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everyone is only set to receive signals and no one is beaming, would SETI External Link: Visit the website of the SETI Institute, dedicated to the scientific search for extraterrestrial intelligence. be doomed to fail? Not necessarily. Even as we speak, our daily weather reports and reruns of I Love Lucy are streaming into space at the speed of light. Our radio and television signals fill a growing bubble of our galaxy, now extending more than 50 light-years from Earth External Link: Learn more about Earth from an astronomical perspective.--far enough to encompass hundreds of other stars. Although these broadcasts are much weaker than an intentionally beamed message would be, they might register in sensitive telescopes on the planet Grok, and vice versa.

Our species has taken some baby steps to communicate with our possible neighbors. In 1974 Drake and his colleagues used the giant Arecibo radio telescope External Link: Arecibo Observatory, the world's largest radio dish! in Puerto Rico to beam a three-minute message toward a cluster of stars. The message, encoded as a binary sequence, contained basic information about our planet, our solar system, and the biology of humans. Four of our planetary explorers--Pioneer 10 External Link: The NASA homepage of the Pioneer missions -- learn about them and their discoveries., Pioneer 11 External Link: The NASA homepage of the Pioneer missions -- learn about them and their discoveries., Voyager 1 External Link: The NASA homepage of the Voyager missions -- learn about them and their discoveries., and Voyager 2 External Link: The NASA homepage of the Voyager missions -- learn about them and their discoveries.--carry greetings as well. Each Pioneer has an engraved plaque about us, while each Voyager features a gold-plated phonograph record with sounds and audio-encoded images from Earth External Link: Learn more about Earth from an astronomical perspective.. But these efforts are symbolic, not practical. For instance, the Arecibo signal will reach its target in 24,000 years. Even if a civilization there sent a reply, we wouldn't get it until the year 50,000.

Another approach to SETI External Link: Visit the website of the SETI Institute, dedicated to the scientific search for extraterrestrial intelligence. relies not on radio waves but on visible and infrared light Internal Link:  . Think of spotting the light from a handheld laser pointer across a football stadium. Even with all the light entering your eyes from the stadium lights, the playing field, and other sources, you'd probably notice the laser pointer right away. All its energy is concentrated into the familiar red laser color, and its beam remains intense as it crosses the field. In a similar way, powerful single-color lasers Internal Link:   directed into space by a large telescope would be visible across great stretches of the galaxy. Brief but energetic pulses of laser light could outshine the parent star within that part of the color spectrum. Some SETI External Link: Visit the website of the SETI Institute, dedicated to the scientific search for extraterrestrial intelligence. researchers have adapted their equipment to watch for such pulses.

It's fascinating to ponder the possible outcomes of SETI External Link: Visit the website of the SETI Institute, dedicated to the scientific search for extraterrestrial intelligence.. If the project succeeds, our awareness of the universe will undergo a far greater upheaval than Copernicus External Link: A biography of Nicolaus Copernicus - from University of St. Andrews, Scotland caused by displacing Earth External Link: Learn more about Earth from an astronomical perspective. from the center of all things. If SETI External Link: Visit the website of the SETI Institute, dedicated to the scientific search for extraterrestrial intelligence. fails after many years, our descendants would confront this challenging question: Despite the rich interactions between matter and energy throughout the cosmos, are we indeed alone?

Symbolic Greetings from Earth External Link: Learn more about Earth from an astronomical perspective.

In 1972 and 1973, Pioneer 10 External Link: The NASA homepage of the Pioneer missions -- learn about them and their discoveries.and Pioneer 11 External Link: The NASA homepage of the Pioneer missions -- learn about them and their discoveries.headed toward the outer planets and interstellar space carrying plaques (left) describing the solar system, Earth External Link: Learn more about Earth from an astronomical perspective., and humankind. In 1977, Voyager 1 External Link: The NASA homepage of the Voyager missions -- learn about them and their discoveries. and Voyager 2 External Link: The NASA homepage of the Voyager missions -- learn about them and their discoveries. set off on similar journeys, bearing a recording (above) of the sights and sounds of Earth External Link: Learn more about Earth from an astronomical perspective..

Where Did the UNIVERSE Come From?

Long before humans wondered whether other beings lived among the stars, they questioned the origin of the universe itself. Cultures invented creation myths External Link: An index of creation myths from around the world. and passed them down through generations, forming the richest of all stories for anthropologists to decipher. Modern Western culture has devised a story of universal creation as well. This particular story goes beyond myth because we can back it up with scientific data.

The modern creation story is called the Big Bang Internal Link:  . It is grounded in Edwin Hubble External Link: A brief biography of Edwin Hubble.'s discovery of the expanding universe Internal Link:   in 1929. The American physicists Ralph Alpher External Link: A biography of physicist Ralph Alpher. and George Gamow External Link:   were the first to propose the theory seriously, in 1948. According to Alpher and Gamow, the universe began with a burst of nuclear fusion from which all elements arose. Astrophysicists later learned that giant stars forge most elements heavier than helium External Link: Learn more about Element 2., but the nugget of the idea was in place. It appeared the universe had an explosive birth and is still flying apart after billions of years, like a fireworks blast that literally fills all of space.

For a time, proponents of the Big Bang Internal Link:   waged an intellectual war with supporters of another theory of the universe, called the steady-state theory External Link: Learn more about this interesting model of the universe.. In this view, the universe obeyed the "perfect cosmological principle"--it had always and would always (continued)