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, but it will also have DNA from the
apple flower that pollinated the see
ds, which may well be a different typ
e. This means that the tree which wou
ld grow from planting would be a mixt
ure of two. In order to grow a certai
n type of apple, a small twig, or 'sc
ion', is cut from the tree that grows
the type of apple desired, and then
added on to a specially grown stump c
alled a rootstock. The tree that grow
s will only create apples of the type
needed.There are more than 7,500 kno
wn cultivars (varieties) of apples. D
ifferent cultivars are available for
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temperate and subtropical climates. O
ne large collection of over 2,100 app
le cultivars is at the National Fruit
Collection in England. Most of these
cultivars are grown for eating fresh
(dessert apples). However, some are
grown simply for cooking or making ci
der. Cider apples are usually too tar
t to eat immediately. However, they g
ive cider a rich flavor that dessert
apples cannot.Most popular apple cult
ivars are soft but crisp. Colorful sk
in, easy shipping, disease resistance
, 'Red Delicious' apple shape, and po
pular flavor are also needed. Modern
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apples are usually sweeter than older
cultivars. This is because popular t
astes in apples have become different
. Most North Americans and Europeans
enjoy sweet apples. Extremely sweet a
pples with hardly any acid taste are
popular in Asia and India.In the Unit
ed Kingdom In the United Kingdom ther
e are about 3000 different types of a
pples. The most common apple type gro
wn in England is the 'Bramley seedlin
g', which is a popular cooking apple.
Apple orchards are not as common as t
hey were in the early 1900s, when app
les were rarely brought in from other
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countries. Organizations such as Com
mon Ground teach people about the imp
ortance of rare and local varieties o
f fruit.In North America Many apples
are grown in temperate parts of the U
nited States and Canada. In many area
s where apple growing is important, p
eople have huge celebrations: Annapol
is Valley Apple Blossom Festival - he
ld five days every spring (May-June)
in Nova Scotia Shenandoah Apple Bloss
om Festival - held six days every spr
ing in Winchester, Virginia. Washingt
on State Apple Blossom Festival - hel
d two weeks every spring (April-May)
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in Wenatchee, WashingtonVarieties of
apples There are many different varie
ties of apples, including: Aport Cox'
s Orange Pippin Fuji (apple) Gala Gol
den Delicious (sometimes called a Gre
en Delicious Apple) Granny Smith Jona
than Jonagold McIntosh Pink Lady Red
Delicious WinesapFamily Apples are in
the group Maloideae. This is a subfa
mily of the family Rosaceae. They are
in the same subfamily as pears.Refer
encesFurther reading Potter D. et al
2007. Phylogeny and classification o
f Rosaceae. Plant Systematics and Evo
lution. 266 (1–2): 5–43.Other website
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s Basic English 850 words Rosaceae
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An Abrahamic Religion is a religion w
hose followers believe in the prophet
Abraham. They believe Abraham and hi
s sons/grandsons hold an important ro
le in human spiritual development. Th
e best known Abrahamic religions are
Judaism, Christianity and Islam. Smal
ler religious traditions sometimes in
cluded as Abrahamic religions are Sam
aritanism, Druze, Rastafari, Babism a
nd Bahá'í Faith. Mandaeism (a religio
n that holds many Abrahamic beliefs)
is not called Abrahamic because its f
ollowers think Abraham was a false pr
ophetTrue Abrahamic religions are mon
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otheistic (the belief that there is o
nly one God). They also all believe t
hat people should pray to God and wor
ship God often. Among monotheistic re
ligions, the Abrahamic religions have
the world's largest number of follow
ers. They are also all ethical monoth
eistic religions. This means they hav
e rules that they have to follow.Reli
gions
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Algebra (from Arabic: الجبر, transli
terated "al-jabr", meaning "reunion o
f broken parts") is a part of mathema
tics. It uses variables to represent
a value that is not yet known. When a
n equals sign (=) is used, this is ca
lled an equation. A very simple equat
ion using a variable is: . In this ex
ample, , or it could also be said tha
t " equals five". This is called solv
ing for .Besides equations, there are
inequalities (less than and greater
than). A special type of equation is
called the function. This is often us
ed in making graphs because it always
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turns one input into one output.Alge
bra can be used to solve real problem
s because the rules of algebra work i
n real life and numbers can be used t
o represent the values of real things
. Physics, engineering and computer p
rogramming are areas that use algebra
all the time. It is also useful to k
now in surveying, construction and bu
siness, especially accounting.People
who do algebra use the rules of numbe
rs and mathematical operations used o
n numbers. The simplest are adding, s
ubtracting, multiplying, and dividing
. More advanced operations involve ex
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ponents, starting with squares and sq
uare roots. Algebra was first used t
o solve equations and inequalities. T
wo examples are linear equations (the
equation of a straight line, or ) a
nd quadratic equations, which has var
iables that are squared (multiplied b
y itself, for example: , , or ).Histo
ry Early forms of algebra were develo
ped by the Babylonians and the Greek
geometers such as Hero of Alexandria.
