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Before a new medicine reaches patients, it goes through a long series of tests designed to find problems early. Researchers first study how the substance behaves in cells and in animals, looking for obvious harm.
A solar farm is a large set of panels, but getting its electricity to homes takes more equipment than panels alone. Solar panels produce direct current. Inverters convert it into the alternating current the grid uses.
Step goals are popular, but the benefits of walking don't depend on hitting one exact number. Studies generally find that people who walk more each day tend to have better heart health than those who walk very little.
Wind turbines cost almost nothing to run once they are built, so they offer power cheaply whenever the wind blows.
Most of the world sets clocks in whole hours from Coordinated Universal Time, but a handful of places use half or quarter hours. Time zones are meant to keep midday roughly when the sun is highest.
A little warmth while charging is expected: moving energy into a battery is never perfectly efficient. Higher power means more heat, which is why phones often slow charging as the battery fills.
Stem cells are cells that can make copies of themselves and develop into more specialised cells. Some come from early embryos, while adult stem cells live in places like bone marrow and help repair tissue.
Your body clock runs on cues, and a few of them are easy to adjust. Daylight early in the day helps set the clock so you feel sleepy at a sensible time.
Global average sea level is rising, but what a particular coastline experiences can be quite different. Large ice sheets pull water towards them; as they melt, that pull weakens and water redistributes.
The International Space Station is often visible without a telescope, if you know when to look. It shines by reflected sunlight, so it is easiest to see when your sky is dark but the station is still lit.
Forests are among the largest stores of carbon on land. Through photosynthesis, trees take carbon dioxide from the air and build it into wood, leaves and roots.
Despite the name, a light-year measures distance: how far light travels in one year. 5 trillion kilometres. Light from a star 100 light-years away left it a century ago — you see it as it was.