the-french-artist/wikipedia_20220301.simple_sentence_split huggingface dataset:
Navigable streams are sometimes called waterways, though the term may apply to any size of permanent and natural water feature except oceans.
In the United States, an intermittent stream is one that only flows for part of the year and is marked on topographic maps with a line of blue dashes and dots.
In desert areas of the American Southwest, this also includes washes, which only flow after thunderstorms or other significant rains.
A blue-line stream is one which flows for most or all of the year and is marked on topographic maps with a solid blue line.
In Australia, an intermittent stream is usually called a creek, and marked on topographic maps with a solid blue line.
Streams in geographic terms are awarded order designations.
A stream of the first order is a blue-line stream which does not have any other blue-line stream feeding into it.
A stream of the second order is one which is formed by the joining of two or more blue-line streams.
A third-order stream is one below the confluence of two or more second-order streams; a fourth-order stream is formed by the confluence of at least two third-order streams, and so forth.
Typically, streams are said to have a particular profile, beginning with steep gradients, no flood plain, and little shifting of channels, eventually evolving into streams with low gradients, wide flood plains, and extensive meanders.
The initial stage is sometimes termed a "young" stream, and the later state a "mature" or "old" stream.
However, a stream may meander for some distance before falling into a "young" stream condition.
The gradient of a stream is a critical factor in determining its character, and is entirely determined by its base level of erosion.
The base level of erosion is the point at which the stream either enters the ocean, a lake or pond, or enters a stretch in which it has a much lower gradient, and may be specifically applied to any particular stretch of a stream.
In geologic terms, the stream will erode down through its bed to achieve the base level of erosion throughout its course.
If this base level is low, then the stream will rapidly cut through underlying strata and have a steep gradient, and if the base level is relatively high, then the stream will form a flood plain and meanders.
When a stream flows over an especially resistant stratum and forms a waterfall or cascade, or the same results because for some reason the base level of erosion suddenly drops, perhaps as a result of a fault, the resulting sudden change in stream elevation is called a nickpoint.
The stream, of course, expends kinetic energy in "trying" to eliminate the nickpoint.
Meanders are looping changes of direction of a stream.
These may be somewhat sine-wave in form.
Typically, over time, the meanders don't disappear but gradually migrate downstream.
However, if some resistant material slows or stops the downstream movement of a meander, a stream may erode through the neck between two legs of a meander to become temporarily straighter, leaving behind an arc-shaped body of water termed an oxbow lake or bayou.
A flood may also result in a meander being cut through in this way.
The point of origin of a stream is often called the headwaters or source.
The entire basin drained by the stream is termed the watershed.
Every watershed is made up of smaller watersheds, while most watersheds are parts of larger watersheds.
For instance, the Continental Divide in North America divides the Atlantic Ocean watershed from the Pacific Ocean watershed, but the Atlantic Ocean watershed may be first divided into the Atlantic Ocean drainage and the Gulf of Mexico drainage.
This delineation within the United States is termed the Eastern Divide.
The Gulf of Mexico watershed may be divided into Mississippi River basin and a number of smaller watersheds, such as the Tombigbee River watershed.
The point at which a stream empties into an ocean or other large body of relatively level water is termed the mouth.
There may often be an estuary or delta at the mouth.
Some streams flow underground through unconsolidated sediments or through caves.
Especially with caves, a stream may flow aboveground for part of its course, and underground for part of its course.
When a stream emerges from an underground course, it is termed a spring.
waterway
The Solar System is the Sun and all the objects that orbit around it.
The Sun is orbited by planets, asteroids, comets and other things.
The Solar System is about 4.6 billion years old.
It formed by gravity in a large molecular cloud.
Most of this matter came together in the center, and the rest flattened into an orbiting disk that became the Solar System.
It is thought that almost all stars form by this process.
It makes up 99.9% of the Solar System's mass.
This means that it has strong gravity.
The other objects are pulled into orbit around the Sun.
The Sun is mostly made out of hydrogen, and some helium and higher elements.
From closest to farthest from the Sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
The first four planets are called terrestrial planets.
They are mostly made of rock and metal, and they are mostly solid.
The last four planets are called gas giants.
This is because they are much larger than other planets and are mostly made of gas.
Titan, one of Saturn’s moons, is the only moon in the solar system to have an Atmosphere.
The Solar System also contains other things.
There are asteroid belts, mostly between Mars and Jupiter.
Further out than Neptune, there is the Kuiper belt and the scattered disc.
These areas have dwarf planets, including Pluto, Makemake, Haumea, Ceres and Eris.
There are thousands of very small objects in these areas.
There are also comets, centaurs, and interplanetary dust.
In Ancient Greece, Aristarchus of Samos proposed the heliocentric model of the Solar System, where the Sun, is at the center of the known universe.
He is sometimes known as the "Greek Copernicus".
Six of the planets and three of the dwarf planets are orbited by moons.
There are about 200 moons in the Solar System.
Mercury and Venus have no moons, and Jupiter and Saturn have the largest number of moons.
The largest moon is Ganymede which is a moon of Jupiter.
Furthermore, planetary dust orbits the gas giants.
Many other systems like the Solar System have been found.