However the word "algebra" is a Lati
n form of the Arabic word Al-Jabr ("c
asting") and comes from a mathematics
book Al-Maqala fi Hisab-al Jabr wa-a
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l-Muqabilah, ("Essay on the Computati
on of Casting and Equation") written
in the 9th century by a Persian mathe
matician, Muhammad ibn Mūsā al-Khwāri
zmī, who was a Muslim born in Khwariz
m in Uzbekistan. He flourished under
Al-Ma'moun in Baghdad, Iraq through 8
13-833 AD, and died around 840 AD. Th
e book was brought into Europe and tr
anslated into Latin in the 12th centu
ry. The book was then given the name
'Algebra'. (The ending of the mathema
tician's name, al-Khwarizmi, was chan
ged into a word easier to say in Lati
n, and became the English word algori
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thm).ExamplesHere is a simple example
of an algebra problem:Sue has 12 can
dies, and Ann has 24 candies. They de
cide to share so that they have the s
ame number of candies. How many cand
ies will each have?These are the step
s you can use to solve the problem: T
o have the same number of candies, An
n has to give some to Sue. Let repre
sent the number of candies Ann gives
to Sue. Sue's candies, plus , must b
e the same as Ann's candies minus . T
his is written as: Subtract 12 from
both sides of the equation. This give
s: . (What happens on one side of the
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equal sign must happen on the other
side too, for the equation to still b
e true. So in this case when 12 was s
ubtracted from both sides, there was
a middle step of . After a person is
comfortable with this, the middle ste
p is not written down.) Add to both
sides of the equation. This gives: D
ivide both sides of the equation by 2
. This gives . The answer is six. Thi
s mean that if Ann gives Sue 6 candie
s, they will have the same number of
candies. To check this, put 6 back in
to the original equation wherever wa
s: This gives , which is true. They
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each now have 18 candies.With practic
e, algebra can be used when faced wit
h a problem that is too hard to solve
any other way. Problems such as buil
ding a freeway, designing a cell phon
e, or finding the cure for a disease
all require algebra.Writing algebra A
s in most parts of mathematics, addin
g to (or plus ) is written as ;sub
tracting from (or minus ) is writt
en as ;and dividing by (or over )
is written as or .In algebra, multi
plying by (or times ) can be writt
en in 3 different ways: , or just .
All of these notations mean the same
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thing: times . The symbol "" used in
arithmetic is not used in algebra, b
ecause it looks too much like the let
ter , which is often used as a variab
le.When we multiply a number and a va
riable in algebra, we can simply writ
e the number in front of the letter:
. When the number is 1, then it is no
t written because 1 times any number
is that number () and so it is not ne
eded. And when it is 0, we can comple
tely remove the terms, because 0 time
s any number is zero ().As a side not
e, you do not have to use the letters
or in algebra. Variables are just
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symbols that mean some unknown number
or value, so you can use any letter
for a variable (except (Euler's numb
er) and (Imaginary unit), because th
ese are mathematical constants). and
are the most common, though.Functio
ns and Graphs An important part of al
gebra is the study of functions, sinc
e they often appear in equations that
we are trying to solve. A function i
s like a machine you can put a number
(or numbers) into and get a certain
number (or numbers) out. When using f
unctions, graphs can be powerful tool
s in helping us to study the solution
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s to equations. A graph is a picture
that shows all the values of the vari
ables that make the equation or inequ
ality true. Usually this is easy to m
ake when there are only one or two va
riables. The graph is often a line, a
nd if the line does not bend or go st
raight up-and-down it can be describe
d by the basic formula . The variable
is the y-intercept of the graph (wh
ere the line crosses the vertical axi
s) and is the slope or steepness of
the line. This formula applies to the
coordinates of a graph, where each p
oint on the line is written (, ). In
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some math problems like the equation
for a line, there can be more than o
ne variable ( and in this case). To
find points on the line, one variable
is changed. The variable that is cha
nged is called the "independent" vari
able. Then the math is done to make a
number. The number that is made is c
alled the "dependent" variable. Most
of the time the independent variable
is written as and the dependent vari
able is written as , for example, in
. This is often put on a graph, using
an axis (going left and right) and
a axis (going up and down). It can a
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lso be written in function form: . So
in this example, we could put in 5 f
or and get . Put in 2 for would get
. And 0 for would get . So there wo
uld be a line going through the point
s (5,16), (2,7), and (0,1) as seen in
the graph to the right.If has a pow
er of 1, it is a straight line. If it
is squared or some other power, it w
ill be curved. If it uses an inequali
ty ( or ), then usually part of the g
raph is shaded, either above or below
the line.Rules In algebra, there are
a few rules that can be used for fur
ther understanding of equations. Thes
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e are called the rules of algebra. Wh
ile these rules may seem senseless or
obvious, it is wise to understand th
at these properties do not hold throu
ghout all branches of mathematics. Th
erefore, it will be useful to know ho
w these axiomatic rules are declared,
before taking them for granted. Befo
re going on to the rules, reflect on
two definitions that will be given. O
pposite: the opposite of is . Recipr
ocal: the reciprocal of is .Commutat
ive property of addition 'Commutative
' means that a function has the same
result if the numbers are swapped aro
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und. In other words, the order of the
terms in an equation does not matter
. When two terms (addends) are being
added, the 'commutative property of a
ddition' is applicable. In algebraic
terms, this gives .Note that this doe
s not apply for subtraction (i.e. ex
cept if ).Commutative property of mul
tiplication When two terms (factors)
are being multiplied, the 'commutativ
e property of multiplication' is appl
icable. In algebraic terms, this give
s .Note that this does not apply for
division (i.e. , when and , except i
f ).Associative property of addition
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'Associative' refers to the grouping
of numbers. The associative property
of addition implies that, when adding
three or more terms, it doesn't matt
er how these terms are grouped. Algeb
raically, this gives . Note that this
does not hold for subtraction, e.g.
(see distributive property).Associat
ive property of multiplication The as
sociative property of multiplication
implies that, when multiplying three
or more terms, it doesn't matter how
these terms are grouped. Algebraicall
y, this gives . Note that this does n
ot hold for division, e.g. .Distribut
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ive property The distributive propert
y states that the multiplication of a
term by another term can be distribu
ted. For instance: . (Do not confuse
this with the associative properties!
For instance: .)Additive identity 'I
dentity' refers to the property of a
number that it is equal to itself. In
other words, there exists an operati
on of two numbers so that it equals t
he variable of the sum. The additive
identity property states that any num
ber plus 0 is that number: . This als
o holds for subtraction: .Multiplicat
ive identity The multiplicative ident
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ity property states that any number t
imes 1 is that number: . This also ho
lds for division: .Additive inverse p
roperty The additive inverse property
is somewhat like the opposite of the
additive identity. When we add a num
ber and its opposite, the result is 0
. Algebraically, it states the follow
ing: , which is the same as . For exa
mple, the additive inverse (or opposi
te) of 1 is -1.Multiplicative inverse
property The multiplicative inverse
property means that when we multiply
a number and its inverse, the result
is 1. Algebraically, it states the fo
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llowing: , which is the same as . For
example, the multiplicative inverse
(or just inverse) of 2 is 1/2. To get
the inverse of a fraction, switch th
e numerator and the denominator: the
inverse of is .Advanced AlgebraIn a
ddition to "elementary algebra", or b
asic algebra, there are advanced form
s of algebra, taught in colleges and
universities, such as abstract algebr
a, linear algebra, and universal alge
bra. This includes how to use a matri
x to solve many linear equations at o
nce. Abstract algebra is the study of
things that are found in equations,
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going beyond numbers to the more abst
ract with groups of numbers.Many math
problems are about physics and engin
eering. In many of these physics prob
lems time is a variable. The letter u
sed for time is . Using the basic ide
as in algebra can help reduce a math
problem to its simplest form making i
t easier to solve difficult problems.
