Google doodle commemorates 340th anniversary of determination of speed of light

Google is celebrating the 340th anniversary of the determination of the speed of light with a Google Doodle today. On December 7, 1676 the discovery was reported by the first scientific journal in Europe Journal des s�avans.

Google doodle commemorates 340th anniversary of determination of speed of light

Google is celebrating the 340th anniversary of the determination of the speed of light with a Google Doodle today. On December 7, 1676 the discovery was reported by the first scientific journal in Europe Journal des sçavans.

The Speed of light was discovered by a Danish astronomer called Ole Romer. But before Romer it was Galileo who tried to measure the speed of light in 1638. Galileo’s method involved two people standing on a hill top miles part with a lamp each.

The premise was that one of the pair would flash their lamp at the other, who would respond by flashing back immediately.

No matter how far apart the two lamps were Galileo couldn't measure a time difference, leading him to determine that light was too fast to measure like this. Finally, Galileo came to a conclusion that light was 10 times faster than sound.


Roemer began his research decades later in 1673 when he noticed the time elapse between the eclipses of a Jupiter moon called Io, which Galileo had discovered in 1610.

By monitoring the time difference, Roemer estimated "light seems to take about 10 to 11 minutes [to cross] a distance equal to the half-diameter of the terrestrial orbit", or Earth's orbit around the Sun. This means that light travels at about 200,000,000 metres per second, which is around 26 per cent below the established speed.


Royal Observatory in Paris, for whom Romer was doing research works, wasn't convinced with his conclusions. When other philosophers of the period, such as Christiaan Huygens and Isaac Newton backed the theory, it started gaining support.

It was finally confirmed nearly two decades after Romer's death, when English astronomer James Bradley in 1728 discovered the "aberration" of starlight and a speed of 295,000,000 metres per second for light.