Childrens Illustrated Encyclopedia

335

Sending a Spacecraft to a distant planet is like trying

to throw a stone at an invisible moving target. Space scientists

do not use trial and error; instead they use the science of

mathematics to direct the spacecraft precisely to its target.

Mathematics is the study of number, shape, and quantity. there are

several different branches of mathematics, and they are valuable both

in science and in everyday life. for instance, arithmetic consists of

addition, subtraction, multiplication, and division of numbers;

it helps you figure out the change when you buy something.

geometry is the study of shape and angle; it is useful in

carpentry, architecture, and many other fields. algebra

is a kind of mathematical language in which problems

can be solved using symbols in place of varying or

unknown numbers. Branches of mathematics that

relate to practical problems are called applied

mathematics. However, some mathematicians study

pure mathematics—numerical problems which have

no known practical use.

partS of a circle

a circle is a shape in

which every point on its

circumference, or outside

margin, is the same

distance from the center.

the diameter is the line

that exactly bisects a circle,

passing through the center.

the distance from the

center to the circumference

is the radius. the slice of

circle between two radii is a

sector, and the part of the

circumference that bounds

a sector is an arc.

aBacuS

the abacus, or counting

frame, is an ancient

calculating device which

comes from china. it consists

of rows of beads that represent

units of tens, hundreds, and

thousands. the abacus is

worked by moving the beads

along the rows. people in

asian countries still use the

abacus as a rapid tool for

adding, subtracting,

multiplying, and dividing.

SyMMetry

a symmetrical object is made up of alike parts. Many

symmetrical patterns and shapes occur in nature.

a starfish exhibits bilateral symmetry, since it

looks the same when reflected in a line drawn

along the length of one of its arms. this line

is called an axis. the starfish also displays

rotational symmetry, as it looks the same

when rotated around its central point.

EuCliD

the ancient greek

mathematician euclid

(c. 330-275 bce) was the first

to formulate theories on the

nature of shapes and angles.

His book Elements outlined the

principles of geometry, and it

was a standard

textbook for

centuries.

euclid

found many

practical uses

for geometry,

such as in

optical

science.

The human face is asymmetrical.

If the left and right sides of this boy’s

face are reflected, the images that

result are different from

his actual face.

infinity

pure mathematicians study the fundamental

ideas of numbers and shapes. one such idea

is the concept of infinity, which means “never-

ending.” the pattern shown above is called

a fractal. it is produced by a computer

according to a strict formula (rule). you can

enlarge any part of the pattern again and

again, but you will still get a pattern that is just

as intricate. the pattern is infinitely complex.

Mathematics

Diameter

Center

Sector

Arc

Circumference Radius

Find out more

computers

numbers

Science, history of

Weights and measures

proBaBility

tHeory

probability theory is

the analysis of chance.

for instance, if you repeatedly

roll two dice, you can use probability

theory to work out how often you can

expect a certain number to come up.

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