Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). This wavelength means a frequency range of roughly 430–750 terahertz (THz).

The primary properties of visible light are intensity, propagation-direction, frequency or wavelength spectrum and polarization. Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature, as with all types of electromagnetic radiation (EMR), light is found in experimental conditions to always move at this speed in a vacuum.In physics, the term 'light' sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. Like all types of electromagnetic radiation, visible light propagates as waves. However, the energy imparted by the waves is absorbed at single locations the way particles are absorbed. The absorbed energy of the electromagnetic waves is called a photon and represents the quanta of light. When a wave of light is transformed and absorbed as a photon, the energy of the wave instantly collapses to a single location and this location is where the photon "arrives".

Light

Sarcasm is the use of words usually used to either mock or annoy someone, or for humorous purposes. Sarcasm may employ ambivalence, although it is not necessarily ironic. 
Most noticeable in spoken word, sarcasm is mainly distinguished by the inflection with which it is spoken and is largely context-dependent.


== Etymology ==
The word comes from the Greek σαρκασμός (sarkasmós) which is taken from σαρκάζειν (sarkázein) meaning "to tear flesh, bite the lip in rage, sneer".It is first recorded in English in 1579, in an annotation to The Shepheardes Calender by Edmund Spenser:

Tom piper, an ironicall Sarcasmus, spoken in derision of these rude wits, whych ...
However, the word sarcastic, meaning "Characterized by or involving sarcasm; given to the use of sarcasm; bitterly cutting or caustic", doesn't appear until 1695.


== Usage ==
In its entry on irony, Dictionary.com describes sarcasm thus:

In sarcasm, ridicule or mockery is used harshly, often crudely and contemptuously, for destructive purposes. It may be used in an indirect manner, and have the form of irony, as in "What a fine musician you turned out to be!," "It's like you're a whole different person now...," and "Oh... Well then thanks for all the first aid over the years!" or it may be used in the form of a direct statement, "You couldn't play one piece correctly if you had two assistants." The distinctive quality of sarcasm is present in the spoken word and manifested chiefly by vocal inflection ...

Distinguishing sarcasm from banter, and referring to the use of irony in sarcasm, Derek Bousfield writes  that sarcasm is: The use of strategies which, on the surface appear to be appropriate to the situation, but are meant to be taken as meaning the opposite in terms of face management. That is, the utterance which appears, on the surface, to maintain or enhance the face of the recipient actually attacks and damages the face of the recipient.

Sarcasm

Apple Inc. is an American multinational technology company that specializes in consumer electronics, computer software, and online services. Apple is the world's largest technology company by revenue (totalling $274.5 billion in 2020) and, since January 2021, the world's most valuable company. As of 2021, Apple is the world's fourth-largest PC vendor by unit sales, and fourth-largest smartphone manufacturer. It is one of the Big Five American information technology companies, along with Amazon, Google, Microsoft, and Facebook.Apple was founded by Steve Jobs, Steve Wozniak, and Ronald Wayne in 1976 to develop and sell Wozniak's Apple I personal computer. It was incorporated by Jobs and Wozniak as Apple Computer, Inc. in 1977, and sales of its computers, including the Apple II, grew quickly. They went public in 1980 to instant financial success. Over the next few years, Apple shipped new computers featuring innovative graphical user interfaces, such as the original Macintosh, announced with the critically acclaimed advert "1984". However, the high price of its products and limited application library caused problems, as did power struggles between executives.

Apple Inc.

Apple_Inc.

Eyes are organs of the visual system. They provide animals with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.The most simple eyes, pit eyes, are eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal area to control the pupillary light reflex.


== Overview ==

Complex eyes can distinguish shapes and colours. The visual fields of many organisms, especially predators, involve large areas of binocular vision to improve depth perception. In other organisms, eyes are located so as to maximise the field of view, such as in rabbits and horses, which have monocular vision.

Cattle, or cows (female) and bulls (male), are large domesticated ruminants. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos taurus.
Cattle are commonly raised as livestock for meat (beef or veal, see beef cattle), for milk (see dairy cattle), and for hides, which are used to make leather. They are used as riding animals and draft animals (oxen or bullocks, which pull carts, plows and other implements). Another product of cattle is their dung, which can be used to create manure or fuel. In some regions, such as parts of India, cattle have significant religious meaning. Cattle, mostly small breeds such as the Miniature Zebu, are also kept as pets.
Around 10,500 years ago, taurine cattle were domesticated from as few as 80 progenitors in central Anatolia, the Levant and Western Iran. According to the Food and Agriculture Organization (FAO), there are approximately 1.5 billion cattle in the world as of 2018. In 2009, cattle became one of the first livestock animals to have a fully mapped genome.

