Why is the world like this?

12 questions children actually ask, answered properly — with the real reason, not a shrug, and something you can try yourself at the end of each one.

• Why is the sea blue?The sea looks blue because water absorbs red light and scatters blue light back to your eyes, not because it reflects the sky.
• Why are there time zones?Time zones exist because the Earth is round and spinning, so the Sun rises and sets at different moments in different places.
• Why is it hot at the equator?It is hot at the equator because sunlight hits that part of the Earth almost straight on, year-round, packing more energy into every square metre.
• Why do mountains have snow?Mountains have snow because the air gets colder the higher up you go, roughly 6 to 7 degrees Celsius colder for every 1,000 metres of altitude.
• Why does the Earth spin?The Earth spins because it formed billions of years ago from a swirling cloud of gas and dust that was already turning, and nothing has ever stopped it.
• Why are there deserts?Deserts form where very little rain falls, usually because of dry, sinking air, mountains blocking rain-bearing winds, or being far from any ocean.
• Why do we have day and night?Day and night happen because the Earth spins on its axis roughly once every 24 hours, so different sides face toward or away from the Sun.
• Why do rivers flow to the sea?Rivers flow to the sea because gravity constantly pulls their water downhill, from higher ground near their source toward the lowest point around, which is usually sea level.
• Why is Antarctica a desert?Antarctica is a desert because it receives very little precipitation, less than 200 millimetres of snow a year across most of the continent, which is drier than many sandy deserts.
• Why do we have seasons?Seasons happen because the Earth's axis is tilted about 23.5 degrees, so different parts of the planet lean toward or away from the Sun as Earth orbits it.
• Why do volcanoes erupt?Volcanoes erupt because hot, molten rock called magma, along with dissolved gases, builds up pressure underground until it forces its way out through a weak spot in the Earth's crust.
• Why is the sky blue but space black?The sky looks blue because Earth's atmosphere scatters blue light from the Sun far more than other colours, spreading it across the whole sky.