Max Tegmark admires the 18-tonne, 28in refracting telescope, completed in 1893
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We should have known better than to arrange a stargazing session with the renowned astrophysicist Max Tegmark during London’s stormiest and wettest winter on record. When I reach the Royal Observatory, Greenwich, it is obvious that our plan to use its historic 28in refracting telescope is out of the question; not only are rainclouds obscuring the sky but gale force winds would rip apart the telescope’s onion dome if the staff were foolish enough to open it.

To make matters worse, Tegmark is so late reaching Greenwich because of foul traffic congestion that we miss the planetarium show that was our back-up wet weather plan. But I need not have worried. From the moment he strides through the rain to greet me, it is clear that the combined enthusiasm of Tegmark (on his first visit to Greenwich) and the observatory staff will save the day.

“For me, as an astrophysicist, this is like visiting Mecca,” he says after apologising for the delay. “Greenwich played an amazing role in the history of astronomy.” Tom Kerss and Marek Kukula, the observatory’s resident astronomers, respond by letting us into the telescope dome.

Though we cannot open up the top for stargazing we can at least admire the refractor, completed in 1893 and designed to keep Greenwich at the forefront of contemporary astronomy despite London’s unreliable weather and light and air pollution. (Nowadays, of course, state-of-the-art telescopes are located on remote mountaintops or in space.) “I feel like a kid on Christmas Eve,” Tegmark says as we walk over to the dome – and then “wow” as we enter the telescope chamber and see its masterpiece of Victorian precision technology.

Tegmark, a physics professor at the Massachusetts Institute of Technology, is in London to promote his book Our Mathematical Universe, which looks at cosmology in a futuristic way. His ideas about panoplies of multiple universes, or multiverses, would have been alien to John Flamsteed, the first Astronomer Royal, who founded Greenwich Observatory for Charles II in 1675, and to his 19th-century successors who designed the 28in refractor. But Tegmark loves looking back at the history of astronomy.

Once inside the dome, Tegmark needs no encouragement to get his hands on the 18-tonne telescope. It sits on an earlier mount designed in 1859 for a smaller predecessor instrument by Sir George Biddell Airy, one of the great Astronomers Royal. The mount and telescope are so well balanced that Tegmark has no trouble moving them around with a light touch of the hand. “What a magnificent piece of engineering,” he exclaims. “In the old days, they were building the best observatories in the worst possible locations.”

Max Tegmark and Clive Cookson (left) in the observatory dome.

Then he sets off up the technicians’ stairs inside the dome to view the instrument from an upper gallery. “Health and safety are going to have a fit,” murmurs Kerss but there is no stopping Tegmark. “I normally have terrible vertigo but this is too exciting,” he says in an American accent with a slight Scandinavian tinge from his upbringing in Stockholm. I am freezing in the unheated dome but the cold does not worry Tegmark: “Don’t worry, I’m Swedish.”

The mount was designed so that the telescope could observe one object in the sky for a long period, so it has a clock drive that moves it at the same speed as the Earth’s rotation. It was powered by falling water until an electric motor was installed in the early 20th century. The 28in was used for research – making a particular contribution to understanding double star systems – until the late 1960s when it became an educational tool.

Tegmark has been keen on astronomy since boyhood. “When I was a little kid, I found a book on the solar system on my grandmother’s shelves,” he says. “Some people feel powerless and small looking up and thinking about the cosmos but I felt – and still feel – the opposite.

It is inspiring that we can discover so much about what is out there. Indeed a key reason I wrote my book was to make people feel more empowered.”

He still takes time to stargaze at home. “I bought a small 8in telescope, officially as a Christmas present for my kids but they knew that it was secretly a present for myself. Although I can see much sharper images – for example, of Saturn and its rings – online taken by large telescopes, they look much more real and vivid when I see them through my own telescope.”

Although Tegmark’s professional life is not primarily concerned with observational astronomy, he enjoys teaching an undergraduate astronomy course at MIT and holding rooftop stargazing parties for students. He is struck by how little experience of looking at the night sky many students have had – even the science-oriented ones at MIT – and how many misconceptions they have about the relative motions of Earth, moon, sun and stars.

The Greenwich Meridian Line laser beam

Tegmark believes parents can contribute to their children’s intellectual and scientific development by buying an inexpensive telescope to use in the garden. “With a sturdy Dobsonian telescope [suitable for amateur astronomers] you get a good view of Jupiter and its moons even from London,” he says. There are many astronomy magazines and websites to provide guidance.

But providing the hardware is not enough. Parents should also take time to discuss what their children see. “My father gave me another gift,” Tegmark adds. “He would always ask: ‘What do you think, Max?’”

By now, the time has come for us to leave the observatory and get out of Greenwich Park before the gates are locked for the night. First, though, Tegmark wants to see and photograph the spectacular Meridian laser beam, which originates from the transit circle built by Sir George Biddell Airy in 1850 and shoots north across the Thames. The green laser line marks a notable achievement of 19th-century international standardisation, the world’s officially defined zero degrees of longitude, in a 21st-century idiom.

In some of the universes offering an infinite variety of outcomes, which Tegmark describes in his book, we would have enjoyed a cloudless night of stargazing through the 28in telescope. But it is hard to imagine a visit to Greenwich being more fun than it has been on our wet evening. And, as Tegmark observes, the weather gave us one bonus: the laser beam looks better when it is cutting through rain than clear air.

‘Our Mathematical Universe: My Quest for the Ultimate Nature of Reality’ is published by Allen Lane at £25.

Clive Cookson is the FT’s science editor

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