Each of the billions of stars in the Milky Way galaxy might have a planetary system.
This model, known as the nebular hypothesis, was developed in the 18th (1700s) century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace.
It has been adjusted by scientific disciplines such as astronomy, physics, geology, and planetary science.
As our knowledge of space has grown, the models have been changed to account for the new observations.
The Solar System has evolved considerably since its initial formation.
Many moons have formed from circling discs of gas and dust around their parent planets, while other moons are believed to have formed and were later captured by their planets.
Still others, as the Earth's Moon, may be the result of giant collisions.
Many collisions between bodies have occurred, and have been important to the evolution of the Solar System.
In the early stages, the positions of the planets sometimes shifted, and planets have switched places.
This planetary migration is thought to have been responsible for much of the Solar System's early evolution.
The Earth's orbit around the Sun is nearly a perfect circle, but when mapped it is found that the Earth moves around the Sun in a very slightly oval shaped orbit, called an elliptical orbit.
The other planets in the Solar System also orbits the Sun in slightly elliptical orbits.
Mercury has a more elliptical orbit than the others, and some of the smaller objects orbit the Sun in very eccentric orbits.
Discovery and exploration
For thousands of years, people had no need for a name for the "Solar System".
They thought the Earth stayed still at the center of everything (geocentrism).
Although the Greek philosopher Aristarchus of Samos suggested that there was a special order in the sky, Nicolaus Copernicus was the first to develop a mathematical system that described what we now call the "solar system".
This was called a new "system of the world".
In the 17th century, Galileo Galilei, Johannes Kepler and Isaac Newton began helping people understand physics more clearly.
People began to accept the idea that the Earth is a planet and moves around the Sun, and that the planets are worlds with the same physical laws that control Earth.
More recently, telescopes and space probes have led to discoveries of mountains and craters, and seasonal meteorological phenomena such as clouds, dust storms and ice caps on the other planets.
The eight planets
The planets are the biggest objects that go around the Sun.
It took people many years of using telescopes to find the objects that were farthest away.
New planets might still be found, and more small objects are found every year.
Most of the planets have moons that orbit around them just as the planets orbit the Sun.
There are at least 173 of these moons in the solar system.
Dwarf planets
This all changed on August 24, 2006, when the International Astronomical Union (IAU) gave a correct definition to the word "planet" for the first time.
By this definition, Pluto was not a planet anymore due to its irregular orbit and size.
It became a "dwarf planet" along with Eris and many others.
After this, Pluto was put on the list of minor planets and was downgraded in 2006 by astronomer Michael E Brown.
Instead they defined a new category of dwarf planet, into which Pluto did fit, along with some others.
These small planets are sometimes called plutinos.
There are a few main parts of the Solar System.
Here they are in order from the Sun, with the planets numbered, and the dwarf planets marked with the letters a - e.
The first four planets closest to the Sun are called the inner planets.
They are small and dense terrestrial planets, with solid surfaces.
They are made up of mostly rock and metal with a distinct internal structure and a similar size.
Three also have an atmosphere.
The study of the four planets gives information about geology outside the Earth.
Most asteroids are also often counted with the inner planets
Terrestrial planets region contains the four planets closest to the sun, all are rocky planets
(1) Mercury
(2) Venus
(3) Earth
(4) Mars
Asteroid belt region contains;
(a) Ceres (the only dwarf planet in this region)
Outer solar system
Gas giant planets region contains;
(5) Jupiter
(6) Saturn
(7) Uranus
(8) Neptune
Trans-Neptune region
Kuiper belt region contains;
(b) Pluto
(c) Haumea
(d) Makemake
Kuiper belt objects and possibly other dwarf planets
short-period comets
Scattered disc region contains;
(e) Eris
Scattered disk objects and possibly other dwarf planets
The Oort cloud is separate from the trans-Neptune region, and much farther out.
It contains the long-period comets.
Ecliptic plane
The plane of the ecliptic is defined by the Earth's orbit around the Sun.
All of the planets orbit the Sun roughly around this same orbital plane.
The farther away from this plane a planet orbits, the more inclined is its orbit to the ecliptic.
If you could look at the solar system "edge on" then all the planets would be orbiting more or less in the plane of the ecliptic.
Your Weight on Other Worlds
Solar System Citizendium
The Planets in the Solar System
Saturn is the sixth planet from the Sun located in the Solar System.
It is the second largest planet in the Solar System, after Jupiter.
Saturn is one of the four gas giant planets, along with Jupiter, Uranus, and Neptune.
Saturn is the English transliteration from the Latin word Saturnus, in Roman religion, the god of sowing or seed.
The Romans equated him with the Greek agricultural deity Kronos.
Saturn was named after the Roman god Saturnus (called Kronos in Greek mythology).
Saturn's symbol is ♄ which is the symbol of Saturnus' sickle.
Saturn has 82 known moons orbiting the planet.
53 are officially named and 29 are waiting to be named.
The largest moon is Titan, which is larger in volume than the planet Mercury.
Titan is the second-largest moon in the Solar System.
The largest moon is Jupiter's moon, Ganymede.
There is also a very large system of rings around Saturn.
These rings are made of ice with smaller amounts of rocks and dust.
