Hitting the wall

How do you know if you ran through a wall? Testing the nature of dark energy and dark matter

Researchers from Canada, California, and Poland have devised a straightforward way to test an intriguing idea about the nature of dark energy and dark matter. A global array of atomic magnetometers – small laboratory devices that can sense minute changes in magnetic fields – could signal when Earth passes through fractures in space known as domain walls. These structures could be the answer to the universe's darkest mysteries.

Can't say I've ever heard of "domain walls" before.  Interesting.