LIGO made the first detection of gravitational waves

Gravitational waves are detected at LIGO by measuring shifts in interfering lasers

The instruments at each site send lasers down equally long arms, which should take the same amount of time to travel between suspended mirrors. Passing gravitational waves alter the shape of space—lengthening one arm and shrinking the other—altering how long it takes the lasers to complete their path, which scientists can measure.

According to general relativity, gravitational waves are ripples in spacetime

First detected a century after Albert Einstein predicted their existence, gravitational waves transmit information about cosmological events by altering the shape of spacetime. Like ripples in water, these waves travel outward and can be detected on Earth, even for objects that do not emit light, such as black holes.

Listen to the pair of colliding black holes detected by LIGO

As ripples in spacetime, gravitational waves do not produce sound, which is the perception of specific vibrations in matter (e.g., vocal cords vibrating air molecules). The "chirp" of gravitational waves comes instead from converting the spacetime ripples into sound waves that the human ear can hear.

Between 2002 and 2025, upgrades have increased LIGO's detection range tenfold

After the construction of Initial LIGO was completed in 1999, no gravitational waves were detected during operations between 2002 and 2010. Instrument redesigns and significant technological improvements brought about Advanced LIGO, which began observations in 2015. Continued upgrades between continuous laser runs have improved detection sensitivity and stability.

LIGO is part of the advanced gravitational wave detector network

Like the Laser Interferometer Gravitational-wave Observatory, Europe's Virgo Gravitational Wave Interferometer and Japan's Kamioka Gravitational Wave Detector reflect laser beams down perpendicular tunnels to detect gravitational waves in the patterns created by the recombined waves. Future observatories are expected to contribute to this network, further improving gravitational wave detections.

Watch the director's cut of the award-winning documentary about LIGO

Production on the film began in August 2015, shortly before the facilities detected gravitational waves for the first time on September 14. Those interviewed, including future Nobel Laureates Kip Thorne and Barry Barish, provide their accounts of the discovery as events unfold in real time.

In 1974, a pair of neutron stars provided the first evidence of gravitational waves

Observations of a pulsar—a rapidly rotating neutron star that emits light—revealed it to be part of a system of two stars that orbited one another in a shrinking orbit, indicating gradual energy loss. Calculations showed that the changing orbit was consistent with gravitational waves predicted to carry energy away from such a system.

The 2017 Nobel Prize in physics was awarded to LIGO's founders

Rainer Weiss, Kip Thorne, and Barry Barish won the award for their contributions to the detector a year after the discovery of gravitational waves was announced. Acknowledging the Nobel statutes limited the prize to no more than three people, Thorne stated, "our marvelous discovery is the work of more than a thousand."

The first interferometric gravitational wave detector was invented in 1972

Robert Weiss completed the designs after his students asked about an earlier apparatus that used stretched aluminum cylinders to detect passing gravitational waves. Unfamiliar with general relativity and hoping to keep the course focused on experimental tests rather than mathematics, Reiss later asked his students to consider his device for homework. (Some readers may experience a paywall.)

LIGO can detect changes in spacetime one ten-thousandth the width of a proton

Gravity is the weakest of the fundamental forces in nature, meaning the length of objects only changes by minuscule amounts as gravitational waves ripple through space from distant, albeit massive, cosmic events. LIGO's sensitivity can measure an object shifting its position by one seven-hundred-trillionth of the width of a human hair.

Potential LIGO sites were selected in pairs, approximately 3,000 kilometers apart

The 1,864-mile distance meant gravitational wave signals would be detected no more than 10 milliseconds apart, ruling out many background signals. The sites needed sufficient plots of nearly flat land, proximity to infrastructure (e.g., electricity), and adequate distance from urban areas and geologically active areas to reduce environmental noise.

Since 2017, Virgo has helped LIGO localize astronomical phenomena

The detector near Pisa, Italy, coordinates its experimental runs with those in Hanford, Washington, and Livingston, Louisiana. Scientists can triangulate the locations of celestial events that generate gravitational waves using signal arrival times, just as earthquake locations can be determined from measurements at three seismic stations.

When they merge, black holes release multiple solar masses of energy

The energy emanates outward in the form of gravitational waves, which can be detected at observatories like LIGO. After merging, it is impossible to determine the characteristics of the two black holes that merged to create it.

Watch an artist's impression of two neutron stars merging in a kilonova explosion

Such an event produces enough light to briefly outshine an entire galaxy and to produce characteristic gravitational wave and gamma-ray signals. On August 17, 2017, these signals were captured by the LIGO–Virgo and Fermi/INTEGRAL observatories, respectively, from a kilonova about 130 million light-years away.

