In the 16th century, Nicolaus Copernicus demonstrated that the Earth was not the centre of the solar system. Astronomers, since then, have show our solar system to be a tiny part of our galaxy, the Milky Way, which is, in turn, only a pin prick in the billions or trillions of galaxies that make up the Universe.
Earth is thus a minuscule part of creation. And it is this insignificance that leads to the Principle of Mediocrity, which says that the Earth holds no special position in the universe. Consequently, among the billions of stars and the planets circling them, there will be other Earth-like planets on which intelligent life has also developed.
There is no reason to believe otherwise — if life can develop here, life, even intelligent life, can develop elsewhere, too. It’s just that we haven’t detected it, yet.
It is this sort of thinking that have led scientists at Nottingham University, in the UK, to re-consider the famous Drake equation for calculating the number of instances of intelligent life that are out there, somewhere.
The Drake equation
In 1961 the American astronomer and astrophysicist, Frank Drake, formulated an equation for estimating the number of active communicating extraterrestrial civilizations. Drake presented it at the first scientific meeting of SETI (Search for ExtraTerrestrial Intelligence) not so much as a method for quantifying the precise number of civilizations that might be found but rather as a way of stimulating scientific dialogue about the topic.
The equation consists of seven parameters that when multiplied together should give an approximation of the number of intelligent civilizations. The problem is that while some of the parameters are measurable, such as the rate of star formation, others are not, such as the number of planets that could support life and then actually go on to do so, or the length of time that an intelligent civilization emits detectable signals (before, presumably, dying off).
This has led to people using the equation with widely differing assumptions and producing wildly different results (from there being millions of other intelligent civilizations to there being none at all).
The Nottingham approach
The researchers at Nottingham University have come up with a new Drake-like equation by making the assumption that if an Earth-like planet exists for enough time in the right orbit around a suitable star, then intelligent life will develop in the same way as it has on Earth.
In other words, since the Earth is assumed not to be unique, life must have developed on other similar planets in much the same way.
This simplifies the calculations as we know the age of the Earth is around 5 billion years, we know the type of star it orbits and the distance from it, and we know its physical makeup. We also can make the assumption that an intelligent civilization will emit detectable signals for at least 100 years because that’s what has happened here.
So, looking for planets that fit the same pattern as Earth, we should be able to estimate how many CETIs are out there.
It should be said that the researchers understand that this is speculative exercise, that there is an overwhelming lack of solid evidence, and that basing their calculation on a single data point (that is to say us) is debatable.
However, from their calculations, they consider that the most likely number of CETIs in our galaxy is around 30 (although it could be in a range from only a handful up to hundreds), and that the nearest ought to be around 17000 light years away. A two way communication is consequently unlikely as a signal and its response will entail a round trip of 34000 years.
That being said, if we do find a CETI closer than that, according to the researchers, that would imply that intelligent communicating civilizations last longer than 100 years, which, is good news for us.
Originally published at http://mralanjones.blogspot.com.