Posts Tagged 'Time measurement'

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 ].

Moon between NASA’s Solar Dynamics Observatory and the Sun, giving a partial solar eclipse from space on Jan. 30, 2014. Image NASA.

Moon between NASA’s Solar Dynamics Observatory and the Sun,
giving a partial solar eclipse from space on Jan. 30, 2014. Image NASA.

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 2.4 radians. We will denote the golden angle by γ. Its exact value, as a fraction of a complete circle, is ( 3 – √5 ) / 2 ≈ 0.382 cycles.

GoldenAngle 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 change.

Left:  Image of Hammurabi in the US Congress. Right: Part of an inscription of the Code of Hammurabi.

Left: Image of Hammurabi in the US Congress.
Right: Part of an inscription of the Code of Hammurabi.

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.  The first storm, around 65 BC, wrecked a Roman vessel bringing home loot from Asia Minor. The ship went down near the island of Antikythera, between the Greek mainland and Crete. 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. 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, is available here.  To run it, just enter the width of the sundial, the latitude and longitude, and the timezone. The script will generate all the required dimensions.

Here is a technical article, The Equation of Time and the Analemma (PDF), submitted to the Bulletin of the Irish Mathematical Society.


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