Some people believe that the rings were caused by a moon impact or other event.
Saturn is about 1,433,000,000 km (870,000,000 mi) on average from the Sun.
Saturn takes 29.6 Earth years to revolve around the Sun.
Physical features
Saturn is an oblate spheroid, meaning that it is flattened at the poles, and it swells out around its equator.
The planet's equatorial diameter is , while its polar diameter (the distance from the north pole to the south pole) is ; a 9% difference.
Saturn has a flattened shape due to its very fast rotation, once every 10.8 hours.
Saturn is the only planet in the Solar System that is less dense than water.
Even though the planet's core is very dense, it has a gaseous atmosphere, so the average specific density of the planet is 0.69 g/cm3.
This means if Saturn could be placed in a large pool of water, it would float.
The outer part of Saturn's atmosphere is made up of about 96% hydrogen, 3% helium, 0.4% methane and 0.01% ammonia.
There are also very small amounts of acetylene, ethane and phosphine.
Saturn's clouds show a banded pattern, like the cloud bands seen on Jupiter.
Saturn's clouds are much fainter and the bands are wider at the equator.
Saturn's lowest cloud layer is made up of water ice, and is about  thick.
The temperature here is quite low, at 250 K (-10°F, -23°C).
However scientists do not agree about this.
The layer above, about  thick, is made up of ammonium hydrosulfide ice, and above that is a layer of ammonia ice clouds  thick.
The highest layer is made up of hydrogen and helium gases, which extends between  and  above the water cloud tops.
Auroras are also known to form in Saturn in the mesosphere.
The temperature at Saturn's cloud tops is extremely low, at 98 K (-283 °F, -175 °C).
The temperatures in the inner layers are much higher than the outside layers because of the heat produced by Saturn's interior.
Storms and spots
Saturn's atmosphere is also known to form oval shaped clouds, similar to the clearer spots seen in Jupiter.
These oval spots are cyclonic storms, the same as cyclones seen on Earth.
In 1990, the Hubble Space Telescope found a very large white cloud near Saturn's equator.
Storms like the one in 1990 were known as Great White Spots.
These unique storms only exist for a short time and only happen about every 30 Earth years, at the time of the summer solstice in the Northern Hemisphere.
Great White Spots were also found in 1876, 1903, 1933, and 1960.
If this cycle continues, another storm will form in about 2020.
The Voyager 1 spacecraft found a hexagonal cloud pattern near Saturn's north pole at about 78°N. The Cassini−Huygens probe later confirmed it in 2006.
Unlike the north pole, the south pole does not show any hexagonal cloud feature.
The probe also discovered a hurricane-like storm locked to the south pole that clearly showed an eyewall.
Until this discovery, eyewalls had only been seen on Earth.
Saturn's interior is similar to Jupiter's interior.
It has a small rocky core about the size of the Earth at its center.
It is very hot; its temperature reaches 15,000 K ().
Saturn is so hot that it gives out more heat energy into space than it receives from the Sun.
Above it is a thicker layer of metallic hydrogen, about  deep.
Above that layer is a region of liquid hydrogen and helium.
The core is heavy, with about 9 to 22 times more mass than the Earth's core.
Saturn has a natural magnetic field that is weaker than Jupiter's.
Like the Earth's, Saturn's field is a magnetic dipole.
Saturn's field is unique in that it is perfectly symmetrical, unlike any other known planet.
This means the field is exactly in line with the planet's axis.
Saturn generates radio waves, but they are too weak to be detected from Earth.
The moon Titan orbits in the outer part of Saturn's magnetic field and gives out plasma to the field from the ionised particles in Titan's atmosphere.
Rotation and orbit
Saturn's average distance from the Sun is over 1,400,000,000 km (869,000,000 mi), about nine times the distance from the Earth to the Sun.
It takes 10,759 days, or about 29.8 years, for Saturn to orbit around the Sun.
This is known as Saturn's orbital period.
Voyager 1 measured Saturn's rotation as being 10 hours 14 minutes at the equator, 10 hours 40 minutes closer to the poles, and 10 hours 39 minutes 24 seconds for the planet's interior.
This is known as its rotational period.
Cassini measured the rotation of Saturn as being 10 hours 45 minutes 45 seconds ± 36 seconds.
That is about six minutes, or one percent, longer than the radio rotational period measured by the Voyager 1 and Voyager 2 spacecraft, which flew by Saturn in 1980 and 1981.
Saturn's rotational period is calculated by the rotation speed of radio waves released by the planet.
The Cassini−Huygens spacecraft discovered that the radio waves slowed down, suggesting that the rotational period increased.
Since the scientists do not think Saturn's rotation is actually slowing down, the explanation may lie in the magnetic field that causes the radio waves.
Planetary rings
Saturn is best known for its planetary rings which are easy to see with a telescope.
There are seven named rings; A, B, C, D, E, F, and G rings.
They were named in the order they were discovered, which is different to their order from the planet.
From the planet the rings are: D, C, B, A, F, G and E.
Scientists believe that the rings are material left after a moon broke apart.
A new idea says that it was a very large moon, most of which crashed into the planet.
This left a large amount of ice to form the rings, and also some of the moons, like Enceladus, which are thought to be made of ice.
