Needles in the Haystack
Hearing the Cosmic Symphony
The gravitational-wave detectors now being built and operated are the most exquisitely sensitive instruments ever designed by humans. But because they are so sensitive, they are burdened by measurements — not of astrophysical gravitational waves (Gravitational Wave: A gravitational disturbance that travels through space like a wave. This type of wave is analogous to an Electromagnetic Wave. Gravitational waves are given off by most movements of anything with mass. Usually, however, they are quite difficult to detect. Physicists are currently working hard to directly detect gravitational waves. Experiments like LIGO and LISA are designed for this purpose. ) — but of more mundane noise. Nearby trucks passing on the highway, trains going along railroad tracks many miles away, even waves crashing on the beach
The tremendous racket of the world's most sensitive microphone
Detecting Resonance
A powerful soprano takes an empty wine glass in her hand. She flicks the glass with her finger to hear the ping it makes. After taking a deep breath, she hits a similar note. As she changes her voice's pitch to match the sound of the ping, the glass begins to vibrate more and more intensely. Finally, as she hits precisely the same note, the ear-splitting sound waves cause the glass to vibrate just as it did when struck by her finger. The vibrations grow stronger and stronger as the sound resonates throughout the glass. Finally, the vibrations become so large that the wine glass breaks. It has been destroyed by the phenomenon of sympathetic resonance (Sympathetic Resonance: A phenomenon in which an object with a natural resonant frequency is excited by the vibrations of another object vibrating at the same frequency. For example, a singer breaking a wine glass with her voice demonstrates an extreme sympathetic vibration of the glass, excited by the vibrations of the singer's voice.).
This type of resonance is the basic principle behind the detection of gravitational waves. Scientists develop possible waveforms that could be detected in their instruments. Each of these “template” waveforms is then tested in a computer against the detector data to see if the template rings sympathetically. The louder a template rings, the closer that template is to a signal that is actually in the data.
Find out more about Compact ObjectsRead about Numerical Relativity (Numerical Relativity: The branch of Relativity research which deals with simulating the development of Spacetime (Spacetime: A concept in physics which merges our usual notion of space with our usual notion of time.), using computers. This is believed to be the only possible way to understand things like the merger of two Black Holes.)