Earth’s core could contain helium from the early solar system. The noble gas tucks into gaps in iron crystals under high pressure and temperature.

Whereas helium-4 is a common product of the decay of radioactive elements, helium-3 comes almost entirely from the initial cloud of dust and gas that formed the solar system. This primordial ...

He wrote the properties of the elements on pieces of card and rearranged them until he realised that, by putting them in order of increasing atomic weight, certain properties of elements regularly ...