How The Life Begin

Subsequent evolution The planets were originally thought to have formed in or near their current orbits. From that, a minimum mass of the nebula i.e. the protoplanetary disc was derived that was necessary to form the planets – the minimum mass solar nebula. It was derived that the nebula mass must have exceeded 3585 times that of the Earth. However, this has been questioned during the last 20 years. Currently, many planetary scientists think that the Solar System might have looked very different after its initial formation: several objects at least as massive as Mercury were present in the inner Solar System, the outer Solar System was much more compact than it is now, and the  Kuiper belt  was much closer to the Sun. Terrestrial planets At the end of the planetary formation epoch, the inner Solar System was populated by 50–100 Moon- to Mars-sized  planetary embryos . Further growth was possible only because these bodies collided and merged, which took less than 100 mil

The  giantplanets  ( Jupiter ,  Saturn ,  Uranus , and  Neptune ) formed further out, beyond the  frost line , which is the point between the orbits of Mars and Jupiter where the material is cool enough for volatile icy compounds to remain solid. The ices that formed the Jovian planets were more abundant than the metals and silicates that formed the terrestrial planets, allowing the giant planets to grow massive enough to capture hydrogen and helium, the lightest and most  abundant elements. Planetesimals beyond the frost line accumulated up to 4  M ⊕  within about 3 million years.  Today, the four giant planets comprise just under 99% of all the mass orbiting the Sun. heorists believe it is no accident that Jupiter lies just beyond the frost line. Because the frost line accumulated large amounts of water via evaporation from infalling icy material, it created a region of lower pressure that increased the speed of orbiting dust particles and halted their motion toward the Sun. In effec

Formation of the planets See also:  Protoplanetary disk The various planets are thought to have formed from the solar nebula, the disc-shaped cloud of gas and dust left over from the Sun's formation. The currently accepted method by which the planets formed is  accretion , in which the planets began as dust grains in orbit around the central protostar. Through direct contact, these grains formed into clumps up to 200 metres in diameter, which in turn collided to form larger bodies ( planetesimals ) of ~10 kilometres (km) in size. These gradually increased through further collisions, growing at the rate of centimetres per year over the course of the next few million years. The  inner Solar System , the region of the Solar System inside 4 AU, was too warm for volatile molecules like water and methane to condense, so the planetesimals that formed there could only form from compounds with high melting points, such as metals (like  iron ,  nickel , and  aluminium ) and rocky  si

Pre-solar nebula The nebular hypothesis says that the Solar System formed from the gravitational collapse of a fragment of a giant  molecular cloud . The cloud was about 20  parsec  (65 light years) across, while the fragments were roughly 1 parsec (three and a quarter  light-years ) across. The further collapse of the fragments led to the formation of dense cores 0.01–0.1  pc  (2,000–20,000  AU ) in size. One of these collapsing fragments (known as the  pre-solar nebula ) formed what became the Solar System. The composition of this region with a mass just over that of the Sun was about the same as that of the Sun today, with  hydrogen , along with  helium  and trace amounts of  lithium  produced by  Big Bang nucleosynthesis , forming about 98% of its mass. The remaining 2% of the mass consisted of  heavier elements  that were created by  nucleosynthesis  in earlier generations of stars. Late in the life of these stars, they ejected heavier elements into the  interstellar medium .

Formation and evolution of the Solar System Jump to navigation Jump to search Artist's conception of a  protoplanetary disk The formation and evolution of the  Solar System  began 4.6  billion years ago  with the  gravitational collapse  of a small part of a giant  molecular cloud . [1]  Most of the collapsing mass collected in the center, forming the  Sun , while the rest flattened into a  protoplanetary disk  out of which the  planets ,  moons ,  asteroids , and other  small Solar System bodies formed. This model, known as the  nebular hypothesis  was first developed in the 18th century by  Emanuel Swedenborg ,  Immanuel Kant , and  Pierre-Simon Laplace . Its subsequent development has interwoven a variety of scientific disciplines including  astronomy ,  physics ,  geology , and  planetary science . Since the dawn of the  space age  in the 1950s and the discovery of  extrasolar planets  in the 1990s, the model has been both challenged and refined to account

What If the Big Bang Wasn't the Beginning? Was the universe created with a Big Bang 13.7 billion years ago, or has it been expanding and contracting for eternity? A new paper, inspired by alternative explanations of the physics of black holes, explores the latter possibility and rejects a core tenet of the Big Bang hypothesis.   The universal origin story known as the Big Bang postulates that, 13.7 billion years ago, our universe emerged from a singularity — a point of infinite density and gravity — and that before this event, space and time did not exist (which means the Big Bang took place at no place and no time).   There is ample evidence to show that the universe did undergo an early period of rapid expansion — in a trillionth of a trillionth of a second, the universe is thought to have expanded by a factor of 10 78  in volume. For one, the universe is still expanding in every direction. The farther away an object is, the faster it appears to move away from an observ

