Dear Data - two women, one in England, the other in America - correspond once a week using physical postcards on a agreed-upon topic. A celebration of communication, point of view, personal filters and visualization
from the about:
Each week we collect and measure a particular type of data about our lives, use this data to make a drawing on a postcard-sized sheet of paper, and then drop the postcard in an English “postbox” (Stefanie) or an American “mailbox” (Giorgia)!
Eventually, the postcard arrives at the other person’s address with all the scuff marks of its journey over the ocean: a type of “slow data” transmission.
By creating and sending the data visualizations using analogue instead of digital means, we are really just doing what artists have done for ages, which is sketch and try to capture the essence of the life happening around them. However, as we are sketching life in the modern digital age, life also includes everything that is counted, computed, and measured.
We are trying to capture the life unfolding around us, but instead we are capturing this life through sketching the hidden patterns found within our data.
So far we’re having a lot of fun while we learn about our own and each other’s lives – and we’re also trying to get better at drawing in the process!
We’ve also noticed that the data collection and visualization process has become a sort of performance and ritual in our lives, affecting our days and weeks, and inherently changing our behaviour.
But really, we also started this project to show how “data” is not scary, is not necessarily “big”, and that you need to know almost nothing about data to start collecting and representing it (just a pencil, a notebook and a postcard!)
Every week we choose a topic we want to explore about our days and lives, and on Monday start our separate-but-parallel data collection.
The data-collecting ends the evening of the following Sunday, and through the course of the following week we analyse our data and draw our postcard, all the while collecting the next dataset.
On Monday we scan and drop our data postcard into the mailbox/postbox and start to plan the next week’s drawing!
Let’s look at how it works for pi. John Heidemann at the Information Sciences Institute at USC has a list of all the best rational approximations (of the first kind) of pi with denominators up through about 50 million. The numbers 3/1, 13/4, 16/5, 19/6, and 22/7 are the first few fractions on this list. 13/4 is a little closer to pi than 3 is. It’s about 0.1084 away instead of 0.1416. But if we multiply the differences by the denominators, 13/4 doesn’t do so well. We get 0.1416×1=0.1416 and 0.1084×4=0.4336, so 13/4 loses pretty badly. The same is true for 16/5 and 19/6. Both of them are a little closer to pi, but they aren’t enough closer to make up for their larger denominators. Thus, 13/4, 16/5, and 19/6 are best approximations of the first kind but not of the second kind. But when we get to 22/7, things change. It’s quite close to pi. Its difference, 0.00126, is very small. If we multiply it by its denominator, we get 0.00126×7=0.00882. This beats 0.1416 pretty handily, so it’s a best approximation of the second kind. It’s also the next convergent in the continued fraction for pi.
My favorite convergent in the continued fraction for pi 355/113. It’s a really good approximation. It’s a continued fraction mic drop. The next best approximation of the first kind has the denominator 16,604. But it isn’t even that much better than 355/113. We don’t get another decimal digit of accuracy, but we have to increase our denominator by two decimal places. No thanks. We have to increase to the denominator 33,215 before we get a new approximation that’s worth bothering with.
We're a long way from practical pure electric airplanes, but a variety of hybrids might make sense. A few groups are advancing technology. Siemens has flown a small general aviation test plane, but more significantly is working on components.
A good lightweight electric motor can produce as much as 1 kilowatt per kilogram of weight and the best automobile electric motors are around 2 kW/kg. The new Siemens motor produces over 5 kW/kg - an amazing power to weight ratio that far exceeds internal combustion engines in cars. Its speed range is such that gearing to the propeller isn't necessary.
This could lead to greater flexibility in airframe design. Some motors may be distributed along the wing with a small gas turbine running a generator located in the airframe. The "transmission" would be power cables. As battery technology progresses one can a hybrid with batteries being used for the power demands of takeoff. Or perhaps an electric motor could be integrated with a turbofan motor connected to a battery to supply more power for takeoff. Ultimately metal air batteries would have power densities such that pure electric airplanes are possible.