The rings were first discovered by Galileo Galilei in 1610, using his telescope.
They did not look like rings to Galileo, so he called them "handles".
He thought that Saturn was three separate planets that almost touched one another.
In 1612, when the rings were facing edge on with the Earth, the rings disappeared, then reappeared again in 1613, further confusing Galileo.
In 1655, Christiaan Huygens was the first person to recognise Saturn was surrounded by rings.
Using a much more powerful telescope than Galilei's, he noted Saturn "is surrounded by a thin, flat, ring, nowhere touching...".
In 1675, Giovanni Domenico Cassini discovered that the planet's rings were in fact made of smaller ringlets with gaps.
The largest ring gap was later named the Cassini Division.
In 1859, James Clerk Maxwell showed that the rings cannot be solid, but are made of small particles, each orbiting Saturn on their own, otherwise, it would become unstable or break apart.
James Keeler studied the rings using a spectroscope in 1895 which proved Maxwell's theory.
The rings range from  to  above the planet's equator.
While the equatorial circumference of Saturn is 378,675 km (235,298 miles).As proved by Maxwell, even though the rings appear to be solid and unbroken when viewed from above, the rings are made of small particles of rock and ice.
They are only about  thick; made of silica rock, iron oxide and ice particles.
The smallest particles are only specks of dust while the largest are the size of a house.
The C and D rings also seem to have a "wave" in them, like waves in water.
These large waves are  high, but only moving slowly at about  each day.
Some scientists believe that the wave is caused by Saturn's moons.
Another idea is the waves were made by a comet hitting Saturn in 1983 or 1984.
The largest gaps in the rings are the Cassini Division and the Encke Division, both visible from the Earth.
The Cassini Division is the largest, measuring  wide.
However, when the Voyager spacecrafts visited Saturn in 1980, they discovered that the rings are a complex structure, made out of thousands of thin gaps and ringlets.
Scientists believe this is caused by the gravitational force of some of Saturn's moons.
The tiny moon Pan orbits inside Saturn's rings, creating a gap within the rings.
Other ringlets keep their structure due to the gravitational force of shepherd satellites, such as Prometheus and Pandora.
Other gaps form due to the gravitational force of a large moon farther away.
The moon Mimas is responsible for clearing away the Cassini gap.
Recent data from the Cassini spacecraft has shown that the rings have their own atmosphere, free from the planet's atmosphere.
The rings' atmosphere is made of oxygen gas, and it is produced when the Sun's ultraviolet light breaks up the water ice in the rings.
Chemical reaction also occurs between the ultraviolet light and the water molecules, creating hydrogen gas.
The oxygen and hydrogen atmospheres around the rings are very widely spaced.
As well as oxygen and hydrogen gas, the rings have a thin atmosphere made of hydroxide.
This anion was discovered by the Hubble Space Telescope.
The Voyager space probe discovered features shaped like rays, called spokes.
These were also seen later by the Hubble telescope.
The Cassini probe photographed the spokes in 2005.
They are seen as dark when under sunlight, and appear light when against the unlit side.
At first it was thought the spokes were made of microscopic dust particles but new evidence shows that they are made of ice.
They rotate at the same time with the planet's magnetosphere, therefore, it is believed that they have a connection with electromagnetism.
However, what causes the spokes to form is still unknown.
They appear to be seasonal, disappearing during solstice and appearing again during equinox.
Saturn has 53 named moons, and another 29 which are still being studied.
Many of the moons are very small: 33 are less than  in diameter and 13 moons are less than .
Seven moons are large enough to be a near perfect sphere caused by their own gravitation.
These moons are Titan, Rhea, Iapetus, Dione, Tethys, Enceladus and Mimas.
Titan is the largest moon, larger than the planet Mercury, and it is the only moon in the Solar System to have a thick, dense atmosphere.
Hyperion and Phoebe are the next largest moons, larger than  in diameter.
In December 2004 and January 2005 a man-made satellite called the Cassini−Huygens probe took lots of close photos of Titan.
One part of this satellite, known as the Huygens probe, then landed on Titan.
Named after the Dutch astronomer Christiaan Huygens, it was the first spacecraft to land in the outer Solar System.
The probe was designed to float in case it landed in liquid.
Enceladus, the sixth largest moon, is about  in diameter.
It is one of the few outer solar system objects that shows volcanic activity.
In 2011, scientists discovered an electric link between Saturn and Enceladus.
This is caused by ionised particles from volcanos on the small moon interacting with Saturn's magnetic fields.
Similar interactions cause the northern lights on Earth.
Saturn was first explored by the Pioneer 11 spacecraft in September 1979.
It flew as close as  above the planet's cloud tops.
It took photographs of the planet and a few of its moons, but were low in resolution.
It discovered a new, thin ring called the F ring.
It also discovered that the dark ring gaps appear bright when viewed towards the Sun, which shows the gaps are not empty of material.
The spacecraft measured the temperature of the moon Titan.
In November 1980, Voyager 1 visited Saturn and took higher resolution photographs of the planet, rings, and moons.
These photos were able to show the surface features of the moons.
Voyager 1 went close to Titan and gained much information about its atmosphere.
