Looking for Astronomy Stuff?
Visit the Stargazer's Room

Whether viewed as good or evil, the presence of aliens from outer space has been a staple of science fiction since the first Martian Invasions described by H.G. Welles in War of the Worlds. So far, however, we have yet to host anyone from the surrounding heavens...although a few who claim to have been abducted may beg to disagree.

Earth, however, is unique among the planets in our Solar System: her temperatue climate and warm blanket of air protect us from the harshness of space, and it is an open question just how common life is---yet alone intelligent life, capable of traveling the stars and seeking out other forms of life.

Of course, for some the existence of intelligent life on Earth remains the subject of debate, and it is far too early for us to close the door on those possibilities. Realistically speaking, however, Man is unlikely to venture too far from home in the near future. We have visited the Moon...and a trip to Mars seems possible, if expensive...but vacationing in the next star system must lie in our future, if it is possible at all. And given the odds against intelligence arising in the first place, our current understanding of physics seems to cast our meeting exotic forms of exo-biology any time soon. As Ken Charnley observes, the extraterrestrials may well be calling each other, but they are unlikely to be calling us any time soon.

The Extraterrestrials Will Not Call

By: Ken Charnley

The Earth is unique within our solar system. It is the only planet with intelligent life and it has features which suggest that planetary situations similar to ours are quite rare.

Earth falls within what is usually called the life corridor of our sun, which lies within distances ranging from about the orbit of Venus to about the orbit of Mars. Mercury is too hot ever to support life, and the gravity and coldness of the gas giants (Jupiter, Saturn Uranus and Neptune) preclude life from arising on them.

Neither Mars nor Venus has produced intelligent life. Mars appears to be too small to hold an atmosphere, and Venus, while about the right size, suffers from a runaway greenhouse effect totally inimical to life.

The gas giants mentioned above do seem to protect the Earth from excessive impact from comets, stray asteroids and the like. Remember Schumacher-Levy 9, the String-of-Pearls comet that impacted Jupiter in 1994? Have no doubt had it impacted the Earth none of us would be here today.

Earth has other special qualities. Firstly, it wobbles. The gentle rocking motion of the Earth during its orbit around the sun gives us our seasons. Secondly, our Moon is the largest satellite in proportion to the size of its planet in our solar system. Large, and relatively close by, the moon gives us our generous tides.

The regular tidal and seasonal rhythms are in my view most likely to give the kind of selection pressures and opportunities to promote the arrival of the earliest life forms capable of emerging from the seas, the first amphibians. If life does not make it to land, then there will be no communicative intelligent life.

As we all know, the Earth has vast oceans of liquid water. Liquid water does function to sustain life, and arguably to allow life to originate in the first place, but it does serve another purpose. Much has been written lately about the problems associated with the greenhouse effect, caused by atmospheric gases absorbing radiation in the infrared band, and causing the Earth to warm unacceptably. We do, however, need some of this effect.

With no greenhouse effect at all we would freeze. Water vapour in the atmosphere supplies that necessary level of greenhouse gas to keep the Earth's surface temperatures liveable. We not only need liquid water, but plenty of it. Time scales are another problem. We have no information on the survival time for civilisations such as our own, except that we seem to be doing our best to provide some statistical data on that point.

We do know we have had some forms of life here for more than 3 billion years, but we have been here less than a quarter of a million years, and about 100 years with radio communications. We and other intelligent life forms may arrive, flourish and die with no opportunity to contact one another. We will not be chatting with the Extraterrestrials.

Article Source: http://mywebauthor.com

Ken Charnley is a personal finance enthusiast with www.online-loans-pro.com/ dedicated to quality information on online loans. For all your online loan needs visit and Apply For Loans Online Article Submission done by: www.articles-submit.com,

Courtesy of: Articleteller.com

On the other hand, there are some things that are simply too nifty or intriguing to let such details as cosmic distances or the Laws of Physics stand in the way. And as long as there are dreamers among us, there will be those who refuse to accept conventional limits on our understanding of the Universe.

Five hundred years ago, science was certain that it was impossible for Man to fly. Among those who refused to accept this physical limitation was a gifted visionary and artist named Leonardo Da Vinci, whose rough design for a flying machine is recognizable today as the imaginings of genius. We do not really know what the future holds in store for us, and our understanding of Science will always be limited by our own imperfect knowledge. And let us hope that there is always a place for dreamers, visionaries, and those whose views of the Future are not constrained by the limits of Today.