Origin of the Universe  Where did Earth, the solar system, & the stars come from? Where did life come from?  Our universe came into existence suddenly as a concentrated single point, containing all known matter & energy.  Approximately 13.7 billion years ago this single point began to expand – an event known as the Big Bang.  It took about 1 million years for matter in the universe to cool for the first elements to form, mostly hydrogen & helium.

 Matter is not distributed uniformly throughout the universe.  A natural property of matter – gravity – began attracting helium & hydrogen atoms together.  As the density increased, matter collapsed & compacted under its own weight, causing a warm, dense core called a protostar to form.

The Theorized “Life-Cycle” of a Star:  The nuclear fusion reaction from protostars creates stars.  The star burns for millions of years, consuming it’s hydrogen.  Heavy elements form as hydrogen atoms fuse during the “life-cycle” of a star.  The core becomes denser & eventually collapses under the extreme gravity forces generated.  The star may explode causing a supernova.  Supernova explosions account for the distribution of heavy elements through-out the universe.

Origin of the Solar System: The Nebular Theory  A shock wave from a supernova caused the cloud to condense, which caused it to spin.  As the cloud collapsed & became denser, it flattened in a disk due to the rotation. At the center a protostar developed & began the nuclear fusion process, becoming the sun.  Some gas continued to revolve around the sun eventually condensing into masses to small to become stars – they became the planets.

Origin of the Earth & Moon  According to the nebular theory, Earth (& other solar system planets) formed through accretion.  Accretion is the process by which small particles clump together because of gravity. As a mass grows the more gravity is has, the more additional mass it attracts.  The Earth’s growing mass caused its core to compress causing the core to heat & become molten liquid. The outer core is still molten.  With this molten liquid, heavy matter (iron & nickel) sank toward the center, while light matter (oxygen & silicon) moved toward the surface.  This process of density stratification formed the layers of the Earth.

Origin of the Moon  The most widely accepted theory for the moon’s origin is the Orpheus Theory.  The Orpheus Theory says that a planet – sized body struck Earth during its early development & sent some of its material into orbit, forming the moon.

Origin of the Atmosphere & the Ocean  When the earth cooled enough for the surface to form a crust, gases from volcanic activity escaped accumulating as an early atmosphere.  The surface was still so hot that when water vapor formed clouds, then rain, the rain boiled off again when it hit the ground.  Finally, the Earth cooled enough to allow the rainwater to accumulate & the ocean formed as water vapor condensed.

 The process that allowed life to form began with the development of the ocean.  Carbon dioxide dissolved into the young ocean, leaving a nitrogen-rich atmosphere. Scientists think these were the conditions required for life.  Interestingly, there was no oxygen in the atmosphere on early Earth.  Although oxygen is essential to almost all life today, according to data recorded in rock, early life didn’t use oxygen.  Oxygen entered the atmosphere about 1.5 billion years ago when photosynthesizing organisms (stromatolites) began using carbon dioxide & releasing oxygen.