LIGO boosts its signal sensitivity by manipulating quantum uncertainty

According to the uncertainty principle, the amplitude, or height of a wave's peak, and its phase—the point in time when the first peak is observed—are inversely linked. Based on the frequency of the gravitational waves of interest, scientists sacrifice precision in one optical property to reduce noise in another.

LIGO confirmed Stephen Hawking's theorem about black hole surface areas

Black holes are known to grow with increased mass but lose energy during mergers through the emission of gravitational waves. Amid these competing factors, the black hole area theorem—confirmed in 2021 using LIGO data—states that a merged black hole's size cannot be smaller than the combined surface area of its progenitors.

Gravity travels at the speed of light

Isaac Newton believed that gravity acted instantaneously between objects with mass, whereas Albert Einstein suggested that spacetime curvature reacted at the universal speed limit. Observations of colliding neutron stars by the Laser Interferometer Gravitational-Wave Observatory in 2017 confirmed Einstein's prediction.

One study suggests that dark matter may have originated from a dark Big Bang

A student-faculty team at Colgate University modeled the event as occurring months after the conventional Big Bang and determined the potential gravitational wave signal that would have been left behind. Future gravitational wave detectors are expected to be sensitive enough to observe this signal, if it exists.

The Event Horizon Telescope captured the first photo of a black hole in 2019

Predicted by Einstein in 1916, these invisible objects can be indirectly seen through their accretion discs and X-ray bursts. Over 40 million trillion black holes may be scattered throughout the universe.

Massive objects can significantly bend light to produce gravitational lensing

The theory of general relativity posits that mass and energy bend space and slow down the passage of time. One consequence is that massive objects, such as black holes, curve spacetime to such an extent that light from background sources can loop around them, producing multiple images or ring-like patterns.

Dark matter detected in the cosmic web

Researchers from Yonsei University detected dark matter on the cosmic web, a network of filaments that feed gas into galaxies. The detection was made possible by using the general theory of relativity to analyze gravitational microlensing around the Coma Cluster. This article explains the phenomenon and how the detection supports the presence of dark matter throughout the cosmic web.

The first image of a black hole was captured by creating an Earth-sized virtual observatory from a network of eight radio telescopes.

A 1919 eclipse validated general relativity and made Albert Einstein a celebrity

According to the theory, starlight should deflect around massive objects due to the warping of spacetime light travels through on its way to Earth. Comparing the locations of stars behind the Sun during the eclipse with their positions at night showed deflections that popularized Einstein's model.

The Hubble Space Telescope made discoveries within our solar system and across the universe

The observatory helped confirm the presence of water on Jupiter's moon Europa, and uncovered seasonal variations on planets like Uranus. It also observed exoplanets and gravitational lensing, proved the existence of supermassive black holes at the centers of galaxies, and detected the accelerated expansion of the universe.

View a timeline of particle discoveries through the Higgs boson in 2012

With few exceptions, the elementary particles that make up the Standard Model were theorized or predicted to exist before their eventual discovery in high-energy environments. These predictions were often the result of inferences drawn from already accepted mathematical models.

A Belgian Catholic priest was the first to come up with the idea for the Big Bang

In 1931, Georges Lemaître presented his radical idea that the universe came from a “primeval atom,” challenging the long-held belief that the universe had always existed. Einstein initially dismissed Lemaître’s work as having “abominable” physical insight, only to accept it later.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

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English mathematician Ada Lovelace wrote the first computer algorithm a century before computers existed and hypothesized that computing devices would one day be able to compose music—foreseeing the generative AI systems of today.

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Fish populations in the Great Barrier Reef have increased after installing waterproof speakers on the ocean floor that played recordings of sounds from healthy coral reefs.

Astronauts have repaired genetic damage in space using CRISPR—a molecular tool that can make precise changes to DNA and is used in single-celled organisms to attack invasive viruses.

In 1915, workers recovered a submarine-like vessel from the Chicago River, prompting fears of German espionage

Explore chaos in this simulation of two double pendulums, where small differences in the release angles produce wildly different outcomes.

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

One disco producer saw 'Star Wars' four times on its opening weekend and was so inspired that he recorded the album 'Star Wars and Other Intergalactic Funk,' which produced a chart-topping single.

Fireworks make a loud booming sound after exploding due to air expanding faster than the speed of sound.

In 1939, baseball star Lou Gehrig delivered his inspirational 'Luckiest Man' speech after retiring due to the health condition that now bears his name.

In 1984, Operation Smash Hit intentionally crashed a 239-ton train into a nuclear waste canister at 100 miles per hour to prove the canister's safety, which remained completely intact and lost just 0.29 of its 100 pounds of pressure.

A researcher recently discovered an interview from 1967 between groundbreaking journalist Joan Didion and the Grateful Dead, years before the band became an institution.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

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Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Double world record holder Hunter Ewen helped conquer his fear of balloons, called globophobia, by training to win Guinness World Record titles for balloon inflation.

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