Origins of the Universe and Solar System From Universe to Galaxy to Solar System

The Big Bang Theory - The theory that the universe began as a point (singularity) and has been expanding ever since. The universe was originally packed into one dense sphere of hydrogen about the size of a pearl! The sphere “exploded”, forming a gigantic, hot expanding cloud As the cloud moved, parts condensed and formed billions of galaxies The galaxies continue to move outward today Most commonly accepted theory of universe formation I. Formation of the Universe

PREVIOUS IDEAS: The Steady State Theory - The belief that the universe doesn’t change with time but more matter is added to the universe as it expands. Popular during the 1950s and 1960s The universe had no beginning (no big bang) and has no end RECENT DEVELOPMENTS: Inflationary Theory - predicts that there was a sudden expansion when the universe was very young, more extreme than predicted by the big bang theory! Considered to be a “revised” Big Bang theory The universe expanded and cooled until about second after the big bang when it became so cool that the forces of nature caused the universe to inflate tremendously. Also works with the concept of a Multiverse--our observable universe is just one of many “parallel” universes that inflate in and out of existence! I. Formation of the Universe

1. In 1965, Panzias And Wilson discovered background radiation interfering with radio antennae, causing a hiss in phone lines. II. Evidence for Big Bang/Inflation That radiation is called cosmic background radiation and is thought to be radiation from the big bang. This radiation can be detected by common radio and television antennae. (ex: “snow” on your television is made up of a small percent of radiation from the formation of the universe!) 2. Astronomers observe “red shifts” throughout the universe. This redness is the result of light being stretched as objects in the universe move away from each other (the result of the big bang).

III. Formation of Galaxies 1. Galaxies begin as a spherical cloud (also called a nebula) in space. 2. The cloud collapses under the force of it’s own gravity, forming galaxies of a variety of shapes. Our solar system is here 3. Our galaxy the Milky Way is a spiral galaxy, consisting of a nucleus surrounded by arms that rotate in a clockwise fashion. 4. Solar systems similar to ours move around in this galaxy in a regular pattern.

IV. Shape of Galaxies 1. Spiral (like the Milky Way--OUR galaxy). See background picture. Our solar system is here … some are Barred Spirals 2. Elliptical 3. Irregular and others

Within each galaxy are many nebulae (plural of nebula). A nebula is a cloud of interstellar dust and gas from which stars and eventually solar systems are formed. Nebula can be many colors depending on the chemical makeup of the gas. V. Formation of a Solar System

How a Nebula becomes a Solar System - The Solar Nebula Hypothesis: Just as an ice-skater’s spin speeds up when she pulls her arms in, so does a cloud of dust in space. As the cloud spins faster, enough pressure is created to produce fusion in the center of the disk, forming a star like our sun. Planets are formed from the rings left behind as the dust disk formed.

Our sun was the center of that cloud of dust and gas. As the planets formed, the more dense ones were pulled closest to the sun. They are called Terrestrial Planets (Mercury, Venus, Earth, and Mars). The less dense planets moved toward the outer portion of the solar system. They are called Jovian Planets, or Gas Giants. (Jupiter, Saturn, Uranus, and Neptune) Pluto is now thought to be a minor planet, most likely a captured comet who was drawn in by the gravity of the sun and placed in an orbit around it (similar to asteroids) VI. Formation of OUR solar system:

More about the planets and moon later!