Big Bang and Cosmology
The universe began hot and dense about 13.8 billion years ago and keeps expanding.
About this topic
The universe began about 13.8 billion years ago from a hot, dense state and has been expanding ever since. Evidence includes Hubble's observation that distant galaxies recede faster (redshift), the cosmic microwave background radiation and the observed abundances of hydrogen and helium.
Imagine dots on a balloon being inflated: every dot moves away from every other, and none is the centre. The cosmic microwave background is a faint glow at 2.7 K, the cooled afterglow from when the universe became transparent about 380,000 years after the beginning. About three quarters of the ordinary matter is hydrogen and a quarter helium, as predicted by the early hot conditions.
Space itself is expanding, not galaxies flying into space. Only about 5% of the universe is ordinary matter, with ~27% dark matter and ~68% dark energy, which is accelerating expansion.
The Big Bang was not an explosion at a point in a pre-existing space, and it says little about what came before. Redshift is a stretching of light by expanding space.
Key ideas
- Cosmic microwave background
- Redshift shows expansion
- Dark matter and dark energy
Quick check
Use cases: where Big Bang and Cosmology helps
- Homework: review the key idea behind Big Bang and Cosmology before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Big Bang and Cosmology without notes.
- Visual learning: play with the interactive lab to see how Big Bang and Cosmology changes when you adjust its inputs.
- Teaching a friend: explain Big Bang and Cosmology in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Big Bang and Cosmology?
The universe began hot and dense about 13.8 billion years ago and keeps expanding.
What will I learn in Big Bang and Cosmology?
Cosmic microwave background. Redshift shows expansion. Dark matter and dark energy.
Is Big Bang and Cosmology part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Big Bang and Cosmology lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Big Bang and Cosmology?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.