Childrens Illustrated Encyclopedia

childrens_illustrated_encyclopedia_template_US_layer_v1

406

Satellites transmit radio

waves for long-distance

communication.

Sound waves

reflected from the

ocean floor bring back

information about

deep-sea structures.

Coal is

burned to

produce electricity.

Laws of mechanics

are put to use to

design and run a car.

Accelerator speeds

up atomic

particles and

forces them

to collide.

ElEctromagnEtism

Physicists have discovered a

group of mostly invisible rays

called electromagnetic

waves. Electromagnetism

is the physics of the

relationship between

magnetism and

electric currents.

kinEtic thEory

Physicists use the

idea of molecules

to explain the

way solids, liquids,

and gases behave.

this branch of

physics is called

kinetic theory.

thE sciEncE of Physics used to be called

natural philosophy, which means thinking about

and investigating the natural world. Physicists seek

to understand and explain the universe from the

largest, most distant galaxy, to the tiniest invisible

particle. great physicists have wrestled with

fundamental questions such as what it is that holds

us to Earth, what time is, and what is inside an atom.

Physicists work with theory and experiment. they

conduct experiments and then think of a theory,

or idea, that explains the results. then they try new

experiments to test their theory. some theories have

become so good at explaining nature that many people

refer to them as the laws of physics. for example, one

such law states that nothing can travel faster than the

speed of light. the german-born physicist albert

Einstein (1879-1955) proposed this in 1905 as

part of his revolutionary theory of relativity.

gEoPhysics

the interior of Earth is hidden from

us, but physicists have discovered

that there is great heat and pressure

beneath Earth’s crust, which

sometimes erupts in volcanoes.

geophysics is the branch of physics

concerned with Earth.

acoustics

the science of sound

is called acoustics.

Physicists can use

sound to study the

interior of Earth

and the oceans.

Quantum mEchanics

Energy can only exist in tiny

packets called quanta. this

idea is very important in the

study of atoms, and it has

given rise to a branch of

physics called quantum

mechanics.

mEchanics

the study of force

and movement is a

branch of physics

known as mechanics.

magnEtism

Physicists study magnets and the forces

that magnets produce. this includes

Earth’s magnetism, which comes from the

movements of the molten metal core at

the center of Earth.

ElEctricity

one of the most useful forms of energy

is electricity. Physicists study the nature of

electricity and find ways of using it in electrical

appliances, microchips, and computers.

statics

statics is the branch of physics

concerned with calculating

and understanding forces

that support

buildings and

bridges.

English physicist Stephen Hawking

(born 1942) published theories

about the nature of matter, black

holes in space, and the origin of the

universe. These have opened doors

to new possibilities in physics.

landmarks in physics

200s bce greek scientist

archimedes explains floating

and how levers work.

1687 English physicist isaac

newton puts forward the laws

of motion and gravity.

1900 german physicist

max Planck introduces

quantum theory.

1905 german physicist albert

Einstein publishes his theory

of relativity.

1938 german physicists fritz

strassmann and otto hahn

split the atom.

2011–2013 scientists at the

large hadron collider at cErn,

geneva, discover evidence of the

higgs boson—the fundamental

particle that gives mass to matter.

Find out more

Einstein, albert

Electricity

force and motion

gravity

heat

light

magnetism

science

sound

Physics

nuclEar Physics

Physicists are constantly searching for

a greater understanding of the particles that

make up the nucleus (center) of an atom. this

branch of physics is called nuclear physics.

Atomic particles

crash into each

other to release

vast amounts

of energy.

BranchEs of

Physics

Physics is the science of

energy and matter (the

materials of which

everything is made).

there are several

branches of physics. they

cover a range of subjects

from atoms to space.

oPtics and thErmal Physics

heat and light are important forms of

energy: the sun sends out light and heat

that make life possible on Earth. the

physics of light is called optics; the

branch of physics concerned

with heat is called thermal physics.

astroPhysics

astronomers

use physics to

find out about

the origins and

interiors of the

sun and stars. this

branch of physics is

called astrophysics.

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