The concept of a human magnetic field often evokes images of an invisible energy field or an aura, ideas rooted in popular culture and metaphysical belief. The scientifically verifiable phenomenon is known as biomagnetism, which refers to the extremely weak magnetic fields naturally produced by the living body. These fields are a direct and measurable consequence of the body’s internal electrical activity, firmly placing them within the domain of physics and biology. Studying biomagnetism allows researchers to gain unique insights into human physiological function.
The Physical Source of Biological Magnetism
The generation of a human magnetic field is based on a fundamental principle of physics: any moving electrical charge creates a corresponding magnetic field. The human body is a complex electrochemical system driven by the movement of charged particles called ions. These ions, such as sodium, potassium, and calcium, move across the membranes of nerve and muscle cells to create electrical currents.
When a current flows through a conductor, a magnetic field encircles the flow, and the collective activity of billions of cells produces a net external magnetic field. While the body’s electrical signals are relatively strong, the resulting magnetic fields are extraordinarily faint, requiring highly specialized equipment for detection.
Mapping Magnetic Fields from the Body’s Organs
The magnetic fields produced by the body are strongest in areas with the highest density of synchronized electrical activity, primarily the heart and the brain. The heart produces the largest biomagnetic signal, measured using Magnetocardiography (MCG). This field is about one millionth the strength of the Earth’s static magnetic field, providing detailed, non-contact information about the heart’s electrical conduction.
MCG offers a functional map of cardiac activity that is not distorted by the electrical resistance of chest tissues like bone and fat. Clinicians use MCG to assess the timing and sequence of the heart’s electrical cycle, helping identify subtle abnormalities in rhythm or conduction pathways.
The brain also generates a complex magnetic field, detected through Magnetoencephalography (MEG). This procedure measures the extremely minute magnetic signals generated by the synchronized firing of neuronal populations in the cerebral cortex. The brain’s magnetic fields are significantly weaker than those from the heart, often measuring one billionth the strength of the Earth’s field.
MEG is useful in mapping brain function with high temporal resolution, allowing specialists to pinpoint the source of abnormal electrical activity. For example, it is used in presurgical planning to precisely locate the focus of epileptic seizures or to map language and motor centers before tumor removal. The magnetic measurement is advantageous because the skull and scalp do not scatter the magnetic field lines, providing clearer spatial localization of the neural source than purely electrical measurements.
Technology Used to Measure Biomagnetism
The extreme weakness of the body’s magnetic signals necessitates the use of ultrasensitive detection instruments operating in a magnetically shielded environment. The primary technology employed is the Superconducting Quantum Interference Device (SQUID). SQUIDs are highly sensitive magnetometers capable of detecting magnetic flux changes down to the femtoTesla range, essential for sensing biomagnetic fields.
The core function of a SQUID relies on the physics of superconductivity, a state achieved when materials are cooled to cryogenic temperatures, typically using liquid helium. In this state, electrical resistance vanishes, allowing the device to measure minute changes in the magnetic field that would be obscured by thermal noise in a conventional sensor. The SQUID converts these tiny magnetic flux variations into a measurable voltage signal.
Because of its sensitivity, this technology must be housed within a magnetically shielded room constructed of high-permeability alloys. This shielding filters out interference from environmental sources like passing cars, elevators, or distant electrical power lines.
Differentiating Scientific Biomagnetism from Popular Beliefs
The measurable, physics-based phenomenon of biomagnetism is often conflated with popular, non-scientific concepts such as human energy fields, auras, or chakras. The magnetic field produced by the human body diminishes rapidly with distance and is far too weak to interact with other people or objects in a noticeable way.
There is no scientific evidence to support the claim that the body’s magnetic field relates to or reflects emotional, spiritual, or metaphysical states. Concepts like auras or energy healing, while prevalent in alternative practices, lack the empirical data and controlled observation necessary for scientific validation. Biomagnetism is exclusively a scientific term that describes a biological byproduct of electrical currents.