Are other planets watching Earth ?
MYSTERY WIRE (AP)  Space exploration  mankinds thirst to seek out far off worlds and learn more about the universe. Astronomers have found stars in our galaxy from where Earth may already have been spotted. They took a technique used to look for life on other planets and flipped it around  so instead of looking to see whats out there, they tried to see what places could see us. One way humans look for potentially habitable planets is by watching them as they cross in front of the star they are orbiting, which dims the stars light slightly. So the astronomers used the European Space Agencys Gaia space telescope to turn that around, looking to see what star systems could watch Earth as it passes in front of the sun. Theres a lot. Astronomers calculated that 1,715 stars in our galactic neighborhood  and hundreds of probable Earth-like planets circling those stars  have had an unobstructed view of Earth, according to a study released Wednesday in the journal Nature. One thing about this geometry is that its actually where we dont look for planets per se, because its in the crowded part of the plane, says Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University and study lead author. So we are actually not as knowledgeable as we are about other parts of the sky about this region, but our paper basically gives people a really good reason to now look there. And its all based on this really old idea of SETI (Search for Extraterrestrial Intelligence), you know, if they could have found us already, SETI is hoping that those would be the people who would send us some signals.  They looked at the 331,312 stars within 326 light-years of Earth. One light-year is 5.9 trillion miles. The angle to see Earth pass in front of the sun is so small that only the 1,715 could see Earth at some point in the last 5,000 years, including 313 that no longer can see us because of shifting views. Another 319 stars will be able to see Earth in the next 5,000 years, bringing the total to more than 2,000 star systems with an Earth view. Some include a few star systems where scientists have already spotted Earth-like planets, prime candidates for contact. Kaltenegger says there is one system she is especially hopeful for. TRAPPIST-1 is always one of the favorites, right, because it has four planets in the habitable zone that are Earth sized, she says. And it cant see us yet. So thats actually, for TRAPPIST, a really interesting thing. Because we can see it, butthey can only see us in about 1,600 years.  If there is alien life in TRAPPIST-1, it will be a long time before they know we are here. Some experts, including the late Stephen Hawking, warn against reaching out to aliens because they could harm us. But Kaltenegger says it doesnt matter. If those planets have sufficiently advanced life, they already know were here. So hiding is not really an option, she explains. It takes a long time for messages and life to travel between stars and civilizations might not last long. Perhaps life in the cosmos could just be rare. Or maybe curiosity is simply a human-only trait. But Kaltenneger still has hope that somewhere, out there, other life forms are trying to make contact. When I look up at the sky, it just looks a little bit friendlier because its like maybe somebody is waving, we just dont know yet.