The Green Bank Formula Help (page 3)

By — McGraw-Hill Professional
Updated on Sep 17, 2011

Technological Advancement: F C

Even if a life form develops intelligence, it might not reach the level where it communicates by radio. On Earth, dolphins (porpoises) and whales can be considered intelligent to a degree. However, they lack hands with which to construct machines. Some porpoises have brains large enough to suggest that their intelligence surpasses that of Homo sapiens in some ways, but even if that is true, “dolphin smarts” are qualitatively different from “human smarts.”

Suppose that there exist planets covered by oceans teeming with marine animals having intelligence greater than our own. These animals would not have the physical ability to develop radio transmitters and receivers, cars, boats, and airplanes. They would have no need of these devices (as some people argue humanity has no need of radios, cars, boats, and airplanes). What proportion f c of intelligent species goes on to manufacture the means to communicate among the stars and to conduct their own SETI programs? It is hard to say. Let us suppose that 1 out of 10 planets with intelligent life harbors civilizations capable of communicating by radio; then that proportion f c is equal to 0.1.

Some scientists lump f i and f c together as a product because there is disagreement on exactly what level of brain power constitutes intelligence. Let’s get around this problem by estimating that f i f c = 0.01.

Average Lifespan Of Technological Civilizations: L

Once a civilization has become intelligent and has developed radio, and once it has turned its electromagnetic “ears” and “voice” to the heavens, how long will such beings remain capable of communicating? It is tempting to suppose that curiosity would drive any intelligent species, anywhere in the universe, to seek out life in other star systems, but we do not know this.

There is a dark point here: As part of our technological “progress,” we humans have created weapons of destruction that could annihilate our whole population or at least throw us back to near stone-age conditions. How likely is this? How long can we expect our society to exist as we know it, with radio telescopes and SETI programs? Let’s say that a civilization lasts for L years before evolving out of existence. What is the value of L ? Again, the best we can do is make a guess. During the 1960s and 1970s, at the height of the Cold War, many people became convinced that human civilization on Earth was doomed to bomb itself out of existence, and soon. Today this view is not as widespread, but unless and until Homo sapiens gets rid of its “war gene,” the danger remains.

Suppose that a planetary population, at least some of whom can communicate by radio, maintains this level of sophistication for at least 10,000 years before something—war, famine, disease, or asteroid impact—puts an end to it. Then L = 10,000. However, even in this case, after the disaster has passed, evolution would continue along its way, and in some cases this would lead to another technologically advanced civilization. This would multiply the value of L . Nevertheless, let’s be conservative and set L = 10,000.

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