February 30th
The calendar date February 30th has happened just once in history: in Sweden in 1712.
Category: Weights & measures
The doomsday algorithm
Want to work out what day of the week for any date? Just use the doomsday algorithm.
Cosmic sound
According to our understanding of the Big Bang, “cosmic sound” is older than neutral hydrogen. We can still spot its echoes today.
Daylight robbery
New Zealand entomologist George Hudson proposed modern daylight saving time so that he could catch more bugs.
Long Hindu time
One of the longest measurements of time appears in ancient Hindu scriptures: the mahā-kalpa, equal to 311.04 trillion years.
Cosmic ladder (Part 2)
To measure distances in deep space, you need to look for candles in the darkness. [2 of 2]
Cosmic ladder (Part 1)
It’s a lot more difficult to measure distances in space than you might think. [1 of 2]
The Year 2038 problem
The Y2K problem threatened to bring down computers worldwide twenty-one years ago. In another seventeen years, the Year 2038 problem may do the same.
Farthest mountain
The summit of Chimborazo, a volcano in Ecuador, is two kilometres farther from the Earth’s centre than Mount Everest.
Long mile
The Scandinavian mile is 10 kilometres long. It used to be longer still.
Kiln cones
In a kiln, a set of three drooping cones can monitor the effects of temperature on the pottery items being fired.
Natural units (Part 2)
Whereas most units of measurement are arbitrary and human, Planck units are based only on four fundamental physical constants. [2 of 2]
Natural units (Part 1)
Most units of measurement are based on specific physical qualities or tangible reference objects. But they don’t have to be. [1 of 2]
Time zone tripoints
At several points around the world, three time zones meet.
Mathematical coincidence
A billionth of a century is approximately pi seconds. The diameter of the Earth is roughly half a billion inches.
Akan goldweights
From the 15th to the 19th century CE, the Akan used sets of ornate statues as a measurement system for weighing gold dust, but also encoding and reinforcing cultural knowledge at the same time.