Galaxies and the Universe
A galaxy is a vast system of stars, gas and dust held together by gravity, and our Sun is in the Milky Way.
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A galaxy is a vast system of stars, gas and dust held together by gravity, and our Sun is in the Milky Way.
- There are billions of galaxies
- The Milky Way is a spiral
- The universe is expanding
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Galaxies and the Universe?
Within Earth & Environmental Science, which covers our planet, its resources and ecosystems, and how people can protect the environment, this topic explains Galaxies and the Universe. Earth and environment topics show how the planet’s systems shape landscapes, climate and life, with models that make these processes visible.
Check that you can explain Galaxies and the Universe in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Galaxies and the Universe helps you explain the environment around you and weigh up how people can protect it.
Galaxies and the Universe in detail
A galaxy is a huge system of stars, gas, dust and dark matter held together by gravity. Our galaxy, the Milky Way, is a spiral galaxy with about 100–400 billion stars, and the Sun lies in one of its arms. Other types are elliptical and irregular galaxies. The nearest large galaxy is Andromeda.
The observable Universe contains hundreds of billions of galaxies. According to the Big Bang theory, the Universe began about 13.8 billion years ago and has been expanding ever since, shown by the redshift of distant galaxies. Dark matter and dark energy make up most of its content, and are not yet fully understood.
How the interactive helps you understand Galaxies and the Universe
Watch the orbit in the interactive. Use any sliders or buttons it offers to change the values and see how the orbit responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Galaxies and the Universe.
Real-life uses and examples
- Use a diagram of Galaxies and the Universe to describe the steps of a process in order.
- Discuss how human activity changes Galaxies and the Universe, using a named example.
- Explain how Galaxies and the Universe affects the landscape or climate near you.
Common mistakes to avoid
- Describing a process without the timescale it works over.
- Presenting one cause as the only cause of an environmental change.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Galaxies and the Universe
What is Galaxies and the Universe?
A galaxy is a vast system of stars, gas and dust held together by gravity, and our Sun is in the Milky Way.
What are the most important points about Galaxies and the Universe?
The main points are: There are billions of galaxies; The Milky Way is a spiral; The universe is expanding.
Why is Galaxies and the Universe useful?
Understanding Galaxies and the Universe helps you explain the environment around you and weigh up how people can protect it.
How can I practise Galaxies and the Universe?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Galaxies and the Universe?
Related topics in Earth & Environmental Science include Structure of the Earth, Fossils and Geological Time, Plate Tectonics.