大树怎么把水从根部送到几十米高的树顶？
How does a tall tree lift water from roots to its crown tens of meters up?
叶片蒸发在细管（导管）里拉出负压，靠水分子间的内聚力和管壁附着力形成连续水柱，像一根长长的吸管被往上抽。
Leaf transpiration pulls a negative pressure; cohesion between water molecules and adhesion to vessel walls keep a continuous column rising like a long straw.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#蒸腾 #毛细 #内聚力
猫从高处摔下，为什么常能四脚先着地？
Why do cats often land on their feet after a fall?
猫有“翻正反射”：先弯身让前半身和后半身朝相反方向转，利用角动量守恒而不改变总旋转，最后伸脚着陆。
Cats use the righting reflex: bending lets front and rear twist oppositely while total angular momentum stays zero, so they orient feet-down without spinning overall.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
T. R. Kane 与 M. P. Scher, 《A Dynamical Explanation of the Falling Cat Phenomenon》, International Journal of Solids and Structures 5, 663 (1969)
T. R. Kane & M. P. Scher, 'A Dynamical Explanation of the Falling Cat Phenomenon', International Journal of Solids and Structures 5, 663 (1969)
独立核验依据 · Independent verification: 核验依据 1 CROSSREF 标识 10.1016/0020-7683(69)90086-9：A dynamical exp
#猫 #角动量 #反射
为什么血液在血管里大多平稳流动，而不是乱成一团？
Why does blood mostly flow smoothly in vessels rather than turbulently?
血液大多平稳流动，是因为黏性占了上风。衡量两种力之比的是雷诺数：管越细、流越慢、血越稠它越低，流动自组织成一层层平行滑动的层流。多数血管又细又慢，层流因此是常态。例外有两处：瓣膜口与狭窄处局部速度骤升，雷诺数越过临界量级便起湍流，听诊的杂音就是它；到毛细血管尺度，红细胞与管径同量级，连续介质假设也开始失效。
Blood flows smoothly because viscosity has the upper hand here. The Reynolds number compares the two competing effects: the narrower the vessel, the slower the flow and the thicker the blood, the lower it is, and the flow organises itself into laminar layers sliding parallel to one another. Since most vessels are narrow and slow, laminar flow is the norm. Two exceptions matter: at a valve orifice or a narrowing the local speed jumps, the Reynolds number passes its critical threshold and turbulence follows, and a murmur heard on auscultation is exactly that; while at capillary scale red cells are comparable in size to the vessel, so the continuum assumption begins to fail as well.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#层流 #雷诺数 #血液
北极熊的毛其实是透明的中空管子，为什么我们却看它是白的？
Polar bear fur is actually transparent hollow tubes; why do we see it as white?
中空毛发把各方向的光反复散射、混合成白光；同时空气层锁住热量，既“显白”又保暖。
The hollow hairs scatter all colors of light together into white, while the trapped air layer insulates, making the bear look white and stay warm.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#散射 #毛发 #保暖
蜻蜓翅膀尖上为什么有一小坨“翅痣”？
Why does a dragonfly wing have a small dark spot near its tip?
翅痣增加局部质量，改变翅膀的重心与阻尼，抑制高速振翅时的共振颤振，让翅膀不易抖裂。
The pterostigma adds local mass, shifting the center of mass and damping, which suppresses resonant flutter at high flapping speeds.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#翅痣 #共振 #阻尼
深海的鱼为什么不会被巨大的水压扁？
Why aren't deep-sea fish crushed by enormous water pressure?
它们体内没有大空腔，体液压强和外部海水基本平衡，里外压力相当，就没有被压扁的净力。
They have no large air spaces; their body fluids match the surrounding pressure, so inside and outside balance and there is no net crushing force.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#压强 #深海 #平衡
鸟群飞“人”字形，真的能省力气吗？
Does flying in a V formation really save birds energy?
