Intelligent life can't be all that common because it's really rare on Earth and especially since we define ourselves to be intelligent. But in the eyes of an alien coming here who has the technology to make it here, they might observe us and conclude that there's no sign of intelligent life on Earth.
Neil deGrasse TysonLuckily, there are some rocks left over from our earliest days, asteroids formed during our solar system's birth. Occasionally, some of them drop in on Earth, and when they do, they're called meteorites.
Neil deGrasse TysonTo achieve this density of a neutron star at home, just cram a herd of 50 million elephants into the volume of a thimble.
Neil deGrasse TysonI [do not know] when the end of science will come. ... What I do know is that our species is dumber than we normally admit to ourselves. This limit of our mental faculties, and not necessarily of science itself, ensures to me that we have only just begun to figure out the universe.
Neil deGrasse Tyson