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Johannesburg - With the recent discovery of an earth-like planet, Kepler 452b, about 1 400 light years away, the recent pictures of Pluto, and the return of the Star Wars movies, the debate around space and the existence of extra-terrestrials is intensifying.
While the search for aliens continues through organisations such as Seti (Search for Extra Terrestrial Intelligence), most of the public gets their information on aliens from Hollywood and science-fiction novels.
Here are five important scientific things to know about the search for life in the universe:
1) According to scientists, a planet that can support life should be in a 'Goldilocks' region
In Goldilocks and the Three Bears, the blonde heroine (or burglar, if you want to think of her like that), attempts to eat porridge, sit in a chair and sleep in the bed of a family of the three Ursidae.
One porridge was too hot, one too cold and one just right. She also finds big chairs, small chairs, a hard bed and a soft bed, before finding ones that are just right.
Earth is in the "just right" position for life to exist. It is the right distance away from the sun - not too close for all our water to be boiled away, and not too far away for all of it to be frozen.
A distant planet that could have life, might just need to be the right distance away from its star.
While scientists put the existence of water high on the list for the possibility of alien life, a few acknowledge that these extra-terrestrial beings might not necessarily need water for life.
2) If they exist, they might not be little green men, but single-celled organisms - like bacteria
While a being with large eyes, saying "take me to your leader" looks fantastic in the movies, it will be exceedingly hard to try and communicate with aliens that are microscopic.
This however, does not rule out the possibility that these potential beings won't exterminate life on our planet.
While larger aliens can blow up the White House and abduct human beings for probes, these little guys might just act like a virus when we interact with them - a virus our immune systems are not equipped to deal with.
3) An equation says aliens have to be out there somewhere
The universe is huge - so huge, in fact, that some estimates say there are more stars in the universe than grains of sand on Earth.
In 1961, American astronomer Frank Drake came up with an equation that determines the possibility of alien civilisations that could communicate through radio signals within our Milky Way galaxy.
This equation looks at the number of stars in the galaxy; the rate of star formation in the galaxy; the number of planets that could potentially support life; the fraction of planets with life that develop civilisations; and the fraction of civilisations that develop a technology that can give off signs to their existence and the length of time these civilisations release signals into space.
Drake, and the late famous astronomer and science writer/presenter Carl Sagan, determined that the Milky Way, which may have as many as 400 billion stars, has the potential for one million alien civilisations that could communicate through radio signals.
4) If the equation is correct, where is everyone?
Physicist Enrico Fermi once asked that if the universe was so big, why have we not yet made contact with extra-terrestrials.
Scientists put forth a lot of theories about why we have not heard from other alien civilisations and these theories include:
- Earth and humans are unique in the universe;
- Aliens could have visited the earth before humans were here;
- The universe is just too big, and signals could take millions of years to reach us;
- They are out there and are communicating with us, but our technology is too simple to pick up their messages;
- Some aliens are colonisers, so other alien civilisations have decided not to draw attention to themselves.
5) So, do aliens exist?
Given the size of the universe, the possibility of life besides that on Earth is high.
So the most scientific lay answer is... maybe.
