There are a quarter of a billion suns in this one galaxy and quarter of a billion galaxies in the universe; maybe more. We already know of hundreds of other planets around other suns, and we’ve only just started looking for them. Scientists tell us that almost every star might have planets. How many of those might harbour life? The Earth is ancient, but the universe is even more ancient. Who knows how many civilisations were around before Earth came into existence, or existed while we were growing up, or exist right now?

“So, if there are civilised aliens, you’d guess they can travel between stars. You’d guess their power sources and technology would be as far beyond ours as supersonic jets, nuclear submarines and space shuttles are beyond some tribe in the Amazon still making dugout canoes. And if they’re curious enough to do the science and invent the technology, they’ll be curious enough to use it to go exploring.

“Now, most jet travel on Earth is for tourism. Not business; tourism. Would our smart, curious aliens really be that different from us? I don’t think so. Most of them would be tourists. Like us, they’d go on cruise ships. And would they want to actually come to a place like Earth, set foot – or tentacle, or whatever – here? Rather than visit via some sort of virtual reality set-up? Well, some would settle for second-best, yes. Maybe the majority of people would. But the high rollers, the super-wealthy, the elite, they’d want the real thing. They’d want the bragging rights, they’d want to be able to say they’d really been to whatever exotic destinations would be on a Galactic Grand Tour. And who knows what splendours they’d want to fit in; their equivalent of the Grand Canyon, or Venice, Italy, or the Great Wall of China or Yosemite or the Pyramids?

“But what I want to propose to you is that, as well as all those other wonders, they would definitely want to see that one precious thing that we have and probably nobody else does.