Big bang basics
The big bang theory is a theory put forward to explain the origins of the universe. The Big bang estimates the age of the universe to be about 14 billion years old.
It states that the universe started as as single concentrated point, then an explosion sent energy and matter outwards. Even today, this matter is moving outwards, so the universe is currently expanding. This means that galaxies are moving further away from us and from each other, causing the universe to expand.
As the universe expanded, it also cooled. You can relate this expansion and decrease in temperature to fire extinguishers. When a carbon dioxide fire extinguisher is used and the gas expands, the gas actually decreases in temperature.
Evidence for the Big Bang!
There are several pieces of evidence for the big bang:
1. Qualitative red-shift of light from galaxies that are receding
2. Galaxies’ speed vs distance = evidence of an expanding universe
3. How red-shift provides evidence for the Big Bang
4. 1998 supernova observations and how scientists develop theories
1. Qualitative red-shift of light from galaxies that are receding
When galaxies move away from us, the light they emit is red-shifted.
This means the light’s wavelength is stretched, so it shifts towards the red end of the spectrum.
The faster a galaxy moves away, the greater the red-shift.
2. Galaxies’ speed vs distance = evidence of an expanding universe
Observations show that more distant galaxies have a larger red-shift, meaning they’re moving away faster.
This shows that space is expanding in all directions.
It suggests that the universe is getting bigger, like a balloon inflating.
3. How red-shift provides evidence for the Big Bang
Since galaxies are moving away from each other, they must have once been closer together.
Red-shift shows the universe is expanding, so in the past, it was small, hot, and dense.
This supports the Big Bang theory, which says the universe began from a single point and has been expanding ever since.
4. 1998 supernova observations and how scientists develop theories
In 1998, astronomers studied the light from distant supernovae (exploding stars).
These supernovae were dimmer than expected, which meant they were farther away than they should have been if the universe’s expansion was slowing down.
This showed the expansion of the universe is speeding up — it’s accelerating.
Scientists used this evidence to improve the Big Bang model by including something called dark energy, which may be causing this acceleration.
This shows how new observations help scientists develop and refine theories over time.
Practice Questions
1.What is the age of the universe?
2. Describe the big bang theory
3. State two pieces of evidence that will support the big bang theory.
Absorption and Emission of EM Radiation
JJ Thomson and Plum pudding model
Ernest Rutherford and the Nuclear Model
Niels Bohr changing the Nuclear Model
Discovering the Proton and Neutron
Measuring radiation from radioactivity
Radiation types and properties
Random nature of radioactive decay
Radioactive contamination or irradiation
Hazards of contamination and irradiation
Studies on the effects of radiation on humans
Different half lives of radioactive isotopes
Nuclear Fission Chain Reaction
Writing nuclear fission equations
Drawing ray diagrams for a concave lens
Drawing Ray Diagram to produce a virtual image for a convex lens
Drawing ray diagram to produce a real image for a convex lens.
Specular and Diffuse Reflection
Seeing Coloured Objects Part 2
Viewing objects through coloured filters
Transparent, Translucent and Opaque