Grand unification epoch Between 10 −43  seconds and 10 −36 seconds after the Big Bang Main article:  Grand unification epoch As the universe  expanded  and cooled, it crossed transition temperatures at which forces separated from each other. These  phase transitions  can be visualised as similar to  condensation and  freezing  phase transitions of ordinary matter. At certain temperatures/energies, water molecules change their behaviour and structure, and they will behave completely differently. Like steam turning to water, the  fields  which define our universe's fundamental forces and particles also completely change their behaviors and structures when the temperature/energy falls below a certain point. This is not apparent in everyday life, because it only happens at far higher temperatures than we usually see in our present universe. These phase transitions in the universe's fundamental forces are believed to be caused by a phenomenon of  quantum fields  called " sy

Electroweak epoch Between 10 −36  seconds (or the end of inflation) and 10 −32  seconds after the Big Bang Main article:  Electroweak epoch Depending on how epochs are defined, and the model being followed, the  electroweak epoch  may be considered to start before or after the inflationary epoch. In some models it is described as including the inflationary epoch. In other models, the electroweak epoch is said to begin after the inflationary epoch ended, at roughly 10 −32  seconds. According to traditional big bang cosmology, the electroweak epoch began 10 −36  seconds after the Big Bang, when the temperature of the universe was low enough (10 28  K) for the  Electronuclear Force  to begin to manifest as two separate interactions, called the  strong  and the  electroweak  interactions. (The electroweak interaction will also separate later, dividing into the  electromagnetic  and  weak  interactions). The exact point where electrostrong symmetry was broken is not certain, becaus

Between 10 −43  seconds and 10 −36  seconds after the Big Bang [6] Main article:  Grand unification epoch As the universe  expanded  and cooled, it crossed transition temperatures at which forces separated from each other. These  phase transitions  can be visualised as similar to  condensation  and  freezing  phase transitions of ordinary matter. At certain temperatures/energies, water molecules change their behaviour and structure, and they will behave completely differently. Like steam turning to water, the  fields  which define our universe's fundamental forces and particles also completely change their behaviors and structures when the temperature/energy falls below a certain point. This is not apparent in everyday life, because it only happens at far higher temperatures than we usually see in our present universe. These phase transitions are believed to be caused by a phenomenon of  quantum fields  called " symmetry breaking ". In everyday terms, as the un

Planck epoch Times shorter than 10 −43  seconds ( Planck time ) Main article:  Planck epoch The  Planck epoch  is an era in traditional (non-inflationary)  Big Bang cosmology immediately after the event which began our known universe. During this epoch, the temperature and average energies within the universe were so high that everyday subatomic particles could not form, and even the four fundamental forces that shape our universe— electromagnetism ,  gravitation ,  weak nuclear interaction , and  strong nuclear interaction —were combined and formed one fundamental force. Little is understood about physics at this temperature; different hypotheses propose different scenarios. Traditional big bang cosmology predicts a  gravitational singularity  before this time, but this theory relies on the theory of  general relativity , which is thought to break down for this epoch due to  quantum effects . In inflationary models of cosmology, times before the end of inflation (roughly 10 −32  

Further information:  Timeline of cosmological epochs ,  Timeline of natural history ,  Geologic time scale ,  Timeline of the evolutionary history of life , and  Timeline of the far future Further information:  Graphical timeline of the universe ,  Graphical timeline of the Big Bang ,  Graphical timeline from Big Bang to Heat Death , and  Graphical timeline of the Stelliferous Era Earliest stages of chronology shown below (before neutrino decoupling) are an active area of research and based on ideas which are still speculative and subject to modification as scientific knowledge improves. "Time" column is based on extrapolation of observed  metric expansion of space back in the past. For the earliest stages of chronology this extrapolation may be invalid. To give one example,  eternal inflation  theories propose that inflation lasts forever throughout most of the universe, making the notion of "N seconds since Big Bang" ill-defined. The radiation temperature re

The universe as it appears today. From 1 billion years, and for about 12.8 billions of years, the universe has looked much as it does today. It will continue to appear very similar for many billions of years into the future. The  thin disk  of  our galaxy  began to form at about 5 billion years (8.8 bn years ago),and the  solar system  formed at about 9.2 billion years (4.6 bn years ago), with the earliest traces of  life  on Earth emerging by about 10.3 billion years (3.5 bn years ago). From about 9.8 billion years of cosmic time,the slowing expansion of space gradually begins to accelerate under the influence of  dark energy , which may be a  scalar field  throughout our universe. The present-day universe is understood quite well, but beyond about 100 billion years of cosmic time (about 86 billion years in the future), uncertainties in current knowledge mean that we are less sure which path our universe will take.

Dark Ages and large-scale  structure emergence , from 377,000 years until about 1 billion years. After  recombination  and  decoupling , the universe was transparent but the clouds of  hydrogen  only collapsed very slowly to form  stars  and  galaxies , so there were no new sources of light. The only photons (electromagnetic radiation, or "light") in the universe were those released during decoupling (visible today as the  cosmic microwave background ) and  21 cm radio emissions occasionally emitted by hydrogen atoms. The decoupled photons would have filled the universe with a brilliant pale orange glow at first, gradually  redshifting  to non-visible  wavelengths after about 3 million years, leaving it without visible light. This period is known as the  Dark Ages . Between about 10 and 17 million years the universe's average temperature was suitable for liquid water (273 – 373K) and there has been speculation whether rocky planets or indeed life could have arisen briefl