About my father: Franz Kahn

My father, Franz Daniel Kahn (FDK) was an astronomer. Or to be more precise, an astrophysicist. The equipment he needed for work consisted of a pad of paper, a slide rule, and a Bic (always). When he was younger he worked all the time. He worked on Sundays, and when we were on holiday he’d spend his time working. Work consisted of writing long series of equations and some text around them. Proper theoretical science. The children were not to make noise in the house, which would disturb him.

In some ways he was the happiest person you could meet. He was utterly passionate and enthusiastic about astronomy and he was very good at it, and that’s what he was paid to do. During his career there was plenty of funding for whatever he wanted to do, and there wasn’t too much interference from the funding authorities. Scientists were trusted to do good research, and were left to get on with it. He got to travel the world, had friends and colleagues from many countries, and was widely respected.

He thought in mathematics, just as a musician might think in harmony, or an artist in form and colour. He would talk to me about his work as if I were one of his colleagues. Much of what he said was far over my head, but nevertheless I could get the drift of what he was saying. This experience of living out of my depth was a useful education for life: I learned that you don’t have to understand everything that you are told at the moment you are told it. Better to retain the general concepts, so that next time you came across them, you’d have a head start. Jargon is a barrier to entry into a field. Grasping the jargon is an important first level of entry.

FDK thought in approximations. When talking about the physics of stars, there are few accurate measures, and many approximations. FDK would talk about quantities as orders of magnitude, so that the size of  a number is characterised by how many digits there are in it, rather that what those digits are. This is an important first approach to many issues in the world, often deliberately ignored by politicians and the media, who can quite happily talk about 10 thousand, 10 million and 10 billion as if they were all the same thing.

Thinking approximately means that you can simplify calculations. If your inputs are approximate, your calculations can also be approximate, because beyond a certain level, precision in the output has no meaning. (I wonder sometimes about Hi Fi, where the focus is on increasing fidelity of reproduction, while often the source music is fairly approximate.)

Sometimes, when I asked FDK for a bit of help with maths or physics homework, he would show me the grown-up, approximate way of doing it. If I submitted this stuff it would get a strange reaction from the teachers, as if they knew it was correct but didn’t quite understand it. At this point I began to realise that what we were being taught wasn’t the real thing. The real thing was simpler and more powerful than the formal stuff that they taught us at school. Maybe it had to be that way.

On holidays (especially in Aberdaron) FDK and I would often go for walks together. The talk was often about fantasies of physics, a bit like what if? by Randall Munroe. We’d cover the world with a roof to prevent rain. We’d calculate how long it would take to get to Mars.

FDK loved facetious jokes that stretched physics (I quite often observe this same facetiousness in my children). When I was about 5 I asked him if the man in the radio could hear us speak. Yes, if you shout loud enough, he said. It was a long time before I understood the joke. At FDK’s funeral, the Rabbi said that in a certain Parasha, God extended daylight for some hours to allow the Israelites to complete a battle. FDK had explained to the Rabbi how, under certain circumstances, this could happen naturally. The Rabbi was the only person in the room who failed to hear the teasing humour in FDK’s voice.

FDK was fascinated with fluid dynamics. We could stand for ages just watching turbulence in flowing water, or waves breaking on rocks. When he was older he talked to me about the Corryvreckan, the third largest whirlpool in the world, off the west coast of Scotland, just at the tip of the Isle Of Jura. About 25 years ago we planned a trip to see it, with my two sons, aged 5 and 7. Before the internet, planning a trip like this was complicated. The journey involved several ferry crossings and we had to book B&B for each night. I planned to travel with the boys to FDK’s house in Manchester on day one. On day 2 we’d go up to Ardrossan and get the ferry to Arran. Day 3 we would cross over to the Mull of Kintyre and from there to Islay. We would stay in a small farmhouse called Craigfad right on the edge of the island. And on day 4 we could take the short crossing to Jura, drive along the island to see the whirlpool. Sitting with FDK at the table in my kitchen with maps, B&B directories, Caledonian McBraine timetables and a telephone, writing letters, sending cheques, it was all so exciting.

It was a feat of planning that had one vital error in it. The Isle of Jura is about 25 miles long. There’s a road that runs along the length of the island, but about 7 miles from the end there’s a gate and you can drive no further. We arrived at the gate in heavy drizzle. We walked maybe 100 yards before turning back.

I made two more trips with FDK to the area, with various combinations of family. For the last one we booked to stay at the Jura Hotel and the owner agreed to set up a trip for us to see the Corryvreckan, travelling in a Land Rover, with permission to drive to the end of Jura. This time we had with us Jonathan, 12 years old, and Anna, nearly 4. It turned out that the Land Rover could accommodate 10 or so passengers and there were several other residents on the trip. After a bumpy ride, we got to the end of the track, and there was still 2 miles to go. FDK had injured his foot and was lagging behind, and Anna was struggling too. In the end, we got left so far behind the main group that we walked back to the truck and ate our sandwiches in the rain. Jonathan stuck with it, got to the top, and saw the whirlpool. FDK observed, ruefully, that a man should always have some ambitions left unfulfilled. He never saw the Corryvreckan.

The first few times we took the ferry to Islay, the ship was a North Sea Loader, a strange cut-off ship, which loads in one direction only. Islay isn’t really a tourist island. A large part of the economy is distilling whisky. Much of the cargo consisted of trailers carrying grain to the island. Each truck had to reverse onto the loader, then the tractor unit would detach. After this, all the cars would have to reverse on to the deck. FDK called this theatre, and loved the buzz of it.

One time we arrived at Achaban House, a B&B at the remote end of Mull. FDK sent me into nearby Fionnphort to buy whisky. After dinner I was sitting in the lounge playing guitar and FDK started offering whisky to the people there. There was a pair of old-fashioned old ladies, the owners and several other guests. A wild party started. I got the impression it was the most exciting thing that had happened there for several years.

We’re driving along a road and FDK spots a sign advertising smoked salmon. So we drive into the smokery and buy some. Right, drive to the next town, he says, and rushes off to buy some salt, pepper and crackers. Then, in a lay-by, sitting in the back of the car with the boys, having this amazing feast with a view of some gorgeous loch.

These trips were mostly shrouded in drizzle. The trick was to travel at the end of August, by which time the Scottish school term had already started, so there were few tourists about. The weather would already have turned cooler, and often the B&Bs would have a fire burning in the lounge. After a hot summer, this was a relief. Many memories of FDK involve wandering around damp green places in a haze of drizzle. Then finding somewhere to have a massive cream tea.

Once in a while you’d get good weather. And then you get beaches with golden sand and sun and no-one else there.

FDK’s life was punctuated by meals and snacks. He had 6 meals a day. Breakfast, morning coffee, lunch, afternoon tea, supper, and at night coffee(!) with cake. Always. Every day.

When my mother, Carla Kahn, was alive, they’d both come home from work at lunchtime. FDK would pop into a delicatessen and buy something special for lunch. I was there a few times (somehow being home from school at lunchtime). There was a peace there that was absent the rest of the time in a family with 4 children.

Yes, FDK was obsessed by food (another trait I observe in all his children and most of his grandchildren). In hospital for a hernia operation, he suggested that I go for lunch at the Little Yang Tse in Manchester’s China Town, while he was in surgery. Which I did. When I came back, I waited in his room until he was wheeled back in. He was asleep. Eventually he opened one eye. “Where did you eat?” he asked. I told him. He slept another 5 minutes, then opened one eye again. “How was it?”