Energy is , force is , mass is , acc
eleration is and speed of light is s
ometimes . This is used in some famou
s equations, like and (although mor
e complex math beyond algebra was nee
ded to come up with that last equatio
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n).Related pages List of mathematics
topics Order of Operations Parabola C
omputer Algebra SystemReferencesOther
websites Khan Academy: Algebra theo
ry and practice algebrarules.com: A f
ree place to learn the basics of Alge
bra Khan Academy: Origins of Algebra,
free online micro lectures Fields o
f mathematics
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Atoms are very small pieces of matter
. There are many different types of a
toms, each with its own name, mass an
d size. These different types of ato
ms are called chemical elements. The
chemical elements are organized on t
he periodic table. Examples of eleme
nts are hydrogen, carbon, chlorine, a
nd gold etc.Atoms are very small, but
their exact size depends on the elem
ent. Atoms range from 0.1 to 0.5 nan
ometers in width. One nanometer is ab
out 100,000 times smaller than the wi
dth of a human hair. This makes atoms
impossible to see without special to
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ols. Scientists discover how they wor
k and interact with other atoms throu
gh experiments.Atoms can join togethe
r to make molecules: for example, two
hydrogen atoms and one oxygen atom c
ombine to make a water molecule, and
many separate molecules make up a gla
ss of water. When atoms join together
it is called a chemical reaction. At
oms can join together without forming
separate molecules, in this case eve
ry atom is connected to a giant web o
f atoms, these are called crystals.At
oms are made up of three kinds of sma
ller particles, called protons, neutr
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ons and electrons. The protons and ne
utrons are heavier, and stay in the m
iddle of the atom, which is called th
e nucleus. The nucleus is surrounded
by a cloud of light-weight electrons,
these are attracted to the protons i
n the nucleus by the electromagnetic
force because they have opposite elec
tric charges.The number of protons an
atom has defines what chemical eleme
nt it is, this number is sometimes ca
lled its atomic number. For example,
hydrogen has one proton and sulfur ha
s 16 protons. Because the mass of neu
trons and protons is very similar, an
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d the mass of electrons is very small
, we can call the amount of protons a
nd neutrons in an atom its atomic mas
s.Atoms move faster when they are in
their gas form (because they are free
to move) than they do in liquid form
and solid matter. In solid materials
, the atoms are tightly packed next t
o each other so they vibrate, but are
not able to move (there is no room)
as atoms in liquids do.History The wo
rd "atom" comes from the Greek (ἀτόμο
ς) "atomos", indivisible, from (ἀ)-,
not, and τόμος, a cut. The first hist
orical mention of the word atom came
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from works by the Greek philosopher D
emocritus, around 400 BC. Atomic theo
ry stayed as a mostly philosophical s
ubject, with not much actual scientif
ic investigation or study, until the
development of chemistry in the 1650s
.In 1777 French chemist Antoine Lavoi
sier defined the term element for the
first time. He said that an element
was any basic substance that could no
t be broken down into other substance
s by the methods of chemistry. Any su
bstance that could be broken down was
a compound.In 1803, English philosop
her John Dalton suggested that elemen
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ts were tiny, solid balls made of ato
ms. Dalton believed that all atoms of
the same element have the same mass.
He said that compounds are formed wh
en atoms of more than one element com
bine. According to Dalton, in a certa
in compound, the atoms of the compoun
d's elements always combine the same
way.In 1827, British scientist Robert
Brown looked at pollen grains in wat
er under his microscope. The pollen g
rains appeared to be jiggling. Brown
used Dalton's atomic theory to descri
be patterns in the way they moved. Th
is was called brownian motion. In 190
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5 Albert Einstein used mathematics to
prove that the seemingly random move
ments were caused by the reactions of
atoms, and by doing this he conclusi
vely proved the existence of the atom
.In 1869, Russian scientist Dmitri Me
ndeleev published the first version o
f the periodic table. The periodic ta
ble groups elements by their atomic n
umber (how many protons they have. Th
is is usually the same as the number
of electrons).Elements in the same co
lumn, or period, usually have similar
properties. For example, helium, neo
n, argon, krypton and xenon are all i
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n the same column and have very simil
ar properties. All these elements are
gases that have no colour and no sme
ll. Also, they are unable to combine
with other atoms to form compounds. T
ogether they are known as the noble g
ases.The physicist J.J. Thomson was t
he first person to discover electrons
. This happened while he was working
with cathode rays in 1897. He reali
zed they had a negative charge, and t
he atomic nucleus had a positive char
ge. Thomson created the plum pudding
model, which stated that an atom was
like plum pudding: the dried fruit (e
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lectrons) were stuck in a mass of pud
ding (nucleus). In 1909, a scientist
named Ernest Rutherford used the Gei
ger–Marsden experiment to prove that
most of an atom is in a very small sp
ace, the atomic nucleus. Rutherford
took a photo plate and covered it wit
h gold foil, and then shot alpha part
icles (made of two protons and two ne
utrons stuck together) at it. Many
of the particles went through the gol
d foil, which proved that atoms are m
ostly empty space. Electrons are so s
mall they make up only 1% of an atom'
s mass.In 1913, Niels Bohr introduced
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the Bohr model. This model showed th
at electrons travel around the nucleu
s in fixed circular orbits. This was
more accurate than the Rutherford mod
el. However, it was still not complet
ely right. Improvements to the Bohr m
odel have been made since it was firs
t introduced.In 1925, chemist Frederi
ck Soddy found that some elements in
the periodic table had more than one
kind of atom.For example, any atom wi
th 2 protons should be a helium atom.
