Thursday, 29 January 2015


"The possession of knowledge does not kill the sense of wonder and mystery. There is always more mystery." – Anaïs Nin

SETI is an acronym that stands for “Search for Extra-Terrestrial Intelligence”, the designation of a series of projects based mainly on attempts to detect artificial radio transmissions from outer space. Here is the web page of the SETI organisation:

I was reminded of this word by a report in the news that yet another batch of new Earth-like planet was discovered close to us, in our backyard, so to speak (in cosmic terms!). Astrophysicists from around the world, including a team from the University of Sydney, have found a Sun-like star with five orbiting planets, which dates back to the dawn of the galaxy. The scientists have determined that the star is 11.2 billion years old, making it the oldest system with Earth-sized planets ever discovered.

The certainty of finding other intelligent life forms in the universe was established by the Drake Equation, which was developed by Frank Drake in 1961 as a way to focus on the factors which determine how many intelligent, communicating civilizations there are in our galaxy. The Drake Equation is:
N = N* fp ne fl fi fc fL

The equation can really be looked at as a number of questions:
N* represents the number of stars in the Milky Way Galaxy
Question: How many stars are in the Milky Way Galaxy?
Answer: Current estimates are 100 billion.

fp is the fraction of stars that have planets around them
Question: What percentage of stars have planetary systems?
Answer: Current estimates range from 20% to 50%.

ne is the number of planets per star that are capable of sustaining life
Question: For each star that does have a planetary system, how many planets are capable of sustaining life?
Answer: Current estimates range from 1 to 5.

fl is the fraction of planets in ne where life evolves
Question: On what percentage of the planets that are capable of sustaining life does life actually evolve?
Answer: Current estimates range from 100% (where life can evolve it will) down to close to 0%.

fi is the fraction of fl where intelligent life evolves
Question: On the planets where life does evolve, what percentage evolves intelligent life?
Answer: Estimates range from 100% (intelligence is such a survival advantage that it will certainly evolve) down to near 0%.

fc is the fraction of fi that communicate
Question: What percentage of intelligent races have the means and the desire to communicate?
Answer: 10% to 20%

fL is fraction of the planet's life during which the communicating civilisations live
Question: For each civilization that does communicate, for what fraction of the planet's life does the civilisation survive?
Answer: This is the toughest of the questions. If we take Earth as an example, the expected lifetime of our Sun and the Earth is roughly 10 billion years. So far we've been communicating with radio waves for less than 100 years. How long will our civilization survive? Will we destroy ourselves in a few years like some predict or will we overcome our problems and survive for millennia? If we were destroyed tomorrow the answer to this question would be 1/100,000,000th. If we survive for 10,000 years the answer will be 1/1,000,000th.

When all of these variables are multiplied together we come up with: N, the number of communicating civilisations in the galaxy.

Considerable disagreement on the values of most of these parameters exists, but the values used by Drake and his colleagues in 1961 were: 
    * R* = 10/year (10 stars formed per year)
    * fp = 0.5 (half of all stars formed will have planets)
    * ne = 2 (2 planets per star will be able to develop life)
    * fl = 1 (100% of the planets will develop life)
    * fi = 0.01 (1% of which will be intelligent life)
    * fc = 0.01 (1% of which will be able to communicate)
    * L = 10,000 years (which will last 10,000 years)

Drake's values give N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10 communicating civilisations in the galaxy.

Some people may shrug off the whole SETI project as a pointless exercise and a waste of time, money, people power. Many more say that it takes up valuable resources that could be used better elsewhere, improving the lot of the underprivileged in this world, for example. Fundamentalists may say that the earth is the only place created by God and hence the only one populated by sentient beings with a soul. Others may object to the search on the grounds that even if many civilizations are there in the stars, they are so far form us that it does not make any difference to us one way or another, as we may never contact them.

As for myself, I am a rational, sentient, logical being who has been trained in the sciences. I possess an inordinate amount of curiosity and my imagination is boundless. I support SETI as I think it utilises only a small fraction of resources compared to the enormous amounts that are spent on other less necessary endeavours - say, military spending. I would like us to find evidence of life elsewhere in the Universe, as the Drake Equation predicts that this is a distinct possibility. Even if we never contact other sentient beings in the universe directly, I think that knowing certainly that they exist will change us as a species…

What do you think? Do you think there is extraterrestrial life? Do you support SETI?

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