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Coriolis force

Submitted by Michel Darche on

Have you already tried to reach a target when you are moving to the right? You need to aim at the left of the target if you wish to reach it. Same thing if the target is moving slower than you. Your target seems to be deviated by a fictitious force, the Coriolis force. It is the French mathematician G. G. de Coriolis (1792-1843) who was the first to explain the influence of the Earth rotation on the winds and marine streams. He did so through theoretical work on composed centrifugal forces.

Solitons and Tsunamis

Submitted by Michel Darche on

Solitons are solitary waves observed for the first time by the Scottish mathematician and engineer J. S. Russell in 1834. Solitons travel very long distances at a constant speed without loss of energy. Their speed is proportional to the square root of the deepness of the channel.

Where are you?

Submitted by Michel Darche on

How many satellites orbiting around the Earth are needed to compute exactly one’s position at each instant?
The GPS system uses a set of satellites (at least 24) orbiting around the Earth and emitting signals.
An ideal GPS receiver measures the travel time of three signals from emitted by three satellites to the receiver. From each measure it computes its distance to each satellite.

Is the core of the Earth solid or liquid?

Submitted by Michel Darche on

Using the anomalies in the propagation of seismic waves detected by analysing seismic data recorded by seismographs around the world, the Danish mathematician Inge Lehmann showed in 1936 that the liquid core of the Earth contains a solid inner core of radius 1,200km. Despite a temperature above 5000° C, the inner core becomes solid because of the pressure, which is more than 3.5 millions stronger at a depth of 5000 km than on the surface.

The melting of glaciers

Submitted by Michel Darche on

Global warming causes the expansion of oceans and the melting of glaciers.

Simulation software like ”Flood map”, based on elevation data coming from satellite radars allows to compute the potential consequences of the rising of the sea level on coastal regions and populations, including large cities like Rio de Janeiro, New York, Tokyo, Shanghai, etc.

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