evidence of the big bang - mr. holz's website
TRANSCRIPT
Evidence of the Big Bang
The year is 1929. You are Edwin Hubble. As a curious
astronomer, you decide to gaze into the cosmos at
distant galaxies. You have recently found out about
absorption spectra and how the composition of stars and
galaxies can be determined by looking at spectra lines.
After collecting data on the absorption spectra of many
distant galaxies, you notice something interesting...
Galaxy UGC 129125
Normal
Emission
Spectrum for
Hydrogen
Observed
Absorption
Spectrum for
UGC 129125
Galaxy UGC 12508
Normal Emission
Spectrum for
Hydrogen
Observed
Absorption
Spectrum for
UGC 129125
How do you explain your observations?
What can you infer about the status of
these galaxies in the universe?
- Galaxies must be moving away from us!
- ALL of them! (with the exception of some that are
within our local group)
- Galaxies that are further away are moving away
from us at a greater rate (as seen by the greater
degree of Red Shift)
What does this tell you about
the Universe?
Hubble’s Law
- The rate at which a galaxy is moving is
directly proportional to its distance from us.
- In other words, the farther away a galaxy is
from us, the faster it travels away from us.
- This the universe is EXPANDING!
Expanding Universe
So if the Universe is expanding, we can
imagine “rewinding” this process.
The Universe must have come from a
single point, infinitely small, and infinitely
dense that contained EVERYTHING and
expanded outwards in all directions!
Evidence of the Big Bang
1. Red Shift of galaxies supporting an expanding Universe
George Gammow 1948
- Used advanced calculations to show that
nucleosynthesis of Hydrogen and Helium from
lone protons, neutrons, and electrons in the
early Universe would yield about 75%
Hydrogen and 25% Helium.
Absorption spectra of Gas Clouds 10-12 billion Light
Years Away show...
75% Hydrogen
25% Helium
Evidence of the Big Bang
1. Red Shift of galaxies supporting an expanding Universe
2. Abundance of Light Elements in Universe (% of H and He)
George Gamow (1940s)
- Predicted there should be “echoes” of the Big Bang
“explosion”.
- If massive amounts of energy was released during the Big
Bang, the energy should have spread out in all directions.
- What type of energy might this have become?
Bell Laboratories (1965)
- Penzias and Wilson were radio
astronomers who worked for Bell
Telephone Laboratories
- Found a mysterious microwave
signal causing consistent
background noise (static) in their
radio telescope
- The signal came from everywhere!
Cosmic Microwave Background Radiation
2.725 degrees above absolute zero (0 degrees Kelvin; -273.15 degrees Celsius)
BIG BANG FOSSIL!
Evidence of the Big Bang
1. Red Shift of galaxies supporting an expanding Universe
2. Abundance of Light Elements in Universe (% of H and He)
3. Cosmic Microwave Background Radiation (leftover light
and heat from the Big Bang)
