May 15th 2017

Making Waves: LIGO Celebrates an Anniversary of Proving Einstein’s Theory


On February 11, 2016, the Laser Interferometer Gravitational-Wave Observatory — LIGO — announced the detection of gravitational waves for the first time. It ended a 50-year search for direct confirmation of the elusive gravitational waves, first predicted by Albert Einstein.

Western leg of LIGO on Hanford Reservation as seen from east. (Wikimedia Commons)

The observatory is sometimes described as two observatories, because its key instrument, a laser interferometer, has two sections. One is located in Livingstone, Louisiana, the other in Hanford, Washington. Working together, they form a single precision instrument a couple of thousand miles across.

If success in detecting gravitational waves marked the end of one era, it signaled the beginning of another: the exploration of the universe using new instruments of fantastic, nearly unimaginable precision, of which LIGO is only a beginning.

Elusive Gravity

Sir Isaac Newton identified gravity as a basic property of nature and described its characteristics, but he did not explain how it worked. Albert Einstein proposed in 1916 that gravity was not a mysterious “force” but rather a bending of space itself in the presence of a heavy mass. He also showed that the massive accelerating objects — such as orbiting black holes — would distort the fabric of space, sending gravitational waves outwards in all directions like ripples expanding on a pond.

Gravitation (curvature of spacetime) and gyrogravity (analogue of EM field) according to Einstein’s theory. (Wikimedia Commons)

Strong indirect evidence supported Einstein’s theory of gravity, but actually detecting gravitational waves was difficult — so difficult that while active efforts to detect them began in the 1960s, no one succeeded until LIGO did a year ago.

The LIGO instrument consists essentially of two vacuum pipes, each two and a half miles long, containing lasers that can measure each pipe’s length with extreme precision. Extreme as in measuring a change equal to 1/5000 the size of a proton. Neil DeGrasse Tyson describes this as “the most precise measurement ever made, by far.”

This unfathomable precision allowed researchers to detect the subtle jostling of the pipes by a powerful gravitational disturbance: the collision of two black holes, each many times more massive than the Sun, in a distant galaxy.

David Yeaton-Massey, an experimental physicist doing basic research at Northrop Grumman, had the opportunity to work on LIGO while completing his PhD at Caltech.

“Being part of a team dedicated to listening to what the universe is whispering to us was a once-in-a-lifetime experience. The concept is relatively simple, much like electromagnetic radiation is produced when you shake an electron, gravitational radiation (a little ripple in spacetime) is produced when you shake matter. Despite the simplicity the analogy offers, it took a pair of massive, distant black holes colliding close enough to earth (140 billion light years) for us to see the event. The scale and scope of what the LIGO community accomplished cannot be underestimated.”

A Quiet Place in the Sky

While scientists were already confident that Einstein was right, LIGO’s success opens the way to a new branch of astronomy, exploring the universe by measuring gravitational waves and mapping their patterns.

This will require even more precision than LIGO achieved, and by far the best place to make such measurements is in outer space. A space mission called LISA Pathfinder has already been launched — not to detect gravitational waves itself but to test the technology needed for a future mission.

A deep space gravitational wave observatory remains years down the road, but 2018 should see the launch of NASA’s James Webb Space Telescope (JWST). A successor to the famed Hubble Space Telescope, it will take precision astronomy in space to a new level. Unlike Hubble, the JWST will primarily observe the universe in infrared light, blocked from ground-based observatories by Earth’s atmosphere.

James Webb Space Telescope face-on (NASA/Goddard/Rebecca Roth)

And instead of orbiting a few hundred miles above Earth, JWST, for which Northrop Grumman is the main industrial partner, will float in space in a position about a million miles from Earth (technically, in the second Sun–Earth Lagrange point). The distant location will help shield the JWST from Earth’s own heat radiation, which otherwise would wreak havoc on infrared sensors that must operate at very low temperature.

The JWST will not observe gravitational waves, but its infrared telescope will be able to look farther into deep space — and further back into the early history of the universe — than any existing telescope. The science is astounding: JWST will help us see the first stars and galaxies, better understand how galaxies form over billions of years and, finally, help identify earth-like planets that potentally support life. Whether earth-based or space-based, a new era of amazingly engineered machines will unlock mysteries that we can only guess at today.

Learn more about how you can play an active role in Northrop Grumman-affiliated projects such as the James Webb Space Telescope.

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