Thursday, March 29, 2007


A lens is a device for either concentrating or diverging light, normally formed from a piece of shaped glass. Analogous devices used with other types of electromagnetic radiation are also called lenses: for instance, a microwave lens can be made from paraffin wax.
The earliest records of lenses date to Ancient Greece, with Aristophanes' play The Clouds (424 BC) mentioning a burning-glass (a convex lens used to focus the sun's rays to produce fire). The writings of Pliny the Elder also show that burning-glasses were recognized to the Roman Empire, and mentions what is possibly the first use of a corrective lens: Nero was known to watch the gladiatorial games throughout a concave-shaped emerald (presumably to correct for myopia). Seneca the Younger (3 BC--65) described the magnifying effect of a glass globe filled with water.Widespread use of lenses did not happen until the invention of spectacles, probably in Italy in the 1280s.

Monday, March 26, 2007


A computer is a device capable of processing data according to a program — a list of instructions. The data to be processed may represent many types of information including numbers, text, pictures, or sound.
Computers can be enormously versatile. In fact, they are universal information processing machines. According to the Church-Turing thesis, a computer with a certain minimum threshold capability is in principle capable of performing the tasks of any other computer, from those of a personal digital assistant to a supercomputer. Therefore, the same computer designs have been adapted for tasks from processing company payrolls to controlling industrial robots. Modern electronic computers also have enormous speed and ability for information processing compared to earlier designs, and they have become exponentially more powerful over the years (a phenomenon known as Moore's Law).
Computers are available in many physical forms. The original computers were the size of a large room, and such enormous computing services still exist for specialized scientific computation - supercomputers - and for the transaction processing requirements of large companies, usually called mainframes. Smaller computers for individual use, called personal computers, and their portable equivalent, the notebook computer, are ubiquitous information-processing and communication tools and be perhaps what most non-experts think of as "a computer". However, the most common form of computer in use today is the embedded computer, small computers used to control another device. Embedded computers control machines from fighter planes to digital cameras.

Wednesday, March 21, 2007


A motorcycle (or motorbike) is a two-wheeled vehicle powered by an engine. The wheels are in-line, and at higher speed the motorcycle remains upright and stable by virtue of gyroscopic forces; at lower speeds repeated readjustment of the steering by the rider gives constancy. The rider sits astride the vehicle on a seat, with hands on a set of handlebars which are used to steer the motorcycle, in conjunction with the rider shifting his weight through his feet, which are supported on a set of "footpegs" or "pegs" which stick out from the frame

Friday, March 16, 2007

Pied-billed Grebe

The Pied-billed Grebe, Podilymbus podiceps, †) is a associate of the grebe family of water birds. Since the Atitlan Grebe, Podilymbus gigas, has become wiped out, it is the sole extant member of the genus Podilymbus.
The Pied-billed Grebe breeds across Canada, parts of the United States and temperate South America. though this species does not appear to be a strong flier, it has occurred in Europe as a rare vagrant on a number of occasions, and one bird in England bred by means of a Little Grebe, producing hybrid young.
The most widespread of North American grebes, it is found on remote ponds, marshes, and sluggish streams. It is frequently the first grebe to arrive on northern inland waters in springtime, and the last to leave in autumn. It is rare on salt water. This grebe rarely flies, preferring to escape danger by diving.
It feeds on fish (carp, catfish, eels), insects (dragonflies, ants, beetles), and amphibians (frogs, tadpoles).
The Pied-billed Grebe is small at 31-38 cm (12"-15") in length, stocky, and short-necked. It has a short, blunt chicken-like bill, which in summer is encircled by a broad black band (hence the name). It is the only grebe that does not show a white wing patch in flight.
This grebe is typically silent, except in breeding season when the male voices a loud, laughing cuck, cuck, cuck or cow, cow, cow.
Folk names of this grebe include dabchick, devil-diver, dive-dapper, hell-diver, and water witch

Sunday, March 11, 2007

Snow cave

A snow cave is a shelter made in snow by mountain climbers and other outdoor winter recreational enthusiasts. The shelter has properties associated to an Igloo and is mainly effective at providing protection from wind as well as low temperatures. A properly made snow cave can be 0 °C (32 °F) or warmer inside, even when outside temperatures are -40 °C (-40 °F).[1] [2]
A snow cave is built by excavating snow in such a way that the entrance tunnel enters from under the main space to retain warm air. Construction is simplified by building it on a steep slope and digging slightly upwards and horizontally into the slope. The roof is domed to prevent dripping on the occupants. sufficient snow depth, free of rocks and ice, is needed. Generally at 4 or 5 feet is enough. The snow must be consolidated, so it retains its structure. The walls and roof be supposed to be at least 12 inches thick.
A narrow entrance tunnel, a little wider than a human leads into the main chamber which consists of a flat area, perhaps with elevated sleeping platform(s), also excavated from snow. Most sources agree that using tools such as a shovel and ice axe are vital; digging by hand is for emergencies only.

Tuesday, March 06, 2007

Fog bow

A fog bow is comparable to a rainbow, but because of the very small size of water droplets that cause fog, smaller than 0.05 mm, the fog bow has no colors and appears white. Fogbows are sometimes called "white rainbows" or "cloudbows". Mariners sometimes call them "sea-dogs".
The fogbow's relative lack of colors are caused by the relatively smaller water drops... so small that the quantum mechanical wavelength of light becomes significant and smears out colors that would be created by larger rainbow water drops.
This is significantly different from a moonbow, where the colours exist but are regularly not seen because the moonbow is so faint.

Thursday, March 01, 2007

Internet vs. Web

The Internet and the World Wide Web are not synonymous: the Internet is a collection of interconnected computer networks, linked by copper wires, fiber-optic cables, wireless connections, etc.; the Web is a collected works of interconnected documents and other resources, linked by hyperlinks and URLs. The World Wide Web is available via the Internet, as are many other services with e-mail, file sharing, and others described below.
The best way to define and differentiate between these terms is with reference to the Internet protocol suite. This collection of standards and protocols is ordered into layers such that each layer provides the foundation and the services necessary by the layer above. In this conception, the term Internet refers to computers and networks that communicate using IP (Internet protocol) and TCP (transfer control protocol). Once this networking structure is recognized, then other protocols can run “on top.” These other protocols are sometimes called services or applications. Hypertext transfer protocol, or HTTP, is the application layer protocol that relations and provides access to the files, documents and other resources of the World Wide Web.