It’s been a few months since my last trip to Radnor Lake—too long, really, and I left the house later than I’d planned so I arrived a little after nine. The parking lot was full, or rather almost full. I found an open spot on my first pass, although I’d been prepared to go back and leave, unsure I wanted to be out. Then, as I started around the lake then took a turn off the popular paths, up and around the longest trail, one that took me up over the hills, out of sight of the lake and away from all other people, I realized how much I’d needed this. I’d needed to turn my mind off and just walk. Or rather let my mind wander since it’s impossible to turn my mind off. And while I was walking I started thinking about something I’d just read about the James Webb space telescope, how it’s being used to look for possible alien life by looking at the atmospheres of other planets. It’s already found carbon dioxide, which may or may not be a sign of life, and some astronomers are talking about looking at Earth-like planets for nitrogen dioxide and ammonia and other gases that, well, here on Earth are pollutants that we’re trying to stop pumping into the atmosphere. They could be a sign of farming or even industrial activity—assuming aliens out there on planets like ours build civilizations and have technology like ours. If we don’t find such evidence it doesn’t mean they aren’t out there but there’s also the sobering thought that it means such civilizations may have existed and burned themselves out.
The possibility of finding life elsewhere in the universe is exciting but I also know it scares some people, and there’s always the argument that we shouldn’t broadcast signals into space, that we should be quiet and not try to draw attention to ourselves because if aliens know we’re here they might invade. My response to that is that if aliens are out there and they have the technology to cross interstellar distances they already know we’re here. If they’re that advanced they’ve known we’re here, or at least that there’s a rocky, watery, oxygen-rich little planet orbiting an unremarkable star in one of the outer arms of the galaxy. Humans have barely started to venture off this planet—we haven’t made it farther than our own moon, unless you count our unmanned probes, and those have barely made it out of the solar system. And yet we’ve discovered thousands of other planets around distant stars.
As I walked along a high ridge between trees it occurred to me that a benefit of broadcasting that we’re here might be taken as a sign that we’re friendly—or at least capable of defending ourselves. Sometimes when we pass a stranger and make eye contact, whether intentionally or not, we’ll say “Hello” or nod—just a little something to say, “Yeah, I see you.”
And of course I was so deep in thought about this as I was walking along that some guy came up behind me and said “Hello!” as he passed me on the trail and I jumped about three feet in the air.