856 degree per day.)
Answer: The Industrial Revolution.
_____________________________________
1. Crust
2. Mantle
3. Inner core
4. Outer core
