Main Idea Worksheets - Free Printable

- Sir Isaac Newton's observation of a falling apple led him to deduce the existence of gravity, a universal force pulling objects toward Earth's center, which he formally presented in his 1687 work, *The Principia*.
- An appropriate title: The Discovery of Gravity
- In 1939, Albert Einstein and Hungarian scientists warned President Roosevelt about Nazi atomic research, prompting the U.S. to develop its own atomic bomb, a decision Einstein later regretted as his greatest mistake after the bomb was used on Japan.
- An appropriate title: Einstein’s Regret Over the Atomic Bomb
- Nicolaus Copernicus revolutionized astronomy by proposing a heliocentric model of the universe, but delayed publishing his findings until 1543 due to potential conflict with the Catholic Church, which did not officially accept his theory until 1822.
- An appropriate title: Copernicus and the Heliocentric Revolution