Communication via neutrino particles has some advantages over radio and optical signals.
Neutrinos are like electrons, but they don't have an electric charge and pass through most everything.
An advanced civilization could use neutrinos in several ways to communicate.
Extraterrestrials may have a better way to communicate across space than radio waves or optical beams. A team of scientists suggests ET could encode neutrinos, for example.
These particles of matter are similar to electrons, but since they have no electric charge, they can pass through anything. This makes them ideal for long-distance travel, as neutrinos are undisturbed by gas, dust and other matter that can block radio waves and other types of electromagnetic radiation.
Astronomers have been scouring the galaxy for decades for alien-produced radio signals -- and more recently for non-naturally occurring light pulses, as well -- to no avail.
"We really have no clue as to how some advanced civilization might want to transmit to us, nor do we have any really good idea why they would want to transmit to us," physicist John Learned, with the University of Hawaii, told Discovery News.
"Everything that we're doing is exploratory science: You don't know the game; you don't know if you're in the game; you don't know the rules of the game... which is what makes it so much fun," said Learned, who, along with colleagues, has written a series of articles about how neutrinos could be used for communication.
ET could, for example, send out a neutrino beam at precise (and non-naturally occurring) energy levels that would be sure to catch a scientist's eye.
"If there's a civilization, like our civilization, which is at the stage of setting up large neutrino detectors, then one would see this signal of a unique signature and you would right away say: 'What the heck is going on here? This is certainly not a natural signature.' This is something that would really get your attention on the very first (detection.) And then on the second one you'd be saying: 'Huh? What in the world is going on here?'"
Another possible communications technique is to use neutrinos to shift the blink rate of a commonly known type of pulsating star called Cepheid variables, which are used to help determine the distances between galaxies.
"The idea would be that the advanced civilization sets up a monster accelerator... and it collects energy from the star, saves it up and then blasts away at the star at just the right period, causing it to flare a little bit early -- or not, depending on what they want to do. Net result is that this star would then be flashing with a varying period. The simplest thing to do would be to have it at just two periods -- the natural time-period and then some point at which you could conveniently trigger it in advance, say 10 percent, or something like that," Learned said.
The best part of this type of search for extraterrestrial intelligence, or SETI, study is that the data may already be in hand.
"We've been recording these stars for over 100 years now... but the way astronomers were doing the analysis, they would not have seen any such phased jiggling around," Learned said. "It may be there in the data. This is SETI on the cheap."
But not for the aliens, points out SETI astronomer Seth Shostak, who hunts for ET the old-fashioned way -- with radio waves.
"Most of today's neutrino experiments detect one particle in a million. If the idea is to get our attention with only 10 detected neutrinos -- a very uncomplicated message that says no more than 'We're trying to get in touch' -- then sending that simple ping will require as much energy as is burned every day by all the cars, trucks, trains, boats and planes on Earth," Shostak wrote in an email to Discovery News.
"If the aliens, in their fervor to find new friends, are pinging likely worlds at the rate of one (per) second, then their energy bill will be $300 million million million a month, assuming they pay the same utility rates you do," Shostak said. "Even for well-heeled aliens, that might be burdensome."