As time continues, these particles begin to cool off by releasing energy, which also allows them to combine and create the first and most simple ion: Hydrogen. More time passes, and more massive atoms form and become more abundant in the universe. These particles begin to pull together through atomic and gravitational forces, and gaseous bodies become more massive. The gravitational force of these early bodies is so great that they attract more and more atoms, and eventually they collapse in on themselves and begin fusion.(1) Hydrogen atoms combine due to the intense heat and pressure, and larger atoms and enormous amounts of energy are created. This energy keeps these early stars from collapsing, but eventually the fusion process will come to an end and the star will explode, sending out more massive atoms into the universe to start the whole process over again. Over time, these atoms and particles collect and combine to create small stars, asteroids, and even planets.
Somewhere during this time when matter was combining and creating new particles and matter was quickly expanding outwards, clusters of gigantic amounts of matter began orbiting around a common center of mass. These eventually became galaxies, which would continue to grow in size through collisions with other objects. Our spiral galaxy known as the Milky Way is just one of an unknown number of galaxies in the universe.
As matter began to condense and stars began to form, one cloud of gas and dust in the Milky Way Galaxy was disturbed, perhaps by the explosion of a nearby star. This explosion made waves in space which squeezed the cloud of gas and dust, causing it to collapse. As gravity pulled the gas and dust together, the cloud began to spin and a solar nebula began to form as it collapsed. Eventually, the cloud grew hotter and denser in the center, with a disk of gas and dust surrounding it that was hot in the center but cooler out towards the edges. As the disk got thinner and thinner, particles circling the center began to attract one another, essentially being held together by gravity and forming larger bodies.(2) Some of these bodies of material got bigger as other particles and bodies became attracted and “stuck” to them, which eventually formed the planets or moons. Planets began to differentiate; near the center of the cloud, terrestrial planets like Earth formed where only rocky material could stand the great heat. Icy matter settled in the outer regions of the disk where the giant Jovian planets like Jupiter formed. As the cloud continued to collapse and fall in on itself, the center eventually got so hot that it became a star, our Sun.(3) By studying meteorites, objects in our solar system which are thought to be left over from the creation of our solar system, scientists have found that the solar system is about 4.6 billion years old.
REFERENCES:
1.) Alden, Andrew. "Birth of Earth." 2009. About.com. 5 Apr. 2009
2.) "Formation of the Earth." 2000. ThinkQuest. 4 Apr. 2009
3.) Nusret, Hajira, and Allen Teal. "How Planet Earth Was Formed." 2009. Helium. 4 Apr. 2009
