The Formation Of The Solar System: Theories Old...
Hervé Reeves' classification also categorized them as co-genetic with the Sun or not, but also considered their formation from altered or unaltered stellar and interstellar material. He also recognized four groups: models based on the solar nebula, originated by Swedenborg, Kant, and Laplace in the 1700s; hypotheses proposing a cloud captured from interstellar space, major proponents being Alfvén and Gustaf Arrhenius in 1978; the binary hypotheses which propose that a sister star somehow disintegrated and a portion of its dissipating material was captured by the Sun, with the principal hypothesizer being Lyttleton in the 1940s; and the close-approach filament ideas of Jeans, Jeffreys, and Woolfson and Dormand.
The Formation of the Solar System: Theories Old...
One other problem is the detailed features of the planets. The solar nebula hypothesis predicts that all planets will form exactly in the ecliptic plane. Instead, the orbits of the classical planets have various small inclinations with respect to the ecliptic. Furthermore, for the gas giants, it is predicted that their rotations and moon systems will not be inclined with respect to the ecliptic plane. However, most gas giants have substantial axial tilts with respect to the ecliptic, with Uranus having a 98 tilt. The Moon being relatively large with respect to the Earth and other moons in irregular orbits with respect to their planet is yet another issue. It is now believed these observations are explained by events that happened after the initial formation of the Solar System.
Scientists have developed three different models to explain how planets in and out of the solar system may have formed. The first and most widely accepted model, core accretion, works well with the formation of the rocky terrestrial planets but has problems with giant planets. The second, pebble accretion, could allow planets to quickly form from the tiniest materials. The third, the disk instability method, may account for the creation of giant planets.
Other models struggle to explain the formation of the gas giants. According to core accretion models, the process would take several million years, longer than the light gases were available in the early solar system.
A relatively new theory called disk instability addresses this challenge. In the disk instability model of planet formation, clumps of dust and gas are bound together early in the life of the solar system. Over time, these clumps slowly compact into a giant planet.
Ideas concerning the origin and fate of the world date from the earliest known writings; however, for almost all of that time, there was no attempt to link such theories to the existence of a "Solar System", simply because it was not generally thought that the Solar System, in the sense we now understand it, existed. The first step toward a theory of Solar System formation and evolution was the general acceptance of heliocentrism, which placed the Sun at the centre of the system and the Earth in orbit around it. This concept had developed for millennia (Aristarchus of Samos had suggested it as early as 250 BC), but was not widely accepted until the end of the 17th century. The first recorded use of the term "Solar System" dates from 1704.
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 and self-organization, these grains formed into clumps up to 200 m (660 ft) in diameter, which in turn collided to form larger bodies (planetesimals) of 10 km (6.2 mi) 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.
According to the nebular hypothesis, the outer two planets may be in the "wrong place". Uranus and Neptune (known as the "ice giants") exist in a region where the reduced density of the solar nebula and longer orbital times render their formation there highly implausible. The two are instead thought to have formed in orbits near Jupiter and Saturn (known as the "gas giants"), where more material was available, and to have migrated outward to their current positions over hundreds of millions of years.
The time frame of the Solar System's formation has been determined using radiometric dating. Scientists estimate that the Solar System is 4.6 billion years old. The oldest known mineral grains on Earth are approximately 4.4 billion years old. Rocks this old are rare, as Earth's surface is constantly being reshaped by erosion, volcanism, and plate tectonics. To estimate the age of the Solar System, scientists use meteorites, which were formed during the early condensation of the solar nebula. Almost all meteorites (see the Canyon Diablo meteorite) are found to have an age of 4.6 billion years, suggesting that the Solar System must be at least this old.
"We want to know how our solar system will evolve as time goes by," said Humi. "There are two theories: one conjecture is that all the planets will be absorbed by the sun. The other conjecture is that planets are running away from the sun.
In 1796, the French mathematical physicist Pierre-Simon Laplace conjectured that the first step for the formation of a solar system from a primordial celestial cloud of gas requires the creation of rings of condensed matter within a cloud.
