explainer Earth
Speed of sound in mph, m/s and km/h: about 343 m/s in 20 °C air
Sound travels about 343 m/s (768 mph, 1,236 km/h) in 20 °C air. See the formula, a temperature table, water and steel speeds, altitude and Mach 1.
Story archive
Latest science stories
Browse SciQuest reporting and explainers in reverse chronological order, with the newest evidence-led stories first.
explainer Physics
Gravity on Europa: how strong is it compared with Earth?
Gravity on Europa is 1.31 m/s², about 13% of Earth's and 81% of the Moon's. See NASA data, the GM/R² maths, what you'd weigh and why it matters for plumes.
explainer Earth
How hot is lightning? About 30,000 K, five times the Sun’s surface
Lightning's channel peaks near 30,000 K (29,727 °C, 53,540 °F), about five times the Sun's surface. See the sources, the unit mix-ups and why it makes thunder.
explainer Physics
Gravity on Uranus: how strong is it compared with Earth?
Gravity on Uranus is 8.69 m/s² at the equator, about 0.89 of Earth's, even with 14.5 Earth masses. See NASA's values, the GM/R² maths and what you'd weigh.
explainer Space
How far can the human eye see? From the horizon to 2.5 million light-years
On flat ground the horizon is about 4.7 km away, but on a dark night you can see the Andromeda Galaxy 2.5 million light-years off. Here is why.
explainer Physics
Gravity on Neptune: how strong is it compared with Earth?
Gravity on Neptune averages 11.27 m/s², about 1.15 times Earth's, despite 17 Earth masses. See NASA values, the maths and what you would weigh there.
explainer Physics
How hot is fire? Flame temperatures by colour, fuel and type
How hot is fire? Most flames burn at about 900–1,400 °C. See candle, wood fire, gas and Bunsen flame temperatures, and why blue fire is not simply hotter.
explainer Earth
Why is the sky orange? Red, yellow and pink skies explained
Why is the sky orange, red, yellow or pink? Air scatters blue light about 6 times more than red, and sunset light crosses ~38 times more air. Smoke adds more.
news Astronomy Evidence status: Peer reviewed · Calculated colours from existing spectra and models
White dwarf colours: most look white, a few would glow green or pink
Nearby white dwarfs look white on average, Warwick astronomers calculate, but about 1 in 30 would look yellow or pink, and one known star would look green.