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Theory Observation
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Universe: Take the Tour!
Since the highest Antiquity, mankind turned to the stars and the sky. The diurnal and nocturnal luminaries were probably among the first things which began to shape men's dreams and thoughts. The following more advanced civilizations like Sumer or Babylone, devised more elaborated views of the Universe, sometimes mixed with astrological purposes, as it was eventually the Greeks who made the real debuts in astronomy as a science. The second great age of astronomy began during the
Renaissance in Europe, in the 15th and 16th centuries. Such men like Copernicus or Galileo Galilei developed a completely new view of how nature was working, or were the first to use telescopes to look at the celestial objects. This finally led to a comprehensive view of the Universe which was developed by Newton in the 17th century. In an everlasting and immaterial cosmos, the laws of gravitation have the planets journey around the Sun in an orderly fashion as the Universe around is populated of stars. This view was added to -and deeply modified too- by Einstein in the 20th century. Spacetime, gravity, mass and energy combine into an Universe, the most recent discoveries allow us to master since its very beginnings We were born 13.7 billion years ago from a quantum singularity which rushed out from nowhere. First elementary particles turned into thebuilding blocks of atoms. Atoms turned into molecules and, eventually, the first stars ignited. Avast network of hydrogen expanded, at the nodes of which quasars, galaxies, and galaxy clusters gradually formed. Our own Milky Way Galaxy has appeared 10 billion years ago, with the Sun and its procession of planets forming 4.5 billion years ago. Life on Earth appeared nearly as soon as the early formation of our planet The Earth is rotating each day at a speed of 320 mph, allowing for the nights and days, as its yearly motion around the Sun is determining the seasons. The Earth is the only place in the solar system where
life has been possible, and has been found. After our planet formed from a primordial cloud of dust and gas which was accompanying the forming Sun, the heat from the inside outgased, creating an atmosphere. It's that which allowed the first, elementary creatures to live and thrive. Such primitive forms of life, in turn, changed the composition of the atmosphere into the one we know today. Life progressively became more complex. Plate tectonics shaped the continents and the oceans. Earth thus became a complicated, vast, efficient, and life-minded medium. Earth is our craddle, illuminated by the Sun, as it's heavily moving in the void of space The companion planets of the Earth in the solar system are at the number of eight. Mercury, Venus, Mars, and Pluto are termed 'terrestrial planets' as they are mostly made of rocks like Earth. Jupiter, Saturn, Uranus, and Neptune are termed 'gas giants', as mostly made of gas. Terrestrial planets, Pluto excepted, formed in the inner part of the primitive solar system, where the radiation of the Sun had expelled most gas, leaving just heavy and
rocky material. Gas giants, at the opposite, formed further from the Sun, accreting vast layers of gas around a rocky core. It's how the solar system formed. Nine planets ranging from just near the Sun, to the far reaches of it. As far as each of the planets are concerned, Mercury is slowly rotating about itself as it'sorbiting the Sun in 88 days. Mercury is a desolated, Moon-like planet with vast swaths of cratered terrain. With space missions to it in the 1970s, Venus revealed how it was covered with a thick layer of clouds hiding its surface to the observer. Venus is a young, active planet where relief features are shaped by volcanism. Back to the Earth, with the Moon which, maybe, originated 4 billion years ago from the blow of an impactor unto the Earth. The debris spread thenaround and eventually accreted to form our Moon. Next is Mars. Mars is the Red Planet. It's about half the Earth's size, as it's now well-known due to a flurry of missions and landers. It's still unknown whether Mars ever sustained life or is still doing.
Large masses of water which once flowed on Mars, or a remaining geothermal activity seems fine places for life however. Once you clear Mars and that you cross the 'asteroid belt', a zone filled with small bodies which are leftovers of the formation of the solar system, you reach the realm of the giant planets. Jupiter, the king of the planets, with its 90,000 miles in diameter and its vast and terrific weather patterns, is surrounded by four main moons. Those moons were first seen by Galileo Galilei. Saturn comes then. Saturn is the famed 'ringed planet'. It's another world of gas and giant swirls of clouds, with a host of icy and coloured satellites.
