Speed of Light History: From Infinity to Finite

 In the past people believed that light travels fast. This belief was mainly influenced by our experiences. When we turn on a light switch the surroundings instantly become illuminated. However in the century Ole Rømer, a Danish astronomer working at the Paris observatory under Giovanni Domenico Cassinis guidance challenged this idea. Rømer proposed that light actually has a speed based on his observations of Io, one of Jupiters well known moons.

Observations and Interpretations

Io completes its orbit around Jupiter in 1.76 days but Rømer noticed some inconsistencies. The time it took for Io to complete its orbit varied throughout the year. When Earth was from Jupiter Ios orbit took longer to complete. On the hand when Earth and Jupiter were closer together Ios revolution appeared to speed up. From these observations Rømer concluded that the speed of light is not infinite. He reasoned that the delay in observing Ios orbit was due, to the time it took for light to travel from Jupiter to Earth.

Calculating the Speed of Light

Rømer faced skepticism from his contemporaries regarding his hypothesis. To prove his theory he made a prediction that the eclipse of Io on November 9 1676 would happen 10 minutes earlier than what other scientists had expected based on transits. This prediction turned out to be correct convincing Cassini that the speed of light was not infinite. Rømer estimated the speed of light to be 220,000 kilometers per second by observing that it took light 22 minutes to travel across the diameter of Earths orbit. Although this estimate was not entirely accurate (the precise speed is 299,792.458 km/s) it was the approximation at that time.

The Speed of Light; The Unbreakable Barrier

There is a hypothesis concerning particles known as "tachyons," which are said to travel faster than light. However if tachyons did exist they would never be able to slow down. Over a century ago Albert Einstein established a relationship between an objects energy (E) and its mass (m) with his equation of relativity; E=mc^2. In this equation 'c' represents the speed of light.

This equation signifies that energy and mass can be converted into each other. When we accelerate an object the applied energy partially increases its mass well. Therefore in order to increase an objects velocity, to the speed of light an enormous amount of energy is required.

For example if an individual weighing 80 kilograms were to travel at 99.9 percent of the speed of light their weight would be equivalent to 2 tons. Any attempt to surpass this velocity would result in an increase in their mass while having minimal impact, on their speed. This is the reason why given our technological capabilities we are unable to exceed or even attain the speed of light.