Speed of Light

• 26 Dec 2024

Source: TH 

The speed of light, a fundamental constant in physics, has been determined with increasing precision over centuries. 

• The speed of light is the rate at which light waves propagate through different materials. In particular, the speed of light in a vacuum is defined as exactly 299,792,458 meters per second.  
  • Light's speed can vary when it propagates through different materials, depending on the material's refractive index (measure of bending of a light ray when passing from one medium to another). 
• Early estimates of the speed of light were based on how long it took light to travel a known distance, with measurements improving as instruments advanced. 
• Ole Roemer (1676) was the first to estimate the speed of light, observing Jupiter’s moons and their varying eclipse timings based on Earth's distance from Jupiter.  
  • His estimate was 225,300 km/s, which was far from the modern value due to limited knowledge of Jupiter's distance. 
• Modern measurements of the speed of light are conducted using laser beams and atomic clocks, resulting in the current precise value. 

Read more: Time Dilation in Early Universe