One of the fun aspects about Google is the ever-changing doodle on the homepage, usually relevant to holidays, historical events, and people. Today’s Google Doodle represents Ole Rømer, a Danish astronomer who was the first person to successfully measure the speed of light. Rømer, along with Galileo, was one of few astronomers who didn’t agree that light speed was infinite. His experiment was much more successful than Galileo’s, though.
While studying Jupiter’s moon Io and its eclipses, he noticed that the time between eclipses varied depending on Earth’s position to Jupiter during its orbit. As Earth drew closer, time between transits became shorter, and when Earth moved away, time between transits became longer.
He knew Earth’s position wouldn’t have an effect on Io’s eclipses, so he continued to research the idea for the next eight years. Rømer and Dutch astronomer Christiaan Huygens tried unsuccessfully to calculate the exact speed of light.
Rømer’s theory wasn’t accepted until about two decades after his death, but was later supported by scientists like Isaac Newton.
Thanks to Rømer’s observations 340 years ago, we now have a method for calculating the distance of stars and galaxies in the Universe, giving us the light year.
