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Toys Under the Tree: A Desktop Version of LIGO!

Toys Under the Tree: A Desktop Version of LIGO!

- Contributed by Fred Raab

Last month, we began a series of articles on ways to gain a better idea of what LIGO is all about. Taking a tour of a LIGO is cool for people who can get to an observatory in Washington or Louisiana. But even folks unable to travel to the sites can enjoy a basic model of a Michelson interferometer, the working heart of LIGO. With the holiday season upon us, a description of this unique toy is Hanford's contribution to this issue of the newsletter.

Desktop replica of a Michelson interferometer.

The complete kit for building a replica Michelson interferometer, pictured above, costs about $120. This desktop model can readily measure mirror displacements of a few ten-thousandths of a millimeter! If you are a science hobbyist you may want to build one for yourself, or give the parts and instructions to your science-hobbyist friend. And if you grow bored with it, there's no need to let it sit on the shelf. Your local high school science teacher would love to have one for classroom use!

The interferometer uses a laser light source, split into two perpendicular beams that bounce off mirrors and return to the beam splitter. The interference pattern created when the beams recombine on the beam splitter is projected by a lens onto a screen for viewing. This pattern is sensitive to minute changes in the distances between the beam splitter and the mirrors. The complete instructions for the kit can be found here, and it includes internet addresses where you can buy any parts not available at your local hardware store.

The Michelson interferometer is an example of how the ever-advancing frontier of knowledge transforms the Nobel Prize experiment of one era into a commonplace tool or even a demonstration model in future eras. The American physicist Albert Michelson began developing his interferometer roughly 120 years ago, before Edison invented the light bulb. At that time it was a device on the cutting edge of research, developed to investigate the propagation of light through space. In fact, we now recognize Michelson's experimental result in searching for the "luminiferous ether" as fundamental to modern theories connecting space, time and gravitation. He was awarded the Nobel Prize for turning interferometry into a high-precision measuring tool. Interestingly, his null result in the ether search was considered so controversial that the Nobel committee never mentioned it in citing him for the prize. Fast forward to the 20th century, and interferometry was at the heart of precision manufacturing. Now, in the 21st century, interferometry is still at the forefront of precision manufacturing in many industries, still at the forefront of science in research projects like LIGO, and easily available in the form of the desktop model pictured above. You can even buy the laser light source in your local stationary store!