Monarch butterflies spend the winter in Mexico. But as the weather warms, they take flight. Millions of orange and black wings flutter on the wind. The butterflies head north. They travel for weeks to reach Canada. When the weather cools, off they go again! The butterflies turn south. Back to Mexico.

As soon as a monarch comes out of its chrysalis, it knows to follow the same path monarchs have used for hundreds or even thousands of years. How do the monarchs know where to go? Scientists wonder.

Now they have a new idea. Maybe butterflies use the Earth’s magnetic field.

If you’ve held a compass, you know that it always points north. Maybe butterflies have a sort of built-in compass. It tells each one which way to go.

Scientists tested the idea. They put some monarchs in a closed room. They used equipment to create a magnetic field in that room. As they changed the direction of the field, the butterflies also changed direction.

Sea birds and sea turtles use the same method to migrate. It is one way God designed the Earth and its creatures to work together.