If you had to guess, what would you say is the most valuable thing in the world by weight?

If you’re a cook, you might pick costly foods like beluga caviar or white truffles. Or perhaps the spice saffron, which can go for thousands of dollars per pound.

If you’re a jewellery lover, your mind might go to precious metals like silver, gold or platinum. You’d know that gold has been revered since ancient times, and sometimes goes for thousands of dollars per ounce.

You’d be getting warmer if you worked in industry and knew that some substances used in things like catalytic converters are very costly indeed. Rhodium and palladium are even more valuable than gold.

These would all be good guesses, but not even close.

What about diamonds as the most valuable thing on earth by weight? Very rare coloured diamonds such as the red can be valued at millions of dollars per gram.

If you’re a scientist, you might get closer by guessing plutonium, used to fuel nuclear reactors. Or you might figure you’ve hit the jackpot by picking antimatter, which might power spaceships one day.

This substance requires inconceivable amounts of energy to generate. It’s estimated that antimatter costs tens of billions or even trillions of dollars per gram.

But there’s one thing on earth more valuable than even that…