Are we alone in the universe?

We have come a long way since then astronomically and now we know that the Earth is just a small planet revolving around a dwarf star we call the Sun in a galaxy containing billions of stars. We also know that our galaxy, the Milky Way, is but one of millions of galaxies in an expanding universe and now that more than 100 extra solar planets have been discovered, we must wonder whether the Earth is the only planet on which life has appeared.

To adherents of the belief that there is a “Divine Plan” behind the creation of the universe and even to those who maintain that it is all due to chance, there must still arise that niggling question – why just the Earth when it has been shown that the elements necessary for a carbon-based life are common throughout the universe? Carbon is an element that is capable of multiple, flexible bonding and it is one of only six elements which are capable of bonding to more than three other elements, a condition necessary for life as we know it, so it is reasonable to suppose that life elsewhere in the universe, if it existed, would also be based on carbon.

The organic compounds which are the building blocks of terrestrial life have been found in meteorites, comets and interstellar clouds and they are common in the Milky Way. The number of stars like the Sun in our galaxy has been calculated by astronomers who have also determined the number of stars which resemble the Sun. Stars bigger and brighter than the Sun have shorter lifetimes and would have exploded before life could develop on any associated planets.

Stars smaller than the Sun with longer lifetimes would be too cold and dim to support life so that leaves sunlike stars as the only possibilities for the presence of life on their planetary systems. Even then, a number of other factors, including the distance of a particular planet from the star, would be important factors in the development of life. It must be remembered that, as far as it is currently known, life only exists on one planet in the Solar System. The presence of “Intelligent Life” on the Earth introduces another factor into the picture and to us, intelligent beings connote the capability of such beings to think creatively, carry out investigations, solve problems and develop technology among a number of other characteristics which distinguish the highest forms of life as we know it, human beings.

There are some, however, who would postulate that a very simple but efficient form of life, the virus, also possesses its own form of “intelligence” which is also manifested by various forms of microbial life.

The capability of microbial forms of life to thrive under a very wide range of conditions inimical to human life and the possibility that fossilised microbes were found on a meteorite known to have come from Mars, open up the possibility that some form of life could be found on other planets or their moons in the solar system.

This is an exciting possibility for astrobiologists who have already pinpointed Jupiter’s giant moon, Europa, and Saturn’s moon, Titan, as sites where such forms of life could have developed. The discovery of such organisms would cause as great an upheaval in astronomy –an other disciplines–as Galileo’s discovery of the moons of Jupiter and spots on the face of the Sun.

Such a discovery would pale, however, before the discovery of the presence of intelligent life in the Milky Way. The SETI ( Search for Extraterrestrial Intelligence) programme has been carrying out this search by looking for radio signals sent from extraterrestrial beings who, being intelligent and knowledgeable and technologically advanced, would use radio waves, which travel at the speed of light, to indicate their presence.

Radio astronomers constantly monitor favourable radio frequencies to look for such signals but, up to now, no such signals have been detected. The search goes on, both to look for lower life forms and signals from intelligent aliens, using ever more sophisticated equipment.

The possibility of the existence of extraterrestrial life will be the subject of a panel discussion led by Dr Brian Cockburn, Head of the Biochemistry Department, UWI, which will be the first item on the agenda of the Trinidad and Tobago Astronomical Society’s Family Day on Saturday from 5-8 pm. The public is invited and can call 645-7238 for details.