Astronomers are used to fielding tough questions, but these are out of this world | Séamas O’Reilly

I suggest to my son that the object of going to the planetarium should be for him to learn something, not to catch the scientists out

Since it was half-term, I took the boy out for the day. My choice was the planetarium at the Royal Greenwich Observatory, which melds my two great loves: space and having to traverse the entirety of London, with a chatty six-year-old, twice in one wet afternoon. Our journey involves two buses, a tube, an overground, and 20 minutes of walking either side. Time was, all these various modes of transport would be a big plus for my son, who used to whoop and cheer as trains arrived and scream with contagious delight at every bus driver he met. As he moans about how long everything is taking, I realise for the first time that those mundane pleasures of the everyday world have left him. No wonder, I think with egregious lachrymosity, he has his eyes set on the stars.

Being a six-year-old, he is stocked with questions. We have both presumed he will get some time with space boffins, ready and eager to answer any queries from 4ft-tall astronomers in training. It's just that my son is equally insistent that they'll be eager to learn something from him. As we take our seats on the tube, he lays out his prolix plan: a set of 14 questions sorted into four distinct classes; 4 x easy, 4 x medium, 4 x hard, and 2 x EXTREME.