How Many Birds Really Live on Tiritiri Matangi?
This investigation explains how an exaggerated statement can arise from confusing the number of bird species on an island with the number of individual birds worldwide.
18 min 9 scenes
Explore by topic
Science & Nature
Physics, chemistry, biology, Earth science, space, and the environment.
Puddle Mirror, Shadow Flip
Reflections and shadows are formed by different interactions of light, so only a reflection produces an image with a top-to-bottom reversal.
16 min 8 scenes
The Moon's Hidden Half
Tidal locking keeps one Moon hemisphere permanently facing Earth because the Moon's rotation period matches its orbital period.
16 min 8 scenes
Why Is It Colder Higher Up?
The difference is explained mainly by how the ground absorbs sunlight and how the atmosphere cools with altitude, not by how far the place is from the Sun.
16 min 8 scenes
Why Do We Yawn?
How yawning relates to brain cooling, alertness, and the spread of yawning between people.
16 min 8 scenes
Counting the Colors of a Rainbow
A rainbow’s seven familiar color bands can be identified by the mnemonic ROYGBIV, from red through violet.
14 min 7 scenes
高原为何更冷
用距离与空气压缩、压力和绝热冷却的实验，解释高海拔气温下降的主因以及近25°C温差如何形成。
18 min 9 scenes
调和级数的收敛之谜
调和级数的项虽趋向零，却因分母增长过慢而累积发散；等比级数则按固定比例缩小，使总面积稳定在1。
20 min 10 scenes
Why Snow Makes Things Quiet
Fresh snow quiets familiar sounds by absorbing sound energy, cushioning impacts, and temporarily damping the vibrations that normally carry noise through surfaces and air.
20 min 10 scenes
降噪耳机为何制造噪声
理解降噪耳机通过实时生成与外界噪声等幅、反相的声音，使两列声波在耳中发生破坏性干涉，而保护听力仍是不同层面的功能。
20 min 10 scenes
Why Is the Handrail Faster?
The handrail is independently driven at a slightly higher speed to circulate continuously around curved pulleys, with the design calibrated so riders do not perceive a significant mismatch.
14 min 7 scenes
Kitchen Dissolving Detectives
20 min 10 scenes
糖为何溶于水而油不溶
糖和水能形成友好分散的微观混合，而油和水彼此排斥并分层。
20 min 10 scenes
Why Cut Apples Turn Brown
Enzymatic browning is a chemical reaction between polyphenol oxidase, oxygen, and phenolic compounds inside apple cells, and the rate can be changed by controlling enzyme activity, oxygen, or substrate.
16 min 8 scenes
Why Are Some Fall Leaves Red and Others Yellow?
Fall colors are not painted onto leaves — yellows were masked by chlorophyll all summer and only revealed as green pigment breaks down, while reds are freshly synthesized from sugars trapped in the leaf when bright light meets cool nights.
18 min 9 scenes
Why Do Geese Fly in a V?
Aerodynamic drafting from wingtip vortices reduces the energy cost of flight, and rotating the leader equalizes that saving across the flock.
18 min 9 scenes
Why Sunset Comes Earlier in Fall
Day length and clock time shift with the season because Earth's axial tilt changes how the Sun's path crosses the sky, not because of any change in how fast Earth spins.
22 min 11 scenes
Why Apples Ripen in Fall
Fall ripening is the result of a timed chemical program inside the apple: daylight, temperature, and the tree's own ethylene signal convert stored starch into sugar, drop acidity, and unmask red color — finishing the fruit weeks after the tree decides to stop feeding it.
16 min 8 scenes
Why Autumn Brings More Fog
Fog frequency in autumn is explained by the combination of long nights, clear skies, and a warm, moist surface layer that loses heat through radiation, dropping below the dew point.
18 min 9 scenes
Why Is There Frost in Fall?
Frost forms on clear, calm autumn nights when surfaces radiate heat into the open sky, drop below freezing, and freeze the dew that condenses on them — a pattern set by long nights and cloud cover, not just by the season's average temperature.
18 min 9 scenes
Why Are Some Trees Evergreen?
Evergreen and deciduous are two leaf strategies shaped by leaf lifespan, energy cost, and climate, with evergreen winning where long-lived, tough, low-nutrient leaves outperform the build-and-discard approach.
18 min 9 scenes
Why Is Fire Hot?
Heat from fire comes from light and invisible waves that excite atoms, and the glow's color reveals how hot the flame is.
20 min 10 scenes
Why Don't Bicycles Fall Over?
Bicycle balance comes from a combination of gyroscopic effect of the wheels, steering geometry (trail and rake), and rider weight correction, and each factor alone is enough to keep a bike upright in the right conditions.
18 min 9 scenes
Why Is Snow White?
Snow looks white because a jumble of countless tiny ice-air interfaces and crystal facets reflects and scatters all visible wavelengths of light in every direction, blending them into white.
18 min 9 scenes