This is an artistic rendering of spacetime being warped by the mass of a galaxy.
CORBIS
On Thursday (Feb. 11) at 10:30 a.m. ET, the National Science Foundation will gather scientists from Caltech, MIT and the LIGO Scientific Collaboration in Washington D.C. to update the scientific community on the efforts being made by the Laser Interferometer Gravitational-wave Observatory (LIGO) to detect gravitational waves.
In the wake of some very specific rumors focused on the possible discovery of these elusive ripples in spacetime, hopes are high that the international LIGO collaboration of scientists will finally put an end to the fevered speculation and announce the discovery of gravitational waves.
But why is this exciting? And what the heck are "gravitational waves"?
Gravitational waves, in their most basic sense, are ripples in spacetime. Theorized by Albert Einstein just over 100 years ago, these ripples carry gravitational energy away from accelerating massive objects in the cosmos. We can imagine gravitational waves as ripples across the surface of a pond; drop a pebble into the water and ripples travel across the surface away from the rock. Gravitational waves are similar; should two black holes collide (for example), "ripples" in spacetime will carry energy away from the impact site at the speed of light. There are indirect observations of the existence of gravitational waves, but detecting them directly has been an all but impossible task... until now.
This artistic rendering shows the possible generation of gravitational waves during a galactic merger.
CORBIS
What Produces Them?
This is an artistic rendering of spacetime being warped by the mass of a galaxy.
CORBIS
On Thursday (Feb. 11) at 10:30 a.m. ET, the National Science Foundation will gather scientists from Caltech, MIT and the LIGO Scientific Collaboration in Washington D.C. to update the scientific community on the efforts being made by the Laser Interferometer Gravitational-wave Observatory (LIGO) to detect gravitational waves.
In the wake of some very specific rumors focused on the possible discovery of these elusive ripples in spacetime, hopes are high that the international LIGO collaboration of scientists will finally put an end to the fevered speculation and announce the discovery of gravitational waves.
But why is this exciting? And what the heck are "gravitational waves"?
Gravitational waves, in their most basic sense, are ripples in spacetime. Theorized by Albert Einstein just over 100 years ago, these ripples carry gravitational energy away from accelerating massive objects in the cosmos. We can imagine gravitational waves as ripples across the surface of a pond; drop a pebble into the water and ripples travel across the surface away from the rock. Gravitational waves are similar; should two black holes collide (for example), "ripples" in spacetime will carry energy away from the impact site at the speed of light. There are indirect observations of the existence of gravitational waves, but detecting them directly has been an all but impossible task... until now.
This artistic rendering shows the possible generation of gravitational waves during a galactic merger.
CORBIS
To find out which astrophysical phenomena produce gravitational waves, click "next" at the top of this page.
This artist's rendering shows two closely-orbiting white dwarf stars generating a spiral of gravitational waves.
NASA
Any massive cosmic object that experiences some kind of acceleration will generate gravitational waves.
Black holes are the most massive and dense objects known to exist in the universe and are likely hotbeds of gravitational wave activity, especially if they collide and merge. Merging black holes are thought to be the key growth mechanism behind these gravitational behemoths -- when two galaxies merge, their central supermassive black holes will begin orbiting one another, eventually spiraling in and then colliding to form an even bigger black hole. In this scenario, gravitational waves will be emitted from the spiraling black holes long before they collide, but as the objects draw closer, gravitational wave energy will increase, sapping more and more orbital energy from the pair until they collide, ringing like a "bell" after they merge.
This computer simulation shows a mathematical rendering of the production of gravitational waves during a black hole merger.
MPI FOR GRAVITATIONAL PHYSICS/W.BENGER-ZIB
Another energetic phenomenon that would generate a rapid eruption of gravitational waves are supernovas. After a massive star runs out of hydrogen fuel it implodes, succumbing to massive gravitational pressure. The resulting explosion will fire a pulse of gravitational waves that will wash through spacetime.
Gravitational waves will also be generated by rapidly spinning objects, but there's a catch. Only massive spinning objects that are asymmetric (i.e. not symmetrical) will produce gravitational waves in a periodic pattern. For example, a rapidly spinning neutron star with a clump of material bulging from one hemisphere will "stir up" spacetime to generate gravitational waves. A perfectly symmetrical neutron star, however, will not generate gravitational waves. The easiest way to visualize this is to imagine spinning an oval-shaped football on the surface of a swimming pool; as the football spins, it will create ripples across the water. A spherical spinning soccer ball, on the other hand, will create very few ripples on the surface.
The Big Bang is also theorized to have generated a powerful hum of gravitational waves when the universe began, nearly 14 billion years ago. However, these primordial gravitational waves are unlikely to be directly detected as their signal is too weak in the modern universe. But efforts are under way to detect their presence in the "background glow" of the Big Bang. Projects like the BICEP2 telescope at the South Pole are looking for a very specific type of polarization in the cosmic microwave background (CMB) that is thought to be caused by primordial gravitational waves. Despite recent announcements to the contrary, this signal has yet to be detected.
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