In DepthSpace Physics

LISA Pathfinder tests spacetime sensor

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Science  20 Nov 2015:
Vol. 350, Issue 6263, pp. 894-895
DOI: 10.1126/science.350.6263.894

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Next month, the European Space Agency will launch a space probe with a deceptively modest goal. The Laser Interferometer Space Antenna (LISA) Pathfinder won't observe Earth or search space for quasars or exoplanets. Instead, it will set two cubes of gold-platinum alloy—each slightly larger than a golf ball—floating freely in weightlessness and attempt to measure their distance apart to the nearest trillionth of a meter. The mission is a proof of concept for the roughly €1 billion Evolved LISA (eLISA). To be launched in roughly 20 years if all goes well, eLISA aims to detect the gravitational waves emitted by some of the universe's most titanic processes, such as the death spiral of the supermassive black holes at the heart of galaxies. Physicists on Earth are hunting gravitational waves with laser interferometers—devices with kilometers-long arms that will change length slightly if a wave ripples past, squeezing and stretching space. eLISA will do the same thing, except that its "arms" will consist of three spacecraft orbiting millions of kilometers apart.