Thursday, June 27, 2013

Gravity, man.

I've always been very interested in gravity. I studied gravity on my own time in high school, having found a book called "The New Gravitation". While reading that book, I learned about neutron stars and black holes. I learned how to calculate orbital periods.

For your enjoyment, consider the Laser Intereferometer Gravitational Observatory (LIGO). It is designed to detect gravity waves. Because gravity is such a weak force, two very large installations have been built, 2,000 miles apart. The estimated variance to be detected is about 10-^16 of one centimeter, or about 100 millionth the diameter of a hydrogen atom.

Though gravity waves have not been detected directly, measurements of a binary system of neutron stars compare favorably with predictions. What did they measure?

To understand what they measured, lets look at how the the observatory is constructed. Each installation in LIGO consists of two laser beams pointed at separate mirrors, 4 kilometers away. The laser beams are set perpendicular to each other to create an intereferometer. The beams are allowed to cross and are kept in phase with each other.

When a gravity wave passes, the beams may be moved out of phase and the alarm is tripped to indicate a possible detection event. When a detection event is seen, the observatory communicates with other optical and radio observatories for correlation.

I've always loved gravity. It keeps me grounded.
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