'Galactic internet' proposed

Aliens might have sent messages by tweaking variable stars.

Charles Choi

Galaxy NGC 1309, snapped by the Hubble Space Telescope, is packed with Cepheid stars of the type that could form a communication network.NASA, The Hubble Heritage Team and A. Riess (STScI)

Just by gazing at the stars, earthling astronomers might have unwittingly picked up broadcasts from extraterrestrial civilizations. So says a neutrino physicist, adding that it might take researchers just a few months of searching to find evidence of this alien internet.

John Learned at the University of Hawaii in Honolulu and his colleagues think that signals could be sent by manipulating Cepheid variable stars. These rare stars can be seen in other galaxies more than 60 million light years from our own.

Cepheids dim and brighten regularly, in a pattern that depends on their brightness. This lets astronomers measure the distance to the stars, helping to resolve mysteries such as the Universe's age and how fast it is expanding. As such, any sufficiently advanced civilization would want to monitor such stars, the scientists reasoned.

To send messages using a Cepheid, Learned and his colleagues suggest that extraterrestrials might change the star's cycle. A Cepheid becomes dimmer as ionized helium builds up in its atmosphere. Eventually, the atmosphere expands and deionizes, restarting the cycle.

Firing a high-energy neutrino beam into a Cepheid could heat its core and brighten the star early — "just as an electric pulse to the heart can make it skip a beat," Learned says.

The neutrinos could be made by blasting a proton beam at a target — sapphire, carbon or tungsten would work, says Learned. The target produces subatomic particles, mostly pions, which decay to produce neutrinos.

The normal and shortened pulses could be used to encode data, to form what the researchers call a 'galactic Internet' in a paper posted to the arXiv preprint server¹.

Low bandwidth

"It's an interesting idea that can be tested — somebody should look at the archives on these stars and see if there are any light variations of the kind they are describing," says physicist Freeman Dyson of the Institute for Advanced Study in Princeton, New Jersey.

Adds Seth Shostak, senior astronomer at the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, California: "It's a great idea, reminiscent of an old Russian idea about bouncing high-energy radiation off the 100 or 200 real supergiant stars in the galaxy to generate anomalous radiation as signals others could see."

Learned admits that the galactic internet would be slow — a Cepheid with a roughly one-day period could transmit about 180 bits per year. Such a transmission would require roughly a millionth of the star's energy, the researchers estimate.

"A millionth of a star's output is a heck of a lot of energy," says Shostak, adding that a high-powered radio beacon could probably transmit more data over similar distances.

Learned says that finding a signal from the galactic internet is a long shot — but, he says, we've got 100 years of data on Cepheids in which to look.

"Analyzing that data would take a graduate student a couple of months, and just think if it turned out to be correct," says Learned. "The implications would be astounding."

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The Yin-Yang of Ultraviolet Radiation

By Lynn J. Rothschild
Research Scientist, NASA Ames Research Center

Now that we have passed through summer, replete with warnings about the health hazards of exposure to ultraviolet radiation, the subdued light of autumn provides the ambiance in which to take a more balanced look at what UV radiation has meant to life on Earth. We need UV radiation to synthesize vitamin D, which is critical for calcium absorption. UV radiation is used by some organisms as an environmental cue, and it aids in some repair mechanisms for DNA damage. Further, UV-catalyzed reactions in the atmosphere and on the early Earth were critical to providing the conditions for life to arise. But the fact remains: UV radiation itself is hazardous to carbon-based life such as ours. Why should this be so, and how has life overcome this obstacle to thrive on Earth?

The apparent diversity of organisms masks the fact that all life on Earth, and possibly in the universe, is based primarily on a few types of organic compounds. Principal among these are proteins and nucleic acids (RNA and DNA), respectively the primary structural and hereditary components of terrestrial biology. Unfortunately, the maximum absorption of radiation for both compounds is in the UV portion of the solar spectrum, 280 nm for proteins and approximately 260 nm for nucleic acids, and such absorption could destroy these molecules. While solar radiation below about 290 nm does not reach the surface of the Earth today, it is still dangerously close to these peak absorptions.

If this weren't enough, UV radiation can catalyze the production of reactive oxygen species, such as the hydroxyl radical, which themselves damage organic compounds. And the situation was far worse on early Earth, prior to the formation of a protective ozone shield. Without the ozone shield (but with CO₂ in the atmosphere, which we have had from the earliest times), we would be bathed in UV radiation down to 200 nm — a horrifically dangerous situation for life.

Natural sunscreens

With this background, one might forgive an extraterrestrial biologist from assuming that all life on Earth seeks refuge underground. But yet we know this not to be universally true. In fact, life underground is at a disadvantage as it cannot access other portions of the solar spectrum, specifically the longer wavelengths that bacteria, algae and plants exploit for photosynthesis and we animals use for vision.

A common evolutionary solution to this problem is to produce biological "sunscreens" for protection from UV radiation while allowing access to the longer wavelengths, and indeed many organisms from prokaryotes to humans use this approach. But it is also possible to exploit minerals that are transparent to longer wavelengths, but attenuate UV radiation. My lab has found that organisms that live under sand grains do just that, as do organisms that live in salt crusts such as the ones in San Francisco Bay's Cargill Salt Company. In collaboration with SETI Institute Principal Investigator Janice Bishop, and under the auspices of an NAI grant to the SETI Institute, we are exploring the possibility that iron-based compounds were particularly important in protecting the earliest organisms on Earth.

Why iron? Iron is one of the most abundant metals in the universe, found in stars such as our sun, in planets, and as a principal constituent of certain types of meteorites and asteroids known as iron meteorites and M-type asteroids. On Earth it accounts for about 5.6% of the crust, and nearly the entire core. Iron is arguably the most important metal for life because of its role in many metabolic processes, including being the critical component of hemoglobin, the compound that transports oxygen in red blood cells.

Near the surface of the ocean, iron concentrations exist in the nanomolar to picomolar range. But the iron compounds that are there, for example nanophase ferric oxides/oxyhydroxides, are capable of absorbing UV radiation. Thus, we have proposed that such compounds allowed early organisms to become photosynthetic — on the one hand, the iron compounds were available for use in metabolism, while on the other they attenuated harmful UV radiation while transmitting the longer wavelengths needed for photosynthesis. Through combining our expertise in biology and geochemistry, and through lab and field work, we plan to test this hypothesis in the coming years.

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Satellite That Predicts Climate Change About to Launch

Written by Ariel Schwartz

British scientists are preparing to launch a revolutionary satellite that will provide precise measurements of the earth’s gravitational field, which will in turn provide exact measurements of ocean currents. So why is that important? Well, ocean currents transport heat around the planet— and that means that the currents have a huge impact on the earth’s climate.

The €330 million satellite will map the planet’s gravitational field once every 70 days for 18 months. It will orbit at a low altitude—160 miles—in order to measure tiny gravitational fluctuations.

Expect the satellite to be in orbit in the next two weeks. And if you happen to be at the Plesetsk cosmodrome near Moscow, you can even watch it launch.

I do wonder about the practical applications of the satellite besides the knowledge of which areas of the world are about to be clobbered by global warming. Still, even that is useful, as people in affected regions will be able to prepare for what lies ahead. And maybe it will once and for all prove to global warming deniers that climate change isn’t a farce.

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