Redefining the kg – Bean Thinking

Antipode coffee Hammersmith — Outside Antipode, Hammersmith.

At the end of Fulham Palace Road, just next to the Hammersmith gyratory is Antipode, an Australian influenced (the clues to this are not so subtle) cafe. In truth, I have been to Antipode a few times now but not to take time to properly take it in. Once was after a tricky teaching session where it was difficult to sit back and reflect on anything but what had happened in the previous few hours, another time I was talking to someone rather than taking time to think about the location. There seems an urgent need for us now to take some time out and think about where we are and what we think. Indeed, part of the point of Bean Thinking is to explore how this space to ponder can be found in any cafe, if we but pause to look. Would this visit to Antipode be different?

Outside the cafe, a few tables were arranged so that you can enjoy your coffee in the open, next to the glass front window. Strangely the chairs/stools for these tables were stacked inside, possibly because it had become chilly again after a brief warm spell earlier in the year. A picture of a takeaway cup was drawn on the window as if to emphasise what you may expect to find inside, reminiscent of the old signs advertising coffee houses of the past. Going in, the counter is on the right and, while there was a selection of cakes etc. I opted to stick with the long black that afternoon. A seating area is at the back of the cafe where there are about 4 separated tables with a bench seat running along behind them with a fifth table along the rear wall.

Coffee at Antipode, pink salt, brown sugar, reflections and shadows. And a hint as to Bean Thinking — Coffee, salt and sugar. What do you see?

The coffee was drinkably fruity. More apples and redcurrants to my palette. On the table behind my coffee was a jar of pink salt and another of brown sugar. Which got me thinking about crystal structures and how it is often impurity, rather than purity that gives precious stones their colour. Is there a metaphor there?

But a second effect jolted to my attention. Someone sat down on the bench seat just along from me and as she sat down so I went up: a little see-saw. Across the room from me was a picture which, somewhat strangely, had two picture hooks either side of it, almost balancing each other on an imaginary line across the frame. Behind the table adjacent to me was a picture with a caption, to the effect of there being a very thin line between love and hate. Was this another instance of balance and equivalence?

Balance is something that we use in physics a lot, from the balance of forces to the use of balances in experiments. The imminent redefinition of the unit of the kilogram is based on a balance of forces. In the new definition, a balance is used so that the gravitational force pulling a mass down will be perfectly balanced by an electrically induced magnetic field pushing the mass up. The redefinition means that to calibrate 1Kg, scientists will no longer have to compare their 1Kg mass to the mass of a lump of platinum-iridium kept in Paris. The redefined kilogram will instead be calibrated based on its relation to Planck’s constant. This means that any lab around the world can calibrate the kg, they do not have to rely on copies of the mass kept in Paris.

Victoria Regina: What changes have happened since this post box was installed here in Hammersmith? What changes will do so before it is finally retired?

The redefinition of the kg is going to happen on 20 May, 2019 (world metrology day). On a day to day basis, it probably will not affect many of us that much. Our 20g of coffee measured out to brew our morning coffee is going to be, to all intents and purposes, the same 20g as we would have measured on the 19 May 2019. Nonetheless, the changes are important not just for the metrology community but also for the way that we do science. In the past, all of our units were related to fixed, physical objects. The metre was defined by the length of a metal rod, the second was originally defined as being 1/86400 of the mean solar day and the kilogram by the aforementioned lump of PtIr in Paris. The kg was the last of the units to still be defined by a unique physical object. As of 20 May 2019, each of these units will be related to physical constants meaning that at no point will we have to go to a lab elsewhere and check that my kg is the same as your kg.

As I left Antipode, I noticed the post box just outside with “VR” on it. The post box has been there since the time of Queen Victoria. How things have changed since scientists wrote to each other with news of their latest experiments, scientific papers were posted to journals and measured lengths were compared to a physical ‘metre’ long metal rod! How things change as we move ever faster emailing results around and tweeting our latest news. We are, in 2019, moving from calibrations based on weighing physical objects to measuring the balance relative to physical constants that were just being discovered at the point that post box first came into service. And yet we humans don’t change much. We still need time to ponder balance from false balance, equivalence from false equivalence. It is not a contradiction to say that it is urgent that we find a way of pausing and reflecting on some very weighty issues.

Antipode is at 28 Fulham Palace Road, W6 9PH