Second day save – BBC

July 1 inhabitants of the earth, scientists will add one extra second. Extend one day in the year required deceleration of the Earth caused by the sun and the moon.

Wednesday, July 1, 2015, will be one second longer than normal hours. The decision adopted the International Earth Rotation Service and reference systems (IERS), based in Paris. This day should be lengthened so-called leap seconds (leap seconds) – an amendment designed to synchronize the clock with a world constantly slows down the rotation of the Earth.

«The Earth’s rotation is slowing down a little, so leap seconds are able to take this into account,” – said Daniel McMillan of nasovskogo Center Goddard Space Flight Center.

Every day in the world consist of 86 400 seconds. This second, on which people synchronize watches, counts the so-called universal time tied to the atomic clock. They countdown since 1970 conducted by counting the natural oscillations between two states of the cesium atom.

The time between these fluctuations are so constantly that the stability of the atomic clock is one second in 1.4 million years. However, the average solar day is equal to the period of revolution of the Earth around its axis in the order of 86 400.002 seconds and gradually increase.

This is due to the fact that our planet is constantly experiencing the tidal forces from the Sun and the Moon, which inhibit its rotation around its axis. According to scientists, the mean solar day is approximately 86,400 seconds in 1820.

This is an average lag of the Earth from the atomic standard 2 milliseconds per day is minuscule amount but for the year accumulates quite tangible extra seconds. Although on average the Earth really is inhibited, the duration of the individual solar day can fluctuate in a large, and in the smaller side.

The fact that the rate of rotation of the Earth is influenced by many factors, and the characteristic scale less than a year plays an important role, for example, the behavior of the atmosphere. It is proved that the daily and seasonal weather changes can affect the length of the individual solar day within a few milliseconds. Other factors include the dynamics of rotation of the inner core of the Earth (at longer time scales), changes in ocean currents, the movement of underground waters and glaciers (on the scale of months or decades), as well as ocean and atmospheric currents.

For example, atmospheric phenomena such as El Niño, can temporarily slow the Earth’s rotation by increasing the solar day by 1 millisecond.

Follow the speed of rotation of the Earth with an accuracy to help astronomers. With very long baseline interferometry – a network of radio telescopes, separated by thousands of kilometers away from each other. Watching on a remote quasars billions of light-years, different antennas receive signals from them with a slight delay, depending on where the “saucer”. Analyzing these microscopic delays, scientists can calculate the current speed of rotation of the Earth and its average rate of deceleration. Modern methods of radio interferometry give a 3 microsecond accuracy, NASA developed a new project “Geodesy” using a greater number of diversity antennas, can achieve an accuracy of 0.5 microsecond.

«next-generation system designed to meet the needs of most of the scientific challenges today and in the near future “, – said Stephen Merkovits of Goddard. According to the accepted rules, if necessary, an extra second is added coordination evening of June 30 or December 31 to UTC. Therefore, on July 1 after 02.59: 59 Moscow time will not come 03.00: 00 MSK and 02.59: 60 MSK and then 03.00: 00 MSK.

The introduction of extra seconds may not go unnoticed. Airlines stock exchanges and technology companies are already preparing for possible disruptions. The last time a second coordination was introduced in 2012, were marked by failures in the Mozilla, Reddit, Foursquare, Yelp, LinkedIn and StumbleUpon, a problem arose in the Linux operating system and programs written in Java. And in Australia, I had to put 400 airlines Qantas flights due to a failure in the registration system.

According to experts, the greatest number of failures can occur in Asia, where the transfer clock will be in the midst of the day.

Since 1972 , when it was first introduced a second coordination until 1999. These amendments were introduced about a year. However, later the Earth “pulled up” its braking and began to add a second less. Scientists do not know what it is connected, one of the reasons may serve as a major earthquake or volcanic eruptions, which can affect the rotation of the Earth in the short term.