Usually, a helium nucleus also conta
ins two neutrons. However, some heliu
m atoms have only one neutron. This m
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eans they truly are helium, because a
n element is defined by the number of
protons, but they are not normal hel
ium, either. Soddy called an atom lik
e this, with a different number of ne
utrons, an isotope. To get the name o
f the isotope we look at how many pro
tons and neutrons it has in its nucle
us and add this to the name of the el
ement. So a helium atom with two prot
ons and one neutron is called helium-
3, and a carbon atom with six protons
and six neutrons is called carbon-12
. However, when he developed his theo
ry Soddy could not be certain neutron
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s actually existed. To prove they wer
e real, physicist James Chadwick and
a team of others created the mass spe
ctrometer. The mass spectrometer actu
ally measures the mass and weight of
individual atoms. By doing this Chadw
ick proved that to account for all th
e weight of the atom, neutrons must e
xist.In 1937, German chemist Otto Hah
n became the first person to create n
uclear fission in a laboratory. He di
scovered this by chance when he was s
hooting neutrons at a uranium atom, h
oping to create a new isotope. Howeve
r, he noticed that instead of a new i
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sotope the uranium simply changed int
o a barium atom, a smaller atom than
uranium. Apparently, Hahn had "broken
" the uranium atom. This was the worl
d's first recorded nuclear fission re
action. This discovery eventually led
to the creation of the atomic bomb.F
urther into the 20th century, physici
sts went deeper into the mysteries of
the atom. Using particle accelerator
s they discovered that protons and ne
utrons were actually made of other pa
rticles, called quarks.The most accur
ate model so far comes from the Schrö
dinger equation. Schrödinger realized
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that the electrons exist in a cloud
around the nucleus, called the electr
on cloud. In the electron cloud, it i
s impossible to know exactly where el
ectrons are. The Schrödinger equation
is used to find out where an electro
n is likely to be. This area is calle
d the electron's orbital.Structure an
d partsParts The complex atom is made
up of three main particles; the prot
on, the neutron and the electron. The
isotope of Hydrogen Hydrogen-1 has n
o neutrons, just the one proton and o
ne electron. Protons have a positive
electric charge and electrons have a
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negative charge. A positive hydrogen
ion has no electrons, just the one p
roton. These two examples are the on
ly known exceptions to the rule that
all other atoms have at least one pro
ton, one neutron and one electron eac
h.Electrons are by far the smallest o
f the three atomic particles, their m
ass and size is too small to be measu
red using current technology. They ha
ve a negative charge. Protons and neu
trons are of similar size and weight
to each other, protons are positively
charged and neutrons have no charge.
Most atoms have a neutral charge; bec
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ause the number of protons (positive)
and electrons (negative) are the sam
e, the charges balance out to zero. H
owever, in ions (different number of
electrons) this is not always the cas
e, and they can have a positive or a
negative charge. Protons and neutrons
are made out of quarks, of two types
; up quarks and down quarks. A proton
is made of two up quarks and one dow
n quark and a neutron is made of two
down quarks and one up quark.Nucleus
The nucleus is in the middle of an at
om. It is made up of protons and neut
rons. Usually in nature, two things w
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ith the same charge repel or shoot aw
ay from each other. So for a long tim
e it was a mystery to scientists how
the positively charged protons in the
nucleus stayed together. They solved
this by finding a particle called a
gluon. Its name comes from the word g
lue as gluons act like atomic glue, s
ticking the protons together using th
e strong nuclear force. It is this fo
rce which also holds the quarks toget
her that make up the protons and neut
rons.The number of neutrons in relati
on to protons defines whether the nuc
leus is stable or goes through radioa
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ctive decay. When there are too many
neutrons or protons, the atom tries t
o make the numbers the same by gettin
g rid of the extra particles. It does
this by emitting radiation in the fo
rm of alpha, beta or gamma decay. Nuc
lei can change through other means to
o. Nuclear fission is when the nucleu
s splits into two smaller nuclei, rel
easing a lot of stored energy. This r
elease of energy is what makes nuclea
r fission useful for making bombs and
electricity, in the form of nuclear
power.The other way nuclei can change
is through nuclear fusion, when two
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nuclei join together, or fuse, to mak
e a heavier nucleus. This process req
uires extreme amounts of energy in or
der to overcome the electrostatic rep
ulsion between the protons, as they h
ave the same charge. Such high energi
es are most common in stars like our
Sun, which fuses hydrogen for fuel.El
ectrons Electrons orbit, or travel ar
ound, the nucleus. They are called th
e atom's electron cloud. They are att
racted towards the nucleus because of
the electromagnetic force. Electrons
have a negative charge and the nucle
us always has a positive charge, so t
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hey attract each other.Around the nuc
leus, some electrons are further out
than others, in different layers. The
se are called electron shells. In mos
t atoms the first shell has two elect
rons, and all after that have eight.
Exceptions are rare, but they do happ
en and are difficult to predict. The
further away the electron is from the
nucleus, the weaker the pull of the
nucleus on it. This is why bigger ato
ms, with more electrons, react more e
asily with other atoms.The electromag
netism of the nucleus is not strong e
nough to hold onto their electrons an
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d atoms lose electrons to the strong
attraction of smaller atoms.Radioacti
ve decay Some elements, and many isot
opes, have what is called an unstable
nucleus. This means the nucleus is e
ither too big to hold itself together
or has too many protons or neutrons.
When this happens the nucleus has to
get rid of the excess mass or partic
les. It does this through radiation.
