Stephen Hawking was wrong about aliens on TV, so here's my rebuttal. His first dumbass bullshit error was thinking aliens would be interested in Earth, as if they would need things like oxygen, water, food, and comfy temperatures. They would not. A species advanced enough to leave its planet behind would also leave its biology behind. That's to say they'd turn themselves into robots. More specifically, they'd turn themselves into creatures that can make use of the 99.999999999% of planets that don't support delicate little meatbags like us. If they're interested in our planet, it would only be because they want to grind down all the mass in our solar system to make space concrete, and Earth is just one more pebble for the pebble machine. (Aside: A more plausible motive is that they want to assassinate us in case we're a threat to them in the future.)
Hawking, the vast majority of 20th century science fiction, and almost every person, have made the same error. When we speculate on aliens, we have a biological blind spot: ET might be advanced enough to turn the laws of physics upside down, but reengineering their own bodies would be too much for them. Or they'll have some spiritual reason to avoid it. However plausible those excuses might be, there's one gigantic fact that puts them in perspective: If just one species could enable itself to inhabit the 99.999999999% of planets that the others couldn't, it would rule the galaxy. All the other species who find bioengineering too difficult or ungodly would find themselves either wiped out or irrelevant.
Hawking seems convinced aliens will be amoral. His reasoning is that their intentions will be determined by the universal law of evolution. For morality is given to them by natural selection, and if it ever becomes a liability, natural selection will taketh away. That's no longer true once you remove your bio-blind spot. If Earth is just one more pebble, they have much less to lose by sparing us.
His third significant dumbass bullshit error is thinking for a second that any of this matters. If aliens want to find us, they will, with or without our help. The only difference we can make is how they'll judge us by the messages we intentionally send them. Exhibit A, from the Pioneer 10 probe:
Those symbols might seem confusing at first, but they utilize the universal language of mathematics to explain that we're gay. We may as well have sent this out:
That's why, despite my disagreement on some details, I have to side with Hawking. He's at least trying to use logic. The other side is just gay. I didn't want to call them out like this, but they started it, with their emotional appeals and 69ing with the same sex. The possibilities surrounding aliens are vast. So vast that almost everyone's wild speculation is valid and awesome, and criticizing another's speculation is (a) a waste of time that could be better used to wildly speculate, and (b) asinine. Whoops.
Less importantly, I hate when those speculations invoke Columbus and other intercultural incidents. Way to suck all the fun out of the discussion, guys. We're supposed to be talking sci fi, not history. I get that history has important lessons in it, but this is one case where it does not. Humans all breathe the same air, have the same mental quirks, and swim up the same fallopian tubes. It would be impossible to tell whether any lesson gleaned from a human-on-human encounter is applicable to an alien-on-human encounter, or irrelevant human noise. If you want reliable information, you should invoke only the most basic principles of evolution and game theory.
(Aside 2: I know I heard Hawking say this exact same stuff on TV like 10 years ago. I guess he wants to say it again now that he has a blogosphere to set ablaze.)
(Aside 3: Anyone else notice how they used the lettering from the Alien movies, complete with the vagin-I, for this episode subtitle?
My opinions of the people I've characterized in this post are the opposite of what you've just read.