JUNE 30, THE DAY WITH AN EXTRA SECOND Scientists have been forced to adjust the clocks because of the slowing of the Earth

  • Italiano

Today will be a day longer than usual, even if only slightly … only a poor second longer. At the end of 30 June, in fact, after 23h 59m 59s, it will be 23h 59m 60s, and then – finally – 0h 0m 0s, July 1. The last beats of this month will be so marked by a minute made up of 61 seconds instead of the canonical 60! The reason? The Earth’s rotation on its axis. Earth’s rotation is slowing down- about 2 milliseconds per day – and then scientists had to take account of it. Length of the day depends precisely on how long the Earth takes to make one complete rotation. Normally 24 hours, or 86,400 seconds, but it is not always so. In some cases the Earth “takes it easy” due to various factors. First, for the attraction moon-sun, which among other things is the one that generates the tides, then there is the displacement of the masses in the deep layers of the subsoil produced by earthquakes of high magnitude and even the melting of glaciers …

Other reasons are the different distribution of the masses within the “great unknown” that is the core of the Earth, its fluctuations, and the fact that the Earth, in the motion of revolution around the Sun, forms an ellipse. The task of overseeing the calibration operation of the so-called Coordinated Universal Time (UTC) is assigned to the International Earth Rotation Service (IERS), a body that calculates the exact duration of the rotation of the Earth and of the solar day. Cesium atomic clocks (which calculate the second on the resonance frequency of this atom), the most precise tools we have to measure time, will have to take account of this small but important difference of a second. The first adjustment of time, called “leap second”, was introduced on 31 December 1971, and the last on June 30, 2012. These changes are critical because on them depends the timing of the satellites (and therefore of Gps) and of a variety of systems, such as information technology and financial services.

Translation provided by Maria Rosaria Mastropaolo

Avviso: le pubblicità che appaiono in pagina sono gestite automaticamente da Google. Pur avendo messo tutti i filtri necessari, potrebbe capitare di trovare qualche banner che desta perplessità. Nel caso, anche se non dipende dalla nostra volontà, ce ne scusiamo con i lettori.