Earth

When humans gaze out across the universe we see galaxies colliding, supernova explosions, and a huge diversity in values such temperature, distance, and time. Events happen on such a grand scale that it is hard not to feel a little insignificant in comparison. In reality, one of the most remarkable features of our Solar System is the near-constant stability of factors such as temperature, which have nurtured the development of life on Earth. A difference of few degrees was sufficient to turn Venus into a suffocating inferno, and yet Earth has retained the delicate balance required for millions of years.

While no single factor is responsible for the regulation, plants have an important role to play in the recycling of oxygen. If no plants existed on Earth the humans and animals would use up all the oxygen in less than 300 years. The future of the Earth's ecosystem is by no means assured. The use of phrases such as the greenhouse effect and global warming are now commonplace; in a geological blink of an eye we threaten to destroy the very balance that we depend on for life.

Water is a very unusual material, with lots of perculiar properties, and many scientists have now concluded that it is an essential component for the development of life. The search for life in our solar system has now turned into the search for water. Where ever water existed in a liquid form, life may have developed and thrived. The most likely candidate at present is Europa, one of Jupiter's icey moons. It is thought that geological activity could result in a warm water ocean beneath its frozen surface. The rarity of liquid water is another indication of how lucky we are here on Earth. Our tiny planet contains so much water that if the Earth was a perfectly smooth sphere it would be covered by a single ocean 2.8 kilometres deep.

One of our planets less obvious features is its magnetic field. Charged particles from the Sun, called the Solar Wind, pass the Earth at speeds of around a million miles per hour. As they slam into the magnetic field, a protective cocoon is created that surrounds the Earth. When the Solar Wind is particularly strong, some of the particles slip through and collide with the Earth's atmosphere, creating the spectacular aurora around the north and south poles.