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ET Phone Earth

Here's how scientists are bracing themselves for the moment aliens make contact; and what form it might take

By Matt Ransford Posted 6.17.08 at 1:18 pm 2 Comments

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The Birth of SETI
2001aspaceodyssey.org
Giuseppe Cocconi and Philip Morrison—two physicists at Cornell—began their 1959 article in Nature magazine quite frankly: we can't reliably estimate the probability of intelligent life out in the universe, but we can't dismiss the possibility of it either. We evolved and we're intelligent, so wouldn't it stand to reason that alien civilizations could arise on planets around other sun-like stars? In all likelihood, some of those civilizations would be older and more advanced than ours and would recognize our Sun as a star which could be host to life, with whom they would want to make contact. The central question of the paper was then: how would the beings send out their message?
Electromagnetic waves were the most logical choice. They travel at the speed of light and would not disperse over the tremendous distances between stars. But at which frequency? The electromagnetic spectrum is far too wide to scan in its entirety, so they made an assumption that has remained central to SETI research ever since. They would listen in at 1420 MHz, which is the emission frequency of hydrogen, the most abundant element in the universe. They reasoned it was the one obvious astronomical commonality we would share with an unknown civilization and that they would recognize it too.
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Military, Aviation & Space, aliens, Matt Ransford, SETI, space, ufos
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The Drake Equation
Cielo Sur
Only a few years later, in 1961, the nebulous assumptions Cocconi and Morrison parlayed in their article got a bonafide mathematical equation. Frank Drake [with equation, at left], along with a handful of other astronomers and scientists (including Carl Sagan) met in Green Bank, West Virginia to hash out the formula and variables necessary to make an educated guess at just how many intelligent civilizations might be living in our galaxy. As it turns out, assigning numbers to nebulous assumptions nets you an answer with enough variance to make you wonder if you were really clarifying those assumptions in the first place. The group came up with a range from less than a thousand to nearly a billion.
You might think the formula would have been refined over the years, but that is not the case. It has held up surprisingly well (though, for such a nebulous equation "held up" is a relative phrase). Data collected since the 1960s, which can be used to support the original estimates of measurable quantities like how often sun-like stars form and how many of those stars have planets, has proven those estimates to have been relatively accurate. The rest of the variables will never be quantified, such as what fraction of life evolves to become intelligent and what the average lifetime of an intelligent civilization is. Still, the equation has served as a focal point for SETI investigations over the years and continues to be valuable framework, however controversial.
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Military, Aviation & Space, aliens, Matt Ransford, SETI, space, ufos
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2 Comments

link to this comment

SeaDour

from Dayton, OH

06/20/08 at 2:57 pm

Why is there a little building drawn into the Mars Rover image? Is that a house with a smokestack?

See: http://csatweb.csatolna.hu/tagok/csa/mars/rover.jpg

link to this comment

prronred

07/21/08 at 2:20 pm

What other types of frequencies have been tried? What about lokking at Carbon. another abundant element?

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