Developments in ways to measure the extremely weak magnetic fields emanating from organs such as the heart, brain and lungs are leading to important new methods for diagnosing abnormal conditions.
In France, around 1780, many Parisians believed in curing their illnesses by magnetism. To perform this cure, they sat in a group around a tub containing “mesmerized” water and iron filings; this was part of the cult introduced to Paris by Dr Franz Mesmer. He proclaimed that animal magnetism of the human body controlled the flow of a universal fluid through the body and that illness resulted when there was an obstacle to that flow. The illness would be cured by magnetically redirecting the fluid with arrangements such as the filings and water.
With strong magnetic fields and intense lasers or pulsed electric currents, physicists can reconstruct the conditions inside astrophysical objects and create nuclear-fusion reactors.
A crude device for quantification shows how diverse aspects of distantly related organisms reflect the interplay of the same underlying physical factors.