(From left) Albert Michelson, Albert Einstein, Robert A. Millikan on the Caltech campus in Pasadena

Virtual Interferometer Albert Michelson: The pioneer of interferometry Interferometry: A new window on the universe

Interferometry takes advantage of the fact that light behaves like waves on an ocean. We can see our surroundings because our eyes receive waves of different wavelengths or frequencies and translate them into different colors.

In some situations two waves can interact in a surprising, counterintuitive way. If we add up two rays of light, we might get a brighter light; if we add them up slightly differently, we might get darkness. Because the wavelength of visible light is incredibly short compared to everyday objects (more than 1000 wavelengths will fit across a dust speck), visible light provides us with an extremely accurate scale for measuring distances. And as you can measure an angle by measuring the lengths of the side of a triangle, we can also use this scale to measure angles with extreme accuracy.

Interferometry was first used by Albert Michelson in the second half of the last century to measure the velocity at which light itself travels through space. His work laid the foundations for Albert Einstein's Theory of Relativity. Michelson became the first American to be awarded the Nobel Prize in Physics in 1907. Michelson was also the first to apply interferometry to astronomy.

Today we use the interaction of light waves, also called interference, to measure distances and angles precisely. The word interferometry itself illustrates this: interfere + measure = interfer-o-metry (with an extra vowel thrown in for good measure).

We still use Michelson's setup of an interferometer to measure angles of the sky. The capability of modern computer technology and state-of-the art light sensors enables us to combine many of these basic measurements into high-resolution images. In a separate mode we can block out, or null, light from bright sources to study faint objects close to bright stars, such as dust disks which may be forming planets.