In August 1981, Voyager 2 continued to study the planet.
Photos taken by the space probe showed that changes were happening to the rings and atmosphere.
The Voyager spacecraft discovered a number of moons orbiting close to Saturn's rings, as well as discovering new ring gaps.
On July 1, 2004, the Cassini−Huygens probe entered into orbit around Saturn.
Before then, it flew close to Phoebe, taking very high-resolution photos of its surface and collecting data.
On December 25, 2004, the Huygens probe separated from the Cassini probe before moving down towards Titan's surface and landed there on January 14, 2005.
It landed on a dry surface, but it found that large bodies of liquid exist on the moon.
The Cassini probe continued to collect data from Titan and a number of the icy moons.
It found evidence that the moon Enceladus had water erupting from its geysers.
Cassini also proved, in July 2006, that Titan had hydrocarbon lakes, located near its north pole.
In March 2007, it discovered a large hydrocarbon lake the size of the Caspian Sea near its north pole.
Cassini observed lightning occurring in Saturn since early 2005.
The power of the lightning was measured to be 1,000 times more powerful than lightning on Earth.
Astronomers believe that the lightning observed in Saturn is the strongest ever seen.
Refers to the level of one bar atmospheric pressure
Orbital information is based on the barycentre of the Saturn system, the centre of mass, not the geometric centre.
Barycentre measurements are used because they are not changed by the daily movement of the moons.
Theoretical description of the rings of Saturn.
A WAV file of radio emissions from Saturn.
Slavery is when a person is treated as the property of another person.
This person is usually called a slave, with the owner being called a slavemaster.
It often means that slaves are forced to work, or else they will be punished by the law (if slavery is legal in that place) or by their master.
There is evidence that even before there was writing, there was slavery.
There have been different types of slavery, and they have been in almost all cultures and continents.
Some societies had laws about slavery, or they had an economy that was built on it.
Ancient Greece and Ancient Rome had many slaves.
During the 20th century almost all countries made laws forbidding slavery.
The Universal Declaration of Human Rights says that slavery is wrong.
Slavery is now banned by international law.
Nevertheless, there are still different forms of slavery in some countries.
The English word "slave" comes from the medieval word for the Slavic peoples of Central Europe and Eastern Europe, because these were the last ethnic group to be captured and enslaved in Central Europe.
According to Adam Smith and Auguste Comte, a slave was mainly defined as a captive or prisoner of war.
Slave-holders used to buy slaves at slave auctions.
In many cases slaves are not allowed rights.
Early civilizations
Slavery has existed for a long time.
Early hunter-gatherers had no use for slaves.
They did everything for themselves.
Having another pair of hands to help them meant another mouth to feed.
Slavery or owning another person made no sense to these people.
Once men gathered in cities and towns and there was more than enough food, having a cheap supply of labor made sense.
This is when the earliest forms of slavery appeared.
Slavery can be traced back to the earliest records, such as the Code of Hammurabi (c. 1760 BC).
This refers to it as an established institution.
In the Ancient Near East, captives obtained through warfare often became slaves.
This was seen by the laws in the Bible book of  Deuteronomy as a legal form of slavery.
But the Israelites were not allowed to enslave other Israelites.
The Deuteronomic Code calls for the death penalty for the crime of kidnapping Israelites to enslave them.
In Ancient Egypt, slaves were mainly prisoners of war.
Other ways people could become slaves was by inheriting the status from their parents who were slaves.
Someone could become a slave if he could not pay his debts.
People also sold themselves into slavery because they were poor peasants and needed food and shelter.
The lives of slaves were normally better than that of peasants.
Young slaves could not be put to hard work, and had to be brought up by the mistress of the household.
Not all slaves went to houses.
Some also sold themselves to temples, or were assigned to temples by the king.
Slave trading was not very popular until later in Ancient Egypt.
Afterwards, slave trades sprang up all over Egypt.
Slavery in ancient Rome
Slaves were important in society and the economy of ancient Rome.
They did simple manual labor and domestic services, but also could have complex jobs and professions.
Teachers, accountants, and physicians were often slaves.
Greek slaves were often highly educated.
Most slaves, like those sentenced to slavery as punishment, worked on farms, in mines, and at mills.
Their living conditions were brutal, and their lives short.
Slaves were considered property under Roman law and had no legal personhood.
Unlike Roman citizens, they could suffer corporal punishment, sexual exploitation (sex workers were often slaves), torture, and summary execution legally.
Slave's words could not be accepted in a court of law unless the slave was tortured—a practice based on the belief that slaves would be too loyal to their masters reveal damaging evidence unless coerced.
Over time, however, slaves gained some legal protection, including the right to file complaints against their masters.
Attitudes changed in part because of the influence among the educated elite of the Stoics, whose egalitarian views of humanity extended to slaves, and because of slave rebellions.
Roman slaves could hold property which, even though it belonged to their masters, they were allowed to use as if it were their own.
Upper class slaves were allowed to earn their own money.
With enough money they could buy their freedom.
The Arab slave trade
Historians estimate that between 650 AD and the 1960s, 10 to 18 million people were enslaved by Arab slave traders.
They were taken from Europe, Asia and Africa across the Red Sea, Indian Ocean, and Sahara desert.
