In Astronomy's New Messengers, beauty is more than mere spectacle. It is an indication of something extremely profound. If carefully studied, it is a key to unlocking even more bewildering cosmological mysteries and secrets. Visitors' first experience with beauty in Astronomy's New Messengers will be from afar, mimicking our familiar perspective of the universe's distant wonders. A constantly changing, artwork of light is elevated above the exhibit. This art is not merely aesthetic, this dazzling light sculpture suspended overhead represents the universe. On a tabletop, a model interferometer, protected in a vibration-dampening case works as a real one, although responding to disturbances caused by visitors, rather than gravitational waves. What are gravitational waves?
Albert Einstein predicted the existence of gravitational waves in 1916 as part of the theory of general relativity. In Einstein's theory, space and time are aspects of a single measurable reality called space-time. Matter and energy are two expressions of a single physical entity. We can think of space-time as a fabric; the presence of large amounts of mass or energy distorts space-time causing the fabric to "warp." We observe this warping as gravity. Freely falling objects, whether soccer balls, satellites, or beams of starlight, simply follow the most direct path in this curved space-time. When large masses move suddenly, space-time ripples outward, spreading in much the way as ripples on the surface of an agitated pond. When two dense objects such as neutron stars or black holes orbit each other, space-time is stirred by their motion and gravitational energy ripples throughout the universe. In Astronomy's New Messengers, you have the opportunity to manipulate a model space-time fabric, and you can mimic the curvature of space-time by placing the masses on the drum-like membrane.
Another model interferometer uses a split laser beam to project fringe patterns on a screen. A photodiode is used to illustrate the effect of a vibration on the interferometer. By tapping the interferometer kiosk, you can mimic the effect a gravitational wave has on LIGO - it alters the relationship between the two halves of the split beam. In the model, you can see this when the fringe pattern on the screen is disturbed. The photodiode in the model detects this interference and translates a sound to a speaker for you to hear. The model interferometer was designed and constructed by the Ann Arbor Hands On Museum in collaboration with University of Michigan physicists.
Any accelerating mass emits gravitational waves in much the same way as an accelerating charged particle emits electromagnetic radiation.
Even as you move, your movements emit very weak gravitational waves. These gravitational waves are similar to light and radio waves in many respects and carry energy from their sources.
Since gravitational waves are so weak, our most likely sources to detect them are from cataclysmic events in the universe, such as supernovae explosions and collisions of massive objects, like a pair of orbiting black holes merging.
When binary black holes merge, the gravity wave produced vibrates at varying frequencies that depend, among other factors, on the mass of the initial black holes. These frequencies can be converted to sounds that we can hear. When you hear a black hole in the black hole hunter game, you are hearing the representation of a black hole merger in an audible format. You can play the game on-line by visiting The Black Hole Hunter Game. The Black Hole Hunter game was created by physicists at Cardiff University.
LIGO is funded by the National Science Foundation and operated by the California Institute of Technology and Massachusetts Institute of Technology. This material is based upon work supported, in part, by the National Science Foundation under Grant PHY-0852870. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Image Credits: LIGO Lab, Tobin Fricke, NASA, The Hubble Heritage Team, E. Herren, B. Rankins