Exploring the Big Bang Theory and the Age of the Universe

1. Bell Ringer • According to The Cosmos, how old is the universe? • Define the Big Bang.

2. Agenda • Notes: The Universe and Galaxy Types • What is a theory? • The Big Bang theory • After the Big Bang • Evidence of the Big Bang theory • The Future of the Universe

3. What is a Scientific Theory? • A scientific theory an explanation of some aspect of the natural world • Theories are supported by a significant amount of evidence and years of research • When we say that the Big Bang is a theory, we mean that it is widely accepted by the scientific community due to an overwhelming amount of evidence

4. The Big Bang Theory • You are not required to agree with the Big Bang theory • However, you are required to know: • What it is • The scientific evidence that supports it

5. The BBT: What Happened? • The Big Bang theory states that the universe came into being at a single moment • All of the matter and energy of the universe were at one time concentrated in an incredibly hot region smaller than an atom • The universe began in an instant about 13.8 billion years ago in an enormous explosion

7. After the Big Bang • Shortly after the Big Bang, the universe expanded and cooled • After a few hundred thousand years, the universe was still hot and small, but cool enough for atoms to form • Gravity pulled atoms together into gas clouds that eventually became stars • Our sun and solar system formed about 4.6 billion years ago when the universe was about 2/3 of its present size

9. Evidence of the Big Bang • What led scientists to the conclusion that the Big Bang happened? • 2 Main Pieces of Evidence: • Cosmic background radiation (micro and radio waves) • Red shift (Hubble’s Law)

10. Cosmic Background Radiation • Scientists use radio telescopes to study the universe. These telescopes can detect many different wavelengths of light – much more than the visibly light that we can see with our eyes • In 1965, American physicists detected faint signals in all directions • Scientists eventually learned that this faint glow is caused by microwave and radio wave radiation that was produced by the big bang and still travels throughout the universe

12. Red Shift: Hubble’s Law • Edwin Hubble was an American astronomer that studied distant galaxies • Hubble noticed that most galaxies exhibit a red-shift in their light wavelengths • Red-shift means that the light waves are getting longer • If light waves are getting longer, they are moving farther away from the Earth

15. Red Shift: Hubble’s Law • The farther away a galaxy is, the greater the red shift will be • This means that the farther the galaxy, the faster that galaxy is moving away from Earth • Hubble’s law states the relationship between a galaxy’s increasing distance from Earth and its increasing speed away from Earth

16. http://astro.wku.edu/astr106/Hubble_law_anim.gif

17. Age of the Universe • Since astronomers know the current speed that the universe is expanding we can calculate how long it has been expanding • This is how we infer that the universe started from a single point about 13.8 billion years ago

18. What Will Happen in the Future? • Scientists are currently trying to predict whether or not the universe will continue to expand forever or whether gravity will pull galaxies back together • The answer depends on the amount of matter in the universe • If the amount of matter is sufficient enough to overcome the gravitational force then the universe will expand • If the amount of matter is NOT sufficient enough to overcome the gravitational force then the universe will reverse its expansion

20. Assignment • Big Bang Theory & Hubble’s Law worksheet