“Weakest” is rarely a superlative worth celebrating, but experiments began this summer in a room (below) with the weakest magnetic field in our solar system—and scientists are excited. Built by physicists at the Technical University of Munich, the room achieves a millionfold reduction in the intensity of ambient magnetic fields, a 10-fold improvement on any previous man-made structure, registering even less such activity than the vast, empty space between planets. The facility's shielding consists of layers of a highly magnetizable metal that ensnare fields so they do not pass through to the structure's interior. Within, ultraprecise experiments can take place with only minute interference from the results-mucking effects of Earth, electronics, living bodies, and more. The room's special type of silence therefore offers a unique opportunity to probe important questions in physics, biology and medicine.

1 Why is there more matter than antimatter in the universe? The Munich physicists will observe whether a neutron's magnetic properties behave evenly in the presence of high electric fields and precisely controlled magnetic fields. Strong discrepancies in how the particles are balanced, such as a slight difference in charge, could hint at how the asymmetry of matter occurred.

2 Do magnetic monopoles exist? If particles with a single pole are out there, they will be able to pass through the room's shielding. Without interference, sensors would register the increased magnetic activity.

3 What is dark matter made of? Researchers plan to monitor the room for theorized “axionlike” dark matter particles, which could affect the spins of some atoms.

4 How do animals use magnetic fields to navigate? By raising organisms in an environment with very little magnetic activity, researchers may be able to discern whether use of such fields is a learned or an innate trait.

5 What can magnetism reveal about human health? Any space with very little magnetic noise opens up the possibility for more detailed diagnoses: for instance, distinguishing the magnetic field of a mother's heart from that of her unborn child to determine irregularities.