The universe as we know have still many unnamed galaxies and stars out there from the system that we lie in. So how did our solar system and earth came to be? There are numerous theories that provides insight of how the universe came to be, and so far the most popular among all theories and would be the following listed down below.
Cosmic Inflation is the idea that the very early universe went through a period of accelerated, exponential expansion during the first 10-35 of a second before settling down to the more sedate rate of expansion we are still experiencing, so that all of the observable universe originated in a small (indeed, microscopic) causally-connected region.
It is still not clear to scientists, however, exactly what caused the inflationary phase, the best guess being some kind of a negative “vacuum density energy” (or positive “vacuum pressure”) triggered by the separation of the strong nuclear force from the other elementary forces at this time. It is hypothesized that this separation caused a kind of symmetry breaking or phase transition (analagous to the phase transition when water turns to ice), which left the universe in a highly unstable state with much more energy than it would otherwise have had, causing a sharp outward anti gravitational effect, smoothing out most of the irregularities in the existing matter and creating vast quantities of particles in a very short time.
This theory allows for some kind of very slight unevenness (so-called quantum fluctuations) on a sub-atomic scale at a very early stage in the growth of the universe which provided starting points for the large-scale structures we see in today’s universe. This suggests the rather bizarre possibility that the largest structures in the universe, the great clusters of galaxies, may actually have been spawned by sub microscopic seeds.
Another understanding from this theory is that the quick emergence of the elements hydrogen and helium, prompted a series of reactions known as nucleosynthesis which then triggered the next theory that came to light, The Big Bang theory.
THE BIG BANG THEORY
Scientists have gathered a lot of evidence and information about the Universe. They have used their observations to develop a theory called the Big Bang. The theory states that about 13.7 billion years ago all the matter in the Universe was concentrated into a single incredibly tiny point. This began to enlarge rapidly in a hot explosion, and it is still expanding today.
Evidence for the Big Bang includes:
- all the galaxies are moving away from us
- the further away a galaxy is, the faster it is moving away.
These two features are found in explosions – the fastest moving objects end up furthest away from the explosion.
Scientists have also detected a cosmic microwave background radiation or CMBR. This is received from all parts of the Universe and is thought to be the heat left over from the original explosion.
The continuous synthesis of the early elements made it possible for galaxies and the system to exist.
According to this theory, the Sun and all the planets of our Solar System began as a giant cloud of molecular gas and dust. Then, about 4.57 billion years ago, something happened that caused the cloud to collapse. This could have been the result of a passing star, or shock waves from a supernova, but the end result was a gravitational collapse at the center of the cloud.
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.
CORE ACCRETION MODEL
Approximately 4.6 billion years ago, the solar system was a cloud of dust and gas known as a solar nebula. Gravity collapsed the material in on itself as it began to spin, forming the sun in the center of the nebula.
With the rise of the sun, the remaining material began to clump together. Small particles drew together, bound by the force of gravity, into larger particles. The solar wind swept away lighter elements, such as hydrogen and helium, from the closer regions, leaving only heavy, rocky materials to create terrestrial worlds. But farther away, the solar winds had less impact on lighter elements, allowing them to coalesce into gas giants. In this way, asteroids, comets, planets and moons were created.
DISK INSTABILITY MODEL
“Giant planets form really fast, in a few million years,” Kevin Walsh, a researcher at the Southwest Research Institute (SwRI) in Boulder, Colorado, told Space.com. “That creates a time limit because the gas disk around the sun only lasts 4 to 5 million years.”
According to a relatively new theory, disk instability, 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. These planets can form faster than their core accretion rivals, sometimes in as little as 1,000 years, allowing them to trap the rapidly vanishing lighter gases. They also quickly reach an orbit-stabilizing mass that keeps them from death-marching into the sun.
The biggest challenge to core accretion is time — building massive gas giants fast enough to grab the lighter components of their atmosphere. Recent research probed how smaller, pebble-sized objects fused together to build giant planets up to 1,000 times faster than earlier studies.
“This is the first model that we know about that you start out with a pretty simple structure for the solar nebula from which planets form, and end up with the giant-planet system that we see,” study lead author Harold Levison, an astronomer at SwRI, told Space.com in 2015.