Why do all mobile number start with the digit 9.   

According to the Telecome Regulatory Authority of India (TRAI), 
local numbering allowed is in the range of 2-8. while 0 is used for  STD access. 1 is used for special numbers. So the only digit left is 9.

If energy is neither created nor destroyed where does is comes from ? 

In the universe, all forms of energy must be associated with some mass. This means that a system or a particle of mass (m) is equivalent to an energy, E= mc2, where c is the velocity of light in vacuum, There are several forms of energies like nuclear energy (fusion and fission), energy from collision of particles and also relativistic energy. Solar energy is the outcome of fusion process resulting from small particles fusing into a large particle. Fission process produces energy by breaking up a heavy particle into small particles. Thermal energy is obtained by collision of particles. So fusion, fission and thermal processes are the main sources of energy in the universe.

Why is a sting operation called so ?

A sting operation most likely owes its etymological origin to the bee. Typically, a sting operation involves an investigative agency such as the police or the media, who lure a criminal to commit a crime in order to trap them red handed. They might pose as a criminal themselves, and thereby set up a trip in terms of an a honey trap. Once the target takes the bait, the trappers “sting” them by way of arrest or publication, the way a bee would sting someone who tries to take honey from a beehive.

Why do banks insist on customers giving their mother’s maiden name ?

This is one of the security measures taken by banks to verify a customer’s identity. Today, Internet banking, phone banking and multi -purpose ATMs are used to conduct money transactions. All of them depend on entering passwords. If any miscreant finds out someone’s user ID or debit/ credit card, she may try to misuse it and may even try to misuse it and may even try to generate a fresh set of passwords or change the address, etc. To prevent this, security measures are taken while such a request is being made and mother’s maiden name is one of them. It is believed that usually only very close people are aware of such information and a stronger would not be able to furnish it. Combined with other confirmatory questions like date of birth, exact address, etc. this provides a reasonable level of security.

Is Earth the only planet to have water ?

For long, it was believed that intelligent life existed on Earth because it was the only planet to have water. But recently, an astronomer Traviz Barman at Lowell Observatory, Arizona stated that in the atmosphere of a Jupiter-like large, gaseous planet, water vapour was found. The planet in question has been named HD 209458b and it lies about 150 light years away from Earth in a constellation called Pegasus. Earlier, there have been reports of traces of water being found on Mars by the Global Surveyor spacecraft.

What is the difference between a subwoofer and a woofer?

There are no stark differences between these two speaker systems as both are used to reproduce low frequencies below 30Hz level and woofers produce sounds above it. At times, the bands may overlap. The smallest diaphragm of a decent halfway woofer is 8 inches, in a subwoofer it is 12 inches. 

What is the difference between an acne and pimples ?

While acne is a disease (acne vulgaris), a pimple is just one type of lesion found in acne patients. Other lesions could be a papule or a nodule. However, in common parlance, these are interchangeably used.