If ET phoned over the summer he would have received the embarrassing I-didn’t-pay-my-phone-bill message stating ‘The planet you are calling has been temporarily disconnected.’ In April the SETI (Search for Extraterrestrial Intelligence) Institute shuttered the Allen Telescope Array due to budgetary woes. Thanks to the SETIStars initiative and generous donations we’re back to listening for that call.
In a recent Popular Science article SETI director, Seth Shostak, said he believes we’ll detect alien life in the next twenty years. He lists a few ways he thinks this may come about. Last but not least he mentions SETI’s improving technology and its anticipated ability to search a million star systems over the next twenty years.
He touched on the idea that an alien race might detect the radio signals we’ve been emitting for decades and send a reply. Minimizing the possibility he pointed out that only a few tens of thousands of stars have been exposed to our transmissions.
If one employs conservative/pessimistic numbers in the Drake Equation then life is probably too rare and scattered about to expect a reply anytime in the next several thousand years. However, if you plug slightly more optimistic values into the equation you see a galaxy teaming with life.
This later scenario presents exciting possibilities, and is an area I think warrants more consideration.
Given the relatively slow speed of light (relative to the size of the galaxy anyway) only a tiny fraction of the galaxy may know we exist. Arguably the most powerful unnatural radio signals mankind ever sent out were our aboveground nuclear detonations. Considering the speed limit of 186,000 miles per second, that energy has blazed across the galaxy and covered a whopping 66 light-year radius in the intervening 66 years. That’s a bubble of information roughly 122 light-years across.
Not really, it’s only 3/100,000 of 1 % (0.000003%) of the galaxy.
Hard to visualize? Imagine you shrunk the galaxy down to the volume of the Superdome. Now imagine you’re up in the nosebleed section. At that scale picture a four-foot-wide beach ball at mid-field. That sphere, a few centimeters over a meter, would represent the 122 light-year bubble of stars exposed to the energy waves emitted from the planet in 1945. It’s unlikely anything outside of that beach ball even knows we exist.
Our galaxy is not as boxy. The Superdome’s interior volume is roughly as tall as it is wide, or 1:1. With a 100:1 width-to-height ratio our galaxy is 100,000 light-years across and only 1,000 light-years thick. Now imagine trying to see that four-foot sphere from a mile away instead of the upper-deck. And remember, if you’re not in that bubble all you hear from its center point is cosmic white noise.
Knowing how small the portion of the galaxy is that may know of our existence, consider this: every day that sphere’s radius grows, its surface grows exponentially. In other words the potential pool of star systems learning of our existence is growing daily, and at an ever-increasing rate.
Complicating the issue is the time a reply takes to reach us. If a civilization decides to beam an instant reply it will take just as long for us to receive it as our signal took to get to them.
What if 33 years ago, back when that bubble was the size of a basketball, a relatively advanced civilization in our galactic backyard received the signal and blasted a return message our way? We’ll receive it thirty-three years later (today). Therefore, any instant replies beamed in the last 32+ years are still en route.
That’s all if they decide to reply immediately. Considering the signal they received was a nuclear detonation they may want to listen for a while. After a few decades of I Love Lucy, Gilligan’s Island, Cheers, Seinfeld, and Lost they decide ‘what-the-hell let’s say hello to our wacky neighbors.’
Side note: I often muse over the idea that somewhere there’s an alien race agonizing over who shot JR as they painfully wait for the next season of Dallas to reach their planet. Who knows, there may even be a cultural niche of Elvis Presley fans on some remote rock (there’s some bad news heading their way circa 1976).
People and politicians often ask, ‘Why should we spend money listening for aliens? It’s not like they’ll balance the federal budget for us.’ That’s tantamount to a five year old asking, ‘Why should I go to school? There’s nothing they can teach me.’ Setting aside man’s innate curiosity and our desire to answer the burning questions: ‘Are we alone?’ and ‘Is there anybody out there?’ there are more practical reasons to search.
In regards to social and scientific development we are likely babes in the Galactic woods. Any data gathered from alien contact would probably be more enlightening than Pythagoras’ Theorem. Spanning decades, it would be an inefficient discussion, but we most certainly would be the prime beneficiary of that interaction. Thus a tiny-tiny-tiny-miniscule investment (relative to GDP) lands us invaluable knowledge.
In Carl Sagan’s Contact aliens send us blueprints for a wormhole generator. But saving that, what if they merely said ‘Hello, here’s the perfect mouse trap,’ or ‘free energy and the cure to world hunger,’ or whatever.
I for one am glad we’re paying our phone bill again.
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