"After billions of years of biological evolution - on their planet and ours - an alien civilization cannot be in technological lockstep with us. There have been humans for more than twenty thousand centuries, but we've had radio only for about one century. If alien civilization are behind us, they're likely to be too far behind us to have radio. And if they're ahead of us, they're likely to be far ahead of us."
- Carl Sagan -
SETI
Search for Extraterrestrial Intelligence
Gravitational waves, like EM waves, can be used to transport intelligent signals. Alien civilizations may be advanced enough to have discovered how to generate (and/or modulate) gravitational waves. These waves could be detected using gravitational wave detector technology.
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Gravitational waves would probably be the preferred method of extraterrestrial communication for the following reasons:
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They can be monitored 24 hours a day, 365 days a year, regardless of weather conditions.
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Gravitational waves are more like sound waves, which can be detected (or heard), regardless of detector orientation.
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Gravitational waves are not impeded by interstellar dust.
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Gravitational waves produced by natural sources have a relatively low frequency (< 5 kHz). Intelligent signals are likely to be much higher.
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Only the most advanced civilizations would have the technology to receive gravitational waves.
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Currently, there are no terrestrial sources of gravitational waves that we know of.
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Since the demand for wireless (EM) services is constantly growing, radio interference will become more and more of a problem. Satellites orbiting the earth also cause major interference. For this reason, advanced civilizations will be forced to use gravitational waves as a method of extraterrestrial communication and reserve EM waves for terrestrial communication. I predict that once we develop the technology to transmit and receive gravitational waves, we will also use it for interplanetary communication.
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Since the Einstein@Home project is based on SETI@Home software, SETI scientists can also analyze the output of gravitational wave detectors for intelligent signals. A Time Variance detector would be the most suitable for SETI since it is designed to detect high frequency gravitational waves.
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Detection of intelligent signals may be achieved by implementing the following:
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Design and build a Time Variance gravitational wave detector.
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Send the data output of the gravitational wave detector to the SETI team.
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SETI processes this data and converts it to a format that is compatible with the SETI@Home desktop application.
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Modify the SETI@Home application to analyze gravitational waves for intelligent signals.
I had the pleasure of presenting a poster at the AbSciCon 2008 conference at the Santa Clara Convention Center; Session 19 - Future SETI: Technologies, Techniques, and Strategies. The poster gives a more detailed view of my idea: Searching gravitational waves for intelligent messages.