Male slaves were often employed as servants, soldiers, or workers by their owners.
Many male slaves were castrated.
It is estimated that as many as 6 out of every 10 boys bled to death during the process.
But the high price of Eunuchs made it worthwhile.
According to Ronald Segal, author of Islam’s Black Slaves: The Other Black Diaspora (2002), "The calipha in Baghdad at the beginning of the 10th Century had 7,000 black eunuchs and 4,000 white eunuchs in his palace”.
Women and children taken as slaves were mainly used as servants and concubines.
While the later Atlantic slave trade concentrated on men for labor, the Arab slave trade started with men and boys, but shifted over time to concentrate more on woman and young girls for sexual purposes.
By the 1900s, Arab slave traders had taken between 10 and 20 million slaves out of Africa.
The Atlantic slave trade
For four centuries, beginning in the late 15th century, millions of Africans were taken as slaves by Europeans.
Europeans began exporting Africans to the New World as a source of cheap labor on colonial plantations.
Between 1452 and 1455, Pope Nicolas V issued a series of papal bulls authorizing the Portuguese to take African slaves.
At first slave traders raided coastal areas and carried black people off.
But the mines and fields of the colonies needed more and more slaves.
In the early 16th century Spain began to issue licenses and contracts to supply slaves.
By the 1750s large slaving companies were established.
Most of Europe at the time was involved in the slave trade.
Many Europeans who arrived in North America during the 17th and 18th centuries came under contract as indentured servants.
The change from indentured servitude to slavery was a gradual process in Virginia.
The earliest legal documentation of such a shift was in 1640.
This is where an African, John Punch, was sentenced to lifetime slavery for attempting to run away.
This case also marked the disparate treatment of Africans as held by the Virginia County Court, where two white runaways received far lesser sentences.
After 1640, planters started to ignore the expiration of indentured contracts.
They kept their servants as slaves for life.
This was demonstrated by the case Johnson v. Parker.
The court ruled that John Casor, an indentured servant, be returned to Johnson who claimed that Casor belonged to him for his life.
According to the 1860 U. S. census, 393,975 individuals, representing 8% of all US families, owned 3,950,528 slaves.
One-third of Southern families owned slaves.
Slavery in United States was legally abolished by Thirteenth Amendment to the United States Constitution in 1865.
Slavery today
Millions of people are still slaves in some parts of the world, mostly in South Asia and Africa.
It is less common in the developed world because of better law enforcement, but it still happens there as well.
The ways in which it is done have changed.
Today, slaves may work because of things like a high debt (for example, slaves have to work to pay off a debt).
Many victims are told that their families will be harmed if they report the slave owners.
Many slaves are forced to be domestic servants.
In some cases, their families sell them to the slave owners.
Some slaves have been trafficked from one part of the world to another.
These people are illegally in their host country, and therefore do not report the abuse.
Forced prostitution is a type of slavery.
Another form of slavery still happening today is forced child labor.
Some children have to work in mines or in plantations, or they have to fight wars as child soldiers, for no pay.
Some of the countries where there is still slavery are in Africa, the Middle East, and South Asia.
In summer 2007, 570 people were found to be slaves for brick makers in China.
They included 69 children.
The Chinese government made a force of 35,000 police check northern Chinese brick kilns for slaves, and sent lots of kiln supervisors and officials to prison and sentenced one kiln foreman to death for killing a worker who was a slave.
In Mauritania, it is thought that up to 600,000 men, women and children, or 20% of the population, are slaves, and that many of them are used as bonded labour.
Slavery in Mauritania was made illegal in August 2007.
In Niger, there is also much slavery.
A Nigerian study has found that more than 800,000 people are slaves, almost 8% of the population.
Child slavery has commonly been used when making cash crops and mining.
According to the United States Department of State, more than 109,000 children were working on cocoa farms alone in Côte d'Ivoire (Ivory Coast) in 'the worst forms of child labour' in 2002.
In November 2006, the International Labour Organization said that it would prosecute members of the junta that rules Myanmar (also called Burma) at the International Court of Justice for "Crimes against Humanity".
This is because the military makes some citizens do forced labour.
The International Labour Organisation says that it thinks that about 800,000 people are forced to work this way.
Stopping slavery
An agitation called Abolitionism against slavery began in Christian countries in the 18th century.
First they abolished the slave trade so more people wouldn't become slaves.
In 1833, the British Empire stopped slavery.
Several other countries followed.
In the United States, disagreement over slavery led to the American Civil War and the Emancipation Proclamation.
In 1865, when the North won, all slaves were made free.
Still more countries abolished slavery afterwards.
Pedro II of Brazil abolished it in 1888.
Forced labor however continued, either against the law or by debt peonage or other methods which the laws of the various countries did not count as slavery.
Famous people who were slaves
Aesop circa 6th century BC
Spartacus (died 71 BC)
Epictetus (about AD 55 - AD 125)
Pope Callixtus I (died AD 222)
Saint Patrick (about AD 387-461)
Olaudah Equiano (about 1745-1790)
George John Scipio Africanus (1763-1834)
Denmark Vesey (about 1767-1822)
Sojourner Truth (about 1797-1883)
Dred Scott (about 1799-1845)
Nat Turner (1800-1831)
Harriet Jacobs (about 1813-1897)
Frederick Douglass (about 1818-1895)
Harriet Tubman (1820-1913)
(1830-1882)
Booker T. Washington (1856-1915)
Unfree labour
Many philosophies and religions say that a soul is the part of a living human being which is supernatural and lives after death.
