Tech

Can a compass work underground?

Old compass on white background with soft shadow

The compass app on your phone probably won’t

Old compass on white background with soft shadow

work because it relies on radio signals that are
easily blocked by rock or water, but
for a compass with a wobbly needle, it just
depends on how far underground. A compass
works because its magnetised needle lines up
with the magnetic fi eld that runs between
Earth’s north and south poles, and that fi eld is
just as powerful if you go down a mineshaft
or into the depths of the ocean. But the fi eld is
created by swirling molten iron in Earth’s core,
and if you could drill that far down, you’d fi nd
your magnetic needle going haywire.