Gravitational waves are disturbances in space-time, the very fabric of the universe, that travel at the speed of light. The waves are emitted by any mass that is changing speed or direction. The simplest example is a binary system, where a pair of stars or compact objects (like black holes) orbit their common center of mass.
We can think of gravitational effects as curvatures in space-time. Earth’s gravity is constant and produces a static curve in space-time. A gravitational wave is a curvature that moves through space-time much like a water wave moves across the surface of a lake. It is generated only when masses are speeding up, slowing down or changing direction.
Did you know Earth also gives off gravitational waves? Earth orbits the sun, which means its direction is always changing, so it does generate gravitational waves, although extremely weak and faint.
What do we learn from these waves?
Observing gravitational waves would be a huge step forward in our understanding of the evolution of the universe, and how large-scale structures, like galaxies and galaxy clusters, are formed.
Gravitational waves can travel across the universe without being impeded by intervening dust and gas. These waves could also provide information about massive objects, such as black holes, that do not themselves emit light and would be undetectable with traditional telescopes.
Just as we need both ground-based and space-based optical telescopes, we need both kinds of gravitational wave observatories to study different wavelengths. Each type compliments the other.
Ground-based: For optical telescopes, Earth’s atmosphere prevents some wavelengths from reaching the ground and distorts the light that does.
Space-based: Telescopes in space have a clear, steady view. That said, telescopes on the ground can be much larger than anything ever launched into space, so they can capture more light from faint objects.
How does this relate to Einstein’s theory of relativity?
The direct detection of gravitational waves is the last major prediction of Einstein’s theory to be proven. Direct detection of these waves will allow scientists to test specific predictions of the theory under conditions that have not been observed to date, such as in very strong gravitational fields.
In everyday language, “theory” means something different than it does to scientists. For scientists, the word refers to a system of ideas that explains observations and experimental results through independent general principles. Isaac Newton’s theory of gravity has limitations we can measure by, say, long-term observations of the motion of the planet Mercury. Einstein’s relativity theory explains these and other measurements. We recognize that Newton’s theory is incomplete when we make sufficiently sensitive measurements. This is likely also true for relativity, and gravitational waves may help us understand where it becomes incomplete.
One hundred years after Albert Einstein predicted the existence of gravitational waves, they have been detected directly.
In a highly anticipated announcement, physicists with LIGO revealed today, on 11 February, that their twin detectors have heard the gravitational ‘ringing’ produced by the collision of two black holes about 1.3 billion light-years from Earth.
This means we now have a new tool for studying the Universe. For example, waves from the Big Bang would tell us a little more about how the universe formed.
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A century after being proposed by physicist Albert Einstein, scientists have made the first detection of gravitational waves – massive celestial objects on the move causing spacetime itself to ripple – a historic discovery that opens up an entirely new way of studying the cosmos.
The detection was made by the twin LIGO interferometers on Sept. 14, 2015, located in Livingston, La., and Hanford, Wash., just two days after the system was significantly upgraded to boost its sensitivity.
Gravitational radiation has been directly detected. The first-ever detection was made by both facilities of the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Washington and Louisiana simultaneously last September. After numerous consistency checks, the resulting 5-sigma discovery was published today. The measured gravitational waves match those expected from two large black holes merging after a death spiral in a distant galaxy, with the resulting new black hole momentarily vibrating in a rapid ringdown.
A phenomenon predicted by Einstein, the historic discovery confirms a cornerstone of humanity’s understanding of gravity and basic physics. It is also the most direct detection of black holes ever. The featured illustration depicts the two merging black holes with the signal strength of the two detectors over 0.3 seconds superimposed across the bottom. Expected future detections by Advanced LIGO and other gravitational wave detectors may not only confirm the spectacular nature of this measurement but hold tremendous promise of giving humanity a new way to see and explore our universe.
Defying Gravity: Behind the Scenes of OK Go’s Spacey New Music Video
To see more of OK Go’s video, check out @okgo on Instagram. For more music stories, head to @music.
The band OK Go (@okgo) was walking through the cosmetics aisle at a local store, trying to decide what liquids look good floating in zero gravity.
“If you squeeze a tube of toothpaste, can you make a wire sculpture with it?” asked lead singer Damian Kulash (@damiankulash). “Or is it just going to come out sideways like you’re used to and just sort of hang there? If you break an egg in the air, does it look like you think it’s going to look?”
They were prepping for their spacey new music video, “Upside Down & Inside Out,” which would be shot during a parabolic flight over Russia. Because when you’ve danced on treadmills, been shot with paint cannons, driven into a series of pianos and led an 8-mile (13-kilometer) musical parade through the streets of Los Angeles, all in the name of art, you have to keep things interesting.
“There is no explicit desire to top ourselves for anyone else’s sake,” said Damian, about the band’s ability to dish out viral video after viral video. “We don’t really mean it to, but things that seemed really ambitious and crazy to us five years ago seem normal to us now. So it’s just a question of keeping ourselves challenged and thrilled.”
