This installment is heavy on images that emphasize the enormity of the universe.
College students huddled around their lava lamps (iPads?) tell themselves that as big as the universe is, there *must* be other intelligent life out there. Well, actually… as large as it is, it’s also very old: Big Bang = 12-14B years ago, Solar System = 4.5B years old. In this case, old trumps large: there actually ought to be so many millennia-old advanced civilizations that we should have been contacted or visited by at least one of them by now.
In other words, if human civilization can advance to space travel in a relatively short time (take your pick = 50,000 years since the Stone Age, 4000/Bronze, 1500/Iron), why hasn’t some alien civilization that is thousands (hundreds? millions?) of years more evolved made contact by now?