Earth's Magnetic Field
Earth's field shields us and guides compasses.
About this topic
Earth behaves as if it has a giant bar magnet inside, tilted about 11° from the rotation axis, generated by flowing molten iron in the outer core (the geodynamo). Compass needles align with the field lines, pointing to the magnetic north.
The field is weak, about 50 microtesla at the surface, yet it extends tens of thousands of kilometres into space. The magnetosphere deflects the solar wind, protecting life and creating auroras where charged particles hit the atmosphere near the poles, producing green and red curtains of light.
The field has reversed many times in geological history, recorded in rocks that froze in the direction of the field when they formed, and the magnetic poles slowly wander. Animals such as birds and sea turtles navigate using it, and humans use it for compasses.
A common mistake is to think the geographic and magnetic poles coincide; they differ by hundreds of kilometres, and the difference, called declination, matters for accurate navigation.
Key ideas
- Magnetic north differs from true north
- Auroras form near the poles
- Field reverses over long times
Quick check
Use cases: where Earth's Magnetic Field helps
- Homework: review the key idea behind Earth's Magnetic Field before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Earth's Magnetic Field without notes.
- Visual learning: play with the interactive lab to see how Earth's Magnetic Field changes when you adjust its inputs.
- Teaching a friend: explain Earth's Magnetic Field 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 Earth's Magnetic Field?
Earth's field shields us and guides compasses.
What will I learn in Earth's Magnetic Field?
Magnetic north differs from true north. Auroras form near the poles. Field reverses over long times.
Is Earth's Magnetic Field 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 Earth's Magnetic Field 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 Earth's Magnetic Field?
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.