Newton’s theory of universal gravitation says that every particle in the universe attracts every other particle through the force of gravity. The theory helps us predict how objects as large as planets and as small as individual colliding molecules will interact; it shows us the way earthquakes ripple through the Earth’s crust and how to build building that can withstand them. His simple equation for universal gravitation, written in 1666 when he was 23, helped overthrow more than a thousand years of Aristotelian thinking (reinforced by Greek astronomer Claudius Ptolemy) which said that objects only moved if an external force drove that motion.

Newton’s three laws of motion, published 20 years later in his Principia, established that every object in a state of uniform motion will remain in that state of motion unless an external force acts on it, that force equals mass times acceleration and that for every action there is an equal and opposite reaction. These laws were among the first to explain fundamental aspects of nature with simple mathematical formulas that were useful in a vast range of real life scenarios. Although the laws were later replaced by Albert Einstein’s more accurate theories about spacetime and general relativity, they laid the groundwork for this and all other modern thought about physics and the nature of reality.

On May 8, 1945, Germany surrendered. After the atomic bomb was dropped on Hiroshima and Nagasaki, Japan surrendered on September 2, 1945, and the Second World War came to an end. The war cost the lives of more than 330,000 American soldiers. Many more were permanently injured or maimed. Why was it so important?World War II was, arguably, the most significant and influential event of the twentieth century. The devastation is almost incalculable: total military and civilian deaths are estimated at 70 to 85 million, about 3% of the global population during that time. World War II also saw the dawn of the nuclear age.