It is usually said to be immortal.
It cannot be discovered by science, because it cannot be tested in any controlled way.
Many different opinions exist as to what happens to personal experience after death.
Reincarnation is a belief that after the body dies, the soul will be born again in another body.
It is important to Hinduism.
Buddhists understand the idea of an eternal soul, and the idea of simple annihilation as delusion; they say that there is no unchanging, permanent self, soul or essence in phenomena.
Buddhists believe in transmigration, or rebirth in samsara or other planes of existence, based on how they understand kamma (Pāli; karma in Sanskrit), and nibbana (nirvana in Sanskrit) for Enlightened ones.
Resurrection is the Christian belief that a soul returns in the same body.
In most Christian denomination this was realized in Jesus Christ but is also the promise for all souls; see heaven, hell, and Final Judgement.
In popular culture, soul usually means deep feeling and commitment.
It is in this sense that the word appears in the term soul music.
However that music was also influenced by gospel music which was religious.
One popular idea about souls that is easy to express, is that a person is a soul, and has a body.
The soul is the "I" in "I exist" that feels and lives life.
What people call the mind could be part of the soul: one soul started this article, other souls have edited it, and another soul is reading it.
This view, however, implies that the human body is a possession, and seems to devalue bodies that do not have souls as defined or understood by the speaker (some people say that animals, heretics, and people of another religion do not have souls).
Like most uses of the verb to be, there is an ideology in these simple words.
Christianity teaches that all humans have an immortal soul.
This means that it is a part of them which does not die when their physical body dies, but lives on with them to heaven or to hell.
Christians believe that the soul is the 'breath of life' which God gave to Adam.
In Japan the soul is believed to weigh 21 grams.
This belief may have been influenced by the observations of Dr. McDougall in the early 1900s.
One distinction often made is between soul, which is distinct from other souls, and spirit which may be combined with that of other beings.
The idea of the Holy Spirit in Christianity, for example, is a universal and shared spirit many souls are part of, and which is expressed on Earth in that faith by "the Church" meaning "the body of Christ" meaning "all bodies that follow Jesus."
This could be more inclusive than the is/has view of souls and bodies.
Death customs
Soap is a chemical compound resulting from the reaction of an alkali (commonly sodium or potassium hydroxide) with a fatty acid.
Soaps are the metallic salts of long chain fatty acids.
When mixed with water during bathing or washing, they help people and clothes get clean by lowering the chance of dirt and oil to get to the skin or fabric.
Soaps are made from animal fats or vegetable oils.
There are two basic steps in making soap.
They are called Saponification and Salting-out of soap.
Some people like to make their own soap.
Soap cleans very well in soft water.
It is not toxic to water life.
It can be broken down by bacteria.
However, it is slightly soluble in water, so it is not often used in washing machines.
It does not work well in hard water.
It cannot be used in strongly acidic solutions.
Mild hand soaps are only basic enough to remove unwanted skin oils.
For other forms of oil, dishwashing soap is strong enough to remove almost all forms of oil without damaging petroleum products such as plastics.
It does not damage skin either.
Soap has been made in many ways.
Humanity has used soap-like things for thousands of years.
The earliest recorded evidence of the making of soap-like materials dates back to around 2800 BC in Ancient Babylon and Sumeria.
They were soap solutions, or soapy water.
People made them by mixing ashes with water and fat and boiling them.
The Babylonians used water, alkali and cassia to make soap.
A recipe for solid soap appeared in about 800 c.e.
Gauls added salt to the soap solution to make the solid soap fall out.
The Ebers papyrus (Egypt, 1550 BC) suggests that ancient Egyptians bathed often and had animal and vegetable oils with alkaline salts to make a soap-like substance.
Egyptian documents say that a soap-like substance was used in the preparation of wool for weaving.
A summary is a condensed explanation of an event, story, document, etc.. i.e. "summing up the facts."
They are not constrained to any medium or topics.
Not to be confused with abstract, which is a summary of a document.
There are many different levels of summarization that can be done.
The summarizer may choose any length, but the sumarees may not appreciate anything more than absolutely necessary to get the required facts.
Summaries help to spread information fast.
They also help people make decisions on if it is something worth looking further into.
A quick "good/bad" can suffice in some situations.
In other situations, the summary may rival the length of the original.
"This book was really cool.
This guy drives a pickup to work everyday, and has a dangerous job."
A service is a job or work done for someone else.
All the service trades in a place form a service economy.
The service economy can be in a region like a country or in a town or city.
Often, the person who gives the service will get something in return for the service.
The person who gives the service can get money in return.
The person who gives the service can get goods in return.
The person who gives the service can get another service in return.
This is a type of trade.
There are several meanings of the word sense.
This page is for disambiguation - there are more detailed articles on each meaning:
When a word has several meanings, one can refer to it as being used "in the sense of..." some context or other.
