Light travels at about 186,000 miles per second.
Figure another 500 years to build new ships, set out again, and so on and so on, and the calculations show that civilizations starting out from the oldest stars in our galaxy would have had epochs of time to reach us by now. So where are they?
"They've either passed us by, or they stay around their home star systems and contemplate their navels," Hair said.
There could be several reasons why we're not listed in intergalactic Yelp. Perhaps most important is that we don't have anything aliens need.
"Any ancient civilization is probably not biological. They don't need a place like Earth. They don't need to come here and steal our water. There's plenty of it out in the outer solar system where the gravity is not so great and they can just take all they want," Hair said.
Or perhaps modern-day extraterrestrials are following routes laid out long ago, all of which bypass Earth, he added.
Whatever the reason we're being ignored, there is no chance ET, if he exists, does not know we are here, Hair said, pointing to telescopes, such as NASA's Kepler observatory, which can detect planets around other stars.