Neutrino Beam Carries Message Through 240 Meters Of Solid Rock
One of the earliest demonstrations of the Samuel Morse’s telegraph was used to bring updates of the Democratic National Convention in Baltimore to lawmakers in Washington D.C. The year was 1884, and newspapers all over the world were stunned at this new way to instantaneously transmit information over long distances. Paris’ Galignani’s Messenger remarked, “This is indeed the annihilation of space.” Now scientists have tested a new type of communication that conquers matter. Scientists have beamed a message carried by neutrinos, particles so small they pass through solid rock, to an underground detector about a kilometer away. Neutrinos could one day be used to communicate to submarines at depths that radio waves can’t penetrate, or even send messages right through the Earth’s core.
Neutrinos are naturally-occurring particles created through radioactive decay. They are really, really small. In fact, until recently they were thought to have no mass at all. But they do, somewhere between a ten-millionth and a millionth the mass of an electron. And unlike protons and electrons, neutrinos don’t have a charge. Their electrical neutrality allows them to pass vast distances through matter without being affected by it. The Earth is continually awash with neutrinos thrown off by the sun – each second about 65 billion solar neutrinos pass through every square centimeter of the Earth.
The scientists created the neutrino beam at the Fermilab Tevatron particle accelerator in Batavia, Illinois. Smashing protons against a target, in this case a wall of carbon, the protons break down into short-lived particles such as kaons and pions, which then break down further into muons, which break down into neutrinos. A steady flow of (extremely) accelerated muons produces a beam of neutrinos. Detecting neutrinos works the opposite way. When they interact with matter they emit easily detectable muons.
The so-called NuMI (Neutrinos at the Main Injector) beam was aimed at a detector behind 240 meters of solid rock. But for the same reason they can pass through matter, neutrinos are difficult to detect. To maximize the chance of a neutrino interaction the detector in the cave was stacked with dense materials including carbon, lead and iron. Even so, only about one out of every 10 billion neutrinos passing through the detector caused a detectable event, according to Dan Stancil, head of Electrical and Computer Engineering at North Carolina State University and the study’s lead author.
To encode a message, the beam was turned on and off to represent the binary “1” and “0,” respectively. Trillions of neutrinos were sent with each pulse so that detection was guaranteed. In this way they encoded the word “neutrino.”
So will those areas in the office with bad cell phone reception be a thing of the past? Probably not for a while, but possibility for the neutrino beam would be to send communications to submarines deep beneath the ocean surface. Radio transmissions don’t travel well through water so fast communication with submarines is only possible near the surface, exactly where submarines don’t want to be during covert operations. The subs can still receive messages down in the deep but the extreme low frequency waves necessary to penetrate the water transmits at a clunky 1 bit per minute. In 2009 Virginia Tech physicist Paul Huber suggested that neutrino beams could transmit data to subs at about 100 bits per second. However, the formidable technology needed to produce the beams means communication would only be one way. And then there’s the problem of turning a sub into a neutrino detector. Huber proposes that it might be possible to coat the sub’s hull with a thin muon detector. He also mentions that the light caused by muons moving through the seawater could be used as a signal. Either way, we’re probably stuck with radio transmissions for a while yet.
In addition to deep sea communications, neutrinos could potentially be used to transmit messages straight through the Earth’s core to the other side of the planet. It could also solve a limitation we saw with the moon missions. Whenever the command module went around the far side of the moon it experienced a communication blackout. In the future, human and robotic missions to space needn’t worry if they’re receiving signals from a neutrino transmitter.
Neutrinos caused a stir in the quantum mechanics field last year when they were alleged to have broken Einstein’s speed limit to travel faster than light. Turns out to have been a break with careful experimentation instead. The current demonstration, with a message Morse code-like in its simplicity, could one day prove to be just as revolutionary.