An atom that does this can be called
radioactive. Unstable atoms continue
to be radioactive until they lose eno
ugh mass/particles that they become s
table. All atoms above atomic number
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82 (82 protons, lead) are radioactive
.There are three main types of radioa
ctive decay; alpha, beta and gamma. A
lpha decay is when the atom shoots ou
t a particle having two protons and t
wo neutrons. This is essentially a he
lium nucleus. The result is an elemen
t with atomic number two less than be
fore. So for example if a beryllium a
tom (atomic number 4) went through al
pha decay it would become helium (ato
mic number 2). Alpha decay happens wh
en an atom is too big and needs to ge
t rid of some mass. Beta decay is whe
n a neutron turns into a proton or a
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proton turns into a neutron. In the f
irst case the atom shoots out an elec
tron. In the second case it is a posi
tron (like an electron but with a pos
itive charge). The end result is an e
lement with one higher or one lower a
tomic number than before. Beta decay
happens when an atom has either too m
any protons, or too many neutrons. Ga
mma decay is when an atom shoots out
a gamma ray, or wave. It happens when
there is a change in the energy of t
he nucleus. This is usually after a n
ucleus has already gone through alpha
or beta decay. There is no change in
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the mass, or atomic number or the at
om, only in the stored energy inside
the nucleus.Every radioactive element
or isotope has what is named a half-
life. This is how long it takes half
of any sample of atoms of that type t
o decay until they become a different
stable isotope or element. Large ato
ms, or isotopes with a big difference
between the number of protons and ne
utrons will therefore have a long hal
f life, because they must lose more n
eutrons to become stable.Marie Curie
discovered the first form of radiatio
n. She found the element and named it
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radium. She was also the first femal
e recipient of the Nobel Prize.Freder
ick Soddy conducted an experiment to
observe what happens as radium decays
. He placed a sample in a light bulb
and waited for it to decay. Suddenly,
helium (containing 2 protons and 2 n
eutrons) appeared in the bulb, and fr
om this experiment he discovered this
type of radiation has a positive cha
rge.James Chadwick discovered the neu
tron, by observing decay products of
different types of radioactive isotop
es. Chadwick noticed that the atomic
number of the elements was lower than
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the total atomic mass of the atom. H
e concluded that electrons could not
be the cause of the extra mass becaus
e they barely have mass.Enrico Fermi,
used the neutrons to shoot them at u
ranium. He discovered that uranium de
cayed a lot faster than usual and pro
duced a lot of alpha and beta particl
es. He also believed that uranium got
changed into a new element he named
hesperium.Otto Hahn and Fritz Strassm
ann repeated Fermi's experiment to se
e if the new element hesperium was ac
tually created. They discovered two n
ew things Fermi did not observe. By u
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sing a lot of neutrons the nucleus of
the atom would split, producing a lo
t of heat energy. Also the fission pr
oducts of uranium were already discov
ered: thorium, palladium, radium, rad
on and lead.Fermi then noticed that t
he fission of one uranium atom shot o
ff more neutrons, which then split ot
her atoms, creating chain reactions.
He realised that this process is call
ed nuclear fission and could create h
uge amounts of heat energy.That very
discovery of Fermi's led to the devel
opment of the first nuclear bomb code
-named 'Trinity'.ReferencesOther webs
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ites General information on atomic s
tructure Atomic structure timeline
Atom (science) -CitizendiumChemistryN
uclear physics
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Astronomy (from the Greek astron (ἄστ
ρον) meaning "star" and nomos (nόμος)
meaning "law") is the scientific stu
dy of celestial bodies. The patterns
in the night sky are called constella
tions.The objects studied include sta
rs, galaxies, planets, moons, asteroi
ds, comets and nebulae. Phenomena th
at are studied include supernovae exp
losions, gamma ray bursts, and cosmic
microwave background radiation. Ast
ronomy concerns the development, phys
ics, chemistry, meteorology and movem
ent of celestial bodies, as well as t
he structure and development of the U
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niverse.Astronomy is one of the oldes
t sciences. Ancient Greek people use
d the positions of the stars to navig
ate, and to find when was the best ti
me to plant crops. Astrophysics is a
n important part of astronomy. A re
lated subject, cosmology, is concerne
d with studying the Universe as a who
le, and the way the universe changed
over time. Astronomy is not the same
as astrology, the belief that motion
of the stars and the planets may aff
ect human lives.Since the 20th centur
y there have been two main types of a
stronomy, observational and theoretic
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al astronomy. Observational astronom
y uses telescopes and cameras to obse
rve or look at stars, galaxies and ot
her astronomical objects. Theoretica
l astronomy uses maths and computer m
odels to explain the observations and
predict what might happen. Working
together, theories predict what shoul
d happen and observations show whethe
r the predictions work. The main wor
k of astronomy is to explain puzzling
features of the universe. For many
years the most important issue was th
e motions of planets; now many other
topics are studied.History of astrono
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myAncient Early astronomers used only
their eyes to look at the stars. The
y made maps of the constellations and
stars for religious reasons and cale
ndars to work out the time of year. E
arly civilisations such as the Maya p
eople and the Ancient Egyptians built
simple observatories and drew maps o
f the stars positions. They also bega
n to think about the place of Earth i
n the universe. For a long time peopl
e thought Earth was the center of the
universe, and that the planets, the
stars and the sun went around it. Th
is is known as geocentrism.Ancient Gr
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eeks tried to explain the motions of
the sun and stars by taking measureme
nts. A mathematician named Eratosthen
es was the first who measured the siz
e of the Earth and proved that the Ea
rth is a sphere. A theory by another
mathematician named Aristarchus was,
that the sun is in the center and the
Earth is moving around it. This is k
nown as heliocentrism. Only a few peo
ple thought it was right. The rest co
ntinued to believe in the geocentric
model. Most of the names of constella
tions and stars come from Greeks of t
hat time.Arabic astronomers made many
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advancements during the Middle Ages
including improved star maps and ways
to estimate the size of the Earth.
They also learned from the ancients b
y translating Greek books into Arabic
.Renaissance to modern era During the
renaissance a priest named Nicolaus
Copernicus thought, from looking at t
he way the planets moved, that the Ea
rth was not the center of everything.
