Introduction | Mission Description | All About Gravitational Waves | Mission Benefits
Gravitational waves offer a new way to observe the Universe. Through them we will learn more about the mergers of giant black holes and the death spirals of stars that black holes capture and swallow. The Laser Interferometer Space Antenna (LISA) will look for gravitational waves coming from our Galaxy and other galaxies. LISA will also map the structure of space and time around black holes and determine if Einstein's theories are correct. But, what are gravitational waves, how do we know that they exist, where can we find them, and why should we study them?
What are Gravitational Waves?
Gravitational waves in some ways resemble optical (visible light) waves. Both are traveling waves, spreading outward from their sources——like waves on an ocean. They both tell us something about the matter that generated them. For example, light carries information about the structure of the matter that generated it——what it is made of or its temperature. Gravitational waves tell us something different about the matter that generated them. They tell us about the its mass and motion.
Gravitational waves, generated by the motion of massive bodies, are a varying strain or distortion of space-time. This means that there are changes in the distance between points of space-time, and the size of the change is proportional to the distance between the points. This is much like changes in the distance between points of a vibrating rubber sheet, one illustration of space-time. On this rubbery sheet, stars, planets, and galaxies ride. So, when a celestial object embedded in this sheet moves, the movement generates ripples of strain and distortion that spreads. This spreading is caused in the same way someone bouncing on a trampoline causes the canvas to jiggle.
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Artist's concept of the distortions of space-time, known as gravitational waves. Courtesy of Jet Propulsion Laboratory.
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Waves of different frequencies are caused by different motions of mass. Differences in the phases of the waves (the timing of when the wave crests pass) allow us to figure out the direction of the source and the motions, or dynamics, of the matter that generated them. Even though they may have been generated billions of years ago, and their weak signals make them hard to detect, they will be able to tell us about their sources. This is because they travel across space essentially unaffected by intervening matter such as planets, stars, gases, or dust in space.
On to About Graviational Waves II
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