How does Brian Cox tell the time

“We don’t know what it’s measuring, because we don’t know what time is.” This is not a phrase you might expect to hear in promotion of a watch — particularly at the top end of an industry that competes over accuracy and
complications.

But Brian Cox views IWC Schaffhausen’s Portugieser Eternal Calendar from the point of view of the physicist that he is. And he has to point out that: “The study of black holes is strongly suggesting that space and time are made of something else. So we’re beginning to think in terms of building blocks of space and time . . . the field is called emergent space-time.”

The British musician-turned-popular science presenter — who is professor of particle physics at the University of Manchester — has collaborated with the Swiss watchmaker to help explain its first secular perpetual calendar. Hence, his cosmic perspective on our collective fascination with time and space.

Cox admires IWC’s ambition with its new product launch, unveiled at the Watches and Wonders show in Geneva in April, and the “engineering challenge” involved. As a calendar watch, he says it is representing “violent celestial motions”: the spin rate of Earth on its axis about once every about 24 hours (day); the orbit of the moon (roughly a month); and Earth’s orbit around the sun (a year) . . . and “distilling them down to this little thing on your wrist”.

However, as well as recognising differing lengths of months and adding a leap year every four years, the Portugieser Eternal Calendar also accounts for the complicated leap-year exception rules of the Gregorian calendar. Only centurial years that can be divided by 400 are leap years (so 2000 and 2400 are, but 2100, 2200 and 2300 are not). The watch accounts for this with a newly developed 400-year gear that makes the calendar skip three leap years over four centuries.

The watch also has moon phase accuracy of 45mn years. That means it is designed to deviate from the moon’s orbit only by one day after this period of time. By then, the sky will look very different anyway, observes Cox. The star Betelgeuse in the constellation of Orion will have died, for example. But Cox — who is also the Royal Society professor for public engagement in science — is hopeful “our descendants will still be around”.

“If we do well, they’ll be scattered among the stars [living on different planets] by that point,” he suggests.

Cox exchanged ideas on science and philosophy with the Oscar-winning film score composer Hans Zimmer as part of the IWC collaboration, with Zimmer creating a piece of music, “A Tribute to Eternity”, inspired by the watch and IWC’s new Portugieser collection. This was played by a live orchestra — the Britten Sinfonia, conducted by Daniel Harding — for the first time last month, during Cox’s Symphonic Horizons show at the Royal Opera House in London. This concert paired his exploration of cosmology with classical music.

A quick glance at wider industry launches this year — which include a proliferation of moon phase complications and meteorite dials — points to the interest that many watch enthusiasts take in space. Timekeeping and astronomy “have always gone hand in hand”, says Cox, referencing the Royal Observatory, Greenwich in London, the site of Greenwich Mean Time.

“I’m sure a lot of people think about this connection between the way we divide time up and the motion of the Earth and the motion of the moon, and the motion of the Earth around the sun,” he says. “It is almost an obvious thing to say, although most of us don’t think about it from day to day. But that connection is always there. That’s, surely, why moon phase is a popular thing to have on a watch, because it’s pretty explicit then — this is what this thing is doing.”

A watch that is particularly special to Cox is the one he is wearing when we meet in London, just over a month after he reunited with his former bandmates in D: Ream, to play keyboard on the group’s 1993 song ‘Things Can Only Get Better’ at the Glastonbury Festival. It is an on-brand IWC Portugieser Perpetual Calendar, which features the moon phase for the northern and southern hemispheres, and “lots of stars”.

“This one’s a really beautiful, explicit link for me to the sky,” says Cox, who wore it when performing a concert at Sydney Opera House last year.

But, if we don’t know what time is, and therefore what a watch is measuring, why are so many people fascinated by timepieces?

“Our motion through time is the thing we care about the most,” argues Cox. “It’s probably the single most powerful thing that happens to us — we age — and . . . it seems that the universe is built such that we can go forward in time relative to other people pretty much however we want to.

“As far as we understand physics, you [can] get in a rocket ship, go very close to speed of light and you can come back arbitrarily far in the future. In principle, not in practice. We don’t know how to do it, but you could. But, as far as we understand the way the universe is built, you can’t go back. And that’s an evocative thing to say.”