Our Expanding Universe

What is a theory? What is the Big Bang Theory? Draw a picture of the Big Band Theory Come up with your own theory of how the universe was created: What evidence supports that theory? 1. 2.

What is a theory? What is the Big Bang Theory? What evidence supports the Big Bang? What is the Oscillating-Universe Theory? What is the Steady State Theory? Come up with your own theory of how the universe was created: 1. 2.

What is a Theory? A theory is not a fact. A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. A theory is valid as long as there is no evidence to dispute it. Therefore, theories can be disproven. Basically, if evidence accumulates to support a hypothesis, then the hypothesis can become accepted as a good explanation of a phenomenon. One definition of a theory is to say it's an accepted hypothesis.

Big Bang Theory The most popular theory for the creation of the universe is known as the Big Bang. The Big Bang Theory suggests that everything in the universe was once condensed into an incredibly small area. Because this area was extremely hot, a powerful expansion of energy was created. It sent everything that was densely packed in the small area flying out in all directions. In a blink of an eye, this microscopic area expanded into something larger than the Milky Way galaxy. Within seconds, everything began to cool down. Still expanding, the building blocks of the universe began to form. As millions of years went by, the universe’s temperature cooled enough to allow galaxies and stars to form. To this very day, the universe is still cooling and expanding. DO NOT DRAW THIS PICTURE

Big Bang Theory Picture

What supports the Big Bang Theory (1)? Scientists have discovered that galaxies are traveling away from Earth. They know this by studying the color of light that the galaxies give off. If light from a galaxy appears to be shifted toward the red end of the electromagnetic spectrum, then this means it is traveling away from Earth. This is called Red Shift. If light looks more blue, it means it is traveling towards the earth. This supports the idea of a great expansion from the Big Bang as we continue to see a red shift.

What Supports the Big Bang Theory (2)? Another piece of evidence that supports the Big Bang was found in 1992 by the Cosmic Background Explorer satellite. It precisely measured the temperature of the Cosmic Microwave Background radiation. The temperature it found matched with the predictions astronomers had made of the hot Big Bang. This radiation (cosmic background microwave radiation) is believed to be caused by the energy released during the first year of the Big Bang.

Oscillating-Universe Theory This theory states that when the universe began, all matter was located within a specific region of space. An explosion occurred, sending matter forcibly outward. However, this theory also states that the universe undergoes periods of expansion and contraction (gets larger than smaller). Eventually, all the matter in the universe will get hotter and brighter and eventually collapse together in an event called the “Big Crunch”, then a new Big Bang would occur resulting in a new universe. According to supporters of this theory, our universe is now in a period of expansion.

Steady State Theory This theory suggest that the universe has always looked as it does not, and its overall composition does not change. In this theory, galaxies are not moving away from each other, but new stars are being made from energy in the center of galaxies. The new stars spiral out from the center. The galaxy reabsorbs the energy given off by the stars throughout their life cycles. The energy is then reused to produce new stars. This model avoids the idea of expansion and contraction.