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Carnivore
A carnivore is an animal which eats only meat. Predators commonly hunt and kill their own prey. Scavengers are carnivores which eat animals they did not kill themselves. Carnivores which eat mainly or only insects are called insectivores. Carnivores which eat mainly or only fish are called piscivores.
The word "carnivore" describes more than just the scientific order Carnivora. However, almost all animals in the Carnivora do eat meat, though a few do not.
Cologne
Cologne (, Kölsch: "Kölle") is a city on the Rhine River in the state of North Rhine-Westphalia in Germany. About 1,060,000 people live there, making Cologne the biggest city in North Rhine-Westphalia. It is in the southern part of the 'Rhine-Ruhr agglomeration' of cities with a combined total population of about 10 million people. This is one of the most densely populated areas of the world.
Cologne has an oceanic climate ("Cfb" in the Koeppen climate classification).
The city was founded by the Romans in the year 50 AD. Before that, it was a Roman castle ("castellum") and a town inhabited by a local German tribe named "Ubier" at least for 100 years. Archaeologists have found out that the surrounding area was populated already during the Stone Age.
Traditionally, the city was always Roman Catholic. That changed only recently after the Second World War,as a result of massive immigration of Protestants from the East of Germany. Still the largest number of people, 41.6%, are Roman Catholic, compared to 17% Protestant. 10% of the people are Muslim.
The most interesting thing to see there is Cologne Cathedral. This church was built from about 1248 to about 1550, but completed only in 1880. The United Nations list it as 'World Cultural Heritage'. Cologne's archbishop Rainald von Dassel brought the relics of the biblical Three Wise Men there in 1164. They are kept in a very beautiful golden shrine in the cathedral. Three golden crowns in the coat of arms of the city symbolize them. They made Cologne a major place of pilgrimage.
The University of Cologne alone has more than 50,000 students. It was founded 1919 and is one of the biggest universities in Germany. There are several specialized Schools in addition to the university. The "Hochschule für Musik" is the biggest Academy of Music in Europe. Cologne has two Colleges of Arts and the Sports College again is one of the biggest institutions of its kind worldwide.
Cologne has 31 museums and has one of the busiest train stations in Europe. It is the only train station located next to a big cathedral.
People in Cologne and nearby have their own dialect. They call it Kölsch. During carnival time it even appears on nationwide broadcasts.
Cologne has a handful of broadcasting stations. The Westdeutscher Rundfunk, part of the network ARD, is the biggest producer of television and radio programs in Germany.
Cologne is also famous for Eau de Cologne ("Kölnisch Wasser").
Senegal
The Republic of Senegal (French "République da Sénégal") is a country in West Africa. The capital is Dakar.
Senegal covers a land area of almost 197,000 square kilometres. It has population of about 13 million. The climate is tropical with two seasons: the dry season and the rainy cold season . Senegal was given independence by France in 1960.
Major industries are fish processing, phosphate mining, fertilizer production, petroleum refining, construction materials, ship construction and repair. Peanuts, sugarcane, cotton, green beans, industrial tomato, cherry tomato, melon, and mango are important cash crops.
French is the official language. Since April 2012 Senegal's president has been Macky Sall.
In the 15th century, Portuguese people came to Gorée Island off the coast of Dakar. In the 17th century, French people and Dutch people came there, too. These European countries used the island as a trading post in slaves from the mainland, controlled by the Muslim Wolof Empires. Slavery was later made illegal by France, but soon after, around 1850, the French started to conquer the Wolof. By 1902 Senegal was a part of the French colony French West Africa.
In January 1959, Senegal and the French Sudan became one to form the Mali Federation, which became fully independent on June 20, 1960, as a result of the independence and transfer of power agreement signed with France on April 4, 1960. This did not last long and Senegal and Mali broke apart into separate nations. Between 1982 and 1989 Senegal and The Gambia joined together to make Senegambia.
In the north of Senegal is the Senegal River. To the north of the river is Mauritania. The nation borders Mali in the east, Guinea-Bissau in the south, and Guinea in the south-east. The Gambia is another country inside of Senegal, along the Gambia River. It is about 300 km long.
The north of Senegal is part of the Sahel. The highest mountain is 581 m high. The rainy season is between June and October. The average temperature on the coast is about 24° C, and inland about 27° C.
