It looks like there is a theme going around the science blogosphere, triggered by a few remarks from Stephen Hawking.
Stephen Hawking says we should avoid any aliens—they’ll destroy us.
Ethan Siegel is optimistic and wants to run out waving his arms for attention. He scares me the most.
As the token biologist, I’ll differ from all of them. If I were in charge of humanity’s expansion into the universe, and if light-speed is the absolute limit it seems to be, I’d be sending out robot probes all right…all loaded with the biological seeds to impose human-compatible biospheres on any remotely human-compatible geospheres it encountered. It would bombard atmospheres with bacteria, sow the planet with algae, fungi, and lichens, and work its way up to grasses and trees and rodents and birds. And then it would start unspooling the stored genetic information of millions of humans into infants that would be raised onboard, educated by machines, and eventually transported onto the now hospitable planet surface to build a new technological civilization. Communication between planets would be limited and slow, and all the planning would be long-term — thousands to tens of thousands of years — so this wouldn’t be so much the growth of a human empire, but an organic expansion.
I’d expect that any intelligent aliens aspiring to expand would be doing the same thing. There would be variants: maybe Phil Plait is right, and advanced alien civilization will discard biology and advance in machine mode; it may also turn out that it is easier to modify biology than planets, so my bioprobes will produce radically gene-engineered humans who don’t look much like us anymore in order to more rapidly take over new worlds.
Anyway, my bet would be on interplanetary biowarfare, the slow infiltration of engineered organisms to change environments for alien compatibility. The only way we’d be able to survive is to fight them on the same ground. Don’t expect alien tripods with lasers, watch out for alien viruses and bacteria turning the soil and atmosphere poisonous or unsupportive. I’d also side with the people who are arguing we ought to worry about aliens, if they exist — if they’re so advanced over us that they can travel here, they aren’t going to be as interested in our primitive conversations as they are in our real estate.
I also think the possibility of that happening to us is unlikely. Intelligent life with grand schemes of interstellar expansion don’t seem to be evident out there, or maybe there are interesting obstacles that thwart such growth that we haven’t quite discovered yet.
By the way, I also caught an episode of Hawking’s Into the Universe on the Discovery Channel, the one on alien biology. I have to say I thought it was just awful, with no useful content and was merely a contrived excuse for the Discovery Channel to trot out more cgi of imagined weird animals. Biology is definitely not Hawking’s strength. Maybe his other episodes on time travel and cosmology will be more thoughtful and interesting.