George Washington US presidentGeorge Washington’s teeth aren’t what you think.Wikimedia CommonsOver time, even facts we consider steadfast truths can change.

People used to think doctors could forgo washing their hands before surgery. Knowledge is ever-evolving.

Other facts might have been taught incorrectly because the truth is more nuanced than grade-school students can understand.

The nine facts below probably changed since your school days, or were taught to you the wrong way.

Re-educate yourself.