Your Microwave Will Not Give You Cancer
Microwave radiation cannot cause cancer. The only thing your microwave can do is heat up objects. There are many different types of radiation that cause cancer, but microwave radiation is one of those types that will not.
People in the Middle Ages Didn't Think the Earth Was Flat
During the Middle Ages, there are actually no writings in which people stated that the Earth was flat. Those rumors didn't surface until the 1800's when religious and scientific interest clashed. Make sure you tell this to your crazy uncle who believes anything he reads.