Some animals also navigate using the earth’s magnetic field. From the idea that there may be some relationship with these two things, this experimental earthquake detector was born. [ ...

The needle is being affected by the Earth’s magnetic field. One end points towards magnetic north and the other end points south. You can use a compass to check which direction each end is facing.

Here’s a great magnetic levitator build ... That measurement is compared to a second detector mounted slightly lower. The circuit adjusts the electromagnetic field, making sure the object ...