Earth, Weather & Life
Water, clouds, weather, plants, microbes, immune memory and biological rhythms.
How the water cycle moves water around Earth
The water cycle describes water stored and moving through the atmosphere, surface, ground, ice and living systems.
GuideHow clouds form
Clouds form when moist air reaches conditions where water vapour can condense onto tiny particles or freeze into ice crystals.
GuideHow air pressure relates to weather
Atmospheric pressure reflects the weight and motion of air, and pressure patterns help organize winds and weather systems.
GuideHumidity, relative humidity and dew point
Humidity describes water vapour in air, but relative humidity and dew point answer different questions.
GuideWeather and climate: different time scales
Weather describes atmospheric conditions over short periods, while climate describes statistical patterns over longer periods.
GuideWhy leaves change colour in autumn
Many deciduous leaves change colour as plants respond to shorter days and seasonal conditions by breaking down chlorophyll and reallocating nutrients.
GuideHow photosynthesis stores solar energy
Photosynthesis uses light energy to drive chemical reactions that build energy-rich molecules from carbon dioxide and water.
GuidePlant growth: light, water, carbon and mineral nutrients
Plants grow by combining carbon from carbon dioxide with water and mineral nutrients while using energy captured through photosynthesis.
GuideBacteria and microbes in everyday life
Microorganisms live in soil, water, food, built environments and on living organisms, with roles ranging from decomposition to disease.
GuideImmune memory and how vaccines use it
The adaptive immune system can remember specific features of pathogens, allowing faster and more effective responses after later exposure.
GuideCircadian rhythms and the daily biological clock
Circadian rhythms are roughly 24-hour biological cycles coordinated by internal molecular clocks and environmental cues such as light.
GuideWhy Earth has seasons
Earth's seasons are caused mainly by the tilt of its rotation axis, not by large changes in distance from the Sun.