The document discusses the Big Bang theory and provides evidence that supports it. It describes how Belgian cosmologist Georges Lemaître first proposed the theory in the 1920s that the universe expanded from an initial hot, dense state. It then gives three key pieces of observational evidence: 1) Hubble's discovery of the expansion of the universe, 2) the cosmic microwave background radiation discovered in 1964, and 3) primordial nucleosynthesis, which produced the light elements in the early universe. The document aims to clarify misconceptions about the Big Bang theory and explain what it describes.

1. Physical Science 12
ABM
Prepared By: Jerome A. Bigael, Leyte Progressive High School
Lesson 1 (Big Bang Theory)

2. Big Bang Theory

3. Abbe Georges Edouard
Lemaître (1894-1966)
Belgian cosmologist and priest
Born in 1894 in Charleroi, Belgium
professor of physics at the Catholic
University of Leuven
He proposed the theory of the expansion of
the universe, widely misattributed to Edwin
Hubble.

4. Give Your Insights
“The Big Bang model is not a theory
of the origin of the universe, as it is
often described, Rather it is a
description or model of the early
universe.”

5. Misconception:
The Big Bang is not a theory of the origin
of the universe, as it is often described.
Rather, it is a description or model of the
very early universe.
The Big Bang was not an explosion of
matter.

6. What is Big Bang Theory?
The Big Bang Theory is a description or model of the
very early universe.
This theory explains that the universe developed 13.7
billion years ago and started as a very dense and hot
“singularity” which eventually cooled and began to
form different particles.
The term Big Bang does not imply that there was an
explosion but the truth is that there was an
expansion.

7. Three Observational pieces of evidence that
support Big Bang Model:
1. Hubble or Cosmic Expansion
Edwin Hubble, an American
astronomer in the 1930’s made a major
discovery at MountWilson Observatory
in California, USA with the use of 100-
inch HookerTelescope.

8. Hubble and his assistant, Milton Humason,
formulated Hubble’s law (also known as Hubble
expansion).

9. It states that other galaxies are moving
away relative to the MilkyWay galaxy at
a rate of proportional to distance, was
the first observational evidences of
Lemaître’s Big Bang Model.

10. 2. Cosmic Microwave Background
George Gamow, a theoretical phycisist
and cosmologist in 1940’s.

11. Together with Robert Herman and Ralph
Alpher, predicted that if the early stage
of the universe was hot and dense, then
an afterglow of radiation must have filled
up the universe brought about by the
cooling process.

12. This Afterglow is detected today
as the Cosmic Background
Radiation also known as the
Cosmic Microwave
Background(CMB).

13. In 1964, two radio astronomers of Bell Laboratories in
New Jersey, USA-Arno Penzias and RobertWilson
confirmed the presence of the CMB with an average
temperature of 2.7 Kelvin.

15. Primordial or Big Bang
Nucleosynthesis (BBN)
Gamow, Herman and Alpher also
believed that the high temperature of
the universe is an appropriate
condition for nuclear processes to
occur during the first few minutes of
Big Bang.

16. The process began with the fusion of
protons and neutrons to form nuclei in a
process known as “nucleosynthesis”.
Primordial or Big Bang Nucleosynthesis
refers to the process of producing the
“light elements” shortly after the Big
Bang.