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Economic Times
3 days ago
- Science
- Economic Times
Do human sperm defy Newton's third law? Scientists finally crack the mystery of their swim through thick fluids
Scientists at Kyoto University unravelled a biological mystery. They discovered how human sperm navigate thick fluids. Sperm tails use 'odd elasticity' to bypass Newton's laws. This allows efficient movement in viscous environments. The finding explains sperm's rapid swimming. It could inspire new designs for microscopic robots. This principle applies to other microscopic swimmers like algae. Scientists decode the Physics trick that lets sperm speed through fluids that should stop them. (Representative Image) Tired of too many ads? Remove Ads The physics problem in the micro world Tired of too many ads? Remove Ads Odd elasticity: The tail's secret weapon Biology and robotics Rethinking newton in active systems Scientists have been puzzled by a biological mystery: how human sperm, just 50 microns long, can glide so effortlessly through thick cervical mucus or viscous lab-made gels that should slow them researchers from Kyoto University say they have decoded the secret: sperm tails exploit a phenomenon called 'odd elasticity,' enabling them to move in ways that sidestep one of Newton's basic laws of findings, published by researchers Kenta Ishimoto, Clément Moreau, and Kento Yasuda, help solve a decades-old puzzle: how sperm can travel swiftly through thick cervical mucus or gel-like fluids that should slow such tiny swimmers to a the human scale, swimmers push water backward to propel forward, with inertia balancing the forces. But at the microscopic level, inertia disappears and is replaced by syrupy drag, a situation physicists call low Reynolds number such conditions, a simple back-and-forth flick of a tail wouldn't work. Instead, objects like sperm must perform a continuous, asymmetrical wiggle pattern that never repeats in reverse, allowing forward high-speed video of human sperm and the green alga Chlamydomonas, the team mapped tail movements in 'shape space' and created an elastic matrix to calculate internal forces. They found that the tails are powered by molecular motors that constantly inject energy instead of acting like passive creates odd elasticity, an imbalance where a bend in one part of the tail sends tension through the entire structure without a mirrored counterforce. The result is a traveling wave that moves forward without an equal push in the opposite study suggests that as odd elasticity increases, so does propulsion speed. This explains how human sperm beat their tails around 20 times per second, even in thick principle also applies to other microscopic swimmers like algae, and could inspire soft robots that navigate through viscous environments using similar mechanics, without rotating work doesn't overturn Newton's third law, which still governs passive systems. Instead, it shows that force symmetry can be bypassed in active systems, where energy is constantly absorbed and nature, this flexibility may help sperm adapt their swimming mechanics in response to chemical cues or changes in viscosity on their way to the egg.
Time of India
3 days ago
- Science
- Time of India
Do human sperm defy Newton's third law? Scientists finally crack the mystery of their swim through thick fluids
Scientists have been puzzled by a biological mystery: how human sperm, just 50 microns long, can glide so effortlessly through thick cervical mucus or viscous lab-made gels that should slow them down. Now, researchers from Kyoto University say they have decoded the secret: sperm tails exploit a phenomenon called 'odd elasticity,' enabling them to move in ways that sidestep one of Newton's basic laws of motion. The findings, published by researchers Kenta Ishimoto, Clément Moreau, and Kento Yasuda, help solve a decades-old puzzle: how sperm can travel swiftly through thick cervical mucus or gel-like fluids that should slow such tiny swimmers to a crawl. by Taboola by Taboola Sponsored Links Sponsored Links Promoted Links Promoted Links You May Like Undo The physics problem in the micro world At the human scale, swimmers push water backward to propel forward, with inertia balancing the forces. But at the microscopic level, inertia disappears and is replaced by syrupy drag, a situation physicists call low Reynolds number flow. Live Events In such conditions, a simple back-and-forth flick of a tail wouldn't work. Instead, objects like sperm must perform a continuous, asymmetrical wiggle pattern that never repeats in reverse, allowing forward motion. Odd elasticity: The tail's secret weapon Using high-speed video of human sperm and the green alga Chlamydomonas, the team mapped tail movements in 'shape space' and created an elastic matrix to calculate internal forces. They found that the tails are powered by molecular motors that constantly inject energy instead of acting like passive springs. This creates odd elasticity, an imbalance where a bend in one part of the tail sends tension through the entire structure without a mirrored counterforce. The result is a traveling wave that moves forward without an equal push in the opposite direction. Biology and robotics The study suggests that as odd elasticity increases, so does propulsion speed. This explains how human sperm beat their tails around 20 times per second, even in thick fluids. The principle also applies to other microscopic swimmers like algae, and could inspire soft robots that navigate through viscous environments using similar mechanics, without rotating motors. Rethinking newton in active systems The work doesn't overturn Newton's third law, which still governs passive systems. Instead, it shows that force symmetry can be bypassed in active systems, where energy is constantly absorbed and expended. In nature, this flexibility may help sperm adapt their swimming mechanics in response to chemical cues or changes in viscosity on their way to the egg.
