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We could build a laser capable of sending signals to extraterrestrial intelligence.
Not us as in the staff of Live Science. (That probably exceeds our skills.) But we, as humanity. A new article published yesterday (November 5) in The Astrophysical Journal revealed that humanity could build a sufficiently hot and bright infrared laser so that – if we project it directly on nearby exoplanets – extraterrestrial astronomers can detect it using the sky – look at technology not too advanced than ours. (Assuming they're there, of course.) [9 Strange, Scientific Excuses for Why We Haven’t Found Alien Life Yet]
It should be pretty big, but not unthinkable. One of the models proposed by the researchers would require a 1 to 2 megawatt laser and a primary mirror of a diameter of at least 100 feet (30 meters).
In a statement, James Clark, an MIT graduate student and lead author of the newspaper, did not say whether the aliens would immediately recognize the laser as a signal of intelligent life forms. But, he added, "it would certainly attract attention."
The authors wrote in the newspaper that the main challenge for building an extraterrestrial laser beacon was that the Earth was not the only one in the space. Instead, it is a relatively minor of the eight planets orbiting a much brighter star than any laser that a man could reasonably hope to produce. From the point of view of an extraterrestrial astronomer to hundreds of light-years away, the entirety of human civilization and any infrared source that it might produce would be drowned in the gigantic source of light white of our local space.
The goal of the laser would not be to create a flashing lighthouse in the dark so that aliens can sit and see it. Instead, explain the authors, it would be a matter of giving our sun a strange aspect from an extraterrestrial point of view to allow it to look again.
A set of strangers scanning the sky may have noticed that our sun is surrounded by planets or that at least one of these planets might be habitable. But that does not seem to be so rare. Perhaps if they are on Trappist-1, which hosts the largest number of exoplanets that may eventually contain liquid water on the surface, they will have specifically taken note of our system for the same reasons as us: the possibility of habitable worlds a few tens of years of light.
However, if we pointed a laser of the size that Clark imagines directly on these extraterrestrials while they were watching our sun, our sun would appear to exhibit very unusual behavior.
Under normal circumstances, the amount of light produced by the stars varies a bit. And there are models to this variation. However, a focused infrared laser could vary the light output of our sun much more in the infrared spectrum than normal. Instead of creating a flashing beacon in the dark, the laser would give our sun the appearance of an existing light becoming tasteless.
If nearby aliens detected the signal and understood its meaning, it may be possible to configure a communication channel using lasers with data transfer rates of up to 2 Mbps (megabits per second). It looks like a slow modern internet connection. Of course, there would be delays of several decades between sending and receiving messages, thanks to the speed of light.
The researchers discovered that, further from Earth, the laser could still be used to spread a more general message: "Hey, we're here!" detectable signal at a distance up to 20 000 light-years. (Of course, the space is much larger than that – a 20,000 light-year signal would only reach the other stars in our Milky Way region.)
It could be dangerous to project a super bright infrared laser into the sky. Infrared is not visible to the human eye, but a focused intense beam can always blind somebody. As long as reasonable safety precautions have been taken to prevent anyone from taking care of it, it should go, he wrote.
As to whether this is a good idea, readers should answer for themselves. (Maybe after reading Cixin Liu's novel "The problem of the three bodies".)
Originally posted on Live Science.
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