Developmental biology
Developmental biology is the study of the process by which organisms grow and develop.
Modern developmental biology studies the genetic control of cell growth, differentiation and morphogenesis. These are the processes which turn a zygote into an adult animal.
Differentiation is the formation of cell types, from what is originally one cell – the zygote or spore. The formation of cell types like nerve cells occurs with a number of intermediary, less differentiated cell types. A cell stays a certain cell type by maintaining a particular pattern of gene expression. This depends on regulatory genes.
Embryogenesis is the step in the life cycle after fertilisation – the development of the embryo, starting from the zygote (fertilised egg). Organisms can differ drastically in the how embryo develops, especially when they belong to different phyla.
Growth is the enlargement of a tissue or organism. Growth continues after the embryonic stage, and occurs through cell division, enlargement of cells or accumulation of extracellular material. In plants, growth results in an adult organism that is strikingly different from the embryo. The dividing cells tend to be distinct from differentiated cells (see stem cell).
In some tissues dividing cells are restricted to special areas, such as the growth plates of bones. But some stem cells move to where they are needed, from the bone marrow to form muscle, bone or adipose (fat) tissue.
Many animals have a larval stage, with a body plan different from that of the adult organism. The larva abrubtly develops into an adult in a process called metamorphosis. For example, caterpillars (butterfly larvae) are specialized for feeding whereas adult butterflies (imagos) are specialised for flight and reproduction. When the caterpillar has grown enough, it turns into an immobile pupa. Here, the imago develops from imaginal discs found inside the larva.
Regeneration is the reactivation of development so that a missing body part grows back. This phenomenon has been studied particularly in salamanders, where the adults can reconstruct a whole limb after it has been amputated. Researchers hope to one day be able to induce regeneration in humans. There is little spontaneous regeneration in adult humans, although the liver is a notable exception. Like for salamanders, the regeneration of the liver involves reversing some cells to an earlier state.
Solidarity
Solidarity can refer to:1924
1924 was a leap year starting on Tuesday.
1929
Year 1929 (MCMXXIX) was a common year starting on Tuesday in the Gregorian calendar. By January 1 of this year, every state in the entire world had adopted the Gregorian calendar, having abandoned the Julian calendar.
1920s
The 1920s was the decade that started on January 1, 1920 and ended on December 31, 1929. This decade was known as the Roaring Twenties or the Jazz Age.
Outer space
Space, also known as outer space, is the near-vacuum between celestial bodies. It is where everything (all of the planets, stars, galaxies and other objects) is found.
On Earth, space begins at the Kármán line (100 km above sea level). This is where Earth's atmosphere is said to stop and outer space begins. This is not a natural boundary but is a convention used by scientists and diplomats.
However, the space near Earth is quite crowded by astronomical standards. A list of spaces goes like this:
Exploring space is very difficult because it contains no air and is so large that even the fastest ships can only explore a tiny part of it. It takes 3 days of traveling to reach the Moon and, depending on speed, it would take a long time to reach the closest star Proxima Centauri.
Manned spacecraft are designed to keep good air inside them and to protect astronauts from extreme temperatures.
We gain most of our information about the items in space from different kinds of telescopes. Some of them are space telescopes, put in outer space for a better view. Space probes also explore planets, comets and other space objects that are not too far.
Natural satellite
A natural satellite in astronomy is a smaller body which moves around a larger body. The smaller body is held in orbit by gravitation. The term is used for moons which go around planets, and it is also used for small galaxies which orbit larger galaxies.
Bodies which orbit planets are called moons. They vary in size. The Earth has only one moon. Some other planets have many moons, and some have none. When people write just ""the" moon", they are usually talking about the moon of the Earth. Earth's moon is written with a capital letter, "Moon". The Latin word for the moon is "luna", which is why the adjective used to talk about the moon is "lunar". For example, lunar eclipse.
Anything that goes around a planet is called a satellite. Moons are natural satellites. People also use rockets to send machines into orbit around the Earth. These machines are called artificial (man-made) satellites.
Moons do not make their own light. We can see the Earth's moon because it acts like a mirror, and reflects the light of the Sun. The same half of the moon faces toward Earth at all times, no matter where it moves. But different parts of the moon are lit up by the Sun, so it looks different at different times of the month. This change as seen from Earth is called the phases of the moon, or lunar phases.
