The Papophoplon in 1 minute
Just a short presentation (you scroll, you choose): Brief recap: Sundials indicate true solar time. There are three adjustements to convert it to the time
April 27, 2026
Just a short presentation (you scroll, you choose): Brief recap: Sundials indicate true solar time. There are three adjustements to convert it to the time
In La Ciotat, on the port, there is a nice sundial: It is an equatorial sundial, dating from 1873 called the barometer sundial, because it
The customisable Papophoplon You can now make your own Papophoplon. Enter your longitude and time zone offset from Coordinated Universal Time (UTC) to find out
Since 1901, the Lépine Competition has been showcasing passionate inventors, both amateur and professional, who devise ingenious solutions to improve our daily lives. It does
The back of the Papophoplon is only needed if you’re using the instrument somewhere other than the location for which it was designed. It features
Stop looking for noon at 2 pm — just find it! Note for non-French speakers: there is an expression in French about : “Looking for
We know that solar time differs from legal time and that this difference varies throughout the year. Are there any days when the difference is
World Sundial Day was on 20 March 2026, the day of the equinox. For the second year running, it provided the occasion for amajor online
Going from this: a marble slab at the stonemason’s… To this : As you can see in the GIF above, the virtual Papophoplon (see here)
Here is a Geogebra animation that allows you to visualise the equation of time due to obliquity (the tilt of the Earth on its axis
If you do not have a physical papophoplon, you can still find out the difference between legal time (the time on your watch) and solar
In this article, we explain the three adjustments made by the Papophoplon. 1. Summer time or winter time? The first difference between solar time and
How to convert solar time to clock time? Frustrated by looking at a sundial and finding that it doesn’t show the same time as your
Place the glass flat, with the eyepiece facing the Sun. On the side oppposte to the Sun the shadow of the eyepiece should fall on
Depending on the region and culture, the beginning of the day has been defined as the moment when the Sun rises or when it sets.
As the name suggests, a nova is initially detected as a new star. In reality, it is an existing star, which suddenly becomes much brighter:
The Sun peaks in the sky at true noon. For example, at the latitude of Bordeaux (45°N), it reaches a height of 45° on the horizon
Taking stock at sea As long as navigators keep their eyes on the coast, navigation is quite easy: you just need to find your bearings
1. What is daytime? True solar day vs. mean day According to the simplest definition, the day is the period that separates two successive passages
Warning: it is not known for sure whether this instrument was actually used by the Vikings. Such an instrument would have been made of wood
There are situations in which using a magnetic compass is unreliable. This is the case inside a military vehicle (plane or tank). Indeed, the presence of continuous
Among the modern solar compasses used during the Second World War, it is undoubtedly the simplest and most effective model for this purpose. It is
Astronomical compasses were used by both sides during World War II, when other alternatives could not be used. For example, a magnetic compass can be
Finding the North without a Compass Plant a stick (gnomon) on flat ground. Locate the length of the shade throughout the day (by placing a
Plant a vertical stick in flat ground (gnomon). Locate the end of the shadow (by placing a pebble, or by planting another stick). Wait about
With a regular watch (graduated from 1 to 12) Orient the watch so that the small hand is pointing in the direction of the Sun,
Some watches have a 24-hour hand. It is normally used by travelers to keep a reference time, which is why it is often found on
To use a sun compass you must know the time, and therefore you must have a watch or a radio. So how do you find
Instructions for use This GeoGebra animation replaces the reduction tables used in astronomical navigation. Step 1: Enter your estimated position Use the first two sliders:
We know that the days of the week correspond to the planets visible to the naked eye. Let’s start by clarifying a point of vocabulary: planet
In the geocentric system, which prevailed from the Babylonians to Copernicus, we distinguish two cycles of rotation: The diurnal cycle: all the stars revolve around
In French, there is no doubt from Monday to Friday: Lundi (Monday) Lunae dies Moon Mardi (Tuesday) Martis dies March Mercredi (Wednesday) Mercurii dies Mercury