Are We Alone?
by Louise Good
© Seth Shostak, SETI Institute
Does intelligent life exist beyond Earth? If so, how might we find it? These are some of the questions addressed by Jill Tarter, Bernard Oliver Chair at the SETI Institute in a Sheraton Waikiki Explorers of the Universe talk held at UH Mānoa’s Kennedy Theatre on May 3.
SETI, the search for extraterrestrial intelligence, seeks to answer the question, are we alone? “We don’t know the answer,” but it is a “legitimate scientific question to pose,” Tarter said. “Our journey thus far has brought us to the realization that we on this planet orbit one star out of something like 400 billion in the Milky Way and that that Milky Way galaxy is one of perhaps 100 billion galaxies in the observable Universe.”
Tarter said that the rover Curiosity is exploring Mars, not to find life, but to determine whether conditions for life ever existed on Mars. “If we find a second independent genesis of life in this one small solar system, we can be sure that life will be ubiquitous elsewhere among the stars.” Tarter listed other places in our solar system that might harbor life: Jupiter’s giant moons Ganymede, Callisto, and Europa, which are frozen on the outside but have salty oceans beneath the surface, and Saturn’s largest moon, Titan, which has liquid methane on its surface.
What about life beyond our solar system? The Kepler spacecraft has been looking for Earth-size planets that cross in front of (transit) their stars in a 100-square-degree section of the sky. The ultimate goal of Kepler’s work is to find what Tarter termed “Earth 2.0,” an Earth-size planet orbiting a Sun-like star in its habitable zone. She said she expects that we will find such a planet soon. (The recent troubles of the Kepler spacecraft may make this somewhat less likely.) Eventually, we may have telescopes capable of finding bio-signatures of life on other planets, for example, oxygen and methane coexisting in a planet’s atmosphere, but we are not there yet.
For now, the SETI Institute is looking for what Tarter termed “techno-signatures” of intelligent life: narrow radio signals and time-compressed optical signals, such as laser flashes that last only a billionth of a second, “the kind of thing that we have the technology to do but nature can’t do.” As our technology advances, SETI will be able to search the sky more and more efficiently.
Whether or not SETI will succeed depends on two things: Whether there is anyone out there and whether they will be there long enough for us to find them. She said technological civilizations would have to survive 100,000 years on average to be detected by other civilizations.
Tarter quoted MIT scientist Phil Morrison, who wrote the first serious SETI paper, saying, “SETI is the archeology of the future,” meaning that if we detect a signal from a distant civilization, we will be learning about another civilization’s past, since their signal will have taken a long time to reach Earth. But even if we detect a signal with “no information content,” it will still have a very important message for us: “If we work at it hard enough, we too can have a long future.”
In closing, Tarter said that SETI is something “we absolutely should be pursuing as a global project.” If there is a signal out there, it is coming to the planet Earth, and “should be information that becomes the property of all humans, so it should never be kept a secret.” She expressed the hope that her talk had gotten the audience “to look at who you are and where you are from a more cosmic perspective” and to understand that “we are all earthlings,” are not so different from each other, and that we can all work together and cooperate on both SETI and all of Earth’s challenges.
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