Magnetic sense

The Turtle That Felt the Earth

If the sky is dark and the water has no road, how does she know the way?

Generated interpretation

A drawing of Earth's magnetic field. Animals do not see glowing rails. Some detect direction, some also detect a rough sense of place.

Listen, or read

The words

A young turtle leaves the beach at night. The shore disappears. There is no trail in the water. Earth is quietly magnetic, and she can feel something of that field. Not as a picture. As a sense. A traveler needs two things. Which way. And where am I. Sea turtles appear to have both.

A young turtle leaves a beach at night. Waves lift her. The shore disappears.

There is no trail in the water. Clouds can hide the stars. She still turns the right way.

Earth is quietly magnetic. The turtle can feel something of that field. Not as a picture. As a sense.

What we know

Evidence, held lightly

We know

Loggerhead turtles orient to magnetic fields in the laboratory and in the sea.

They can use both the tilt and the strength of the field as information about place.

The evidence suggests

Compass and map are built from different mechanisms.

We are still figuring this out

Where in the body the sensors live, and how the map is stored.

We do not know yet

Exactly what it feels like, from inside a turtle, to read the field.

Try this

A child can try this

Stand still outside

Close your eyes. Point toward the Sun if you can feel the warmth. Then point toward home. You used heat, memory, and maybe sound. The turtle has instruments you do not. Notice how many clues you already use without naming them.

Also nearby

A question to carry outside

What is Earth telling living things that we usually miss?