The neutrino was 30 times more energetic than any other previously observed particle of its kind. Scientists still don’t know ...

Density describes how closely packed the particles are in a solid, liquid or gas. There is little difference between the density of a liquid and its corresponding solid (eg water and ice).

Matter is made up of small particles called atoms. Atoms can exist on their own or together as molecules. Atoms are very small and around 100,000,000 of them end to end would measure 1 centimetre.