Through the Spectrum

1666

Sir Isaac Newton discovers that the sun’s white light could be dispersed into a continuous series of colors using an instrument he invented — now called the spectroscope — essentially beginning the science of spectroscopy.

In the early 1800s, German physicist Joseph von Fraunhofer found that when sufficiently dispersed, the sun’s spectrum is crossed by many fine, dark lines; these are now known as Fraunhofer lines. He later developed diffraction grating and the spectrometer.

Joseph von Fraunhofer. Photo courtesy of The Fraunhofer Society.

1860

A paper by physicist Gustav Kirchhoff and chemist Robert Bunsen is published in the journal Annalen der Physik, detailing their examination of the spectra of chemical compounds. Their findings established spectroscopy (while not yet fully defined) as a new scientific tool for probing atomic and molecular structures.

Using a spectroscope with photography, Swedish physicist Anders Jonas Ångström (in his study of the solar system) discovered that the sun’s atmosphere contains hydrogen. The angstrom unit of length that is equal to 10−10 meter is also named for him.

1882

Sir Arthur Schuster, a British physicist, is the first to use the term “spectroscopy,” during a lecture at the Royal Institution of Great Britain.

Williamina Paton Stevens Fleming was the first female astronomer at the Harvard College Observatory. Under its director, astrophysicist Edward C. Pickering, she developed a new system for the classification of stellar spectra. With it, she classified 10,000+ stars based on their photographed spectra.

The first maser (microwave amplification by stimulated emission of radiation) instrument was conceived by Charles Hard Townes, as he sat on a park bench in Washington, D.C. It was first demonstrated at Columbia University in 1954, showing its ability to operate in the optical and infrared regions.

Charles Hard Townes (left) and James P. Gordon (right). Photo courtesy of Smithsonian Institution.

1960

Charles Hard Townes and Bell Labs researcher Arthur L. Schawlow are granted a U.S. patent for the optical maser, now called laser (light amplification using stimulated emission of radiation).