"Copied by E. Grosser, Esqr, from an Ancient Drawing said to have been made by LIVENS, a Disciple of Rembrant. London Pub May 1790, by E. Harding, No 132 Fleet Street".
Might this be true? Lievens was in England in the 1630's.
Thanks to the Semantic Web and europeana.eu I could answer that question:
This is still part of the school I went to. It was founded in the year 948.
When Lievens was in St Albans, it already existed nearly 700 years!
This is the only remaining mediaeval
clock tower in England.
It contains a bell that was cast around 1350.
I used to walk past it every day on the way to school.
While searching the web for pictures of the clock tower, I came upon this one. I had never seen this picture before, I don't know who took it: but that is me with my best friend at the time, walking in the direction of school.
Here it is looking from the other direction. Why build a clock tower in the shadow of a cathedral?
"kepe, make and rewle the clokke, beyng in seid tenement, and to smyte and kepe his resonable howres, and dayly and nyghtly to rynge or do rynge the bell of the same clok by the space of half amyle wey betwene the houres of viij and ix of the same clok at after noone, and immediatly as he can or may after the houre of iiij of the same clok before noone, at hys owne propre costes, expenses, and labour, or hys assignes duryng the seid terme. And shall make and kepe all reparacons necessarye to the seid tenement and clokke Excepte the reparacons of the bell and the claper perteynyng to the seid bell, and excepte also the stone werk and lede werk of the seid tenement, etc."
So one of the purposes of the Clock Tower was to sound the curfew (From French: Couvre Feu).
What this shows us is that in those days people slept from 8pm to 4 am: They still slept 8 hours, just from early evening to early morning.
Why?
In those days, light was mostly provided by candles.
Candles were very important products.
In fact there were two guilds for chandlers: one for those who made wax candles, and one for those who made tallow candles.
And candles were very expensive. It was not uncommon for people in some jobs to be partly paid in fire wood and candles.
So people went to bed at 8, and got up at 4 for economic reasons: if you slept in the hours of darkness, you would use the least number of candles.
Which meant that Midnight was the time of the night furthest from daylight, furthest from waking, the darkest part of the night, when no one would be about.
Nowadays, Midnight is not as special, in fact the time of night furthest from sleep is likely to be around 4 a.m., when the least people are on the street, and when traffic is at its quietest.
I am going to talk about the development of the cost of lighting over the years.
But first a reminder about graphs.
When you turn a tap on,
you are adding a certain amount of water per minute to the
bath.
So if we look at the graph of the bath filling, we get something like this:
We call this a linear function.
However, for instance, when a bank gives you interest on a bank account, it is not adding a fixed amount every year, but an amount based on how much you already have in the bank.
For instance, if they offer a 3% interest, then every year your money gets multiplied by 1.03.
If you have €1000 in your account, then at the end of the year you will have €1000 × 1.03, which is €1030. At the end of the second, you will have €1030 × 1.03, which is €1060.90.
This is called an exponential function.
Note the 'knee' around iteration 15. People often talk about an exponential function 'passing the knee'. This is a mistake.
Note how there now seems to be nearly no action before iteration 26. The 'knee' is a fiction, a visual effect of the scaling used.
It is better to graph exponential functions in a different way.
On the vertical axis, rather than going in steps of 1, 2, 3, ... we use steps of 1, 10, 100, 1000, ... Then the exponential graph looks like this:
(It actually doesn't matter what the step size is, as long as it is a multiplication: the graph still ends up looking the same).
Note the exponential decrease in costs.
It goes from candles, through oil lamps, to gas, and then electricity.
It has a halving time of about 13 years.
In 1800 you would have had to work between 6 and 12 hours to pay for the amount of light that an old-fashioned 100W bulb would supply in an hour.
Now you only have to work a bit under a half second to pay for that hour's worth of light.
And the price is dropping even faster now.
The data pre-dates LEDs
The cost of light produced by LEDs is decreasing exponentially.
Haitz's 'law':
Every decade the price per lumen drops by a factor of ten.
This is a halving rate of about 3 years.
Computers: Moore's Law.
Just one of 21 cabinets making up the computer
The first general-purpose computer that was so cheap it was given away free on the cover of a magazine.
The Elliot ran for about a decade, 24 hours a day.
How long do you think it would take the Raspberry Pi Zero to duplicate that amount of computing?
The Elliot ran for about a decade, 24 hours a day.
How long do you think it would take the Raspberry Pi Zero to duplicate that amount of computing?
The Raspberry Pi is about one million times faster...
The Raspberry Pi is not only one million times faster. It is also one millionth the price.
A factor of a million million.
A terabyte is a million million bytes: nowadays we talk in terms of very large numbers.
Want to guess how long a million million seconds is?
The Raspberry Pi is not only one million times faster. It is also one millionth the price.
A factor of a million million.
A terabyte is a million million bytes: nowadays we talk in terms of very large numbers.
Want to guess how long a million million seconds is?
30,000 years...
A really big number...
In fact a million million times improvement is about what you would expect from Moore's Law over 58 years.
Except: the Raspberry Pi is two million times smaller as well, so it is much better than even that.
Each order of magnitude change in cost has meant we have used computers in a different way:
| 1,000,000 | Mainframe |
| 100,000 | Minicomputer |
| 10,000 | Workstation |
| 1,000 | Home computer/Laptop |
| 100 | Netbook/Tablet |
| 10 | Project |
| 1 | Embedded |
Similarly, the reduction in cost of lighting has meant that people have adapted their sleep behaviour (and by the way, that cyclists in Amsterdam actually use lights now).
Network bandwidth: 
1988: 64Kbps
1989: 128Kbps
2018: 5.3Tbps (this represents a doubling period of just over a year).
And look! Lowest network use: 4am! The new midnight.
We have seen some effects of network cost reduction:
But as uplink speeds start going above 1MBps, we have an opportunity to make other changes.
What is Facebook?
It is a personalised website, with software that allows you to easily add items, photos, news items, links, and control who can see them.
Your friends are able to comment on your items, and you on theirs.
It then merges your items and your friends items into a stream that you can read and comment on as well.
And Facebook owns this content, and it owns you.
How could we do better?
The amount of content you produce is fairly small.
In the ten years I have been on Facebook, I have produced about 100MB of data, most of which is pictures and videos. The text is about 3½MB.
It would be easy to produce the software that does the same thing, but serves them from your home (the server could be in your modem).
It would be fairly easy to restrict who could see what, using well known techniques.
Knowing who your friends are, it would also be easy to aggregate your friends items, and create a stream to comment on.
And you would own your data, and no one could spy on you.
And no one would be trying to sell you stuff.
I pick on Facebook because of its size and presence, but the same techniques could apply for most other sites that exist thanks to its users providing its content.
In fact one of the big problems with such sites is that there are many of them, and you have to choose which to use, or duplicate your work. Examples are photo sharing sites, geneology sites, selling sites.
But in fact, if you kept your own data, and then allowed sharing sites to aggregate your data, you would only have to do the work once, and you could join and leave sites without any loss of data or work.
Orders of magnitude change can affect how we act.
The next step is to take advantage of the order of magnitude change in the uplink, and start making the internet a true two-way, distributed channel.
For example: Solid