Before the 17th century, scientists believed that there was no such thing as the "speed of light". They thought that light could travel any distance in no time at all. Later, several attempts were made to measure that speed.
- 1667 Galileo Galilei: at least 10 times faster than sound
- 1675 Ole Roemer: 200,000 Km/sec
- 1728 James Bradley: 301,000 Km/s
- 1849 Hippolyte Louis Fizeau: 313,300 Km/s
- 1862 Leon Foucault 299,796 Km/s
- Today: 299792.458 km/s
1667 Galileo Galilei: at least 10 times faster than sound. LIGHT
In 1667, Galileo Galilei is often credited with being the first scientist to try to determine the speed of light. His method was quite simple. He and an assistant each had lamps which could be covered and uncovered at will. Galileo would uncover his lamp, and as soon as his assistant saw the light he would uncover his. By measuring the elapsed time until Galileo saw his assistant's light and knowing how far apart the lamps were, Galileo reasoned he should be able to determine the speed of the light. His conclusion: "If not instantaneous, it is extraordinarily rapid". Most likely he used a water clock, where the amount of water that empties from a container represents the amount of time that has passed. Galileo just deduced that light travels at least ten times faster than sound.
Sunlight takes about 8 minutes, 19 seconds to reach Earth.
.jpg)