The Day the Earthlings Time Stood Still - For a Second - Leap Second to be Added to 30 June 2012

On  30th June 2012  at 23:59:59 (1st July 2012 at 05:29:59 IST) we can say the TIME of the People Living on Earth would Stop for a Second due to decision of organization called International Earth Rotation and Reference Systems Service (IERS)  to add "One Leap Second" to the day 30th June.

What will happen ? What might Clock show ?
If this leap second would have not been added time would just tick ahead instead of stopping for a Second. That is after 23.59.59 it would be 00.00.00 marking begining of new month.

But due to addition of Leap Second after 23:59:59 (23 Hr .59 Min.59 Sec time + 00.00.01 Sec) it   would be 23.59.60 delaying the new month by a Second.

Why leap Second is added ? Is Earth really slowing down ?
Yes, Earth's rotation speed varies in response to climatic and geological events. 

What are the reasons for Earth being slowing down ? How do scientist know that it is slowing down? 
Astronomers with series of careful observation of stars have concluded that Earth Rotation is slightly slowing down at non-uniform rate.

In other words But from their careful observations of the positions of the stars, astronomers have deduced that Earth's rotation is ever so slightly slowing down at a non-uniform rate, probably attributable to its sloshing molten core, the rolling of the oceans, the melting of polar ice and the effects of solar and lunar gravity.  

How often are Leap Seconds added ?  Is it added every year ?

No Its not added every year. They are added at unpredictable intervals as when IERS decides to do so. 

Usually leap second are added on 30 June or 31 Dec

When is the last time Leap Second adjustment were done? So Far how many time Leap Second are added ?
 The last three adjustments were in 2008, 2005 and 1998.

Ever since this practice of adjustment of time began in 1972 So far 25 Times Leap Seconds were added (including 30 June 2012 ). 

What is International Atomic Time ?  How does it measure time ?
International Atomic Time (TAI, from the French name Temps Atomique International) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid. It is the basis for Coordinated Universal Time (UTC), which is used for civil timekeeping all over the Earth's surface, and for Terrestrial Time, which is used for astronomical calculations

TAI  uses the pulsation of atoms to measure time to an accuracy of several billionths of a second.

International Earth Rotation and Reference Systems Service (IERS) what is it ? Where is it located ?

IERS is located in Paris and it is responsible for keeping track of the gap between atomic and planetary time and issuing international edicts on the addition of leap seconds.

How Does or what is need of making adjustments ? 
The UTC time standard, which is widely used for international timekeeping and as the reference for civil time in most countries, uses the international system (SI) definition of the second, based on atomic clocks. Like most time standards, UTC defines a grouping of seconds into minutes, hours, days, months, and years.

Who is responsible to maintain it In India ? Is there a atomic clock located in India ? Where ? 
The National Physical Laboratory of India, situated in New Delhi, is the measurement standards laboratory of India. It maintains standards of SI units in India and calibrates the national standards of weights and measures.

It maintains national standard of time interval, second as well as frequency through four parameters, which can be measured most accurately.

Importantly it maintains Caesium Atomic Clock which are linked to other such institutions all over the world through a set of global positioning satellites.

How Does Leap Second Work ? Can you summarize above matter and explain ?

UTC is the time standard used to determine local times in time zones worldwide. It is primarily based on the combined output of several highly precise atomic clocks, a statistical time scale called International Atomic Time (TAI).

Although a normal day has 86,400 seconds, in this time scale one second is not defined as one 86,400th of the time it takes Earth to rotate around its axis but as the time it takes a Cesium-133 atom at the ground state to oscillate precisely 9,192,631,770 times.

The advantage of this definition is that it is extremely precise: atomic clocks deviate only approximately one second in 20 million years. On the other hand, the Earth's rotation, which is expressed by the time standard UT1, is far less reliable. It slows down over time, which means that days get longer. On average, an Earth day is about 0.002 seconds longer than the daily sum of the 86,400 seconds measured by the atomic clocks. This makes for a discrepancy between TAI and UT1 of around 1 second every 1.5 years.

Leap seconds are added to our clocks (UTC) so this discrepancy does not get too large over time and the time we use is synchronized as much as possible with the Earth's rotation. Before the difference between UTC and UT1 exceeds 0.9 seconds, one second is added to UTC. This means that the time difference between TAI and UTC amounts to an integral number of seconds because whole seconds are added, while the time difference between UTC and UT1 is always less than 0.9 seconds.