The Earth's clocks will stop for one second tonight - The extra second is announced months before its introduction, so that the international community can prepare, and is traditionally added either on the evening of December 31st or the evening of June 30th.
Time will forcibly for one second at midnight on Tuesday, June 30, as the "keepers" of universal time will add a leap second, resulting in the last minute of the month having 61 seconds instead of 60.
So, at 23:59:59 Greenwich Mean Time (02:59:59 Greek Time) the time will "stick" for an additional second (23:59:60), before the clocks show 00:00:00 (03:00:00 Greek Time) and Wednesday, July 1 begins. Other systems will simply "turn off" for a second.
This is the 27th time something like this has happened. The last time something like this happened was in 2012 (previously leap seconds were added in 2008, 2005 and 1998). And that caused some problems in stock market trading and the internet (as the main computers of services like LinkedIn and Reddit were confused), something that many fear could happen again this year.
Typically, our planet takes 86,400 seconds to complete a 360-degree rotation in 24 hours. However, the Earth is constantly subjected to gravitational influences from the Sun, the Moon, and other planets, resulting in its rotation speed not being constant, but rather slowing down imperceptibly. So, in reality, the average length of a day (the time it takes for the Earth to completely rotate around itself) is 86,400.002 seconds.
[alert variation=”alert-info”]The result is a deviation of about two thousandths of a second between natural (astronomical-solar) time and International Atomic Time, which is measured by atomic clocks with a precision of one billionth of a second. Accumulated every day, this deviation amounts to about one second per year. Thus, a correction must be made periodically to Coordinated Universal Time (UTC), the successor to Greenwich Mean Time (GMT), which is measured by atomic clocks.[/alert]
Atomic time is calculated by hundreds of atomic clocks around the world, which measure the perfectly predictable electromagnetic pulses of the cesium atom. Atomic clocks lose only one atomic second every 300 million years.
At times, the discrepancy between atomic time and astronomical time is so great that it is deemed necessary to add a leap second by the International Earth Rotation and Reference Systems Service (IERS), which is based in Germany and was created in 1987 by the International Astronomical Union and the International Union of Geodesy and Geophysics.
The IERS continuously monitors the rotation of our planet and advises the UN's International Telecommunication Union (ITU) on when time should be "stuck". The final decision lies with the ITU. The first correction was made in 1972. Until then, time was measured not by atomic clocks, but by the astronomical relationship between the Earth and the Sun, which was better known as "Greenwich Mean Time" (GMT).
The extra second is announced months before its introduction, so that the international community can prepare, and is traditionally added either on the evening of December 31 or the evening of June 30. However, many systems are not properly prepared to handle the leap second correctly, as its addition is irregular.
The headache that the leap second periodically causes has intensified pressure from various quarters to stop this practice, something that the ITU will consider again at a meeting in Geneva in 2015. This means that time will now be based exclusively on highly accurate atomic clocks, without periodic correction based on astronomical time.
The consequence is that the two times, atomic and astronomical, will diverge increasingly in the future (a difference of one to two minutes over the course of a century), so that the connection between the measurement of time and people's experience of time around them will gradually be lost.
Source: skai.gr