Uranus and Neptune are two other gas giants, with their swarm of moons. Uranus is light blue-green as Neptune bluer. Pluto, at last, is found at the ultimate limits of the solar system. Pluto is the only of the nine planets which has not been visited by any space mission, as one is heading to there for an arrival in 2015. The solar system continues a vast distance beyond Pluto. Two belts of objects are lying in those darknesses, harbouring leftovers of the early solar system. It's such bodies which, from time to time, are perturbed into the inner solar system, where they shine in our skies like comets with their dusty and gaseous tails. Beyond those domains, it's the end of the solar domain and the beginning of the interstellar space
Once you leave the Sun, you enter the realm of stars. The nearest to us is the famed Alpha Centauri, 4.3 light-years from us, that is 25 trillion miles. Most stars are at barely more than that distance from each other. Most of them are usual and ordinary stars, sometimes smaller than our Sun. As we keep on to zoom back from our home port in space, we will begin to see the shape of our Milky Way Galaxy. The Milky Way Galaxy is a galaxy, that is one of those fireworks spirals which have been popularized by the astronomy media. Galaxies are vast ensembles of hundreds of billions stars. Our Sun is one of the swarms of stars of the Milky Way Galaxy. Due to that we are inside the Galaxy, we're not able to see it otherway than under the form of the Milky Way. We are seeing the Galaxy edge-on, from the inside. The stars, in a galaxy, do form from the clouds of gas and dusts, likely due to shockwaves perturbing the equilibrium of them. Yellow stars in a galaxy are the old ones, as blue are the youngests. All stars are orbiting around the center of the galaxy, as, for example, we, with our Sun, we are taking 250 million year to make one orbit in our Galaxy! Most galaxies are now known to harbour at their center monster black holes, of the size of the orbit of Mercury, where matter is swallowed with no hope of return
Most galaxies are living a social life, as they are part of vast groups of them. Such clusters of galaxies have a dynamical life, with the galaxies in there enduring huge collisions! The further we would get from our Sun, our Earth and our Galaxy, the further still from our Galaxy and its galaxy cluster, we would begin to catch the shape of a vast filamentary web of hydrogen gas, stretching along billions of light-years. Such a web is the ultimate structure of our Universe. The Universe, since its inception, is keeping expanding, stretching ever and ever. The filamentary web structure found its origin in the early origins of the Universe. The Universe was born, 13.7 billion years, from what is called a 'quantum event', an event which unfolded according to the physics of the elementary particles. A tremendously energetic field of vacuum-based, anti-gravitational energy was in equilibrium atop an energy field, as quantum fluctuations dumped the field into the trough which was surrounding the plateau of equilibrium. That's better known under the name of the 'Big Bang', as it's from this gigantic flash of energy that our Universe was created, in terms of space like in terms of time. The descent of the plateau into the trough was accompanied of random oscillations. It's those oscillations which got imprinted into the early structure of the Universe, and which later expanded, giving birth to the filamentary structure we can observe today
The whole Universe was already present at the very beginnings of the Big Bang. The rest was just a question of logical evolution. After it endured a phase of swift and important increase in size -that's called the 'inflation', as the Universe inflated enormously- the various forces at work in our Universe progressively became distinct, as all the elementary particles we know today formed. Then the first stars began to form and light some 200 million year after the Big Bang. Galaxies and galaxy clusters appeared then, all this leading to populating the Universe. The Universe, since then, kept expanding, leading to where, and what, we are today. As far as what's ahead is concerned, it seems like, first, our Sun will swollen into a 'red giant', engulfing the orbits of the inner planets -of them of the Earth, hence putting an end to our own history in some 5 billion years from now. The Universe, on the other hand, is bound to expand forever, with the gazeous filaments stretching until the end of times, keeping forming stars and galaxies until all the matter will have be churned again and again, leading to an everlasting void and darkness... The most advanced present researches, at last, thinks that the quantum event which gave birth to our Universe might have given birth to other universes too which, for cause of the singularity of their laws of nature, will forever remain out of reach...
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