The Big Bang Theory

The Big Bang Theory

​An Illustration of the Big Bang:

​Before the Big Bang: Steady State Theory

The Big Bang Theory

• How old is the universe?
  
  ~13.75 billion years old!

  
  

• How did scientists determine its age?
  

  • Distant galaxies were REDSHIFTED

  • Cosmic Background Radiation

  • gravitational waves
    
    

​How did astronomers figure this all out???

​"The Thinker,"
Auguste Rodin, 1905

Georges Lemaitre (1894 - 1966)

Georges Lemaitre, a Belgian priest and physicist, proposed the Big Bang theory.


He suggested that the universe began as a tiny point called the singularity and has been expanding ever since.


(They didn't believe him at first)

Edwin Hubble (1889 - 1953)

​In contradiction to the static "steady-state" theory of the universe accepted at the time, Hubble proved that other galaxies are, in fact, moving away from ours.


By studying the light from distant galaxies, Hubble discovered that the light appeared displaced toward the red end of the light spectrum - called "redshifted."

Stephen Hawking (1942 - 2018)

Stephen Hawking is regarded as one of the most brilliant theoretical physicists in history!

He is considered the "Einstein" of our time, but he died recently, on March 14, 2018.

His work on the origins and structure of the universe, from the Big Bang to black holes, revolutionized the field of astronomy.

Stephen Hawking (1942 - 2018)

​In 2007, Professor Stephen Hawking, the world's expert in gravity, got the chance to experience zero gravity aboard a specially-modified Boeing 727-200 aircraft called G-FORCE ONE.

What made that flight extremely special was that Hawking's illness, a disease called ALS, had rendered him immobile and wheelchair-bound for more than 40 years.

Summary: Super Scientists!!!

• Georges Lemaître proposed that the universe began as a single point called 'the singularity' and expanded to its current size

  
  

• Edwin Hubble observed distant galaxies moving away!
  These distant galaxies appeared REDSHIFTED!!!!!!!!
  
  

• Stephen Hawking studied black holes and their
  gravitational waves - these are ripples in space time!
  

Multiple Choice

Who proposed the Big Bang theory?

• Georges Lemaitre

• Edwin Hubble

• Stephen Hawking

Multiple Choice

Who observed "redshift" in distant galaxies?

• Georges Lemaitre

• Edwin Hubble

• Stephen Hawking

Multiple Choice

Who studied black holes?

• Georges Lemaitre

• Edwin Hubble

• Stephen Hawking

Evidence: Cosmic Background Radiation

Cosmic Background Radiation is the residual energy left over from the early stages of the universe. It provides strong evidence for the Big Bang, supporting the idea that the universe began with a hot, dense explosion.

It was discovered by scientists in 1964 using satellites.

Evidence: Redshifted Galaxies

Redshifted Galaxies: Edwin Hubble's discovery of galaxies moving away from us, confirming Lemaitre's theory that everything was spreading apart.

​What does redshift mean?

​Energy, including light, travels in waves. When the waves are traveling away from the observer, they become stretched out and distorted. When light waves slow down, the are shifted towards the red end of the visible light spectrum.

​As the galaxy moves away, its light is shifted red.

​The Doppler Effect: Redshift & Blueshift

​This is when waves of energy
(including light & sound) are either compressed or stretched as they travel towards something or away
from the observer.

​Compressed light waves have a higher frequency and appear more blue. Stretched out light waves are slower and appear more red.

Multiple Choice

Which indicates that a distant galaxy is moving away?

• Blueshift

• Redshift

The Expanding Universe

Fun Fact:
Distant galaxies are moving away from us, and the farther they are, the faster they are moving.


This expansion is not limited by the speed of light, as galaxies are moving away faster than the speed of light.

Evidence for the Big Bang

• Cosmic Background Radiation: Leftover light & energy from the Big Bang
  
  

• Redshifted Galaxies: Distant galaxies are moving away from us rapidly
  
  

• Gravitational waves: Ripples of gravity through spacetime

Multiple Choice

Which of these provides evidence for the expansion of the universe?

• Edwin Hubble's discovery of galaxies moving away from each other

• Georges Lemaitre's proposal of the Big Bang Theory

• The naming of the Hubble Telescope after Edwin Hubble

Summary: Evidence for the Big Bang

1. Observation of cosmic background radiation:
   The discovery of a faint glow of radiation throughout the universe -
   a remnant of the "explosion"
   
   

2. Observation of redshift in galaxies:
   Hubble observed distant galaxies moving away from us, indicating an expanding universe. By observing distant objects in space, we can see them as they were in the past.
   
   

3. Detection of gravitational waves:
   The recent detection of gravitational waves supports the theory of cosmic inflation during the Big Bang.

Gravitational Waves

These are caused by colliding black holes and supernovae!!!
They were theorized and studied by Albert Einstein and Stephen Hawking, as well as other scientists at MIT. They were proven by experiments in the 1970s & 80s,
but were not observed until 2015.

Gravitational Waves

LIGO, or the Laser Interferometer
Gravitational-Wave Observatory
is a large-scale physics experiment
and observatory designed to
detect & study gravitational waves

Multiple Choice

If distant galaxies are redshifted, this means that they are moving

• towards us

• away from us

Multiple Select

What provides evidence of the 'Big Bang'?
(select more than one!)

• cosmic microwave background radiation

• redshift of distant galaxies

• the discovery of dark matter

Multiple Choice

Who discovered that galaxies are moving apart from one another?

• Edwin Hubble

• Galileo Galilei

• Isaac Newton

• Albert Einstein

Multiple Choice

What was discovered by satellites in 1964 that supported the Big Bang theory?

• Neutron stars

• Dark matter

• Cosmic background radiation

• Black holes

Multiple Choice

What is the universe made of?

• Only planets

• Only stars

• Everything that exists

• Only galaxies

Poll

Do you feel like you learned anything? (no correct answer)

• A little bit

• YES! A LOT!

• No, I'm just confused.