What happens to the hydrogen protons in the human body when exposed to a magnetic field?

When the human body is exposed to a magnetic field, the hydrogen protons, which are abundant due to the high water content in the body, align with the direction of the main magnetic field. This alignment occurs because protons have a property called nuclear spin, and when placed in a magnetic environment, they tend to orient themselves parallel or anti-parallel to the magnetic field lines.

The majority will align parallel to the magnetic field due to the lower energy state associated with this orientation. This alignment is fundamental in magnetic resonance imaging (MRI) as it creates a net magnetization that can be manipulated by radiofrequency pulses, allowing for the creation of images of internal body structures. Thus, the alignment of hydrogen protons with the magnetic field is a key principle that underlies the imaging technique.