We can trace the origin of the modern theory of solar system formation toEmmanuel Swedenborg in 1734, but it was Emmanuel Kant who developedthe idea in 1755. Pierre-Simon Laplace proposed a similar model in 1796. Thisnebular hypothesis was that the solar system began as a contracting and coolingproto-solar nebula. As the nebula contracted, it flattened into a disk, and mostof the material fell to the center. The material in the center formed the sun, andthe material in the disk eventually coalesced to form the planets. Any remainingmaterial formed the satellites of the planets, asteroids, and comets. The nebularhypothesis enjoyed wide support throughout the 19th century, but eventually astronomers realized there was an angular momentum problem. While the sunhas more than 99 percent of the mass in the solar system, the planets possessmore than 99 percent of the angular momentum. If the solar system formedvia the nebular hypothesis, the distribution of angular momentum ought to beproportional to the distribution of mass. Because of this problem, astronomersabandoned the nebular hypothesis in the early 20th century.
There were variations on the tidal interaction theme suggested by Chamberlinand Moulton. For instance, in 1918 Sir James Jeans and Sir HaroldJeffreys suggested that solar prominences were not involved and that a nearmiss by a passing star raised a single filament of material from the sun fromwhich the planets and other bodies in the solar system formed. The tidal theoryenjoyed broad support for much of the first half of the 20th century, but by1940 problems had developed. One problem was that any column drawn outof the sun would dissipate rather than condense. Another problem was thatmaterial drawn out with sufficient speed to account for the angular momentumof the planets (especially Jupiter) would have left the solar system entirely, sothe angular momentum problem remained. Consequently, during the middleof the 20th century, there was no agreed-upon theory for the formation of thesolar system.2
The modern theory of solar system formation has been refined with theaddition of magnetic fields. If a gas cloud contained any magnetic field initially,the magnetic field would intensify as the cloud contracted. And as the cloudcontracted it would have heated and ionized some of the gas. This producesplasma. In the swirling environment of the contracting cloud, models suggestthat electromagnetic effects propel material outward in the two directions alongthe axis perpendicular to the plane of the disk. Astronomers call this bi-polarflow, a phenomenon found in some stars and in many galaxies and quasars. Inmore recent years, astronomers have created computer simulations supposedlyto show how the solar system might have formed. One might question if thesuccess of the simulation merely proves that the programmer was especiallygood at writing a program to produce the intended outcome.
In the 1990s, astronomers first discovered planets orbiting other stars. Sincethen the number of extra-solar planets has grown tremendously. This has shownthat planets must be common in the universe, and hence planetary system formationmust be common in the universe today. However, this conclusion stemsentirely from an evolutionary worldview. That is, the assumption is made thatplanetary systems can arise only through natural means apart from a Creator.Therefore, if planetary systems are common, then all of them must have comeabout through evolutionary processes. Since planetary systems are common,planetary formation must be simple and straightforward, which proves thatour solar system must have formed through such a process. Therefore, the solarsystem formed pretty much the way astronomers think that it did. Of course,this is circular reasoning, and no such inference of naturalism legitimately canbe drawn. A creationist could just as easily state that since all things were madeby God, then anything that exists was made by Him. Since so many otherplanetary systems exist, then God must have made them all, just as He madeour solar system. Therefore, this proves creation. Of course, evolutionists wouldviolently disagree with this conclusion, for it disagrees with their starting premiseof naturalism. This illustrates that the data alone do not allow for a definiteconclusion about the ultimate origin of planetary systems, including our own.
The purpose of looking for extra-solar planets is to show how commonplanets are and how typical our solar system is. But is our solar system common? The evidence thus far suggests otherwise. In our solar system, the large gas giantplanets are far from the sun and the small rocky planets are close to the sun.Planetary scientists have developed models of how this might have happened,and those theories indicate that the large gas giant planets ought to be far fromthe sun, as is the case in the solar system. But extra-solar planets tend to be verylarge and very close to their parent stars,3 the opposite of the situation in thesolar system, and contrary to the prevailing theories of planetary formation.Scientists have concocted multiple encounters of planets (again using computersimulations) to show how extra-solar planets might have formed far from theirstars but then migrated inward. Evolutionists must devise these explanationsbecause the observations defy their theories. 041b061a72