The Big Bang Theory

1
The Big Bang Theory

• A small disclaimer the Big Bang theory is
  taught as a theory. I am not trying to change
  your beliefs in any way. I am just simply stating
  some observations made by some really smart
  people!

2
What is the Big Bang Theory?

• The theory that the universe violently exploded
  in a single event called the Big Bang.
• Occurred 10-20 billion years ago.
• The universe has been expanding since.

3
Notes of Concern!

• It is believed that all matter and radiation was
  packed into a primeval fireball no larger then
  the period at the end of this sentence.
• There was no bang or explosion, it is just a
  term.
• Since there was no space prior, the big bang was
  more of an unfolding of space and matter from a
  very small region. Also time as we know it
  started.

4
Review What was created at the onset of the Big
Bang?

• Matter (Something that has mass and takes up
  space.)
• Energy ( ex. Radiation /Light )
• Time (A condition which has a past, present and
  future.)
• Space (What the universe filled in.)

5
The first second

• In one-millionth of a second after the Big Bang,
  the Universe was a hot, seething mass of
  radiation and exotic particles.
• This mass expanded and cooled, forming protons,
  neutrons and electrons (subatomic particles).

6
Minutes later..

• These subatomic particles grouped together
  forming the first atoms of hydrogen and helium.

7
After several billions of years

• GRAVITY caused clouds of gas to collapse,
  forming planets, stars, and galaxies.

8
After 4.5 BYA

• Our solar system was formed

9
And today

• The present day Universe continues to expand.
• Galaxies and stars are continuing to move away
  from one other.

10
SO WHY DO SCIENTISTS BELIEVE THIS THEORY?

• The Big Bang is accepted because of three very
  persuasive pieces of evidence.
• 1. Red shift
• 2. The relative amounts of certain
• chemical elements in the universe
• 3. The existence of cosmic radiation

11
Red Shift

• When a star or galaxy's light is looked at
  through a special instrument called a
  spectroscope, scientists observe that the
  wavelengths have shifted toward the red end of
  the spectrum.

12
Red shift cont

• The red end of the spectrum has longer
  wavelengths, thus meaning the object is moving
  AWAY from the observer.
• Example When you hear an ambulance siren
  approaching, and then moving away.

13
Chemical Make-up

• Since, according to this theory, all matter
  was created at the Big Bang, the Universe today
  retains an imprint of its initial cosmic mixture.
• Astronomers can analyze a stars chemical
  make-up and the ratio of hydrogen to helium.
• The amounts of these gasses agree with what
  the Big Bang theory predicts.

14
The most convincing piece of evidence

• COSMIC BACKGROUND
• RADIATION

15
Cosmic Background Radiation

• The last signs of heat left over from the Big
  Bang.
• That original energy has cooled to -455F (a
  hundred million times cooler than a typical
  birthday candle!)
• Can be detected at the short end of the radio
  spectrum.

16
How will it end?

• The ultimate fate of our universe will be
  determined by the competition between the outward
  expansion and the inward pull of gravity
• (Ive been told, in the end, gravity always wins)

17
The future of uncertainty

• There are several interesting scenarios, ranging
  from never ending expansion, to a contraction
  inward called the Big Crunch.
• It all depends on the density of the Universe,
  and that depends on the amount of matter it
  contains.