Intelligent life on this planet in the form of two Russian science writers has suggested that Tunguska was mistakenly zapped by a laser sent by ETs from a giant planet orbiting the star 61 Cygni, about eleven light-years away from us. In a lengthy article published in the magazine Zvezda in 1964, Genrikh Altov and Valentina Zhurav-leva said that the violent volcanic eruption of Krakatoa in August 1883 generated strong radio waves. This signal was received eleven years later by Cygnian scientists. But they misread the signal as greetings from a distant civilisation.
Following the ages-old Cygnian custom, the courteous scientists decided to send a return message. As their laser technology was more advanced than the radio technology, they directed a laser beam at our planet. Unfortunately, the well-meaning scientists made another mistake. This time they misjudged the Earth's distance and fired a powerful laser beam that zapped the Tunguska taiga. This 'extra strong' Cygnian message was all Greek to the local Evenki people; they did not have the required technology to read their greeting card from the stars.
How could a volcano generate a radio signal? Altov and Zhuravleva simply said that the volcanic ash, flung high into the atmosphere, disturbed the ionosphere, which could have generated a radio signal. The signal was so strong that it reached far out into space. The writers' choice of the star 61 Cygni was obvious: 61 Cygni is a binary star; in 1964 one of its two stars was the only one known to have an extra-solar planet. Now we know that extra-solar planets are common in our galactic neighbourhood. Now we also know that lasers can be used for interstellar communication.
In 1960 Drake made the first real attempt to listen to ETs. In Project Ozma (named after the queen of The Wizard of Oz), he aimed a 26-metre radio telescope at the stars Tau Ceti and Epsilon Eridani, some eleven light years away. For two months he listened for radio signals at 1.5 gigahertz, the frequency emitted by hydrogen gas. He chose this frequency because hydrogen is the most common element in the universe. Of course, the search yielded nothing. Since then, more than 100 powerful radio searches have also failed to make any contact. Why have no intelligent radio signals been picked up? Some scientists say that listening to radio signals or sending them might not be the right way to make contact. They suggest that an interstellar laser might be a better communicator.
The American physicist Charles Townes, who was awarded the 1964 Nobel Prize for his hand in the invention of laser, realised around the time that Drake aimed his telescope at distant stars that ET civilisations could just as easily exploit the optical and infrared portion of the spectrum as the radio portion. Decades passed before laser technology had advanced to the point where powerful lasers capable of sending interstellar messages could be made.
Lasers have two main advantages over the millions of radio channels available for broadcasting: light is easier to focus into a tight beam than radio waves; and it is a better carrier of information. A tight laser beam can be easily focused on a target, and it can transmit a whole encyclopaedia in a second - much better than simply asking 'Is anyone out there?' by a radio wave. But lasers are not as cheap as chips (or radios); they require billions of kilowatts of energy to broadcast for a fraction of a second.
Scientists may one day succeed in sending a laser message to their Cygnian counterparts who mistakenly zapped the beautiful Tunguska taiga. An apology is overdue.
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