Saving Daylight with Hip-hop Time: a Modest Proposal

At 2:00 AM on Sunday 28 October the clocks throughout Europe will be set back one hour, reverting to Standard Time. In many countries, the clocks are put forward one hour in Spring and set back to Standard Time in the Autumn. Daylight saving time gives brighter evenings in Summer. In Summer, the mornings are … Continue reading Saving Daylight with Hip-hop Time: a Modest Proposal →

Darker Mornings, Brighter Evenings

Today is the winter solstice, the shortest day of the year. We might expect that the latest sunrise and earliest sunset also occur today. In fact, the earliest sunset, the darkest day of the year, was on 13 December, over a week ago, and the latest sunrise is still more than a week away. This … Continue reading Darker Mornings, Brighter Evenings →

Modular Arithmetic: from Clock Time to High Tech

You may never have heard of modular arithmetic, but you use it every day without the slightest difficulty. In this system, numbers wrap around when they reach a certain size called the modulus; it is the arithmetic of remainders [TM126 or search for “thatsmaths” at irishtimes.com]. When reckoning hours, we count up to twelve and start again … Continue reading Modular Arithmetic: from Clock Time to High Tech →

Pedro Nunes and Solar Retrogression

In northern latitudes we are used to the Sun rising in the East, following a smooth and even course through the southern sky and setting in the West. The idea that the compass bearing of the Sun might reverse seems fanciful. But in 1537 Portuguese mathematician Pedro Nunes showed that the shadow cast by the … Continue reading Pedro Nunes and Solar Retrogression →

The Great American Eclipse

Just two years from now, on Monday, August 21, 2017, the Moon's shadow will sweep across the United States at a speed of over 2,000 km/hr. The Great American Eclipse of 2017 will generate a frenzy of activity. [TM074: search for “thatsmaths” at irishtimes.com ]. Solar eclipses are not especially rare, but this one is of … Continue reading The Great American Eclipse →

Golden Moments

Suppose a circle is divided by two radii and the two arcs a and b are in the golden ratio: b / a = ( a + b ) / b = φ ≈ 1.618 Then the smaller angle formed by the radii is called the golden angle. It is equal to about 137.5° or … Continue reading Golden Moments →

When did Hammurabi reign?

The consequences of the Earth’s changing climate may be very grave. It is essential to understand past climate change so that we can anticipate future changes. This week, That’s Maths in The Irish Times ( TM047 ) is about the chronology of the Middle East. Surprisingly, this has important implications for our understanding of climate … Continue reading When did Hammurabi reign? →

The Antikythera Mechanism

The article in this week's That's Maths column in the Irish Times ( TM033 ) is about the Antikythera Mechanism, which might be called the First Computer. Two Storms Two storms, separated by 2000 years, resulted in the loss and the recovery of one of the most amazing mechanical devices made in the ancient world. … Continue reading The Antikythera Mechanism →

Where in the World?

Here's a conundrum: You buy a watch in Anchorage, Alaska (61°N). It keeps excellent time. Then you move to Singapore, on the Equator. Does the watch go fast or slow? For the answer to this puzzle, read on. The Global Positioning System In the Irish Times column this week ( TM009 ), we look at … Continue reading Where in the World? →

Analemmatic Sundials

This week’s That’s Maths article, TM003, describes the analemmatic sundial on the East Pier in Dun Laoghaire. An article in Plus Magazine, by Chris Sangwin and Chris Budd, gives a description of the theory of these sundials and instructions on how to build one. A script to design an analemmatic sundial, written by Alexander R. Pruss, … Continue reading Analemmatic Sundials →