WEBVTT - Einstein's Right Again

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<v Speaker 1>Welcome to brain stuff from how stuff Works. Hey, brain stuff,

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<v Speaker 1>it's Christian Sager. Scientists always seem to be finding new

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<v Speaker 1>evidence of Albert Einstein being right. The latest example comes

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<v Speaker 1>from astronomers using the European Southern Observatories very large telescope

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<v Speaker 1>in Chile. Astronomers there have been studying the stars that

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<v Speaker 1>orbit dangerously close to the supermassive black hole in the

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<v Speaker 1>center of our galaxy. To find that you guessed it.

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<v Speaker 1>Einstein's landmark theory of general relativity is holding strong even

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<v Speaker 1>at the doorstep of the most extreme gravitational field in

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<v Speaker 1>our galaxy. Most galaxies are known to have super massive

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<v Speaker 1>black holes lurking in their cores. In our galaxy, the

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<v Speaker 1>Milky Way is no different. Located approximately twenties six thousand

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<v Speaker 1>light years from Earth, our black hole behemoth is called

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<v Speaker 1>Agittarius A, and it has a mass four million times

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<v Speaker 1>that of our Sun. Astrophysicists are hugely interested in black holes,

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<v Speaker 1>as they're the most compact, gravitationally dominant objects known in

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<v Speaker 1>the universe, and therefore an extreme test for relativity. By

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<v Speaker 1>tracking the motion of stars orbiting close to Sagittarius A,

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<v Speaker 1>a team of German and Czech astronomers have analyzed twenty

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<v Speaker 1>years of observations made by the Very Large Telescope and

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<v Speaker 1>other telescopes using a new technique that pinpoints the positions

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<v Speaker 1>of these stars. One of the stars, called S two

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<v Speaker 1>orbits Sagittarius A every sixteen years and zooms very close

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<v Speaker 1>to the black hole, around four times the distance between

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<v Speaker 1>Neptune and our Sun. Because of its racetrack orbit deep

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<v Speaker 1>inside the black holes gravitational well S two is treated

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<v Speaker 1>as a natural relativity probe into this mysterious strong gravity environment.

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<v Speaker 1>By precisely measuring its motion around the black hole, the

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<v Speaker 1>researchers could compare its orbit with predictions laid out by

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<v Speaker 1>classical Newtonian dynamics, and they found that the star's actual

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<v Speaker 1>orbit deviated from Newtonian predictions exactly as predicted by Einstein's

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<v Speaker 1>general relativity, although the effect was slight. Here's a quick

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<v Speaker 1>example of Einsteinian gravity at work. If you have a

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<v Speaker 1>massive object, it will bend spacetime, like the famous example

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<v Speaker 1>of the bowling ball suspended on a rubber sheet. If

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<v Speaker 1>another object travels past the massive object, the curvature of

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<v Speaker 1>space time will deflect its direction of motion like a

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<v Speaker 1>marble rolling past the bowling ball. Now in two thousand

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<v Speaker 1>and eighteen, S two will swoop to its closest point

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<v Speaker 1>in its orbit around Sagittarius A, and astronomers using the

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<v Speaker 1>Very Large Telescope are preparing a new instrument to get

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<v Speaker 1>an even more precise view of the extreme environment surrounding

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<v Speaker 1>the black hole, called gravity and that's gravity in all caps.

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<v Speaker 1>The instrument is installed on the Very Large Telescopes Interferometer,

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<v Speaker 1>and astronomers not only predict that it will get an

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<v Speaker 1>even more precise gauge on Einstein's general relativity, it might

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<v Speaker 1>even detect deviations away from relativity, possibly hinting at new

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<v Speaker 1>physics beyond relativity. Today's episode was written by Ian O'Neill,

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<v Speaker 1>produced by Dylan Fagan, and for more on this and

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<v Speaker 1>other topics, don't forget to visit how Stuff Works dot com.