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How to Get a Handle on LIGO

How to Get a Handle on LIGO

- Contributed by Fred Raab

OK, so you have read some news about LIGO and you'd really like to know more about the project and its underlying science. Whaddayougonnado? Why not visit one of the sites for a tour? Both LIGO Livingston and LIGO Hanford Observatories offer tours for schools, groups and individuals. Here at the Hanford Observatory, we have had tours for 8th-grade science classes, the bicycle club, various and sundry engineering associations, colleges, business groups, boy scouts, church groups and astronomy clubs. As a matter of fact, about an hour before writing this article I led a tour for the Washington State Science Teachers Association, seen in the photo below.

The WA State Science Teachers Association on tour at LHO.

Above: The Washington State Science Teachers Association is given a tour of the LIGO Hanford Observatory.

By far the most eclectic tour audiences come for the monthly "ad-hoc" tours, held on the second Saturday of every month at 1:30 pm. These are called "ad-hoc" because anyone who shows up gets a tour tailored to whomever shows up. That's all! Month to month, we are never quite sure what will happen, except that someone from LIGO will give a tour. The tours are never the same. Attendance ranges from 6 to 60 people. Anyone old enough to talk can ask whatever they want, so we have wide-ranging discussions of science. There is often quite a mix of backgrounds. People come from Kennewick, Washington; from Portland, Oregon; from Vancouver, British Columbia; even from Logan, Utah. A typical day's "tourists" might include preschoolers, someone from a National Lab, and a retired teacher.

Occasionally we get a few surprises. We have had people come out who worked at B-Reactor during the Manhattan Project. Their stories provide great entertainment for the tour-givers. The Science teachers shown in the photo above brought John Dobson, the pioneer of large aperture telescopes for everyday folks, along on their tour. Guests like that will keep a tour guide on his toes! You never know who you will meet at LIGO.

What do we talk about? Well, first we ask the audience where they have come from and what they would like to know by the time they leave. Then we get down to it. What does a gravitational-wave sound like? We have simulations, sound and waveforms, of inspiralling black holes and neutron stars to show. How do we know gravity waves exist? We discuss the latest data from pulsar measurements, kindly updated by the astronomers in the midst of the action. What is an interferometer? We have a kid-proof, hands-on model that can show an audience how easy it is to see metal bend by 1/3000th of a millimeter. What is gravity? We don't mince words here. We explain General Relativity in familiar terms.

In the photo above I'm using a globe to show the Science teachers how we can learn the geometry of space using simple surveying measurements. We are discussing how the geometry of the two-dimensional surface of earth is different from the geometry of a flat sheet of paper. (Quick: get a globe and trace a trip from Brazil to Africa to the North Pole, and back to Brazil. Then estimate how many degrees you need to turn to complete the trip. Now compare that to a similar trip around a triangle on a flat sheet of paper. The difference tells you how the surface of the earth is curved!) From that we segued into a discussion of how we survey space with our interferometers and eavesdrop for those elusive gravity waves.