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Milestones After Einstein's General Theory of Relativity

One hundred years after Albert Einstein predicted the existence of gravitational waves, scientists have finally detected the first, a burst of ripples in spacetime born of the catastrophic merger many of two black holes. The beginning and end are bookends to many important milestones over the last century.

1915: Albert Einstein lays out his general theory of relativity, revolutionizing the way we understand gravity and establishing the rules for spacetime.

1916: Einstein predicts the existence of gravitational waves, while adding that he doubts anyone will ever be able to detect their astonishingly small physical effects.

1922: Sir Arthur Stanley Eddington, a renowned English astronomer and physicist, celebrated for his work related to the theory of relativity, expresses skepticism for the supposed ripples in spacetime by famously stating, “Gravitational waves move at the speed of thought." The notion of gravitational waves would continue to confound and confuse physicists for decades.

1957: At a conference in Chapel Hill, North Carolina, Felix Pirani, a young postdoc explains for the first time how scientists might one day detect gravitational waves.

1960s: The search for gravitational waves begins in earnest, and Joseph Weber builds the first "resonant bar detectors."

1971: Robert Forward builds the first interferometer for gravitational wave detection at Hughes Aircraft. It is a tabletop experiment.

1972: Rainer Weiss publishes the first serious analysis of the experimental challenges of gravitational wave detection with interferometers. This report is the genesis of the Laser Interferometer Gravitational-Wave Observatory, a large-scale

1999: Construction of LIGO’s original gravitational wave detectors is completed.

2002: LIGO conducts its first search for gravitational waves. 

2010: Upgrades to Advanced LIGO -- the “next step" in gravitational wave astronomy -- begin. The initial LIGO instrument was only sensitive to the nearby Universe, where gravitational wave events are rare. After no detections were made during the first searches, LIGO is redesigned to see 10 times farther out into the Universe.

2015: In September, 2015, LIGO begins a much deeper search for gravitational waves.

Sept. 14, 2015: A century after Einstein’s revolutionary General Theory of Relativity, the LIGO collaboration makes the first detection of a gravitational wave.

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