Bee and Stefan of Backreaction have gone to visit the historical location of the beginnings of how we use interferometers.
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The Cosmos sings with many strong gravitational voices, causing ripples in the fabric of space and time that carry the message of tremendous astronomical events: the rapid dances of closely orbiting stellar remnants, the mergers of massive black holes millions of times heavier than the Sun, the aftermath of the Big Bang. These ripples are the gravitational waves predicted by Albert Einstein's 1915 general relativity; nearly one century later, it is now possible to detect them. Gravitational waves will give us an entirely new way to observe and understand the Universe, enhancing and complementing the insights of conventional astronomy.
LISA, the Laser Interferometer Space Antenna, is a joint NASA–ESA mission to observe astrophysical and cosmological sources of gravitational waves of low frequencies (0.03 mHz to 0.1 Hz, corresponding to oscillation periods of about 10 hours to 10 seconds). This frequency band contains the emission from massive black-hole binaries that form after galactic mergers; the song of compact stellar remnants as they slowly spiral to their final fate in the black holes at the centers of galaxies; the chorus of millions of compact binariesshortly after the Big Bang.
LISA consists of three identical spacecraft flying in a triangular constellation, with equal arms of 5 million kilometers each. As gravitational waves from distant sources reach LISA, they warp space-time, stretching and compressing the triangle. Thus, by precisely monitoring the separation between the spacecraft, we can measure the waves; and by studying the shape and timing of the waves we can learn about the nature and evolution of the systems that emitted them.
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