What creates gravitational waves?
What creates
gravitational waves?
In 1916, German physicist Albert Einstein (1879-1955) revolutionized our understanding of the universe when he published his general theory of relativity. In it, he described the
relationship between the fabric of spacetime and the mass of celestial bodies. Space-time is the combination of three spa- cial directions (height, width, and depth) with the time dimension.
The easiest way to interpret gravitational interactions, Einstein said, is to think of the space-time continuum as a stretchable material that bends as massive objects "sit" inside it. While this two-dimensional analGRAVITATIONAL-
WAVE DETECTOR.The Laser Interferometer Space Antenna (LISA), planned for launch in 2015, will detect low-frequency gravitational waves. It will thus open a new window on the universe.
ogy does not represent what is happening in fourdimensional space, it serves as a capable model.
When you stretch a pliable plastic sheet tautly, and you place a softball on it, the gravity well around the ball pushes the sheet
downward and curves the fabric. The same thing happens in the four-dimensional universe. Near actual massive objects that have large gravitational pulls, the "fabric" of space-time curves and stretches.
Massive objects also cause another effect in the fabric of space-time. Just as a boat creates waves on a lake as it slices forward through the water, stars and other bodies in the universe create ripples in the fabric of space-time. Astronomers call these ripples gravitational waves.
Massive objects like black holes create larger gravitational waves than less massive objects. Likewise, objects moving rapidly through space create more sustained gravitational waves than slower moving ones.
Although scientists have theorized gravitational waves for the better part of a century, studying them is really in its infancy. Astronomers know the interaction of two compact and massive bodies usually produces gravitational waves. Interactions may be merging galaxies, binary black holes, or neutron stars, or normal stars simply encountering each other.
These interactions produce "ripples" in space-time. When this gravitational radiation finally reaches Earth, however, it is weak. Like waves in water, gravitational waves weaken as they move outward from their origin. So gravitational waves prove difficult to detect and interpret once they reach us from a variety of distant locations.
To help detect faint signals, astronomers turn to interferometry. Two large test masses placed a great distance apart serve as detectors. The masses are free to move in
CENTRAL ENGINE. Black holes are important creators of gravitational waves. This artwork shows the central, supermassive one that powers the active galaxy PKS 0521-36.
WAVY BANG. Supernova explosions, like the one that produced the Crab Nebula (M1) in the constellation Taurus in 1054, are significant producers of gravitational waves, nasa/the
HUBBLE HERITAGETEAM
all directions, and lasers continuously measure the exact distance between them. When a gravitational wave passes through them, the ripple in space-time
causes their distance to fluctuate slightly. It's an ingenious technique, and devices to measure gravitational waves are under construction in several places around the world.
Engineers are building the Laser interferometer Gravitational Wave Observatory (LIGO), a joint project between the Massachusetts Institute ofTechnology and Caltech, in Hanford, Washington, and Livingston, Louisiana. In Italy and France,
gravitational waves?
In 1916, German physicist Albert Einstein (1879-1955) revolutionized our understanding of the universe when he published his general theory of relativity. In it, he described the
relationship between the fabric of spacetime and the mass of celestial bodies. Space-time is the combination of three spa- cial directions (height, width, and depth) with the time dimension.
The easiest way to interpret gravitational interactions, Einstein said, is to think of the space-time continuum as a stretchable material that bends as massive objects "sit" inside it. While this two-dimensional analGRAVITATIONAL-
WAVE DETECTOR.The Laser Interferometer Space Antenna (LISA), planned for launch in 2015, will detect low-frequency gravitational waves. It will thus open a new window on the universe.
ogy does not represent what is happening in fourdimensional space, it serves as a capable model.
When you stretch a pliable plastic sheet tautly, and you place a softball on it, the gravity well around the ball pushes the sheet
downward and curves the fabric. The same thing happens in the four-dimensional universe. Near actual massive objects that have large gravitational pulls, the "fabric" of space-time curves and stretches.
Massive objects also cause another effect in the fabric of space-time. Just as a boat creates waves on a lake as it slices forward through the water, stars and other bodies in the universe create ripples in the fabric of space-time. Astronomers call these ripples gravitational waves.
Massive objects like black holes create larger gravitational waves than less massive objects. Likewise, objects moving rapidly through space create more sustained gravitational waves than slower moving ones.
Although scientists have theorized gravitational waves for the better part of a century, studying them is really in its infancy. Astronomers know the interaction of two compact and massive bodies usually produces gravitational waves. Interactions may be merging galaxies, binary black holes, or neutron stars, or normal stars simply encountering each other.
These interactions produce "ripples" in space-time. When this gravitational radiation finally reaches Earth, however, it is weak. Like waves in water, gravitational waves weaken as they move outward from their origin. So gravitational waves prove difficult to detect and interpret once they reach us from a variety of distant locations.
To help detect faint signals, astronomers turn to interferometry. Two large test masses placed a great distance apart serve as detectors. The masses are free to move in
CENTRAL ENGINE. Black holes are important creators of gravitational waves. This artwork shows the central, supermassive one that powers the active galaxy PKS 0521-36.
WAVY BANG. Supernova explosions, like the one that produced the Crab Nebula (M1) in the constellation Taurus in 1054, are significant producers of gravitational waves, nasa/the
HUBBLE HERITAGETEAM
all directions, and lasers continuously measure the exact distance between them. When a gravitational wave passes through them, the ripple in space-time
causes their distance to fluctuate slightly. It's an ingenious technique, and devices to measure gravitational waves are under construction in several places around the world.
Engineers are building the Laser interferometer Gravitational Wave Observatory (LIGO), a joint project between the Massachusetts Institute ofTechnology and Caltech, in Hanford, Washington, and Livingston, Louisiana. In Italy and France,
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