For the “Upside Down & Inside Out” video, they certainly had their work cut out for them. During parabolic flights, you experience weightlessness in only 30-second increments, meaning the video would have to be split up as such. And the possibility of the group practicing all of their moves beforehand was difficult since the methods available — underwater training, wires — didn’t specifically mimic the conditions they were going to experience.
Then there was the issue of nausea. Sitting in an airplane that goes up at a 45-degree angle, levels off, then goes back down at a 45-degree angle, all in the span of four minutes, will typically make your stomach want to punch itself. Though the group ended up holding down their lunches, the rest of the crew wasn’t as lucky. Over a series of 21 flights, there were 58 unscheduled episodes of vomiting.
“The two things that can make it a lot worse are spinning a lot — which of course we were doing the whole time — or trying to concentrate on something tiny, like the screen of an MP3 player,” said Damian. “So our poor audio playback guy, he was strapped down to his chair with the playback system in front of him. There were several flights where he puked twice but he never f—ed up. He’s amazing.”
Damian had a one-up on everyone, though, having gone on a parabolic flight around 2011 with his sister Trish (the video’s co-director), for the explicit reason of seeing whether you could shoot a music video in zero-G. Though he began pitching the concept around, the price range was way outside what the band or label could afford. Then last summer, S7 airlines came to the rescue.
“It was in June and they reached out to us and were like, ‘What kind of collaborative video would you want to do?’ And I was like, ‘You have airplanes!’”
Though the airline was surprisingly open to giving the band full creative reign, there was some trepidation in the beginning, particularly from the more buttoned up pilots operating the aircraft.
“While they wound up being super, super helpful and totally into this, there was some skepticism by these cosmonauts — who are real scientists and do real training — whose plane had been hired and saw us throwing super balls and squirting balloons at each other,” said Damian. “They are like, this is bullsh–.”
The band managed to win them over, and after six months of logistical planning, three weeks of flights (in terms of the zero-G experience, the band did two to three times what a normal cosmonaut does for training in the span of a year) and an untold volume of puke, they got exactly what they came for: a final video featuring the entire band and two acrobats doing a choreographed dance, while mini disco balls, piñatas, candy and balloons filled with paint float through the air.
So where in the world does OK Go head after this? Though Damian says they’re not always looking to up the ante with their music videos, even he admits to being a bit stumped.
“Trying to think of what will challenge and thrill us internally as much as something this demonstrably insane is hard,” he said. “Obviously I know to most of the world we are that video band. But we spend a lot of our time writing and performing and recording music, and we spend a lot of our time chasing creative ideas that aren’t these videos, so I am not at all scared that we are going to run out of things that we aren’t creatively excited about.”
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Somewhere very far away, a long time ago, two black holes smashed into each other.
One was around 36 times more massive than the Sun, and the other 29 times more massive.
So devastatingly powerful was this event that it did something that might not even be obvious to most of us: it sent a sort of ‘quake’ through the fabric of spacetime.
The power radiated by the combining of the black holes is estimated to be more than the combined light power of all the stars and galaxies in the observable universe.
This ripple event is something known as a ‘gravitational wave’ and we’ve known about them for a very long time ~ sort of.
Einstein predicted their existence long ago as a consequence of the theory of general relativity, but up until now we’ve never had a direct observation of them.
A team of researchers from an international collaboration known as LIGO (Laser Interferometry Gravitational-Wave Observatory) seems to have been the first to observe.
Using lasers, LIGO found a subtle stretching and squeezing of spacetime itself was going on. How this happened is actually a remarkably simple concept:
First they shot a laser beam into a tunnel, that got split into two directions:
Here’s an ‘L’ shape to help you imagine the two tunnels it split into.
Next, once both lasers reached the end of their respective tunnels, they bounced back towards the spot where they split so that they could recombine.
A way to think about this is both lasers racing towards the lower-left corner of the ‘L’ again.
Here’s the rub:
Light can be thought of as a wave, with ripples and peaks etc. The waveform of these two laser beams, when combined add into each other.
If the two laser beams have the same wavelength (as they should if there’s no gravitational waves disturbing spacetime) the two split beams will recombine again into the original beam. It looks like this:
If the two laser beams get somehow disturbed and the waves peak on one as the other crests, the resulting combined beam will be that they simply cancel out:
So in the end, if the LIGO researchers detect alterations to their laser when the two beams recombine, they can tell if spacetime’s subtle ripples have morphed the lasers.
The consequences of this discovery are profound.
It, in a sense, opens up the universe to an entire new branch of physics: the universe of gravity.
Ever hear of dark matter? How about dark energy?
These two things are bound to get close scrutiny now as they’re both a part of what’s known as the ‘dark universe’ - basically neither phenomena interact with light (meaning one can’t see them), making it tough to learn much about them.
Yet much of the universe seems to be comprised of these ‘unseeable’ things.
If this discovery holds up, there’s almost certainly a Nobel Prize in the works.
Why? They may have - and I do mean maybe, not did - well…
The folks at LIGO may have just illuminated the 96% of the universe that’s been invisible to our senses for so long. We’ll have to wait and see.
(Image credit: NASA, NSF/LIGO and Brews Ohare respectively)