The search for intelligent aliens on other planets

Reaching out in space

Photo: Marconi Company

In December 1901 Guglielmo Marconi, at Signal Hill, Newfoundland, received the first transatlantic signals.

In the movie Contact, the action starts with the Very Large Array, a large radio telescope in the U.S., picking up an alien radio signal.

This approach is typical of our current attempts to detect alien intelligences. We assume they will use radio messages to announce their presence, basically because that is what we would do.

Problems with this approach include having the need to have the antennas pointed in the right direction at the right time and having the radio receiver tuned to the right frequency.

Things are improving. Radio telescopes in operation or under construction can see larger and larger areas of sky, can monitor many frequencies at once and moreover, the search for alien signals can be piggy-backed on other experiments, making more observing time available.

Finally, we have to recognize the signal as artificial. This depends on how the information is imprinted on the radio transmission. Without knowing that, the signals might just sound like receiver noise or the hiss from the Milky Way.

So, can we assume our alien relatives will use radio communication methods at all?

Radio communication here on Earth really got going with an experiment conducted by Marconi, when he successfully sent a radio signal across the Atlantic, from Poldhu in Cornwall, U.K. to Signal Hill, Newfoundland.

The "experts" said that since radio waves are like light waves, they travel in straight lines and since Newfoundland is well below the horizon as viewed from Cornwall, the radio waves would just uselessly go off into space. Actually, in the introduction to Cosmos, we hear Marconi's transmission, three Morse code dots, way out in interstellar space.

The reason why Marconi succeeded is the signal bounced between the ground and an at-that-time unknown ionized layer in the upper atmosphere, now called the ionosphere. Until the advent of satellites, nearly all our long-distance communication systems used the ionosphere. That meant we had to live with the occasional occurrence of "radio blackouts", when the signals just vanished.

We now know these disasters are due to the Sun. We have ultraviolet radiation and soft X-rays from the Sun to create the ionosphere, but on occasion, solar activity can completely disrupt it, causing those blackouts.

A radio amateur friend told me that during recent outbursts of solar bad behaviour, she could not even get a radio signal from here in the Okanagan Valley to Vancouver, a distance of only a few hundred kilometres. These blackouts can last hours or days.

There are stars much less well-behaved than the Sun, such as many red dwarf stars. Their high levels of flare and other activity would render the ionospheres of their planets largely useless for radio communication. It is true that sending a radio message to the stars does not need an ionosphere to make it possible, but all those years of radio development leading to the technology for doing so grew along with systems that did need an ionosphere.

An obvious (to us) alternative to using radio transmitters to send messages to the stars is the high-power laser. Our optical telescopes could handle this. Orbiting telescopes could handle it better, because if our alien friends live on planets unlike ours, they might transmit their signals using wavelengths in the infrared or ultraviolet region of the spectrum, which are blocked by our atmosphere.

Another possibility is our alien friends might live in water, like dolphins, in which case they would know little about electricity or radio. Even if they can stop the water short-circuiting the electronics, radio waves don't easily pass through water.

Science fiction author Hal Clement imagined aliens who "see" using sound waves or radio waves.

If we can imagine such possibilities, consider what the universe, with its countless billions of stars and probably even more planets, and almost 14 billion years to work with, may have really come up with.

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Saturn rises around midnight and Venus around 2 a.m. Jupiter is low in the east before dawn. Mars is very low in the west after sunset. The Moon will be new July 24.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.