Why Use Spectrum Colors in Our 13.8-Billion-Year Timeline?

"The spectrum is the key that unlocked the universe for us."

—astrophysicist Jonathan McDowell, Harvard-Smithsonian Center for Astrophysics, in a conversation with The Naturalist's Notebook's Pamelia Markwood and Craig Neff about how scientists use the spectrum in their research. (Jonathan uses the spectrum all the time. He looks deep into space with NASA's Chandra X-Ray Observatory, a telescope that orbits 86,500 miles above Earth and "sees" the X-rays given off by hot regions of the universe, such as exploded stars and clusters of galaxies. X-rays are part of the electromagnetic spectrum, which also includes all the colors we see.)   

We wanted to make our 13.8-billion-year timeline fun and helpful. We decided to color-code each era on it.