Answer:
Economic differences between the Union and the Confederacy.
France and the USA cause that what I read about in 5th grade
He explored human emotions and expressions.
The original purpose of dropping atomic bombs were to, instead of sending in troops, drop an atomic bomb on your city of choice and wipe out everyone in a mile's radius. That is the short term effect. But the long term effects include nuclear radiation which poisons people in a much larger radius, while contaminating the environment for an extended period of time.
Hope this helps!