Goldilocks planets

Earth: The Goldilocks Planet

Earth has often been called the “Goldilocks Planet” of our solar system and even our universe. The term derives from the children’s story of “Goldilocks and the three bears” where the girl wanted everything just right, for example “not too hot or cold, not too hard or soft….” Our Earth has the perfect conditions for life, the perfect distance from the sun that is not too hot or cold, allowing a large amount of water to be present in liquid form. These conditions are perfect for life on earth as we know it and even a slight change in its properties could result in the extinction of a species.

The earth is located in the "Goldilocks" zone in our solar system, a remarkably small area of space. It is located approximately 150 million km away from the sun and travels in an elliptical orbit. This exact distance means that the temperature is not too hot to evaporate all of the water and not too cold to freeze it all, leaving a very suitable amount of water and land for a wide diversity of life. Water is essential for life as it is required for chemical reactions that sustain life; such as reactions in our body cells. In addition, ocean water absorbs a large amount of CO2 decreasing the rate of the greenhouse effect drastically, preventing many consequences of global warming. Furthermore, the mass of the earth and distance from the sun mean that "light" gases can be contained in its atmosphere; this includes oxygen which is vital for life on Earth. This also enables the atmosphere to be formed with a protective ozone layer, reducing the number of harmful UV rays from damaging life on earth. The mass of the earth is important as too little would only retain heavier gases whilst too large would retain a large quantity of hydrogen.

The Goldilocks properties of Earth also depend on its geological activity and star. The Sun is in a very stable form which will last for billions of years, allowing life to develop in the first place. Unstable stars with a short "lifespan" prevent life from developing significantly or at all. The earth is also not so big that it attracts large amounts of heavy meteors, preventing damaging disasters to life. Furthermore, the constant geological activity and moving tectonic plates mean that destroyed land is replaced, allowing room for advanced life to remain.

Critiques

Whilst the theory of Earth being the Goldilocks planet is popular, it may not be such a rare occurrence as most believe. The universe is said to be infinite with an uncountable number of solar systems within an equally high number of galaxies. Whilst the probability of a "Goldilocks Planet" existing with perfect conditions for life may be remarkably low, the sheer number of galaxies makes it almost certain that there are hundreds if not thousands of other "Goldilocks Planets". Astronomers have already claimed to have discovered other plants similar to earth; this includes "Gilese 581 g" discovered in 2010. Furthermore, the discovery of extremophiles shows that it is possible for life to exist in very extreme temperatures, pHs and oxygen levels. This suggests that life is not actually limited to the "Goldilocks Zone" in which the earth inhabits but life may be present on unexpected planets.

In addition, an article in the "New Scientist" explains how the earth was thought to be in the centre of the "Goldilocks Zone" but has now drifted a million km away from the "warm edge" of the zone. This suggests that Earth's properties may not be absolutely perfect for life but that the Earth is slowly drifting away into a much colder future.

Sources: http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-earth-k4.html#.Ui7loayvgwo http://www.oneminuteastronomer.com/3844/goldilocks-planet/ http://www.patheos.com/blogs/christandpopculture/2013/02/no-longer-just-right-the-implications-of-the-goldilocks-planet-shift/ http://www.bbc.co.uk/science/space/solarsystem/sun_and_planets/earth http://science1.nasa.gov/science-news/science-at-nasa/2003/02oct_goldilocks/ http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/habzone.htm