| This article
does not have any
sources
.
You can help Wikipedia by finding
good
sources, and adding them.
(
August 2023
)
|
Matter
is the
substance
of which all
material
is made. That means
objects
which have
mass
. More specifically, they must have
rest
mass
, which is a form of energy that matter has even when it is not moving (it has no
kinetic energy
), is extremely cold (it has no
thermal energy
), etc.
Matter
is a word that is sometimes used in varying ways in everyday life, whereas
mass
is a well-defined
concept
and quantity at least in
physics
. They are not the same thing, though they are related.
[1]
Ordinary
matter is made of tiny
particles
called
atoms
. The atoms have spaces between them and they move or
vibrate
all the time. The particles move faster and move further apart when heated, and then reverse when cooled.
Nearly all matter that may be experienced in everyday life is
baryonic
matter. This includes
atoms
of any sort, and gives those the property of mass. Non-baryonic matter, as implied by the name, is any sort of matter that is not composed mainly of baryons. This might include
neutrinos
and free
electrons
,
dark matter
, such as
supersymmetric particles
,
axions
, and
black holes
.
The very existence of baryons is a significant issue in
cosmology
. It is assumed that the
Big Bang
produced a state with equal amounts of baryons and
antibaryons
. How baryons came to outnumber their
antiparticles
is called
baryogenesis
.
Matter can be directly experienced through the
senses
. It has properties which can be measured, such as
mass
,
volume
,
density
, and
qualitative
properties such as
taste
,
smell
and
colour
, for instance.
All physical bodies in the
universe
are made of matter:
galaxies
,
stars
and
planets
,
rocks
,
water
and
air
. Living
organisms
like
plants
,
animals
and
humans
are also composed of matter.
In physics, the universe also contains things that aren't matter, including some elementary particles that have no rest mass. Photons (electromagnetic radiation such as light) are a familiar example.
In addition to its rest mass, matter can contain other forms of
energy
, which aren't matter but allow them to interact with each other by exchanging
kinetic energy
,
heat
,
light
,
sound
waves, etc.
Outside of the physical sciences, there can be many other things that aren't matter or energy. Just for example,
emotions
can be experienced or
ideas
can be had.
The
structure
and
composition
of matter is investigated by breaking matter into smaller and smaller pieces. Hence, living organisms are made up of
cells
. Cells are composed of
molecules
, which are sets of
atoms
bonded together. Each atom, in turn, is an assemblage of
elementary particles
.
Physicists also classify matter in a few broad categories, called
states
, with quite different properties:
- Solids
are material objects made up of molecules and atoms so strongly bonded together that they tend to keep their shape even when moved around, though they can deform under stress. Examples: a rock, a
table
, a
knife
, a block of
ice
.
- Fluids
are amounts of matter composed of molecules and atoms weakly bonded together. They do not have a proper shape. There are two types of fluids:
- Liquids
include condensed forms of matter, like solids, but where the bonds between the constituting elements (molecules, atoms) allow them to move with respect to each other while continuing to stick together in bulk: they maintain a definite surface. Liquids adopt the shape of the recipients in which they are contained. Examples:
water
,
oil
,
blood
,
lava
,
soft drinks
.
- Gases
are amounts of matter where the bonds between the constituting elements (molecules, atoms) are so loose or weak that they can move independently from each other. Gases do not exhibit a proper surface, they tend to expand to occupy the whole volume available. Examples:
air
,
water vapor
,
helium
.
- Plasmas
are made of
ionized
matter, they are mostly of interest to scientists. Examples: the
Earth
's
ionosphere
, the
Sun
's corona. The particles in a
plasma
are a mixture between a liquid and a gas. The particles are free to move, like a
liquid
, and the attraction is weak, like a gas. This state of matter is not fully understood. An example of plasma can be found in
lightning
.
- A
Bose?Einstein condensate
(BEC) is a state of matter of a dilute gas of
bosons
cooled to temperatures very near absolute zero (0 K or ?273.15 °C)
A given amount of matter may change from one state to another depending on its
temperature
and
pressure
. On Earth, water can exist simultaneously in three states: solid (ice), liquid water (lakes, oceans) and gas (vapor or
steam
).
- ↑
Here we ignore that all matter can have its rest mass converted to other forms of
energy
(a form of the
mass-energy equivalence
) by the famous
formula
E = mc
2
, where
E
is the energy of a mass
m
(in this case, rest mass), times
c
2
the
speed of light
squared. A relatively small amount of matter (i.e. having a small rest mass) may be converted to a large amount other forms of energy that can be released, such as kinetic energy (the energy of motion) and electromagnetic radiation. An example is that
positrons
and electrons (matter) may transform into photons (non-matter). However, although matter may be created (if other forms of energy are converted to rest mass) or destroyed (if the rest mass is converted to other energy forms) in such processes, the total quantity of energy does not change during the process, although some of it can be released or "escape" from the original location of the matter.
English translation of Einstein's paper.