A moon's cycle is the time the moon takes to change from looking very bright and round to looking very small and thin, and then back to bright and round again. In the case of the Earth's moon, this is about four weeks. It does this about 13 times in one year. The moon's cycle is about 28 days, a bit shorter than a calendar month.
The Apollo 11 mission helped Neil Armstrong and Buzz Aldrin become the first people to walk on the Moon. They did this on July 20, 1969.
The orbit of a moon or other satellite is affected by two forces: gravity, and the centripetal force.
For example, the Earth's moon is kept in orbit by the gravitational pull from the Earth. This is also the way the Earth is attracted to the Sun, and stays in its orbit. The orbit of the Earth's moon actually causes the tides and waves on Earth.
No moons that belong to moons have been found. In most cases, the tidal effects of the main body would make such as unstable.
However, math completed after the recent finding of a possible ring system around Saturn's moon Rhea show that Rhean orbits would be stable. Also, the rings are thought to be narrow, something that is known with shepherd moons.
The finding of 243 Ida's moon Dactyl in the early 1990s was the proof that some asteroids have moons; indeed, 87 Sylvia has two. Some, such as 90 Antiope, are double asteroids with two same-sized parts.
The biggest moons in the Solar System (those bigger than about 3000 km across) are Earth's moon, Jupiter's Galilean moons (Io, Europa, Ganymede, and Callisto), Saturn's moon Titan, and Neptune's captured moon Triton.
The following is a table grouping the moons of the solar system by diameter. The column on the right has some notable planets, dwarf planets, asteroids, and Trans-Neptunian Objects for comparing. It is normal for moons to be named after people from mythology.
Planets in our Solar System that have moon(s):
Planets in our Solar System that do not have moons:
Galaxies are found in groups called galaxy clusters which are also held together by gravitation. Our own Milky Way is the second largest galaxy in our Local Group (the largest is Andromeda). Many smaller galaxies and star clusters are also held in the Local Group, outside the two main galaxies. They are all in orbits round one of the centres of gravity. That means most of them move round either Andromeda or the Milky Way. so it seems natural for astronomers to use the term 'satellite' for these as well.
Our Local Group is itself part of an even larger group, the Virgo Supercluster. There are other, even larger, groups of galaxies: see the Great Wall for an example.
Gravity
Gravity, or gravitation is one of the fundamental forces of the universe. In this article, we discuss it in three parts:
Some physicists think gravity is caused by gravitons, but they are still unsure.
In everyday talk, we say things fall because the Earth's gravity pulls on them. We talk as if our weight was a "given". Actually, weight changes when the pull of gravity changes. The Moon is much smaller and the pull of gravity on the Moon is about 1/6th that of Earth. So any object on the Moon weighs 1/6th of its weight on Earth. What does not change is the amount of matter in an object. That is called conservation of mass. On Earth, mass and weight are the same for most purposes, though a sensitive gravimeter can detect the difference. The difference can be very different on another world such as the Moon.
From this we learn two things.
The Earth has mass. Every particle of matter has mass. So the Earth pulls on every object and person, and they pull on the Earth. This pulling force is called "gravity" and it gives weight.
These words mean almost the same thing in everyday use. Sometimes scientists use "gravity" for the force that pulls objects towards each other, and "gravitation" for the theory about the attraction.
According to one of his students, Galileo did a famous experiment about gravity where he dropped balls from the Tower of Pisa. He later rolled balls down inclines. With these experiments, Galileo showed that gravitation accelerates all objects at the same rate regardless of weight.
Johannes Kepler studied the motion of planets. In 1609 and 1616 he published his three laws governing the shape of their orbits and their speed along those orbits, but did not discover why they moved that way.
In 1687, English mathematician Isaac Newton wrote the "Principia". In this book, he wrote about the inverse-square law of gravitation. Newton, following an idea that had long been discussed by others, said that the closer two objects are to each other, the more gravity will affect them.
Newton's laws were used later to predict the existence of the planet Neptune based on changes in the orbit of Uranus, and again to predict the existence of another planet closer to the Sun than Mercury. When this was done, it was learned that his theory was not entirely correct. These mistakes in his theory were corrected by Albert Einstein's theory of General Relativity. Newton's theory is still commonly used for many things because it is simpler and is accurate enough for many uses.
