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 complements 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.
Scientists at LIGO have just detected gravitational waves for the second time ever!
This is exciting news as it signals that the first detection wasn’t merely a fluke but that we are in fact on the right track to interacting with such phenomena regularly.
What is a gravitational wave? It’s a literal “jiggle” in spacetime caused by a dramatic event like the collision of two large black holes.
This effectively busts wide open a new field of astronomy: gravitational-wave astronomy!
Many space scientists rely on either rovers, spacecraft, optical, radio or even infrared observatories (or some combination) etc. Well now it seems plausible to expect more astronomers to specialize in the interaction between gravitatyand the fabric of spacetime itself.
Considering things like black holes, dark energy and dark matter leave all have considerable gravitational marks and yet hold many secrets back from light, it could stand to reason we now sit on the threshold of a new era in astronomy.
For now though a new door has opened and it’s time to explore
Gravitational waves are ripples through space-time that happen when something like a star collapses or two black holes merge. The discovery of the second one was announced in San Diego by the Laser Interferometer Gravitational Wave Observatory (LIGO) which utilized extraordinary technological measures to find the signal.
Scientists from the Laser Interferometer Gravitational-Wave Observatory (LIGO)
will make a major research announcement onThursday, at 10:30 a.m.
Eastern Time, at a press conference hosted by the National Science
Foundation. Unfortunately, the press conference is for media only, so there will be no live streaming events.* Nevertheless, we’re skeptically excited about tomorrow. If the rumors are true, and gravitational waves have been discovered, it would mean that the most elusive prediction of
Einstein’s theory of relativity is right, gravitational radiation exists,
and that these waves
can be detected. Finding gravitational waves would be a monumental scientific discovery, it would kick-start a new era forgravitational-wave astronomy!
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.
Naming this piece “Gravitational Fields” on the account of #LIGO’s breakthrough physics finding lead by #MIT and #Caltech scientists observing that #gravitationalwaves first predicted by #Einstein, do exist.
This week we learned that a prediction made by the brilliant, staggeringly counter-intuitive theory of general relativity, formulated by Albert Einstein 100 years ago, has been confirmed.
A billion light-years across the universe, two massive black holes spiraled round and round each other, ever closer, ever faster, until they merged in an extremely brief but tremendous explosion of energy. In that fraction of an instant, more power was produced than that of all the stars in the cosmos, sending subtle ripples in the space-time continuum, of which we are a part, in all directions. A billion years later, on September 14, 2015, these disturbances were intercepted by detectors on Earth, marking the first time we have ever witnessed a gravitational wave.
This is the immense triumph of 50 years of scientific inquiry and technological experimentation, and a watershed in the history of human knowledge.
A new window on the cosmos has just opened. We will be peering through it forevermore.
physicists just observed gravitational waves for the first time by examining a 1.3 billion year old collision of two black holes on the other side of the universe and if that’s not the coolest thing you’ve heard today what the fuck are you doing with your life
My PhD is in materials physics for the next generation of
gravitational wave detectors. That’s a fancy way of saying I spend a lot
of time in a lab trying to understand the behaviour of pieces of
sapphire, silicon and silica. One day this will help to inform the
design of a huge machine which will be used to observe wobbles in space.
The sapphire and silica both look like glass, the silicon is shiny and
This is a sapphire disc suspended on two very thin tungsten fibres.
Those space wobbles, or gravitational waves, as my boss prefers me to
call them, are caused by huge, violent events going on out in the
cosmos. Things like colliding black holes and exploding stars. It’s
dramatic stuff. Turns out that’s because you need a whole lot of energy
to make space wobble even a teeny tiny bit.
When there is enough energy to make waves, the waves are really
small. So they’re really hard to detect. Einstein predicted them about
100 years ago and even he thought we’d never be able to find them
because they’d be too small. However, scientists are tenacious. Here’s a
rough timeline (after the fancy picture):
This is an artist’s impression of two neutron stars in orbit around each other. Eventually they will collide and merge into one. The swirls represent the gravitational waves. Image credit: NASA
1916: Albert Einstein publishes a Review Article on General
Relativity, it is suggested that gravitational waves are a result of
general relativity but it’s not clear that they will be directly
1955: Joseph Weber, an American physicist, takes a sabbatical to
work with John Archibald Wheeler. He develops an early design for a
gravitational wave detector that takes the form of a large aluminium
bar. If a gravitational wave passes the bar, it should cause it to ring.
1968: Joseph Weber claims to have “good evidence” of a detection but
others point out that his equipment should not be able to detect waves
so small. The claim remains controversial.
1972: A “Weber bar” is sent to the Moon with Apollo 17.
1974: Hulse and Taylor discover a binary pulsar. A pulsar is a kind
of neutron star which sends out radio waves periodically as it spins.
This one was orbiting a different star. Hulse and Taylor observed it for
a long time.
1983: Hulse and Taylor published a paper saying that the period of
the pulses from their pulsar was changing. That the system must be
losing energy. From their measurements, the only known way for this
energy to be lost was through gravitational waves.
1992: Kip Thorn, Ronald Dreever and Rainer Weiss cofound LIGO: The
Laser Interferometric Gravitational Wave Observatory. This is a new kind
of gravitational wave detector which uses a laser to measure the
position of mirrors 4 kilometers away. The measurements are very
precise. If a gravitational wave passes the detector the mirrors will
move and that movement will be picked up. There are to be three
detectors: One in Livingston, Louisiana and two in Hanford in Richland,
1993: Hulse and Taylor receive the Nobel Prize for Physics for the first indirect detection of gravitational waves.
