Why Does a Compass Point North?
Learners can explain why a compass needle aligns in a roughly north–south direction by linking it to Earth's magnetic field and magnetic poles, and they can identify the difference between magnetic north and geographic north.
A complete interactive classroom, not just a preview.
Start when you are ready to enter this Stage's 12 scenes and explore, respond, and learn as you go.
Why does a compass needle always settle pointing one way?
- compass-needle-behavior
- A freely pivoted magnetized needle settles into a consistent orientation rather than spinning randomly.
- magnetic-poles
- Every magnet has a north-seeking and south-seeking pole, and like poles repel while unlike poles attract.
- earth-as-magnet
- Earth behaves as if it contains a giant magnet, producing a magnetic field that extends into space.
- needle-aligns-with-field
- The compass needle rotates until it aligns with the local direction of Earth's magnetic field, which is why it points roughly north.
- magnetic-vs-geographic-north
- Magnetic north (where the compass points) and geographic north (the planet's rotation axis) are not in the same place; the angle between them is called declination.
- declination-and-uncertainty
- Declination varies by location and changes slowly over time, which is why a compass reading is not perfectly precise and the difference is a real, measurable phenomenon.
- compass-naming-convention
- The end of the compass labeled 'north' is actually a magnetic south pole in terms of polarity, because it is attracted to Earth's magnetic north pole, which sits near the geographic North Pole. This is a naming clarification, not a separate force.
A compass points directly to the geographic North Pole.
Show evidence that the compass actually points to magnetic north, which is hundreds to thousands of kilometers away from the geographic North Pole, and that the angular difference (declination) is real and measurable.
The north pole of a compass is attracted to the north because opposites attract and the geographic North Pole is magnetic north.
Clarify that what we call the 'north-seeking' pole of a compass is the magnetic pole that is actually a magnetic south pole in terms of polarity; it is attracted to Earth's magnetic north pole (which sits near the geographic North Pole). Use this carefully as a clarification of terminology, not as the main teaching point.
- electromagnetic field equations
- Maxwell's equations
- Lorentz force calculations
- detailed paleomagnetism
- navigation beyond compass orientation
- quantum explanation of magnetism
- magnetic materials engineering
- Learner can state that a compass needle aligns with Earth's magnetic field, not with the geographic North Pole.
- Learner can explain declination as the angular difference between magnetic north and geographic north.
- Learner can describe one piece of evidence that Earth's magnetic field exists beyond the compass itself.
- Learner can correctly identify that the 'north' end of a compass needle is a magnetic south pole.
- Learner can reason about why a compass would behave differently near a strong magnet or on another planet, and can identify the key sign that a location has unusual magnetic conditions.
Curious general learners ages 13 and up with no prior physics background. They are comfortable with simple diagrams and short experiments described in everyday language.
- 01The Needle That Always Knowsslide
- 02Predict Before You Peekinteractive
- 03Observation, Not Magicslide
- 04Two Magnets, One Ruleinteractive
- 05Field Lines You Can Seeinteractive
- 06Earth as a Giant Magnetslide
- 07Why the Needle Lines Upinteractive
- 08Test Your Model: Magnetic or Geographic?interactive
- 09The Honest Gap: Declinationslide
- 10Stray From the Patterninteractive
- 11Recap: What the Needle Is Doingslide
- 12A New Question to Carryslide
Discussion threads for a Stage aren't available yet.
