The Speed of Light

Philosophical Views

The speed of light has long intrigued philosophers and scientists alike. In the fifth century BC, Greek philosopher Empedocles proposed that light had a finite speed, a notion that was contested by Aristotle, who believed light was instantaneous due to its presence rather than movement 1. This Aristotelian view dominated for centuries, largely because many thought light emanated from the eye rather than entering it. The debate over light's speed persisted, with philosophers pondering whether light was truly instantaneous or just incredibly fast 1.

Light is so incredibly fast that from a human perspective, it seems instantaneous.

--- Gary Arndt

These early philosophical discussions laid the groundwork for future scientific inquiries into the nature of light.

   

Scientific Experiments

The quest to determine the speed of light saw significant advancements through experimentation. In the 11th century, Hassan ibn al-Haytham challenged the Aristotelian view with his intromission theory, suggesting that light entered the eye from the outside, implying a finite speed 2. The 17th century marked a turning point with Galileo's proposed experiment using lanterns to measure light's speed, though results were inconclusive. It was Ole Romer in 1676 who provided conclusive evidence of light's finite speed through his observations of Jupiter's moon Io 2.

When the Earth was moving away from Jupiter, the time between eclipses was slightly longer, and when it was moving towards Jupiter, it was slightly shorter.

--- Gary Arndt

Romer's work paved the way for further discoveries, including Christian Huygens' calculations and Newton's insights into the uniform speed of light across colors.