Based on previous works, he said tha
t the Earth was a planet and all the
planets moved around the sun. This br
ought back the old idea of heliocentr
ism. A physicist called Galileo Galil
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ei built his own telescopes, and used
them to look more closely at the sta
rs and planets for the first time. He
agreed with Copernicus. The Catholic
Church thought Galileo was wrong. He
spent the rest of his life under hou
se arrest. Heliocentric ideas were so
on improved by Johannes Kepler and Is
aac Newton, who invented the theory o
f gravity.After Galileo, people made
better telescopes and used them to se
e farther objects such as the planets
Uranus and Neptune. They also saw ho
w stars were similar to our Sun, but
in a range of colours and sizes. They
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also saw thousands of other faraway
objects such as galaxies and nebulae.
Modern era The 20th century after 192
0 saw important changes in astronomy.
In the early 1920s it began to be acc
epted that the galaxy in which we liv
e, the Milky Way, is not the only gal
axy. The existence of other galaxies
was settled by Edwin Hubble, who iden
tified the Andromeda nebula as a diff
erent galaxy. It was also Hubble who
proved that the universe was expandin
g. There were many other galaxies at
large distances and they are receding
, moving away from our galaxy. That w
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as completely unexpected.In 1931, Kar
l Jansky discovered radio emission fr
om outside the Earth when trying to i
solate a source of noise in radio com
munications, marking the birth of rad
io astronomy and the first attempts a
t using another part of the electroma
gnetic spectrum to observe the sky. T
hose parts of the electromagnetic spe
ctrum that the atmosphere did not blo
ck were now opened up to astronomy, a
llowing more discoveries to be made.T
he opening of this new window on the
Universe saw the discovery of entirel
y new things, for example pulsars, wh
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ich sent regular pulses of radio wave
s out into space. The waves were firs
t thought to be alien in origin becau
se the pulses were so regular that it
implied an artificial source.The per
iod after World War 2 saw more observ
atories where large and accurate tele
scopes are built and operated at good
observing sites, normally by governm
ents. For example, Bernard Lovell beg
an radio astronomy at Jodrell Bank us
ing leftover military radar equipment
. By 1957, the site had the largest s
teerable radio telescope in the world
. Similarly, the end of the 1960s saw
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the start of the building of dedicat
ed observatories at Mauna Kea in Hawa
ii, a good site for visible and infra
-red telescopes thanks to its high al
titude and clear skies.The next great
revolution in astronomy was thanks t
o the birth of rocketry. This allowe
d telescopes to be placed in space on
satellites.Space telescopes gave acc
ess, for the first time in history, t
o the entire electromagnetic spectrum
including rays that had been blocked
by the atmosphere. The X-rays, gamm
a rays, ultraviolet light and parts o
f the infra-red spectrum were all ope
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ned to astronomy as observing telesco
pes were launched. As with other par
ts of the spectrum, new discoveries w
ere made.From 1970s satellites were l
aunched to be replaced with more accu
rate and better satellites, causing t
he sky to be mapped in nearly all par
ts of the electromagnetic spectrum.Di
scoveries Discoveries broadly come in
two types: bodies and phenomena. B
odies are things in the Universe, whe
ther it is a planet like our Earth or
a galaxy like our Milky Way. Phenom
ena are events and happenings in the
Universe.Bodies For convenience, this
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section has been divided by where th
ese astronomical bodies may be found:
those found around stars are solar b
odies, those inside galaxies are gala
ctic bodies and everything else large
r are cosmic bodies.Solar Planets As
teroids CometsGalactic StarsDiffuse O
bjects: Nebulas ClustersCompact Stars
: White dwarf stars Neutron stars Bla
ck holesCosmic Galaxies Galaxy clust
ers SuperclustersPhenomena Burst even
ts are those where there is a sudden
change in the heavens that disappears
quickly. These are called bursts be
cause they are normally associated wi
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th large explosions producing a "burs
t" of energy. They include: Superno
vas NovasPeriodic events are those th
at happen regularly in a repetitive w
ay. The name periodic comes from per
iod, which is the length of time requ
ired for a wave to complete one cycle
. Periodic phenomena include: Pulsa
rs Variable starsNoise phenomena tend
to relate to things that happened a
long time ago. The signal from these
events bounce around the Universe un
til it seems to come from everywhere
and varies little in intensity. In t
his way, it resembles "noise", the ba
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ckground signal that pervades every i
nstrument used for astronomy. The mo
st common example of noise is static
seen on analogue televisions. The pr
incipal astronomical example is: cosm
ic background radiation.MethodsInstru
ments Telescopes are the main tool o
f observing. They take all the light
in a big area and put in into a small
area. This is like making your eyes
very big and powerful. Astronomers us
e telescopes to look at things that a
re far away and dim. Telescopes make
objects look bigger, closer, brighter
. Spectrometers study the different
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wavelengths of light. This shows what
something is made of. Many telescop
es are in satellites. They are space
observatories. The Earth’s atmosphere
blocks some parts of the electromagn
etic spectrum, but special telescopes
above the atmosphere can detect tha
t radiation. Radio astronomy uses rad
io telescopes. Aperture synthesis com
bines smaller telescopes to create a
phased array, which works like a tele
scope as big as the distance between
the smaller telescopes.Techniques The
re are way astronomers can get bette
r pictures of the heavens. Light fro
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m a distant source reaches a sensor a
nd gets measured, normally by a human
eye or a camera. For very dim sourc
es, there may not be enough light par
ticles coming from the source for it
to be seen. One technique that astro
nomers have for making it visible is
using integration (which is like long
er exposures in photography).Integrat
ion Astronomical sources do not move
much: only the rotation and movement
of the Earth causes them to move acro
ss the heavens. As light particles re
ach the camera over time, they hit th
e same place making it brighter and m
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ore visible than the background, unti
l it can be seen.Telescopes at most o
bservatories (and satellite instrumen
ts) can normally track a source as it
moves across the heavens, making the
star appear still to the telescope a
nd allowing longer exposures. Also,
images can be taken on different nigh
ts so exposures span hours, days or e
ven months. In the digital era, digit
ised pictures of the sky can be added
together by computer, which overlays
the images after correcting for move
ment.Adaptive optics Adaptive optics
means changing the shape of the mirro
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r or lens while looking at something,
to see it better.Data analysis Data
analysis is the process of getting mo
re information out of an astronomical
observation than by simply looking a
t it. The observation is first stored
as data. This data will then have v
arious techniques used to analyse it.
