Natural Sciences

gold

The symbol 'Au' comes from the Latin 'aurum'. Gold is so unreactive that it does not rust and stays shiny for thousands of years.

💡 Did you know? All the gold ever mined would fit into a cube about 22 metres on each side.

speed of light

Light races through a vacuum at about 300,000 km per second: nothing is faster. It is a fixed constant of nature and the basis of Einstein's relativity.

💡 Did you know? Sunlight takes about eight minutes to reach Earth.

hydrogen

Hydrogen is the lightest and most common element in the universe: stars are mostly made of it. In their cores it fuses into helium, releasing energy.

💡 Did you know? Together with oxygen it forms water (H₂O).

earthquakes

The Richter scale gives the magnitude of an earthquake. It is logarithmic: one point higher means about 32 times more energy released.

💡 Did you know? Scientists today mostly use the more precise moment magnitude scale.

0

At 0 °C water freezes into ice. Oddly, it expands as it does so: which is why ice floats and bottles can burst.

💡 Did you know? Unlike almost all substances, solid water is lighter than liquid water (the 'anomaly of water').

carbon dioxide

In photosynthesis plants take in CO₂ and, using sunlight, release oxygen. This forms the basis of almost all food chains.

💡 Did you know? Practically all the oxygen we breathe comes from photosynthesis.

H2O

H₂O means: two hydrogen atoms, one oxygen atom. Water is the only common molecule that occurs on Earth as solid, liquid and gas.

💡 Did you know? The human body is about 60% water.

oxygen

Oxygen makes up about a fifth of the air and is essential for the breathing of almost all living things. It is produced mainly by plants and algae.

💡 Did you know? In liquid form, oxygen is pale blue.

gravity

Gravity pulls masses towards each other: it keeps us on the ground and the planets in their orbits. Isaac Newton first described it mathematically.

💡 Did you know? On the Moon gravity is only a sixth as strong as on Earth.

voltage

The volt is the unit of electrical voltage: in a sense the 'pressure' that drives current through a wire. It is named after Alessandro Volta.

💡 Did you know? Around 1800 Volta built the first battery, the 'voltaic pile'.

-273

At about −273.15 °C lies absolute zero: the lowest possible temperature, where all thermal motion ceases. The Kelvin scale starts at 0 here.

💡 Did you know? This temperature can be approached ever more closely, but never fully reached.

proton

Protons carry a positive charge and sit with the neutral neutrons in the atomic nucleus. Their number determines which chemical element it is.

💡 Did you know? A single proton is the nucleus of a hydrogen atom.