Gravitational Waves Discovered: A New Window on the Universe

“Ladies and Gentlemen, we have detected gravitational waves. We did it.”

With those words, Dave Reitze, executive director of the U.S.-based Laser Interferometry Gravitational-Wave Observatory (LIGO), has opened a new window into the universe, and ushered in a new era in space science.

Predicted over 100 years ago by Albert Einstein, gravitational waves are ripples in space-time. They travel in waves, like light does, but they aren’t radiation. They are actual perturbations in the fabric of space-time itself. The ones detected by LIGO, after over ten years of “listening”, came from a binary system of black holes over 1.3 billion light years away, called Markarian 231.

The two black holes, each 30 times as massive as the Sun, orbited each other, then spiralled together, ultimately colliding and merging together. The collision sent gravitational waves rippling through space time.

LIGO, which is actually two separate facilities separated by over 3,000 km, is a finely tuned system of lasers and sensors that can detect these tiny ripples in space-time. LIGO is so sensitive that it can detect ripples 10,000 times smaller than a proton, in laser beams 4 kilometres long.

The Laser Interferometer Gravitational-Wave Observatory (LIGO)facility in Livingston, Louisiana. The other facility is located in Hanford, Washington. Image: LIGO
The Laser Interferometer Gravitational-Wave Observatory (LIGO)facility in Livingston, Louisiana. The other facility is located in Hanford, Washington. Image: LIGO

Light is—or has been up until now—the only way to study objects in the universe. This includes everything from the Moon, all the way out to the most distant objects ever observed.  Astronomers and astrophysicists use observatories that can see in not only visible light, but in all other parts of the electromagnetic spectrum, to study objects in the universe. And we’ve learned an awful lot. But things will change with this announcement.

“I think we’re opening a window on the universe,” Dave Reitze said.

Another member of the team that made this discovery, astrophysicist Szabolcs Marka from Columbia University, said, “Until this moment we had our eyes on the sky and we couldn’t hear the music.”

Gravitational waves are a new way to study notoriously difficult things to observe like black holes and neutron stars. Black holes emit no light at all, and their characteristics and properties are inferred from cause and effect relationships with objects near them. But the detection of gravitational waves holds the promise of answering questions about black holes, neutron stars, and even the early days of our universe, including the Big Bang.

It’s almost impossible to overstate the magnitude of this discovery. Once we understand how to better detect and observe gravitational waves, we may come to a whole new understanding of the universe, and we may look back on this day as truly ground-breaking and revolutionary.

And it all started 100 years ago with Albert Einstein’s prediction.

For a better understanding of Gravitational Waves, their sources, and their detection, check out Markus Possel’s excellent series of articles:

Gravitational Waves and How They Distort Space

Gravitational Wave Detectors and How They Work

Sources of Gravitational Waves: The Most Violent Events in the Universe



20 Replies to “Gravitational Waves Discovered: A New Window on the Universe”

  1. “Light is—or has been up until now—the only way to study objects in the universe. ”

    Ummm – neutrinos?

    Still I take your point.

    But how about all that missing mass – transformed into energy and shot out at the speed of light in all directions. If gravity waves essentially take some measure of mass and send it out in waves…. is normal matter (and dark matter for example) evaporating?

    1. Before this discovery there were four sources of information:
      *Probes directly detecting magnetic fields of Sun, Earth, planets, etc.
      *Sampling of physical material. Meteorites, sample returns of Solar wind, asteroid dust, and Moon rocks

      Gravitational waves makes five.

  2. Other non-EM ways we learn of the cosmos… IBEX watch of neutral atoms… and the cosmic ray observances

      1. Sure, but what we observe of them is the cascades they cause in the atmosphere, and those are detected as EM waves.

      2. No – EM is not cosmic rays. Gamma rays yes but not cosmic rays. We detect them by EM phenomena but they are themselves matter.

  3. Does the discovery include a figure for the speed at which these wavs propagate ie is it the speed of light or slower?

  4. How do we know that these gravitational waves are from Markarian 231, as opposed to an event from some other corner of the universe? How ‘directional’ is LIGO?

    1. Definitely not M231, that caption is bonkers (fix it UT!). For one thing, M231 is a binary supermassive BH, way bigger than the 30 solar masses BH that LIGO detected. Also M231 won’t merge for billions of years yet, if at all.

      LIGO is poorly directional atm, 600 square degrees were mentioned and there is an image somewhere that shows the possible area over the sky. Things will get much better when more detectors get online: European VIRGO later this year, then a Japanese machine. It should be possible to locate sources within a few square degrees then, maybe enough for scopes to search for optical counterparts.

  5. I’ve heard this could be a totally new field of science. I propose it should be called “Gravitygraphy”.

  6. My take:
    So, bottom line, we don’t have a clue as to what caused this particular detected event.
    And, even with multiple detectors, we will need optical/radio telescopes to find the ‘likely suspect’.

    @MICH48 – Too many syllables – I’d go with gravigraphy.

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