Spinning water can slightly change the alignment of its hydrogen nuclei, or protons, in a weak magnetic field. In 2019, researchers detected this rotation-associated proton polarization by measuring the size of the water sample’s nuclear magnetic resonance (NMR) signal. The experiment demonstrated a physics effect in a laboratory—not a way to power or improve an MRI scanner.
What happens when water spins?
The effect is called the nuclear Barnett effect: rotation is associated with magnetization. The 2019 experiment by Mohsen Arabgol and Tycho Sleator of New York University examined the nuclear version, in which the relevant spins are those of hydrogen protons in water. It built on the electronic Barnett effect, which concerns electrons rather than atomic nuclei.
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Proton polarization describes a change in how nuclear spins are aligned or distributed. The researchers detected that change through the size of the sample’s NMR signal. The primary paper reports that the polarization change was proportional to the rotation frequency. The study, “Observation of the Nuclear Barnett Effect,” appeared in Physical Review Letters on 2 May 2019.
How did the researchers measure it?
They rotated a water sample in a weak magnetic field and measured its NMR signal. The primary paper reports rotation speeds up to 13.5 kHz. An American Physical Society explanation describes the water as occupying a hollow section measuring 2 mm by 8 mm inside a rotating rod; that dimension describes the laboratory apparatus, not a product specification.
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The APS account puts the signal change in context: at just over 4,000 revolutions per second, magnetization increased by 1% over the small effect induced by the NMR technique; at 13,500 revolutions per second, it rose to just over 3%. These percentages are relative changes reported for that experimental setup, not absolute proton polarization or an imaging-system improvement. The APS account explains the measurement and its reported values.
Did spinning create a magnetic field?
The researchers reported no NMR frequency shift due to rotation. They interpreted that absence as evidence that the measured magnetization was not produced by a real magnetic field. The distinction matters: the experiment measured rotation-associated proton polarization, not a newly generated field that could be treated as an ordinary magnet.
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Does this make spinning water useful for MRI?
The cited reports establish a laboratory measurement, not a practical MRI technique, medical application, or usable imaging system. The effect was measured under high-speed rotation in a weak magnetic field; it should not be taken to mean that ordinary water becomes visibly or permanently magnetized when stirred or spun.
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Chemistry World’s May 2019 account places the result in the context of the electronic Barnett effect and identifies Arabgol and Sleator as the NYU researchers. The available accounts here describe the original 2019 experiment; they do not establish whether it has since been independently replicated or led to practical applications.
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