Yahoo
23-06-2025
- Science
- Yahoo
Scientists Caught Sperm Defying One of Newton's Laws of Physics
Human sperm can swim through surprisingly viscous fluids with ease – and they seemingly defy Newton's third law of motion to do so. To figure out how they slither through substances that should, in theory, resist their movement, a team led by Kenta Ishimoto, a mathematical scientist at Kyoto University, investigated the motions of sperm and other microscopic biological swimmers a few years ago. When Sir Isaac Newton conceived his now-famed laws of motion in 1686, he sought to explain the relationship between a physical object and the forces acting upon it with a few neat principles that, it turns out, don't necessarily apply to microscopic cells wriggling through sticky fluids. Newton's third law can be summed up as "for every action, there is an equal and opposite reaction". It signifies a particular symmetry in nature where opposing forces act against each other. In the simplest example, two equal-sized marbles colliding as they roll along the ground will transfer their force and rebound based on this law. However, nature is chaotic, and not all physical systems are bound by these symmetries. So-called non-reciprocal interactions show up in unruly systems made up of flocking birds, particles in fluid – and swimming sperm. These motile agents move in ways that display asymmetric interactions with the animals behind them or the fluids that surround them, forming a loophole for equal and opposite forces to skirt Newton's third law. Because birds and cells generate their own energy, which gets added to the system with each flap of their wings or movement of their tails, the system is thrust far from equilibrium, and the same rules don't apply. In their study published in October 2023, Ishimoto and colleagues analyzed experimental data on human sperm and also modeled the motion of green algae, Chlamydomonas. Both swim using thin, bendy flagella that protrude from the cell body and change shape, or deform, to drive the cells forward. Highly viscous fluids would typically dissipate a flagellum's energy, preventing a sperm or single-celled algae from moving much at all. And yet somehow, the elastic flagella can propel these cells along without provoking a response from their surroundings. The researchers found that sperm tails and algal flagella have an 'odd elasticity', which allows these flexible appendages to move about without losing much energy to the surrounding fluid. But this property of odd elasticity didn't fully explain the propulsion from the flagella's wave-like motion. So from their modeling studies, the researchers also derived a new term, an odd elastic modulus, to describe the internal mechanics of flagella. "From solvable simple models to biological flagellar waveforms for Chlamydomonas and sperm cells, we studied the odd-bending modulus to decipher the nonlocal, nonreciprocal inner interactions within the material," the researchers concluded. The findings could help in the design of small, self-assembling robots that mimic living materials, while the modeling methods could be used to better understand the underlying principles of collective behavior, the team said. The study was published in PRX Life. An earlier version of this article was published in October 2023. A Cracked Piece of Metal Self-Healed in Experiment That Stunned Scientists A Fifth Force of Nature May Have Been Discovered Inside Atoms Strange Radio Signals Detected Emanating From Deep Under Antarctic Ice
