Why haven't the Borg invaded the Earth yet? I have watched every episode of Star Trek, Star Trek: The Next Generation, Deep Space Nine, Voyager, and Enterprise, and myriad movies where the Earth is invaded by aliens. I love science fiction. But it is only fiction and will remain so. Many people, including renowned scientist Stephen Hawking, are also concerned about extraterrestrials invading the Earth. "To my mathematical brain, the numbers alone make thinking about aliens perfectly rational," said Hawking "I imagine they might exist in massive ships... looking to conquer and colonize whatever planets they can reach." Last week, late-night talk show host Jimmy Kimmel asked President Obama about Area 51 and UFOs; and just last May, two top astronomers told Congress that it would be "bizarre if we are alone" and asked for continued funding to detect extraterrestrial life. If you extrapolate "there are a trillion planets in the galaxy," said Seth Shostak, an astronomer at the SETI Institute "That's a lot of places for life." Dan Werthimer, director of the SETI Research Center added "It would be a cramped mind that didn't wonder what other life is out there." So where is ET? Since the 1960s, Soviet scientists, NASA and others have been searching the cosmos for signs of intelligent life. Scientists estimate the universe contains more than 100 billion galaxies (our own Milky Way alone is home to around 300 billion stars). According to the late Carl Sagan, there should be about a septillion -- 1 followed by 24 zeros -- planets capable of supporting life. Surely, in this lapse of suns, advanced life would have evolved somewhere if life and consciousness were just random accidents. Yet despite half-a-century of scanning the sky, astronomers have failed to find any evidence of life, which our radio telescopes should be able to easily detect. Scientists note that extraterrestrials should have had enough time to have colonized the entire galaxy. Did they blow themselves up or is the problem more fundamental? More via Huff Post Blog | Robert Lanza, M.D..