Cattle

Xmas (also X-mas) is a common abbreviation of the word Christmas. It is sometimes pronounced , but Xmas, and variants such as Xtemass, originated as handwriting abbreviations for the typical pronunciation . The "X" comes from the Greek letter Chi, which is the first letter of the Greek word Christós (Greek: Χριστός), which became Christ in English.
The suffix -mas is from the Latin-derived Old English word for Mass.There is a common misconception that the word Xmas stems from a secular attempt to remove the religious tradition from Christmas by taking the "Christ" out of "Christmas", but its use dates back to the 16th century.


== Style guides and etiquette ==
"Xmas" is deprecated by some modern style guides, including those at the New York Times, The Times, The Guardian, and the BBC. Millicent Fenwick, in the 1948 Vogue's Book of Etiquette, states that "'Xmas' should never be used" in greeting cards. The Cambridge Guide to Australian English Usage states that the spelling should be considered informal and restricted to contexts where concision is valued, such as headlines and greeting cards. The Christian Writer's Manual of Style, while acknowledging the ancient and respectful use of "Xmas" in the past, states that the spelling should never be used in formal writing.


== History ==


=== Use in English ===

Early use of "Xmas" includes Bernard Ward's History of St. Edmund's college, Old Hall (originally published circa 1755). An earlier version, "X'temmas", dates to 1551.

Xmas

A mobile phone, cellular phone, cell phone, cellphone, handphone, or hand phone, sometimes shortened to simply mobile, cell or just phone, is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area. The radio frequency link establishes a connection to the switching systems of a mobile phone operator, which provides access to the public switched telephone network (PSTN). Modern mobile telephone services use a cellular network architecture and, therefore, mobile telephones are called cellular telephones or cell phones in North America. In addition to telephony, digital mobile phones (2G) support a variety of other services, such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, video games and digital photography. Mobile phones offering only those capabilities are known as feature phones; mobile phones which offer greatly advanced computing capabilities are referred to as smartphones.
The development of metal-oxide-semiconductor (MOS) large-scale integration (LSI) technology, information theory and cellular networking led to the development of affordable mobile communications. The first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c. 2 kilograms (4.4 lbs). In 1979, Nippon Telegraph and Telephone (NTT) launched the world's first cellular network in Japan. In 1983, the DynaTAC 8000x was the first commercially available handheld mobile phone.

Mobile phone

Mobile_phone

The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft where it was the only item funded for development. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011, launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST), conducted science experiments in orbit, participated in the Shuttle-Mir program with Russia, and participated in construction and servicing of the International Space Station (ISS). The Space Shuttle fleet's total mission time was 1,322 days, 19 hours, 21 minutes and 23 seconds.Space Shuttle components include the Orbiter Vehicle (OV) with three clustered Rocketdyne RS-25 main engines, a pair of recoverable solid rocket boosters (SRBs), and the expendable external tank (ET) containing liquid hydrogen and liquid oxygen. The Space Shuttle was launched vertically, like a conventional rocket, with the two SRBs operating in parallel with the orbiter's three main engines, which were fueled from the ET. The SRBs were jettisoned before the vehicle reached orbit, and the ET was jettisoned just before orbit insertion, which used the orbiter's two Orbital Maneuvering System (OMS) engines. At the conclusion of the mission, the orbiter fired its OMS to deorbit and reenter the atmosphere. The orbiter was protected during reentry by its thermal protection system tiles, and it glided as a spaceplane to a runway landing, usually to the Shuttle Landing Facility at KSC, Florida, or to Rogers Dry Lake in Edwards Air Force Base, California. If the landing occurred at Edwards, the orbiter was flown back to the KSC on the Shuttle Carrier Aircraft, a specially modified Boeing 747.

Space Shuttle

Space_Shuttle

Gorillas are ground-dwelling, predominantly herbivorous great apes that inhabit the tropical forests of central Sub-Saharan Africa. The genus Gorilla is divided into two species: the eastern gorillas and the western gorillas, and either four or five subspecies. They are the largest living primates. The DNA of gorillas is highly similar to that of humans, from 95 to 99% depending on what is included, and they are the next closest living relatives to humans after chimpanzees and bonobos.
Gorillas are the largest non-human primates, reaching heights between 1.25-1.8 m, weights between 100–270 kg, and arm spans up to 2.6 meters, depending on species and sex. They tend to live in troops, with the leader being called a silverback. The Eastern gorilla is distinguished from the Western by darker fur color and some other minor morphological differences. Gorillas tend to live 35–40 years in the wild.
Gorillas' natural habitats cover tropical or subtropical forest in Sub-Saharan Africa. Although their range covers a small percentage of Sub-Saharan Africa, gorillas cover a wide range of elevations.

