I am pleased that so many people enjoyed my talk about time at RIPE86. I thought I would write a few notes on some of the things I left out.
There were a couple of things that I thought would make a fun talk:
- Just how many layers can I peel back? At least 11, apparently! I thought of doing a joke based on the 9 layer model and Spın̈al Tap, but in the end I kept the intro straight.
- It’s surprising how important the US Naval Observatory has been. What was relatively new to me were the details of how Essen and Markowitz calibrated the first atomic clock, which was enough to give the story a good dose of “repeat until funny”.
Essen & Markowitz
A curious detail I have not found an answer to is why Louis Essen teamed up with William Markowitz to calibrate his clock, not someone more local such as the Astronomer Royal. It’s clear that Markowitz had a good deal of enthusiasm for the project, but I wonder if there were logistical reasons too: at that time the Royal Greenwich Observatory was moving to Herstmonceux.
I did not mention any satellite navigation systems other than GPS. I don’t know much about Galileo’s ground segment (its equivalent to Schriever SFB and the USNO) - I should really read more of Bert Hubert’s writing on the topic!
The layers I was peeling back are all below the complications of time zones; I couldn’t fit them neatly into the narrative. But there’s an interesting parallel (as it were) with the International Meridian Conference, which is the basis of the standard time zones.
Years ago I read the proceedings of the meridian conference, and it struck me that the French were quite opinionated, and grumpy that Greenwich had the lead. The Americans, who were the conveners, preferred Greenwich as the status quo. The British were relatively quiet - perhaps they lobbied off the record, or were just smug?
In the end, Greenwich won largely because it was already the meridian used by the majority of nautical charts. But it’s another example of international science being led by the French and Americans.
I think I was a bit unfair to the Paris Observatory, which had a more important role than my talk suggested.
Before responsibility for international time was split in the 1980s between the IERS and the BIPM, there was the Bureau International de l’Heure, which was responsible for both earth rotation and atomic time. It was based at the Paris Observatory.
Relatedly, I skipped over the awkward history of atomic time between the 1950s and 1970s (and today). I previously wrote about that in my update on leap seconds last year.
Finally, the last slide has the punch line that the Royal Greenwich Observatory did not show up in the story at all. I could have delivered the joke better: I think it needed a bit more context to land effectively.
I think it’s funny to deliver this story as an English person who lives almost on top of the Greenwich meridian; in fact for the last few years of its life, the rump of the RGO was based in Cambridge, and after it finally closed, my spouse Rachel worked in Greenwich House.