Saturday, February 21, 2015

Contacting Aliens

The question of whether intelligent extraterrestrial life exists or not has intrigued millions of people and has led to movies like E.T., Independence Day, and War of the Worlds. Movies like these show how innately curious we are about extraterrestrial beings. Since 1960, our curiosity has led us to start systematically scanning the sky for evidence of aliens, and even to try to contact them.

The first project in the Search for Extraterrestrial Intelligence (SETI) was named "Project Ozma" and was led by Frank Drake, who used a radio telescope in West Virginia to examine the stars Tau Ceti and Epsilon Eridani near the 1.420 Gigahertz frequency. That frequency is dubbed the "water hole" in the radio spectrum because of its proximity to the spectral lines of hydrogen and the hydroxyl radical, which combined make water, a necessity of life, and also because it is where extraterrestrials might gather to communicate, much like animals at the water hole. Since then SETI projects have mainly focused on using radio telescopes to search for signals that might give us any clues on whether extraterrestrial life exists. One of the well-known SETI projects, Sentinel, was led by Paul Horowitz, who built a spectrum analyzer to search for SETI transmissions that had 131,000 narrow band channels. Even then, the search came up empty. 

Not only have astronomers searched for extraterrestrial intelligence, but they have also begun transmitting messages as well, hoping that extraterrestrial life will hear them and respond. The first message was transmitted by the Arecibo Observatory Radio Telescope in Puerto Rico, the world's largest single-aperture telescope, in 1974. The first message described our solar system, the compounds important for life, the structure of the DNA molecule, and the form of a human being.

In the image below we see a color version of the message transmitted, the message consists of seven parts that encode the following:
1. The numbers one to ten.
2. The atomic numbers of the elements hydrogen, carbon, nitrogen, oxygen, and phosphorus, which make up DNA.
3. The formulas for the sugars and bases in the nucleotides of DNA.
4. The number of nucleotides in DNA, and a graphic of the double helix structure of DNA.
5. A graphic figure of a human and the human population of Earth.
6. A graphic of the Solar System indicating which of the planets the message is coming from.
7. A graphic of the Arecibo radio telescope and the dimension of the transmitting antenna dish.
The message was transmitted in the direction of the globular cluster M13, about 21,000 light years away.

The idea of communicating with aliens has caused a stir. The likes of Stephen Hawking and science fiction author David Brine agree that transmitting messages attract the bad kind of aliens depicted in movies ranging from War of the Worlds to Independence Day. Hawking imagines that our first contact with extraterrestrials could be like the Native Americans' first contact with Europeans, "which didn't turn out very well for the Native Americans." Others disagree, saying they will help us advance as a civilization. The deed is done, but it will be still a long time until we hear a response and find out whether sending messages was our greatest feat or our worst error.

- José Uribe