Home to millions of species, including humans, Earth is the only place in the universe where life is known to exist. Scientific evidence indicates that the planet formed 4.54 billion year’s ago, and life appeared on its surface within a billion years. Since then, Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful radiation, permitting life on land.
The orbit of the Earth relative to the Sun is slightly different each year, mostly because the gravity of the other planets pulls the Earth a bit closer to themselves, and the locations of the planets are different each year. Even with these perturbations, the shape of the orbit of the Earth looks very much like an ellipse, and next year's ellipse is very close to this year's ellipse. The exact orbit that the Earth follows is not any well known geometrical shape, and it is not possible to describe that exact orbit in just a few words.
The Big Bang Theory is a cosmological model of the universe originally conceived to describe the origins of the universe that has become well supported by several independent observations. After Edwin Hubble discovered that galactic distances were generally proportional to their red shifts in 1929, this observation was taken to indicate that the universe is expanding. If the universe is seen to be expanding today, then it must have been smaller, denser, and hotter in the past. This idea has been considered in detail all the way back to extreme densities and temperatures, and the resulting conclusions have been found to conform very closely to what is observed.
In cosmology, the cosmic microwave background radiation is a form of electromagnetic radiation discovered in 1965 that fills the entire universe. It has a thermal black body spectrum at a temperature of 2.725 kelvin. Even thou the spectrum peaks in the microwave range at a frequency of 160.2 GHz, corresponding to a wavelength of 1.9 mm. Most cosmologists consider this radiation to be the best evidence for the Big Bang model of the universe. This helps us determine the age and the size of the earth even thou no one was around at the begging of the earth’s time.
The solar system started as a huge cloud of dust and gas called a nebula. This nebula was very cold. However, something caused this nebula to start collapsing under its own gravity. As it collapsed, 99% of the material collected into the center where the Sun would eventually form. The rest of the material collapsed down into a disk of material that swirled around the forming Sun. As the Sun began form, the temperature at the center of our forming solar system rose. This controlled what materials were available to for the formation of planets. Here in the inner solar system, the temperatures we too high for anything but rocky materials, iron, and nickel to form solids. As a result of this, these are the materials from which the inner planets were built. In the outer solar system, it was cold enough for water, methane, and ammonia to form solids. So, the planets of the outer solar system were built from these materials as were as the rocky and metallic solids. With the addition of these ices to the mix, the planets of the outer solar system were able to grow big enough to grab and hold onto even the hydrogen and helium gas that was present in the solar nebula. Thus these planets grew into the gas giants. Comets from this part of the nebula also came into the inner solar system. It is from these comets that the inner planets (Earth included) got what volatiles they did. In Earth's case, it was enough to produce our rather thin atmosphere and our oceans.
The Earth is a one of a kind planet, it is the only planet so far that have living things found on it. There is human life on earth and not even another living thing on any other planet. Because of the cloud of dust call nebula the earth was created and can not be destroyed.
http://en.wikipedia.org/wiki/Solar_system
http://en.wikipedia.org/wiki/Nebula
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