ORIGIN OF THE UNIVERSE

Lesson 1

ORIGIN OF THE

UNIVERSE

Nuclear Reactions and Origin of

Elements

The emergence of the universe brought about the
formation of elements, and consequently of matter.

• Nuclear Reactions – are process in which a

nucleus either combines with another nucleus
(through nuclear fusion) or splits into smaller
nuclei (through nuclear fission).

• Radioactivity – is the emission of energetic

particles of an atom, a phenomenon involved in
nuclear reactions.

• Isotopes – are atoms of an element that have

the

same

number

of

protons

but

different

number of neutrons.

Cosmic Origin of the Elements

• The Big Bang

The existence of all matter is believed to have
started with the birth of the universe.

Big Bang Theory

• The most widely accepted explanation to the

origin of the universe.

• Its evidence was first expressed in the early

1900s,

when

Edwin

Hubble

offered

an

explanation that the universe is expanding. He
observed that many stars and galaxies shine
with light shifted toward the red end of the visible
spectrum.

Red Shift - occurs when
the light waves of cosmic
bodies are stretched into
low-frequency

red

waves

as they move away from an
observer on Earth.

Hubble’s law – a law which suggests that
the size of the red shift is proportional to the
distance and speed of a star that is moving
away from Earth.

• Big Bang Nucleosynthesis – is the process

through which the light elements were formed.

• Tritium – an isotope of hydrogen formed from

big bang nucleosynthesis consisting of two
neutrons and one proton

• Fusion shells – regions or layers where

reactions involved in the formation of each new
element happened.

• Stellar Explosion

As the red giant star exhausted the nuclear fuel of
light elements, its core started to collapse that
eventually led to the explosion of the star. This
violent explosion called supernova released a
huge amount of nuclear energy and produced,
through neutron capture and radioactive decay,
other elements heavier than iron.

Stellar Formation and Evolution

• Fusion shells – regions or layers where

reactions involved in the formation of each new
element happened.

• Younger yellow stars made up of hydrogen

were fueled by the energy released from the
fusion of hydrogen nuclei to form helium.

• https://www.youtube.com/watch?v=5a18y

8YModY&t=56s

• https://spaceplace.nasa.gov/big-bang/en/

Reference