The planet Earth, our home and currently the only known place in the universe where life
exists. Named after the English and German words for "ground" Earth is the only planet
in the solar system that wasn't named after a Greek or Roman deity. It formed around 4.5
billion years ago from a swirling cloud of gas and dust, becoming the third planet from
the Sun, and the fifth largest planet in the solar system with a diameter of roughly 8000
miles or 13000 kilometres. Because of Ancient Greek philosophers, astronomers and mathematicians,
such as Pythagoras, Aristotle and Eratosthenes we have known that the Earth is round for
more than 2000 years. But not perfectly round, as it is really an oblate spheroid, which
is a result of the Earths rotation causing it to slightly bulge at the equator.
Similar to the other terrestrial planets, Earth is composed of four distinct layers,
a solid inner core, a hot liquid outer core, a thick flowing silicate rock mantle and a
thin rocky crust. Around the time of Earths formation, our planet also received a companion,
in the form of a moon that many of us call Luna or simply just "The moon". The moon likely
formed after a Mars-sized object collided with the young Earth, blasting debris out
into space and forming a smaller world that would eventually become the moon see today.
Our planet travels around the Sun at an average distance of 93 million miles away, which is
150 million kilometres away, keeping it well within a region known as the Goldilocks zone.
The Goldilocks zone, which is also known as the habitable zone, is the area around a star,
where the temperature is just right for liquid water to exist on the surface of a planet,
not too hot and not too cold. Currently, Earth is the only known world to
have oceans of freely flowing water on its surface, which covers roughly 71 percent of
the entire planet. In fact, there is so much water here, that if you were able to collect
it all into one ball, it would measure a massive 860 miles wide! Which is 1384 kilometres making
it bigger than the closest dwarf planet, Ceres! Surrounding the surface of Earth is a thick
atmosphere that is roughly 78 percent nitrogen and 21 percent oxygen, with trace amounts
of water vapour, carbon dioxide and other gases. The lowest part of the atmosphere is
known as the troposphere, which is constantly in motion and is where most of the weather
that we experience occurs. Then Around 31 miles, or 50 kilometres above the Earths surface
is the stratosphere and it is within this relatively still region that the ozone layer
exists, which prevents most of the suns harmful ultraviolet radiation from reaching the ground
and damaging life. Because of the Earths thick atmosphere, heat from the sun is also trapped,
causing the "greenhouse effect" to occur, which keeps our planet at a comfortable temperature.
However, if too much heat becomes trapped, then a process known as the "runaway greenhouse
effect" can occur, which is what led to the hellish environment that can now be seen on
Venus. Because of these warm and wet conditions,
as well as other key factors, life has been able to flourish across our magnificent planet
and it comes in all different shapes and sizes. From the strange almost alien-like blue jellyfish,
to the majestic tiger. As it stands, Earth is the only planet out of thousands that have
already been discovered, known to host life and it boasts several millions of species,
many of which are believed to remain undiscovered. Scientists debate a range of ideas about how
life on Earth began, however determining the actual origin of our existence is extremely
difficult because it began such a long time ago and finding fossils that old to study
is rare. However, The oldest known fossils of ancient microbes seem to date back to around
3.5 billion years ago, meaning that If we assume that life began on Earth, then it must
have started within a billion years of our planet's formation. On Earth, where there
is liquid water, there seems to be life and our planets primitive oceans are thought to
have formed around 3.8 billion years ago. Within these giant pools, the first ancient
microbes may have taken shape and over billions of years, their emergence may have given rise
to the millions of life forms that have thrived in Earths seas, lands and skies. Today we
can observe the wonders of this magnificent planet in many different ways, which is possibly
the most bizarre part of Earths history. An intelligent being that can ponder its own
existence and appreciate the majestic nature of this rare world, that we call home.