Gorilla

A camel is an even-toed ungulate in the genus Camelus that bears distinctive fatty deposits known as "humps" on its back. Camels have long been domesticated and, as livestock, they provide food (milk and meat) and textiles (fiber and felt from hair). Camels are working animals especially suited to their desert habitat and are a vital means of transport for passengers and cargo. There are three surviving species of camel. The one-humped dromedary makes up 94% of the world's camel population, and the two-humped Bactrian camel makes up 6%. The Wild Bactrian camel is a separate species and is now critically endangered.
The word camel is also used informally in a wider sense, where the more correct term is "camelid", to include all seven species of the family Camelidae: the true camels (the above three species), along with the "New World" camelids: the llama, the alpaca, the guanaco, and the vicuña. The word itself is derived via Latin: camelus and Greek: κάμηλος (kamēlos) from Hebrew, Arabic or Phoenician: gāmāl.


== Taxonomy ==


=== Extant species ===
3 species are extant:


== Biology ==
The average life expectancy of a camel is 40 to 50 years. A full-grown adult dromedary camel stands 1.85 m (6 ft 1 in) at the shoulder and 2.15 m (7 ft 1 in) at the hump.

Camel

The symbol # is known as the number sign, hash, or, in North American usage, pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare ℔.Since 2007, widespread usage of the symbol to introduce metadata tags on social media platforms has led to such tags being known as "hashtags", and from that, the symbol itself is sometimes called a hashtag.The symbol is distinguished from similar symbols by its combination of level horizontal strokes and right-tilting vertical strokes.


== History ==

It is believed that the symbol traces its origins to the symbol ℔, an abbreviation of the Roman term libra pondo, which translates as "pound weight". This abbreviation was printed with a dedicated ligature type, with a horizontal line across, so that the lowercase letter l would not be mistaken for the numeral 1. Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes "=" across two slash-like strokes "//". Examples of it being used to indicate pounds exist at least as far back as 1850.The symbol is described as the "number" character in an 1853 treatise on bookkeeping, and its double meaning is described in a bookkeeping text from 1880. The instruction manual of the Blickensderfer model 5 typewriter (c. 1896) appears to refer to the symbol as the "number mark". Some early-20th-century U.S. sources refer to it as the "number sign", although this could also refer to the numero sign. A 1917 manual distinguishes between two uses of the sign: "number (written before a figure)"; and "pounds (written after a figure)". The use of the phrase "pound sign" to refer to this symbol is found from 1932 in U.S. usage.

Number sign

Number_sign

The domestic dog (Canis familiaris or Canis lupus familiaris) is a domesticated descendant of the wolf. The dog derived from an ancient, extinct wolf, with the modern grey wolf being the dog's nearest living relative. The dog was the first species to be domesticated, by hunter–gatherers over 15,000 years ago, before the development of agriculture. Their long association with humans has led dogs to be uniquely adapted to human behavior, leading to a large number of domestic individuals and the ability to thrive on a starch-rich diet that would be inadequate for other canids.The dog has been selectively bred over millennia for various behaviors, sensory capabilities, and physical attributes. Dogs are sub classified into breeds, which vary widely in shape, size, and color. They perform many roles for humans, such as hunting, herding, pulling loads, protection, assisting police and the military, companionship, therapy, and aiding disabled people. This influence on human society has given them the sobriquet of "man's best friend."


== Taxonomy ==

In 1758, the Swedish botanist and zoologist Carl Linnaeus published in his Systema Naturae the two-word naming of species (binomial nomenclature). Canis is the Latin word meaning "dog," and under this genus, he listed the domestic dog, the grey wolf, and the golden jackal. He classified the domestic dog as Canis familiaris and, on the next page, classified the grey wolf as Canis lupus. Linnaeus considered the dog to be a separate species from the wolf because of its upturning tail (cauda recurvata), which is not found in any other canid.In 1999, a study of mitochondrial DNA (mtDNA) indicated that the domestic dog may have originated from the grey wolf, with the dingo and New Guinea singing dog breeds having developed at a time when human communities were more isolated from each other.

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