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Recent Podcast
Tour: Astronomers Spy Quartet of Cavities From Giant Black Holes
Tour: Astronomers Spy Quartet of Cavities From Giant Black Holes
Scientists have found four enormous cavities, or bubbles, at the center of a galaxy cluster using NASA's Chandra X-ray Observatory. (2021-12-16)

Light Beyond the Bulb: Over and Beyond the Rainbow

Narrator (April Hobart, CXC): For the millions of years that humans and our ancestors have roamed this planet, we have been familiar with light. While scientists and philosophers have tried to figure out exactly what light is for millennia, it's only been in the past several hundred years or so that we've really started to figure it out.

In 1665, Isaac Newton, then a young scientist at Cambridge University in England, took a glass prism and held it up to a beam of sunlight streaming through the window. He saw the sunlight that passed through the prism spread out into the colors of the rainbow - red, orange, yellow, green, blue and violet. This was a crucial step in beginning to understand some of the properties of light.

Of course, we know today that Newton was experimenting with what we call "visible light." In 1800, William Herschel made a huge step in revealing that there was light outside what humans could see with their eyes with the discovery of infrared light. The prefix "infra" means "below" and "beyond," which makes sense as this type of light falls just outside the red color of visible light. Soon thereafter, Johann Ritter discovered light on the other end of the visible light spectrum and named it "ultraviolet."

The latter half of the 19th century and the early 20th century saw a rapid explosion of discoveries in the field of light, including identifying X-rays, and gamma rays. Important theoretical work by such scientists as James Clerk Maxwell and Albert Einstein helped piece together all of these discoveries and better understand what light is and how it behaves.

Today, light in all its forms is used for countless applications. A vivid example of different types of light being used together is in modern astronomy. While visible light telescopes have been around since Galileo's time in the early 1600's, the last century has seen the development of telescopes in virtually every wavelength known. Telescopes such as NASA's Chandra X-ray Observatory could not be developed until rocket technology advanced far enough because the Earth's atmosphere blocks X-rays from space from reaching our planet's surface. Other types of light, including certain bands of infrared, ultraviolet, and gamma rays, are in the same situation. We are lucky to be in an era where astronomers can combine data from across the electromagnetic spectrum - from both telescopes on the ground and those in space. It's just one of the many ways that light helps us explore and learn about the world we live in and the Universe that surrounds us.

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