Possibility of Life on Other Planets
Based on the Copernican principle, which states that Earth does not occupy a unique position in the Universe, and the mediocrity principle, which suggests that there is nothing special about life on Earth, leading scientists like Carl Sagan and Stephen Hawking have argued that it is improbable for life NOT to exist on other planets except Earth. Stephen Hawking who has won more than 20 different awards also believes that during the habitable Epoch following the Big Bang life may have independently emerged at many different places.
With an intention to stimulate dialogue and as a part of agenda to be discussed at the Green Bank conference, Frank Drake the University of California, Santa Cruz, astronomer devised an equation in 1961 which widely came to be known as the Drake's Equation. Though this is not considered to be a scientific tool for empirical analysis, it is accepted to be a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. The equation multiplies the following variables:
- The rate of formation of suitable stars.
- The fraction of those stars that are orbited by planets.
- The number of Earth-like worlds per planetary system.
- The fraction of planets where intelligent life develops.
- The fraction of possible communicative planets.
- The "lifetime" of possible communicative civilizations.
According to physicist Paul Davis, the universe is teeming with the building blocks of life such as elements of amino acids which connect to form proteins, for example rocks of Moon and surface of Mars have been found to contain these substances, which have been discovered with the help of spectral-analysis. It has been concluded that the whole universe is made up of the same elements as the Earth.
There are trillions of stars and thus at least one/fourth the number of solar systems in the universe and according to scientists one of every 10000 stars is capable of having a planet like Earth revolving around it. Keeping in mind the number of stars in the universe, this is really a big number. Another point given in favor of the possibility of life elsewhere is that carbon which is the most vital component of any life form is present everywhere in the universe. Carbon is capable of forming complex compounds by easily attaching with other elements such as oxygen, nitrogen, phosphorus, hydrogen etc. Thus it would not be a far-fetched idea that there can be other life forms present elsewhere in the universe.
According to scientists life has a lot of odds in favor of it. It can commence and survive in drastic conditions. Organisms are found to survive in areas strongly affected by heat, nuclear radiations, poisonous substances etc. Aquatic life is found in geysers of boiling water and in frozen water bodies. Thus it can be said that some life forms are very tough.
In the quest of extraterrestrial intelligence Dr. Frank Drake assembled a group of scientists. He ingeniously designed a formula called the ‘Drake’s Equation’. This equation is suggested to be the most useful weapon in finding the probability of extraterrestrial intelligence. The universe consists of more stars than there are grains of sand on all the beaches of the earth. The total number of stars which can have life supporting planets in their own solar systems is about 400 000 000 000. This is the first term of Drake’s equation. The second term represents the total number of stars which really have planets. We know now that there are other stars in the universe which have their own planets. In 1999 scientists found that there existed a planetary system around Epsilon Andromeda, a star similar to Sun. The next term in Drake’s equation represents all the earth like planets which can harbor life.
It has been proved that life starts its cycle of commencement, existence, survival and development at the first opportunity that it gets. The same had happened on our own planet when life started here. Thus it is not that difficult to logically assume that life could have originated elsewhere as well. Scientists know that amino acids and organic hydrocarbons are abundant in the universe. Comets, meteorites and interstellar gas have been found to harbor these building blocks of life. Even if intelligent life has been developed elsewhere, does it want to contact us? This is a really big question and the last factor of Drake’s equation. That is the Drake equation in a nutshell gives the number of intelligent lives that want to contact us.
Our Milky Way is estimated to contain another 200 billion planets. At least one of these might be having ideal conditions for commencement of organic life that might have developed into an intelligent one. What about the uncountable number of planets beyond our Milky Way? Life is known to survive in hostile environments such as vents of volcanic sites. So, if all this is true, why do we have to narrow our minds and constrict our notion in believing that only earth contains intelligent life?