Recently I tracked down an article I wrote in 1992 where I claimed (inaccurately) to be the first person to juggle on the moon. The piece was published in Kaskade – the European juggling magazine – and is here on page 14. Obviously I wasn’t on the moon, I was in a virtual reality juggling simulation which let me tweak gravity to whatever I wanted.

One point in the article bears some further discussion – objects on the moon don’t float gently to the ground. I programmed the simulation using Newton’s equations of motion. I ignored air resistance (for this problem it’s insignificant under earth gravity and non-existent on the moon anyway). I did A level^* physics and maths – I’ve solved plenty of problems using these equations. If you asked me to do the calculation I could have told you that if you throw something up at x m/s in constant gravity it will come down past your hand at –x m/s.

Even knowing all of the theory, it still surprised me when I got into the simulation and tried it. My instinct was that everything fell at a constant speed on the moon. I knew that wasn’t true but I hadn’t experienced it. This might seem obvious to everyone else, but it wasn’t obvious to me. Perhaps I had been deceived by cartoon physics. Perhaps I was thinking that everything on the moon would be as light as a feather (not true), and since feathers float gently to the ground on earth (due to air resistance) objects would float to the ground on the moon.

There is a story (that I haven’t been able to find a good reference for so might be false) that NASA scientists were surprised the first time an astronaut tried turning a bolt in space on the outside of the capsule. The astronaut turned, not the bolt.

This piece wouldn’t be complete without a link to the classic NASA video of dropping a hammer and a feather on the moon. Really on the moon this time. Notice that the hammer and the feather are both accelerating.

The conclusion? Theory is one thing, actually experiencing it is another.

^* For those of you who are not Brits but are familiar with Harry Potter, A levels are equivalent to NEWTS^**.

^** For those of you not familiar with Harry Potter, NEWTS are the exams you do at age 18 having specialized in the subject for 2 years.