Fourier analysis Fourier analysis in
mathematics can show if an observatio
n (over a length of time) is changing
periodically (changes like a wave).
If so, it can extract the frequencie
s and the type of wave pattern, and f
ind many things including new planets
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.Subfields of astronomyPulsars pulse
regularly in radio waves. These turn
ed out to be similar to some (but not
all) of a type of bright source in X
-rays called a Low-mass X-ray binary.
It turned out that all pulsars and
some LMXBs are neutron stars and that
the differences were due to the envi
ronment in which the neutron star was
found. Those LMXBs that were not neu
tron stars turned out to be black hol
es.This section attempts to provide a
n overview of the important fields of
astronomy.Solar astronomy Solar astr
onomy is the study of the Sun. The Su
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n is the closest star to Earth at aro
und 92 million (92,000,000) miles awa
y. It is the easiest to observe in de
tail. Observing the Sun can help us u
nderstand how other stars work and ar
e formed. Changes in the Sun can affe
ct the weather and climate on Earth.
A stream of charged particles called
the Solar wind is constantly sent off
from the Sun. The Solar wind hitting
the Earth's magnetic field causes th
e northern lights.Planetary astronomy
Planetary astronomy is the study of
planets, moons, dwarf planets, comets
and asteroids as well as other small
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objects that orbit stars. The planet
s of our own Solar System have been s
tudied in depth by many visiting spac
ecraft such as Cassini-Huygens (Satur
n) and the Voyager 1 and 2.Galactic a
stronomy Galactic astronomy is the st
udy of distant galaxies. Studying di
stant galaxies is the best way of lea
rning about our own galaxy, as the ga
ses and stars in our own galaxy make
it difficult to observe. Galactic as
tronomers attempt to understand the s
tructure of galaxies and how they are
formed through the use of different
types of telescopes and computer simu
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lations.Gravitational wave astronomy
Gravitational wave astronomy is the s
tudy of the Universe in the gravitati
onal wave spectrum. So far, all astr
onomy that has been done has used the
electromagnetic spectrum. Gravitati
onal waves are ripples in spacetime e
mitted by very dense objects changing
shape, which include white dwarves,
neutron stars and black holes. Becau
se no one has been able to detect gra
vitational waves directly, the impact
of dravitational wave astronomy has
been limited.Related pages Asteroid
Astrobiology Black hole Comet Galaxy
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Meteor Planet Planetarium Satellite (
natural) Solar system Star UniverseR
eferencesOther websites Astronomy si
te specifically designed for kids and
their parents. Astronomy Picture of
the Day
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Architecture is designing the structu
res of buildings. It uses both art an
d engineering. Examples include house
s, churches, hotels, office buildings
, roads, viaducts, tunnels and bridge
s. Architecture is the profession of
an architect. Usually, a person must
study at an institution of higher edu
cation (university) to become an arch
itect. There were architects long bef
ore there was higher education. They
learnt by being an apprentice to an e
stablished architect. Architecture ca
n do small designs, such as for a gar
age, or large designs, such as for a
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whole city. The capital cities of Bra
sília, and Canberra were designed. Ar
chitecture often overlaps with struct
ural engineering, and architects and
engineers often work together.History
In the past, people built huts and w
ood houses to protect themselves from
the weather. For safety, they were o
ften close together. Great civilizati
ons like the Ancient Egyptians built
large temples and structures, like th
e Great Pyramids of Giza. The Ancient
Greeks and Romans made what we now c
all "Classical Architecture". The Rom
ans, working over 2000 years ago, cop
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ied the arch from the Etruscans, who
copied it from the Mesopotamians. Cla
ssical architecture was formal, and i
t always obeyed laws. It used symmetr
y, which really means balance, and it
used proportion between shapes. The
Golden Mean was a rule which said, (t
o put it simply) if you are making a
room, or any other thing, it will wor
k best if you always make the long si
de 1.6 times as long as the short sid
e. There are many 'laws' in classical
architecture, like how high the midd
le of an arched bridge needs to be (w
hich depends on how wide the bridge n
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eeds to be). These laws were learned
from thousands of years of experience
and they are often used today. Howev
er, today more notice is taken of spe
cific facts, such as what wind speeds
occur once or twice in a century. Se
veral bridges have blown down because
that was not properly taken into con
sideration.In some parts of the world
, like India, the architecture is fam
ous for carving the stone on temples
and palaces. Different architectural
styles occur in China, Japan, Southea
st Asia, Africa, Mexico, and Central
and South America.Architects in Weste
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rn Europe in the Middle Ages made Rom
anesque architecture, then Gothic arc
hitecture. Gothic buildings have tall
, pointed windows and arches. Many ch
urches have Gothic architecture. Cast
les were also built at this time. In
Eastern Europe, churches usually had
domes. People added their own ideas a
nd decoration to the Classical Archit
ecture of the past. The Renaissance b
rought a return to classical ideas. I
n the late 18th century with the Indu
strial Revolution, people began to in
vent machines to make things quickly
and cheaply. Many factories and mills
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were built during, or after this rev
olution. Decades later, in the Victor
ian era, architects like George Fowle
r Jones and Decimus Burton still foll
owed the Gothic style to build new ch
urches. Up to this point, buildings w
ere limited in size and style by the
strength of the wood and masonry used
to construct them. Gothic cathedrals
were among the largest buildings bec
ause the gothic arch when combined wi
th buttresses allowed stone buildings
to be built taller. For example, the
cathedral in Ulm, Germany is over 50
0 feet tall. However, building with s
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tone has its limits, and building too
tall could result in collapse. This
happened to the Beauvais Cathedral, w
hich was never completed. Towards the
end of the 19th Century with a secon
d Industrial Revolution, steel became
much cheaper. Architects began to us
e inventions like metal girders and r
einforced concrete to build. An examp
le is the Eiffel Tower in Paris. Buil
dings can now be built taller than ev
er before. We call them skyscrapers.
