Name: _____________________________________________ Period: ___________ The Creation of the Universe: The Big Bang Theory The Big Bang Theory is the scientific idea that explains how the universe began. It suggests that the universe started 13.8 billion years ago as a very small, hot, and dense point called a singularity. This singularity was where matter was squished by very intense gravitational pressure. Suddenly the singularity expanded in an event called the Big Bang, and as it expanded, it cooled down. As it cooled, subatomic particles like protons, neutrons, and electrons formed. Eventually these subatomic particles formed atoms which lead to the creation of stars, galaxies, and planets over billions of years. There are three pieces of evidence to support this theory: cosmic microwave background radiation, redshift of distant galaxies, and the abundance of hydrogen and helium atoms. The first piece of evidence to support our universe came from a singularity is the cosmic microwave background radiation (CMB). The CMB is a faint glow spread throughout the universe. It's like a lingering whisper of light and heat from the early stages of our cosmos. The universe was a very, very hot environment shortly after the Big Bang. At that time, light particles called photons were bouncing around, unable to travel freely. They kept bumping into other subatomic particles like electrons and protons. As the universe spread out and cooled over time, these collisions decreased. About 380,000 years after the Big Bang, the universe became clear enough for photons to travel freely. The CMB we detect today is the remnants of these photons from the early universe. They've cooled down so much that they're now like microwave waves from the electromagnetic spectrum. The second piece of evidence to support the Big Bang Theory is the redshift of distant galaxies. Redshift is a phenomenon where the light from an object is shifted towards longer wavelengths, causing it to look redder than it actually is. This happens because the object is moving away from an observer, making the light waves stretch out as the object moves away. In visible light, the longest wavelength is the color red. Edwin Hubble, an astronomer, noticed that the light from galaxies beyond our own Milky Way was shifted towards longer wavelengths, meaning these far away galaxies were moving away from us. This discovery led to the realization that the universe was expanding and making galaxies move away from each other as the universe expands outwards. Astronomers can measure the distances to galaxies and determine how fast they are moving away from us. The final piece of evidence is the abundance of hydrogen and helium atoms in the universe. Approximately 75% of all matter in the universe is made up of hydrogen with about 25% remaining being helium. Only about 1% of the entire universe is made up of all the other elements we know of. When the hot, dense singularity expanded suddenly, subatomic particles like protons and neutrons formed first then electrons. As the universe cooled down, the protons and neutrons joined together then captured electrons to create hydrogen atoms. The hydrogen atoms would fuse together to make helium atoms and eventually other elements in the universe.
