The Earth, our home, is the third planet from the Sun and the fifth largest among the eight planets of our solar system. The formation of the planet Earth along with the other planets of the solar system dates back nearly 4.5 billion years. The origins of the name Earth can be traced back to Old English ‘Earthe’ and German ‘Erde’.
The idea that our Earth too is a planet in the solar system, not unlike the other seven planets became clear only when Nicolaus Copernicus propounded his then controversial theory. He contradicted popular notions that the Earth was at the center of the Universe and claimed that the Earth like other planets revolved around the Sun.
The Earth is, however, quite unique and unlike the other planets in one respect. It is the only planet in our Solar System where the presence of water has been detected. This also means that it is the only planet that we know of in which life exists. Some 7.6 billion human beings and a diverse variety of flora and fauna live on Earth and the planet’s biosphere and natural resources support these species.
The Earth takes a little more than 365 days to complete one revolution around the Sun. It is tilted at an angle of 23.5 degrees and also rotates on its own axis. This rotation causes day and night and the revolution causes the change in season. This orbit of the Earth is elliptical in shape and thus the planet is not at the same distance from the Sun at all times. The Earth is the furthest from the Sun sometime in July and the distance of the aphelion is about 94.5 million miles.
A term that is commonly used when we speak of celestial bodies is Universe. The Earth is a planet in our Solar System. The Solar System is one of billions of such solar systems in our Milky Way galaxy. The Milky Way is only one of 100 billion galaxies that make up the Universe. The difference between the planet Earth and the Universe now starts to get clearer.
The Universe is believed to have been caused by a Big Bang some 14 million years ago. The Universe which contains all the stars, galaxies, dark matter, energy and time then started to expand at a rapid rate and continues to expand. The space occupied by the Universe is not measurable but the Earth’s mass is estimated to be about 5.972 × 10^24 kg with a surface area of 94.5 million miles. While the earth is made up of its Biosphere – lithosphere (rock), hydrosphere (water) and atmosphere (air) – the Universe is made up of matter and energy. These are interconvertible but the sum remains constant. This means that the matter and energy mass in the Universe is becoming less dense with its expansion.
Most of Earth’s life and phenomena have been the matter of in-depth study over the centuries but the Universe is still part of the great unknown since our observation of the Universe comes from light. Light travels at a speed of about 670,616,629 mph and it takes us many light years to observe the phenomena in the far reaches of the Universe.