Written by Carmelo Amalfi Friday, 26 March 2010 12:09
THE fourteenth day of the third month (3.14) celebrates a remarkable constant of nature - pi. It appears in equations describing the orbits of planets and the structure of DNA.
Pi is a mathematical constant whose value is the ratio of any circle’s circumference to its diameter, 3.141593.
This irrational number whose decimal representation never ends or repeats, is also known as Archimedes constant.
Greek mathematician Archimedes was the first to estimate the value of pi more than 2000 years ago. The earliest use of pi dates back to its use to calculating the shapes and designs of the Old Kingdom pyramids in Egypt.
The decimal place of pi calculated to 11 decimal places is accurate enough to estimate the circumference of any circle that fits inside the earth with an error of under one millimetre.
The decimal place of pi calculated to 39 decimal places is accurate enough to estimate the circumference of any circle that fits in the observable universe with precision, comparable to the radius of a hydrogen atom.
Pi is also used in the search for extra-terrestrial intelligence. Multiplying Pi by the frequency of hydrogen creates a ‘cosmic channel’ with which to communicate.
The 21cm hydrogen line refers to the spectral line created by changes in the energy state of neutral hydrogen and occurs at a frequency of 1420 megahertz.
Scientists use this value to search for advanced civilisations transmitting at 1420MHz, on the so-called ‘interstellar communications channel’.
CSIRO Australia Telescope National Facility astrophysicist Ray Norris says most searches to date have focused on radio waves in the frequency range 1000MHz to 3000 MHz because they travel the greatest distance.
The sorts of alien signals we might search for, include directed interstellar communication designed for emerging civilisations such as our own; interstellar communications between two other civilisations; and stray signals from a planet.
The trick is to detect artificially constructed signals buried among the natural radio waves emitted by stars and galaxies.
“In the case of guessing a frequency that an alien will also guess, the problem seems daunting, as we know nothing about the culture of the civilization,” he says.
“Fortunately, however, there are some ‘universal frequencies’ such as the natural frequency of the hydrogen atom, which rings like a tuning fork at a microwave frequency.
“All civilisations anywhere in the universe will be able to agree on this because hydrogen, the most basic element of the universe, is the same everywhere.”
Because of natural interference from the hydrogen gas clouds that drift through the galaxy, scientists combine the frequency of hydrogen with universal constants such as pi - the ratio of the circumference of a circle to its diameter.
Professor Norris says with 100 billion stars in the Milky Way, and the 100 billion galaxies in the observable universe, it seems inconceivable that at least one of these planets does not support life forms.
