What is the source of the Sun's energy output?

It is said that the Sun emits more energy in one second than mankind has consumed in the whole of its history! The inherent source of the solar output, in a word, is fusion! In the core of the Sun, nuclear reactions take place and convert the matter into energy. Within the core, density is about 12 times the density of solid lead or 160 times the density of water. The temperature reaches a peak of some 15 million degrees Celsius. under such extreme conditions, nucleus of one hydrogen atom fuses with that of another. The net result is the conversion of four hydrogen protons into one helium-4 nucleus, but some mass is lost during the process and transformed into energy. (See diagram below).

With many fusion reactions taking place simultaneously, the Sun loses 4.3 million tons of mass every second, by converting 600 million tons of hydrogen into just under 596 million tons of helium. Thus, only a small fraction (0.7%) of the mass of hydrogen going into nuclear fusion reaction does not show up as the mass of helium. Yet this lost mass is converted into huge amount of energy because Einstein's equation E=mc² is at work here. (e denotes energy, m is mass lost and c is speed of light, squared). To take specific example, consider the conversion of 1 kilogram of hydrogen into helium. Despite the fact that a kilogram of hydrogen goes into the nuclear reaction, only 0.993 kilogram of helium is produced. Using Einstein's formula, it is easy to ascertain the energy output:

E=mc² = (0.007 kilogram) (3,00,000)²

= 6.3 x 1014 joules

This is equivalent to energy released by burning 20,000 tons of coal. And remember, we are talking about of only 0.007 kilogram of the Sun’s lost mass, whereas the total mass it loses every second is nearly 40 million tons. Although the Sun has been releasing prodigious amount of energy since last 4.5 billion years, it has so far lost only a few hundredth of 1% of its original mass of hydrogen. 

Additional reading:
Sun (Wikipedia)

How many words are in the English language?

The millionth word entered the English language some time ago. This figure includes about 4,00,000 technical terms, the most in any language. Despite the rich vocabulary the Oxford English Dictionary contains, it is doubtful if any individual uses more than 60,000 words. Even those in UK who have undergone full 16 years of education use perhaps 5,000 words in speech and up to 10,000 words in written communication. The membership of International Society for Philosophical Inquiry (no admission for IQs below 148) have an average vocabulary of 36,250 words -- much better than Shakespeare who used about 33,000 words!

Additional reading:
English language (Wikipedia)

Where does a text SMS go if the receiver's phone is switched-off?

The transmission route of SMS is not different from that of conversation. Whenever a person sends SMS through his mobile, first of all that data is received by the SMS center of the sender's service provider's network, which is nothing but the server meant for directing SMS traffic. It is the job of this server to contact the network of the receiver's service provider and through it the SMS message ultimately reaches the receiver's mobile. For this process to take place it is necessary that the receiver's mobile should be switched-on. This is the normal procedure but its noteworthy feature is that the sender’s network does not relay the message to the receiver's network straightway. The sender's network first ascertains from the receiver's network whether the receiver's mobile is switched-on or not, through the latter's Home Location Register (HLR).

Suppose the receiver's mobile phone is not switched-on. In that case the sender’s network requests the HLR of the receiver's network to pickup the SMS message when the receiver's mobile is switched-on and in the meanwhile it keeps the message pending. How long the SMS message will be kept pending depends upon service provider's policy. There is no uniform practice among the service providers. According to the business policy of individual service providers the period of pendency ranges from 2 hours to 2 days.

Related posts:

• Who is the inventor of modern type mobile phone?
• How does a mobile phone work? And is it harmful for the brain?

Why are dark things warmer than light colored or simply white things?

We can answer this question at once if we know the answer to the question, "Why are dark things dark?" A thing is dark, even in light, because instead of reflecting the light from its surface, it absorbs all the light rays. Light and radiant heat are essentially the same thing. So, when light-colored clothes throw back the light that strikes them, they also reflect the heat that accompanies the light rays. Probably nothing will reflect all the light and heat that strike it, and even the whitest snow will gradually melt under the Sun’s rays.

But while light things keep only a little of light and heat that fall on them, dark things absorb practically the full consignment they receive and so, of course, they get warm. Thus a shirt of white cotton, for instance, will become really warmer to wear if it is simply dyed black.

Is hummingbird the smallest bird? How small is it?

Bee Hummingbird

There are more than 300 species of hummingbird and they vary in size; though only a few are more than 15 retentiveness long. The smallest (shown here in actual size) is the bee hummingbird, which is a native of Cuba. An average adult male measures only 5 centimeters in total length, half of which is taken up by the bill and tail. This tiny flier weighs only 1.6 grams. It builds a thimble-size nest and its egg is less than 1 centimeter in length.

Additional reading:
Bee Hummingbird (Wikipedia)

What kind of atmosphere does Mars have?

Certainly, quite inhospitable. Thin Martian atmosphere is composed of 95% carbon dioxide, 2.7% nitrogen, 1.6% argon and traces of several other gases, including 0.15% oxygen. The abundance of CO2 is simply forbidding. Besides, surface atmospheric pressure is less than 1% of the Earth’s atmospheric pressure, though it does vary by season because most of the atmosphere becomes frozen at the planet's polar caps during the winters. A jet plane flying at about 1,00,000 feet (30,500 meters) from the Earth's surface would encounter an atmospheric pressure similar to the surface of the red planet Mars.

Temperatures on Mars vary widely between day and night, winter and summer, mainly because it is about 80 million kilometers farther from the Sun than the Earth. In the northern hemisphere, summer temperatures range from a low of -88 degrees Celsius just before dawn to a high of -12 degrees Celsius in the mid afternoon. Polar temperatures during the winter drop as low as -140 degrees Celsius.

If an astronaut stepped from his spacecraft onto the Martian surface without protection, he would suffocate from lack of oxygen after only half a minute or so -- much before he would freeze from the cold or would get scorched by cosmic radiation, the influx of which is about 100 times as intense as that on Earth.

Additional reading:
Atmosphere of Mars (Wikipedia)

Which has been the longest and heaviest freight train on record?

In 1968, a U.S. railroad's freight train made up of 500 coal cars traveled from Iaeger, West Virginia to Portsmouth, Ohio. It had six locomotives, three pulling and three pushing. The train was 6.5 kilometers long. This world record stood until 1989, when a South African freight train consisting of 660 wagons (each loaded to some 106 tons) was moved by nine electric and seven diesel-electric locomotives. This train was 7.3 kilometers long and weighed 70,500 tons excluding locomotives which were distributed along the train. It traveled a distance of 861 kilometers in 22 hours and 40 minutes!

Additional reading:
Longest trains (Wikipedia)