In Einstein’s theory of general relativity, gravity is not a force as it was in Newton’s description. In Newton’s view, gravity was due to the attraction of two masses according to the size of the masses and the distance between them.

Although elegant, Newton’s description fell short in explaining certain phenomena, such as how the gravitational force propagated through empty space, and the precession of Mercury’s orbit.

Einstein’s view was that gravity resulted from the warping of space-time by matter: Matter tells space-time how to warp and warped space-time tells matter how to move.

In 1785 Charles-Augustin de Coulomb formulated the law of electricity that bears his name, which has the same mathematical form as Newton’s gravitational relationship. This was the beginning of the quantitative study of electricity that eventually led to the connection between electricity and magnetism, which is a topic for another column.

Seeing an analogy to Maxwell’s equations, which described how electric charges interact with an electromagnetic field, Henri Poincare in 1905 proposed the existence of gravitational waves. This was 10 years before Einstein theorized how a disturbance in the gravitational field would propagate outward in the form of gravitational waves.

The inability to detect gravitational waves for 100 years after Einstein first proposed them is because gravity is a much weaker phenomenon than the other three forces of nature (electromagnetic, strong and weak nuclear).

Debates abounded about the existence of gravitational waves throughout the first half of the 20th century, focusing on whether such waves could carry energy. Richard Feynman settled that debate with a simple and elegant thought experiment in 1956.

Soon thereafter Joseph Weber started designing and building the first gravitational wave detectors that used an antenna made of room-size aluminum cylinders that would be set in motion by gravitational waves.

Weber claimed to have collected what he considered good evidence on several occasions, but other researchers could not verify his claims. His results were largely discredited, and dampened the enthusiasm for the detecting the elusive waves.

In 1974, observations of a binary pulsar indirectly confirmed the existence of gravitational waves by measuring orbital decay that matched Einstein’s predictions of energy loss by gravitational radiation, and won the 1993 Nobel Prize in physics. A similar discovery in 1979 revitalized interest that had been brewing among a select group of physicists led by Kip Thorne, who also designed the black hole graphics for the 2014 movie “Interstellar.” Thorne had been pursuing theoretical studies on gravitational waves since 1968, and was the logical choice to lead the conception, design and construction of the Laser Interferometer Gravitational-Wave Observatory, or LIGO.

The first suggested use of interferometry came in 1960 by two Russian physicists, but the laser technology did not exist at the time. A steering committee led by Thorne convened in 1984 after the National Science Foundation asked the Massachusetts Institute of Technology and Caltech to join forces to lead a LIGO project.

Construction began in 1994 and the first LIGO came online in 2002, but the sensitivity was too low and it detected no waves. A series of upgrades led to dual LIGO setups in Hanover, Wash., and Livingston, La. These devices are sensitive enough to detect movement as small as one-thousandth the size of a proton, or about one-millionth the size of an atom.

In February 2016, the LIGO sites recorded matching signals that offset in time by exactly the amount that it would take light to travel the distance between them. In June 2016, they recorded another one, followed by a third in June 2017.

Researchers are confident that gravitational wave astronomy will be as significant to opening up the secrets of the universe as was Galileo’s 1610 observation of the moon through a telescope.

Richard Brill is a professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.