1993: The Virgo detector, similar to LIGO is founded in Italy, with
collaborators in France, The Netherlands, Poland and Hungary. It gets
final approval in 1994.
1995: Construction of the GEO600 detector begins. This again is
similar to LIGO but has shorter arms. It will become the test bed for
many new technologies
1995: The TAMA project begins in Japan. Like GEO600, this is
another, smaller interferometric detector. Again, it was a test bed used
for developing technologies
2002: The LIGO detectors are built and the search with this kind of
detector begins. It continues until 2010, when they are shut down for
upgrades that will make the detectors even more sensitive.
2003: TAMA stops taking data but is still used as a testing facility.
2003: MiniGRAIL is built. This is a bar-type detector, with one
obvious difference: Instead of being a bar, it’s a sphere. It is
operated at cryogenic temperatures to improve sensitivity.
2003: The construction of the Virgo detector is completed.
2005: A different approach is taken with “pulsar timing.” This is
more like the original indirect detection made by Hulse and Taylor. The
Parkes Pulsar Timing Array begins collecting data.
2006: CLIO, the Cryogenic Laser Interferometry is built in the Kamioka mine in Japan, it will pave the way for KAGRA.
2007: Virgo starts taking data
2008: The Deci-Hertz observatory is proposed. It would be a space based observatory run by Japan.
2009: LIGO India, or IndIGO, is proposed.
2010: The LCGT (Large Scale Cryogenic Gravitational Wave Telescope) is approved in Japan.
2011: Virgo is decommissioned so that upgrades can be made to
improve sensitivity. Advanced Virgo is planned to go online in 2016.
2011: NASA announces that it will be unable to fund LISA due to
funding limitations. ESA now needs to fund it alone which requires
scaling down the mission. The scaled down version is originally called
NGO (the New Gravitational-wave Observatory) but is later renamed eLISA.
2012: LCGT is renamed KAGRA (the Kamioka Gravitational Wave Detector).
2014: BICEP2 reports a detection of gravitational waves which is
later retracted when it is discovered that a different effect has been
2015: The first “Advanced LIGO” observing run begins in September.
Sensitivity is now four times higher than for initial LIGO. On 14th
September a signal is detected.
2015: The LISA Pathfinder mission is launched in December. The
launch is successful but it won’t be until February 2016 that we find
out whether or not everything is working as it should be.
2016: A press conference is held on 11th February (today!)
announcing the first direct detection of gravitational waves. The
detection was made by LIGO.
2016, but 30 seconds later: The whole gravitational waves community celebrates.
Sometimes it takes a full century and literally thousands of
scientists to make something happen. Sometimes science is just hard and
there’s no getting away from that but in the end really amazing things
can be achieved. Not that this is the end, really. This is actually just
Mostly people do astronomy by making observations, or by running
computer models based on those observations and some scientific theories
that they want to test. People don’t often go to space to do
experiments and they certainly don’t do experiments on actual stars and
planets. So astronomy is an observational science. It’s about watching
carefully to see what happens.
The Western leg of LIGO Hanford. A laser beam runs all the way down that
4 km arm and bounces off a suspended fused silica mirror at the far
end, then it runs all the way back. Image from Wikipedia.
Normally people watch with light. That’s just how telescopes work. It
might be a telescope that picks up the same range of light as the human
eye, or it might be a telescope that picks up radio waves, or it might
be a telescope that picks up something else, but it’s all light (except
when it’s neutrinos, but that’s another story altogether). Thing is,
whilst stars make light and planets reflect it so we can see them, not
everything in space glows or shines. Black holes, for example,
definitely don’t. If it doesn’t glow or shine we have to get creative
because ordinarily telescopes won’t pick it up.
However, black holes are heavy, they have mass. That’s true of a lot
of the other stuff in space that doesn’t shine too. Anything with mass
works with gravity and so, in the right circumstances it should produce
some kind of gravitational wave signature. Eventually, the goal is to be
able to observe a wide range of these signatures, to understand them
and to use them to do new astronomy. When we get to that stage we’ll see
things no one has ever seen before, using gravitational waves instead
These are oxidised silicon blocks. This photograph is not in black and white.
So the first detection is significant not only because its been a
long time coming, or because it’s yet another piece of evidence for
Einstein being one smart cookie, but because it leads us that little bit
further along in understanding our Universe.
To read more about this stuff I strongly recommend checking out the
blog posts by other scientists in the collaboration. Notably, the
First detection of gravitational waves
by Sean Leavey, another intrumentalist PhD student at Glasgow who’s
writing on his thoughts and discussion about the event and the
difficulties involved with paper writing and leaks.
Riding the Wave
by Daniel Williams, a relativly new data analysis PhD student at
Glasgow, who talks about his expriences around the event as a new member
of the collaboration.
Einstein was Right! by
Brynley Pearlstone, a Glasgow data analysis PhD student currently based
at LIGO, who’s talking about his experiences and gives a little more in
depth science too.
The Wait is Over
by Matt Pitkin, a Glasgow data analysis research fellow who gives
general information about gravitational waves, this particular signal
and what he was doing at the time.