A petroglyph is an image created by removing part of a rock surface by incising, picking, carving, or abrading, as a form of rock art. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions of the technique to refer to such images. Petroglyphs, estimated to be 20,000 years old and classified as protected monuments and have been added to the tentative list of UNESCO’s world heritage sites. Petroglyphs are found worldwide, and are often associated with prehistoric peoples. The word comes from the Greek prefix petro-, from πέτρα petra meaning "stone", and γλύφω glýphō meaning "carve"...

A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F). The atmospheres of Venus, Mars and Titan also contain greenhouse gases.Human activities since the beginning of the Industrial Revolution (around 1750) have increased the atmospheric concentration of carbon dioxide by over 50%, from 280 ppm in 1750 to 421 ppm in 2022. The last time the atmospheric concentration...

Lymph (from Latin, lympha, meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to be recirculated. At the origin of the fluid-return process, interstitial fluid—the fluid between the cells in all body tissues—enters the lymph capillaries. This lymphatic fluid is then transported via progressively larger lymphatic vessels through lymph nodes, where substances are removed by tissue lymphocytes and circulating lymphocytes are added to the fluid, before emptying ultimately into the right or the left subclavian vein, where it mixes with central venous blood. Because it is derived from interstitial fluid, with which blood and surrounding cells continually exchange substances, lymph undergoes continual change in composition. It is generally similar to blood plasma, which is the fluid component of blood. Lymph returns proteins and excess interstitial fluid to the bloodstream. Lymph also transports fats from the digestive...

Smilodon is a genus of the extinct machairodont subfamily of the felids. It is one of the most famous prehistoric mammals and the best known saber-toothed cat. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats. Smilodon lived in the Americas during the Pleistocene epoch (2.5 mya – 10,000 years ago). The genus was named in 1842 based on fossils from Brazil; the generic name means "scalpel" or "two-edged knife" combined with "tooth". Three species are recognized today: S. gracilis, S. fatalis, and S. populator. The two latter species were probably descended from S. gracilis, which itself probably evolved from Megantereon. The hundreds of individuals obtained from the La Brea Tar Pits in Los Angeles constitute the largest collection of Smilodon fossils. Overall, Smilodon was more robustly built than any extant cat, with particularly well-developed forelimbs and exceptionally long upper canine teeth. Its jaw had a bigger gape than that of modern cats, and its upper canines were slender...

A sabre (French: [ˈsabʁ], or saber in American English) is a type of backsword with a curved blade associated with the light cavalry of the early modern and Napoleonic periods. Originally associated with Central European cavalry such as the hussars, the sabre became widespread in Western Europe during the Thirty Years' War. Lighter sabres also became popular with infantry of the early 17th century. In the 19th century, models with less curving blades became common and were also used by heavy cavalry. The military sabre was used as a duelling weapon in academic fencing in the 19th century, giving rise to a discipline of modern sabre fencing (introduced in the 1896 Summer Olympics) loosely based on the characteristics of the historical weapon in that it allows for cuts as well as thrusts. Etymology The English sabre is recorded from the 1670s, as a direct loan from French, where the sabre is an alteration of sable, which was in turn loaned from German Säbel, Sabel in the 1630s. The German word is on record from the 15th century, loaned from Polish ...

1. loud and unpleasant: 2. loud and unpleasant: 3. loud, excited, and not…

The Palace of Versailles ( vair-SY, vur-SY; French: Château de Versailles [ʃɑto d(ə) vɛʁsɑj] (listen)) is a former royal residence built by King Louis XIV located in Versailles, about 12 miles (19 km) west of Paris, France. The palace is owned by the French Republic and since 1995 has been managed, under the direction of the French Ministry of Culture, by the Public Establishment of the Palace, Museum and National Estate of Versailles. About 15,000,000 people visit the palace, park, or gardens of Versailles every year, making it one of the most popular tourist attractions in the world.Louis XIII built a simple hunting lodge on the site of the Palace of Versailles in 1623 and replaced it with a small château in 1631–34. Louis XIV expanded the château into a palace in several phases from 1661 to 1715. It was a favorite residence for both kings, and in 1682, Louis XIV moved...

Blood circulates through our body and delivers essential substances like oxygen and nutrients to the body’s cells.There are four basic components that comprise human blood: plasma, red blood cells, white blood cells and platelets.