In Simple English for instance we avoid using words in unusual senses.
The sensory system of animals
Hearing is the sense of sound that comes into our ears.
Sight is the sense of seeing things with our eyes.
Touch is the sense of feeling things with our skin.
Taste is the sense of the flavor of things with our tongues
Smell is the sense of smelling things with our noses.
Kinesthetic sense is knowing where your whole body is and where it is not.
Other animals may have other senses.
Fish have lateral lines which detect changes in the water pressure around them, and some can detect changes in electric fields around them.
Sense in language
Another use is to flag whether an argument or statement is correct and understood.
"That makes no sense" or "That is nonsense" are examples from everyday speech.
A variation of this is to say that something does not make "economic sense".
Usually these words signal a political dispute or some failure to define terms correctly.
The term "common sense" is thinking based on a wide experience of life.
It used to mean practical wisdom.
It has a long history of being used in politics, often to mean that some idea will be accepted or rejected because of human nature (what people are like).
In Hebrew, a synagogue is called beit knesset, which means, a "house of gathering".
The word "synagogue" comes from sunagoge, which is a Greek word.
In a synagogue, Jews carry out the Jewish services, which consist of prayers, sometimes with special actions.
A synagogue will usually have a large room for prayers.
There might be some smaller rooms for studying.
There will be some offices.
There will also usually be a big room for special events.
The front of a synagogue faces towards Jerusalem in Israel.
In the front is the holiest part of the synagogue, the Ark. This is a closet which has the Torah scrolls inside.
The Torah scrolls have the holy writings of Judaism on them.
The Ark usually has a curtain in front of it.
On top of the Ark is light which is always lit, called the “Eternal Lamp”.
It is a symbol which means that God is always there.
Every synagogue has a raised platform called the “Bimah”.
The person who reads the Torah scroll stands there when he reads.
The Bimah is either in the middle of the hall, or in front of the Ark.
In some synagogues men and women sit in different places.
Some synagogues even have a short wall so that they can not see each other.
This is so that the people will think about the prayers better.
Jews may call synagogues by different names.
Many Orthodox and Conservative Jews living in English-speaking countries use the name "synagogue" or the word "shul", which is Yiddish.
Jews who speak Spanish or Portuguese call synagogues esnoga.
Some Jews call the synagogue a temple.
Jewish worship does not have to be carried out in a synagogue.
It can be wherever a minyan of ten Jews are.
It could be in someone's home or anywhere such as a cruise liner or an airplane.
Some synagogues have a separate room or torah study, this is called the "beth midrash" meaning house of study.
Some kinds of Jewish worship can be done alone or with fewer than ten people.
Scarcity in economics is the lack of various forms of capital.
Scarcity can be used to describe an economic situation in economics, or it can be used to describe more general situations.
In economics, scarcity is the result of people having "Unlimited Wants and Needs," or always wanting something new, and having "Limited Resources."
Limited Resources means that there are never enough resources, or materials, to satisfy, or fulfill, the wants and needs that every person have.
Scarcity is called the "basic economic problem," meaning that it always exists.
Scarcity exists due to the effects of nature such as drought, floods, storms, pest infestation, fire and other things.
Real scarcity can also exist by over use of non-renewable resources.
Goods (things) and services are also scarce because there are only a limited number of things in the world and due to the limits of technology and our own priorities.
More scarce goods and services have higher prices, because of supply and demand.
Gold is used less than iron, but the price of gold is much higher, because gold is more scarce.
Lawyers are paid more than janitors, because there is scarcity of qualified lawyers.
Scarcity of capital is the main constraint in economic development of developing countries.
Economic growth is an increase in the production and consumption of goods and services.
It entails increasing population or per capita consumption.
It is represented by increasing Gross Domestic Product (GDP).
Scarcity refers to limited resources.
These resources are the inputs of production i.e., land, labor and capital.
Artificial scarcity
Artificial scarcity is when somebody limits the amount of goods or services that are available, although it would be simple to make more.
Artificial scarcity can increase profits for a business.
Some people will pay more for something that is scarce, because it shows that they are rich (a status symbol).
Copyrights, patents, monopolies, cartels, planned obsolesence can make artificial scarcity.
Readability, or textual difficulty, means how easy or hard a text is to read.
Research has shown that two main factors affect the ease with which texts are read.
How difficult the words are: this is lexical difficulty.
Rare words are less well known than common words.
Rare, difficult words are often longer than common, easy words.
How difficult the sentences are: this is syntactical difficulty.
Long, complicated sentences cause more difficulty than short, simple sentences.
Readability predictions
A readability test is a way to measure a text for how easy it is to read.
Readability tests give a prediction as to how difficult readers will find a particular text.
They do this by measuring one or both of the two main causes, as follows:
Word difficulty
In 1923, Bertha A. Lively and Sidney L. Pressey published the first reading ease  formula.
They had been concerned that science textbooks in junior high school had so many technical words.
They felt that teachers spent all class time explaining their meaning.
They argued that their formula would help to measure and reduce the “vocabulary burden” of textbooks.
Their formula used the Thorndike word list as a basis.
Manually, it took three hours to apply the formula to a book.
Vocabulary lists