Why does the Earth not fall into the Sun? The answer is simple but very important. It is because the Earth moving round the Sun is in a dynamic equilibrium. The speed of the Earth's movement creates a centrifugal force which balances the gravitational force between the Sun and the Earth. Why does the Earth continue spinning? Because there is no force to stop it.
Newton's first law: "If a body is at rest it remains at rest or if it is in motion it moves at the same speed "until it is acted on by an external force"".
There is a kind of analogy between "centrifugal force" and "gravitational force", which led to the "equivalence principle" of general relativity.
In free fall an object's motion balances out the pull of gravity on it. This includes being in orbit.
The special theory of relativity describes systems where gravity is not an issue; by contrast, gravity is the central issue of the general theory of relativity.
In general relativity "there is no gravitational force" deflecting objects from their natural, straight paths. Instead, gravity is seen as changes in the properties of space and time. In turn, this changes the straightest-possible paths that objects will naturally follow. The curvature is, in turn, caused by the energy–momentum of matter. Spacetime tells matter how to move; matter tells spacetime how to curve.
For weak gravitational fields and slow speeds relative to the speed of light, the theory's predictions converge on those of Newton's law of universal gravitation. Newton's equations are used to plan journeys in our Solar System.
General relativity has a number of physical consequences.
Gravity influences the passage of time. Light sent down into a is blueshifted, whereas light sent in the opposite direction (i.e., climbing out of the gravity well) is redshifted; collectively, these two effects are known as the "gravitational frequency shift".
More generally, processes close to a massive body run more slowly when compared with processes taking place farther away; this effect is known as gravitational time dilation.
General relativity predicts that the path of light is bent in a gravitational field; light passing a massive body is deflected towards that body. This effect has been confirmed by observing the light of stars or distant quasars being deflected as it passes the Sun.
Closely related to light deflection is the gravitational time delay (or Shapiro delay), the phenomenon that light signals take longer to move through a gravitational field than they would in the absence of that field. There have been numerous successful tests of this prediction.
A parameter called γ encodes the influence of gravity on the geometry of space.
Gravitational waves are ripples in the curvature of spacetime. They move as a wave, travelling outward from the source. Einstein predicted them in 1915 on the basis of his theory of general relativity. In theory, gravitational waves transport energy as gravitational radiation. Sources of detectable gravitational waves might include binary star systems composed of white dwarfs, neutron stars, or black holes. In general relativity, gravitational waves cannot travel faster than the speed of light.
The 1993 Nobel Prize in Physics was awarded for measurements of the Hulse-Taylor binary star system. These measurements suggested gravitational waves are more than mathematical peculiarities.
On February 11, 2016, the LIGO Scientific Collaboration and Virgo Collaboration teams announced that they had made the first observation of gravitational waves, originating from a pair of merging black holes using the Advanced LIGO detectors. On June 15, 2016, a second detection of gravitational waves from coalescing black holes was announced. Besides LIGO, many other gravitational-wave observatories (detectors) are under construction.
Centripetal force
Centripetal force is an accelerating force that acts on any body that revolves around a centre. This force contributes to keeping the body in rotation. This force is always directed towards the centre.
The opposite force (by Isaac Newton's third law of motion) is called centrifugal force. This is the force that acts on the body in a direction away from the centre, which contributes to making the body try to fly away. When you hold a rope with a heavy object attached to it, and rotate it around, the rope becomes tight and keeps the body from flying away. This is caused by centripetal force.
An example is a roller coaster which uses centripetal force to accelerate the carts so they will keep going in a circular motion. Even if an object changes direction but maintains at a constant speed it still counts as acceleration.
In the figure to the right we define the displacement vector formula_2 to represent motion in a circle. The magnitude of formula_2 is denoted as formula_4 and represents the radius of the particle's orbit.
Treaty
A treaty is a written agreement between two or more parties that consists international law. The parties may be countries or other important groups. A treaty may be about any subject.
Two countries might agree to stop a war, or declare war on a common enemy. Very common are treaties where a country promises to come to the aid of another country if the other country is attacked. Treaties about trade are also common. They may allow allow each other's citizens or merchandise to cross borders freely. The European Union is set up by treaties between most of the European nations. It arranges that trade is free between members.
In general, treaties are usually used to settle disputes, or to avoid disputes.