Tuesday, June 30, 2015 will last one second longer than the average day as a "leap second" is added to it by experts. While it may not have a huge impact on the average person, scientists say it can cause numerous disruptions across the World Wide Web and in systems of companies all around the world.
In all its precision and specificity, a day consists of 86,400 seconds based on the Coordinated Universal Time (UTC), which is the standard clock that all people follow. UTC is directed by the changes that happened in the atoms of cesium, in terms of electromagnetic properties. These modifications are so exact that a cesium clock be may relied on for about 1,400,000 years.
Mean solar day is determined by the duration at which the Earth rotates on its axis, and the average length of a day through this is approximately 86,400.002 seconds long. According to experts, the mean solar day has run this duration since 1820 and has not decreased by 0.002 seconds.
Experts use the Very Long Baseline Interferometry (VLBI) to determine the duration of the Earth's complete rotation around its axis. This technique is highly precise as it is powered by a wide network of stations situated all over the globe. The National Aeronautics and Space Administration (NASA) Goddard Space Flight Center helps this endeavor by providing coordination, analyzation and data collection services to the VLBI.
To keep these two time determinants in sync to one another as closely as possible, a leap second is added in a day. The time difference between these two standards must not go beyond 0.9 seconds so when the discrepancy between the UTC and the Mean solar day reaches about 0.6 seconds, scientists usually announce an upcoming leap second. Adding a leap second to a day is decided by a department in the International Earth Rotation and Reference Systems Service. Announcements for a leap second may occur in advance, as is the case of this year's June 30 leap second, which was declared in January.
There are numerous determinants associated with the changes in the length of a day. One determinant is the seasonal changes and weather variations that happen day by day. Long-term changes in the Earth's inner core may also influence the day's length. Atmospheric and oceanic features, seismic activities, water and ice reserves are also some of the many factors that affect a day's length.
A leap second usually occurs either on June 30 or Dec. 1. This year, on June 30, the clock would move from 23:59:60 to 00:00:00 on July 1, instead of the usual 23:59:59 to 00:00:00. Systems are usually turned off for one second during this time as a practice.
Photo: Amanda Slater | Flickr
