Evidence of the Big Bang - MR. HOLZ'S WEBSITE

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)

https://www.stem.org.uk/elibrary/resource/26892