BBC - Light and Dark (2013) Part 1 Light
Professor Jim Al-Khalili shows how scientists have used light to reveal almost everything we know about the universe.
Part 1: Light
The story begins in the 3rd century BC when, by trying to understand the tricks of perspective, the Greek mathematician Euclid discovered that light travels in straight lines, which meant that if we could change its path we could change how we see the world. In Renaissance Italy 2,000 years later, Galileo Galilei did just that by using the lenses of his simple telescope to reveal our true place in the cosmos. In the 1670s, the Danish astronomer Ole Roemer discovered that light travelled at a finite speed, a discovery that had a profound implication. It meant the further one looks out into the universe, the further one looks back in time. And in 1964, by detecting the cosmic microwave background, the afterglow of the big bang, we captured the oldest light in the universe and saw as far back as its possible to see with light.
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