Defying Newton’s Third Law: How Human Sperm Propel Themselves through Viscous Liquids, According to New Study
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Study Reveals How Sperm Move Through Viscous Liquids
A recent study conducted by mathematicians at Kyoto University has found that human sperm are able to propel themselves through thick liquids using their whip-like tails, defying Newton’s third law of motion. This law, which states that every action has an equal and opposite reaction, does not appear to apply to microscopic cells like sperm.
Understanding Nonreciprocal Interactions
The researchers analyzed experimental data on human sperm and modeled the movement of the green algae Chlamydomonas to study nonreciprocal interactions. Nonreciprocal interactions occur in natural systems, such as flocks of birds and molecules in fluids, where forces act asymmetrically, creating a loophole in Newton’s third law.
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Elasticity and Flagellum Mechanics
Highly viscous fluids typically dissipate the energy of flagella, making movement difficult for sperm and algae. However, the researchers discovered that sperm tails and flagella possess a unique elasticity that allows them to move without losing much energy into the surrounding fluid. To describe the internal mechanics of the flagellum, the researchers introduced a new term called the “eccentric elastic modulus.”
Potential Applications and Future Research
The findings of this study could have implications for the development of small, self-assembling robots that mimic living materials. Additionally, the modeling techniques used in this study may contribute to a better understanding of collective behavior in various systems. The study was published in the journal PRX Life.
Source: ScienceAlert
