Posted by “To use Newton’s words, our efforts up till this moment have but turned over a pebble or shell here and there on the beach, with only a forlorn hope that under one of them was the gem we were seeking. Now we have the sieve, the minds, the hands, the time, and, particularly, the dedication to find those gems–no matter in which favorite hiding place the children of distant worlds have placed them.”
-Frank Drake and Dava Sobel
Looking up at the canopy of stars in the night sky, and realizing that each point of light is a star system not so unlike our own, one can’t help but wonder about those extraterrestrial worlds that we know exist around a tremendous fraction of them.
Image credit: Tom's Eye on the Sky.
With hundreds of billions of stars and (possibly) upwards of a trillion planets, it’s been known for a very long time that there’s a definite, real chance that other intelligent life exists right now in our own galaxy.
For decades, we’ve broadcast radio messages out into space, and built giant arrays of radio telescopes, searching for those same types of signals originating from other sources in the night sky.
Image credit: VLA in Socorro, New Mexico, retrieved from geonomis.com.
Of course, this is a tremendously ambitious task. Even a very intense radio signal will lose its power the farther away from it you are. The problem, of course, is that each time you double the distance away from a radio transmitter, you pick up only one-quarter of the intensity you would have received at a closer distance.
Image credit: Arthur's Clip Art.
Even special setups that collimate the beam — assuming, for example, that an alien species had the idea to point their beam directly at us — still suffer from this. Even the best setups for beam collimation of light still wind up having the signal spread out over a substantial angle, and still suffers from the problem that the farther away you are, the less intensity you receive squared: a radio transmitter ten times as far away needs to be a hundred times as powerful for you to pick up the signal.
Image credit: Chris Long.
It’s difficult to imagine that a civilization-generated signal located thousands of light-years away, across the galaxy, would be able to outshine the cosmos by time it reached us.
But we do have one sterling example of a beam we can collimate to an outstanding precision: beams of extremely high-energy particles!
Image credit: Maximilien Brice, 2009.
A pulse of high-energy particles, such as the kinds we create at the Large Hadron Collider, above, achieves speeds around 99.9999% the speed of light, more closely collimated than even the beam from a laser. Now, we sometimes receive high-energy particles — originating from space — here on Earth. When we do, how do we identify them?
Image credit: Randy Russell using a photo via UCAR / Nicole Gordon.
They strike the Earth’s upper atmosphere, producing a shower of particles. Neutrinos and muons make it to the ground, where — if we’re lucky and prepared — we can identify them. Launched from Earth, however, the charged particles would certainly hit the atmosphere on the way out. And since muons are unstable, by time they arrived at their destination, the only recognizable signal would be the neutrinos!
In other words, if we wanted to send a signal to an alien world, alerting them to our presence, our best bet would be to send them collimated, patterned pulses of neutrinos!
Image credit: Jerry Ehman, republished from Smithsonian Magazine.
What’s remarkable about this — even though it wasn’t the experiment’s intention — is that we just demonstrated the ability to detect exactly this type of signal!
How’s that?
Image credit: MINERvA team / University of Rochester.
Last week, scientists announced — for the first time — that they sent a neutrino signal through the solid rock of the Earth, in binary morse code, and received it at a neutrino detector over a kilometer away!
Image credit: MINERvA Collaboration.
Despite the fact that only one out of every ten billion neutrinos can be detected in an apparatus like the MINERvA detector, above, and that the effective transmission rate was only one bit every ten seconds, by repeating the message many times, the detector was able to build up the binary pattern of zeroes and ones, eventually decoding the binary message!
Image credit: D.D. Stancil et al.
What was the message? Why, the name of the particle itself: N-E-U-T-R-I-N-O.
If someone, thousands of light years away, is sending a repeating neutrino signal towards us, we’ve just demonstrated the capability of detecting and identifying exactly that type of communication.
The signals of intelligent life could already be there. We just need to listen in the right way, and neutrinos might be the answer!
(Also, a big thanks to Randall for the elegant new blog banner; hope you like it!)
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. But on the other hand, you’d have to wait for the light to reach the receiving end, which could take a long time. I like thinking about possible methods of superluminal communication, like wormholes or warp drives. 
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