# What is an Angstrom?

scientist with beakers

If you thought the nanometer was small, you didn’t find the angstrom, but that’s probably because it preceded the nanometer. Named after the Swedish spectroscopist and physicist Anders Angstrom (1814-1874), the angstrom is a legacy unit of measurement that equals one ten billionth of a meter, or 1/10,000,000,000 of 3.28 feet. Put another way, it would take 245 million angstroms to equal an inch, 10 million angstroms to equal a millimeter, or 10,000 angstroms to equal a micron. And now you’ve guessed that with a nanometer being one billionth of a meter, it takes 10 angstroms to equal one nanometer.

In 1868, Anders Angstrom was studying solar radiation and compiled a graph of electromagnetic energy that measures light waves in increments of a ten-millionth of a millimeter. It was this unit of measurement that became known as the angstrom. Although the angstrom was replaced by the nanometer as the unit of choice, it was traditionally used to measure very small objects such as atoms and chemical bonds, in addition to light waves and the visible light spectrum.

For humans, visible light includes wavelengths between rich violet and deep red. Violet light, for example, measures in the range of 4000 angstroms, while dark red is closer to 7000 angstroms. Wavelengths at 5500 angstroms (exactly between the two extremes) would be yellow light, in the center of the visible light spectrum. Today, however, the visible light spectrum is most often expressed as ranging from 400 to 700 nanometers (nm).

To offer some real-world examples of the angstrom, a very fine human hair of just 50 microns would be 500,000 angstroms thick. A sheet of paper is about a million angstroms thick, and a credit card is a whopping 8 million angstroms thick.