This new technology has made us free
from traditional limitations, and bec
ause of the new possibilities present
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ed by these materials, many tradition
al methods of construction and ideas
about style were reevaluated, replace
d, or abandoned. Cheap, strong glass
soon brought transparent exterior wal
ls, especially for office buildings.M
odernism is the name for the architec
tural style which developed because o
f these new building technologies, an
d its beginnings can been seen as ear
ly as 1890. Modernism can also refer
to a specific group of architects and
buildings from the early to late 20t
h century, and so may not be the prop
er term to use for many building buil
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t since then, which are sometimes cal
led "post-modern".Many of the world's
greatest structures were built by mo
dern-day architects such as Frank Llo
yd Wright; Sir Hugh Casson; Norman Fo
ster; I. M. Pei; Adrian Smith; Edward
Durell Stone; Frank Gehry; Fazlur Kh
an; Gottfried Böhm; and Bruce Graham.
Related pages Acoustics Architect Ar
t Building code Building materials Ea
rthquake engineering List of building
s Pattern language Skyscraper Structu
ral Engineering World Heritage SitesR
eferencesOther websites American Inst
itute of Architects Australian Insti
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tute of Architects Royal Institute of
British Architects Royal Architectur
al Institute of Canada New Zealand In
stitute of Architects Architecture Ci
tizendium Architecture sciencesConstr
uction
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Anatomy is the study of the bodies of
people and other animals. Anatomy is
the study of the inside of the body
and outside the body. Anatomy notes t
he position and structure of organs s
uch as muscles, glands and bones. A p
erson who studies anatomy is an anato
mist. The history of anatomy dates ba
ck to 1600 BC when Egyptians began st
udying human anatomy. They discovered
the functions of many organs like th
e liver, spleen, kidneys, heart etc.
and were the first to discover the st
ructure and functions of the lymphati
c system.For long periods the dissect
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ion of deceased people was forbidden,
and correct ideas about human anatom
y was a long time coming.Academic hum
an anatomists are usually employed by
universities, medical schools and te
aching hospitals. They are often invo
lved in teaching and research. Gross
anatomy studies parts of the body th
at are big enough to see. Micro-anato
my studies smaller parts.Body systems
There are different organ systems, s
uch as the cardiovascular system, als
o known as the circulatory system (th
e system that gets blood around the b
ody), the muscular system (the system
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that contains muscles), the nervous
system (the system that controls the
nerves,and the brain) and the skeleto
n (the bones).Anatomy, physiology and
biochemistry are similar basic medic
al sciences.Related pages Medicine Zo
ology Comparative anatomy Organ (anat
omy) Gray's Anatomy Vesalius William
HarveyReferences
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An asteroid is a space rock. It is a
small object in the Solar System that
travels around the Sun. It is like a
planet but smaller. They range from
very small (smaller than a car) to 60
0 miles (1000 km) across. A few aster
oids have asteroid moon.The name "ast
eroid" means "like a star" in the anc
ient Greek language. Asteroids may lo
ok like small stars in the sky, but t
hey really do move around the Sun, wh
ile stars only seem to move because t
he Earth spins. Like planets, asteroi
ds do not make their own light. Becau
se of this, some people think "astero
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ids" is not a good name, and think th
at the name "planetoid" ("like a plan
et") would be a better name.Giuseppe
Piazzi found the first asteroid, in 1
801. He called it Ceres, and it is th
e biggest object in the asteroid belt
. Others, like Juno, Pallas, and Vest
a were found later. In the 1850s so m
any had been found, that they were nu
mbered by a Minor planet designation
starting with 1 Ceres. Today, astrono
mers using computerized telescopes fi
nd thousands of asteroids every month
. Asteroid impact prediction is one o
f the purposes. Asteroids are the le
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ftover rock and other material from t
he formation of the Solar System. The
se rocks were too small to come toget
her to make a planet. Some are made o
f carbon or metal. Depending on what'
s on the surface, they are classified
into various asteroid spectral types
including Type M (metal), Type S (st
one), and Type C (carbon).Most astero
ids in our Solar System are in the as
teroid belt between Mars and Jupiter.
Many are not in the main asteroid be
lt. The ones that come close to Earth
are called Near-Earth asteroids. Man
y scientists think asteroids striking
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the Earth killed off all the dinosau
rs and caused some of the other extin
ction events.
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Afghanistan, officially the Islamic E
mirate of Afghanistan (Pashto/Dari: )
, is a country in South Asia. It bord
ers Pakistan in the south and east, I
ran in the west, Turkmenistan, Uzbeki
stan and Tajikistan in the north, and
China in the far northeast. Kabul se
rves as the country's capital city.Af
ghanistan is currently governed by th
e Taliban, after the collapse of the
internationally recognized Islamic Re
public of Afghanistan on 15 August 20
21. In early times people passed thro
ugh it with animals and other goods a
s it connected China and India with C
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entral Asia and the Middle East. More
recently, Afghanistan has been damag
ed by many years of war. This has res
ulted in there not being enough jobs.
The country is around in size. There
are 30 million people in Afghanistan
. There are about 3 million Afghan re
fugees (people who had to leave the c
ountry) who are in Pakistan and Iran
for some time. In 2011, its capital,
Kabul, had about 3,691,400 people liv
ing in it.United Nations Human Rights
Council decided in October to appoin
t (an independent expert, or) United
Nations special rapporteur on "Afghan
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istan to [find out about, or] probe v
iolations carried out by the Taliban
and" others who are now part of a [bi
g] conflict, media said.Geography Afg
hanistan has many mountains. The moun
tains are called the Hindu Kush and H
imalayas. The tallest mountain in Afg
hanistan is Mount Nowshak. There are
plains (which have soil that is good
for growing plants) and foothills. Pa
rts of the country are also dry, espe
cially the Registan Desert.Afghanista
n has snow and glaciers in the mounta
ins. Amu Darya is the big water strea
m, or river.The country has an abunda
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Subsets and Splits