前面鸟的翼尖会产生向上的气流（上洗），后面鸟待在合适位置就能借这股“免费升力”，整体编队更省力。
The leading bird's wingtip makes an upwash; followers riding it get free lift, so the flock flies more efficiently as a team.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
H. Weimerskirch、J. Martin、Y. Clerquin 等, 《Energy Saving in Flight Formation》, Nature 413, 697 (2001)
H. Weimerskirch et al., 'Energy Saving in Flight Formation', Nature 413, 697 (2001)
独立核验依据 · Independent verification: 核验依据 1 CROSSREF 标识 10.1038/35099670：Energy saving in flight for
#鸟群 #升力 #编队
为什么人的眼睛对绿色光最敏感？
Why is the human eye most sensitive to green light?
白天视锥细胞在约555纳米的黄绿光处响应最强，而太阳光也以可见绿光最丰富，眼睛便在最“划算”的波段最灵敏。
Cone cells peak near 555 nm yellow-green, and sunlight is richest in visible green, so the eye evolved to be keenest where light is abundant.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#视觉 #感光 #光谱
蝙蝠为什么用超声波而不是我们听得到的声音来“看”世界？
Why do bats use ultrasound rather than audible sound to 'see'?
波长越短分辨率越高；超声波波长短，能分辨小虫子，也不易被环境杂音掩盖。回声到达时间差还能定位距离。
Shorter wavelengths resolve smaller objects; ultrasound pinpoints tiny insects and avoids low-frequency noise, while echo timing gives distance.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#蝙蝠 #超声 #回声
我们怎么靠两只耳朵判断声音从哪边来？
How do two ears tell which side a sound comes from?
声音先到近的那只耳（时间差），且近耳听起来更响（强度差）；大脑综合这两点就定位了方向。
Sound reaches the nearer ear first (time difference) and louder (level difference); the brain combines both to locate the direction.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#听觉 #定位 #双耳
蜜蜂看起来翅膀小、身体重，为什么它还能飞？
Bees look too heavy for their small wings; why can they still fly?
蜜蜂用高频振翅制造不稳定的“前缘涡”，产生远超固定机翼估算的升力。简单估算失效，不等于违反空气动力学。
Bees flap rapidly to create unsteady leading-edge vortices, generating far more lift than a fixed-wing estimate predicts; the simple model fails, not the physics.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
M. H. Dickinson、F.-O. Lehmann 与 S. P. Sane, 《Wing Rotation and the Aerodynamic Basis of Insect Flight》, Science 284, 1954 (1999)
M. H. Dickinson, F.-O. Lehmann & S. P. Sane, 'Wing Rotation and the Aerodynamic Basis of Insect Flight', Science 284, 1954 (1999)
独立核验依据 · Independent verification: 核验依据 1 CROSSREF 标识 10.1126/science.284.5422.1954：Wing Rotation
#蜜蜂 #升力 #涡
眼睛里明明有一块“盲点”，为什么我们平时看不见它？
There is a blind spot in your eye; why don't you see a hole?
视神经离开眼底的地方没有感光细胞，但两只眼互补、大脑又会自动用周围信息“补上”那块空缺。
Where the optic nerve leaves, there are no receptors, but the two eyes compensate and the brain fills the gap using surrounding information.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#盲点 #视觉 #脑补
用力搬东西时肌肉为什么会发热？
Why do muscles get warm when you strain to lift something?
肌肉把化学能变成机械能的效率不高，大部分变成了热，所以用力时会觉得发烫、出汗散热。
Muscles convert chemical energy inefficiently; most becomes heat, so straining makes you warm and prompts sweating to cool off.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#肌肉 #能量 #热
瞳孔在暗处放大、亮处缩小，像相机的什么零件？
The pupil widens in the dark and shrinks in light; what camera part is it like?
像相机的光圈：暗时开大进更多光，亮时缩小吃少一点，既看得清又不被晃坏。
Like a camera aperture: it opens in the dark to let in more light and closes in brightness to protect the eye and keep images clear.
难度 入门 · 适合 幼儿(3-6)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Russell K. Hobbie 与 Bradley J. Roth 著《Intermediate Physics for Medicine and Biology》（医学与生物学中的中级物理）
Russell K. Hobbie & Bradley J. Roth, Intermediate Physics for Medicine and Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-3-319-12682-1 / DOI 10.1007/978-3-319-12682-1 (
#瞳孔 #光圈 #眼睛