The image above shows a focused laser beam shooing into space from Earth, which some researchers hope might attract the attention of alien astronomers.
According to a new study by James Clark and Kerri Cahoy, both from MIT (Massachusetts Institute of Technology), it may be possible to focus a 2-Megawatt laser beam through a 30-45 meter telescope, and then to fire the focused laser beam into space like a search light. According to James Clark, the lead author of the study, the objective of the exercise would be to announce our presence to alien civilizations up to about 20,000 light years away.
However, the authors also point out that due to long turnaround times (40,000 years) at maximum range, it may be more productive to focus the beam on Proxima b, which is an Earth-mass planet only a few light years away, or even the TRAPPIST 1 system, which is about 39 light years away.
The idea of using a laser beam to communicate our presence to the galaxy at large is predicated on the notion that the laser beam would be noticed by an alien race that is advanced enough to recognize the beam as being artificial. Moreover, the study also assumes that the intercepting race would be intelligent enough to decipher the message that would be contained in the flashing beam, which according to authors, could be used as a sort of Morse code transmitter to send data at the rate of a few hundred bits per second.
In practice, the proposed infrared laser beam would be at least ten times brighter than the Sun, but its actual energy density would be about 800 watts/per square meter, which compares favorably with the roughly 1,368 watts/square meter of the Sun. Given these values, the study suggests that as a practical matter, no intelligent alien race could possibly confuse the Sun with the laser beam, the implication (or hope) being that an intelligent alien race will necessarily interpret the flashing laser beam as our desire to be found.
In terms of practicalities, the technology to construct a megawatt-class laser already exists; a few years ago, Chinese scientists successfully tested a laser whose output reached several million billion watts, although these energy levels cannot be sustained for more than about a billionth of a second. Thus, a simple 2-megawatt laser should not present undue technical difficulties. In fact, a now-defunct US military laser, known as the “U.S. Air Force Airborne Laser”, could perhaps be revived since its power output is measured in megawatt. Moreover, a suitable optical telescope, the 39-metre European Extremely Large Telescope (ELT), is currently under construction in South America.
However, should we build a cosmic-scale searchlight/calling card just because the technology to do so is available (or within easy reach), but more to the point, do we want to be found? While the philosophical aspects of this question fall outside the scope of this article, there are several, and serious practical problems with the proposed project that need to be overcome, including, but not limited to the following:
The Laser Could Destroy Satellites
With a power output of 2 million watts, this laser is powerful enough to damage or even destroy the electronic circuitry and/or instruments of any of the hundreds of communication, weather monitoring and other scientifically oriented satellites that swarm around Earth, despite their built-in protection against solar radiation. In fact, trying to aim a laser this powerful through a dense halo of orbiting satellites is akin to throwing a stone at a swarm of bees and hoping not to hit any.
It Could Be Illegal
Although the USA has steadfastly refused to ratify the Outer Space Treaty, which among other things forbids the placing of weapons of mass destruction is space, the authors of the study suggest that the laser could be placed on the far side of the Moon. However, given its destructive potential, nations that have ratified the Treaty could argue that the laser is dangerous, and a de facto Weapon of Mass Destruction, Article IV of the Treaty may become relevant. This article reads thus:
“Parties to the Treaty undertake not to place in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner.”
In the interest of fair reporting though, the authors of the study have gone to some pains to point out that the exercise is nothing but a “feasibility study” and that apart from anything else, the laser could conceivably be used to analyze the atmospheres of exoplanets. These types of studies could include focused searches for the presence of gases and other substances that might indicate the presence of life, but chances are that this will raise more questions- given the fact that methane, which is one of the principal indicators of biological activity, almost certainly has an inorganic origin on Mars.
What do you think; should we build this laser and hope aliens find us at the end of it?