Table Of ContentA Dictionary of
Science
SIXTH EDITION
1
1
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First published 1984 as Concise Science Dictionary
Second edition 1991
Third edition 1996
Fourth edition 1999
Fifth edition 2005
Sixth edition 2010
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ISBN 978–0–19–956146–9
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Preface
This sixth edition of A Dictionary of Science, like its predecessors, aims to provide
school and first-year university students with accurate explanations of any unfamiliar
words they might come across in the course of their studies, in their own or adjacent
disciplines. For example, students of the physical sciences will find all they are likely to
need to know about the life sciences, and vice versa. The dictionary is also designed to
provide non-scientists with a useful reference source to explain the scientific terms
that they may encounter in their work or in their general reading.
At this level the dictionary provides full coverage of terms, concepts, and laws
relating to physics, chemistry, biology, biochemistry, palaeontology, and the earth
sciences. There is also coverage of key terms in astronomy, cosmology, mathematics,
biotechnology, and computer technology. In addition, the dictionary includes:
• over 160 short biographical entries on the most important scientists in the history
of the subject
• ten features (each of one or two pages) on concepts of special significance in
modern science
• ten chronologies showing the development of selected concepts, fields of study,
and industries
• eight Appendices, including the periodic table, tables of SI units and conversion
tables to and from other systems of units, summary classifications of the plant and
animal kingdoms, and useful websites.
For this sixth edition nearly 700 new entries have been added to the text, incorporating
recent advances in all the major fields and increased coverage of astronomy, forensic
chemistry, and computing.
In compiling the dictionary, the contributors and editors have made every effort to
make the entries as concise and comprehensible as possible, always bearing in mind
the needs of the readers. Particular features of the book are its lack of unnecessary
scientific jargon and its extensive network of cross-references. An asterisk placed
before a word used in an entry indicates that this word can be looked up in the
dictionary and will provide further explanation or clarification. However, not every
word that is defined in the dictionary has an asterisk placed before it when it is used in
an entry. Some entries simply refer the reader to another entry, indicating either that
they are synonyms or abbreviations or that they are most conveniently explained in
one of the dictionary’s longer articles. Synonyms and abbreviations are usually placed
within brackets immediately after the headword. Terms that are explained within an
entry are highlighted by being printed in boldface type. Where appropriate, the entries
have been supplemented by fully labelled line-drawings or tables in situ.
JD
EM
2009
Credits
Editors
John Daintith BSc, PhD
Elizabeth Martin MA
Advisers
B. S. Beckett BSc, BPhil, MA(Ed)
R. A. Hands BSc
Michael Lewis MA
Contributors
Richard Batley PhD, MInstP Malcolm Hart BSc, MIBiol
Tim Beardsley BA Robert S. Hine BSc, MSc
Lionel Bender BSc Elaine Holmes BSc, PhD
John Clark BSc Valerie Illingworth BSc, MPhil
H. M. Clarke MA, MSc Anne Lockwood BSc
W. M. Clarke BSc J. Valerie Neal BSc, PhD
Derek Cooper PhD, FRIC R. A. Prince MA
John Cullerne DPhil Richard Rennie BSc, MSc, PhD
R. Cutler BSc Michael Ruse BSc, PhD
E. K. Daintith BSc Jackie Smith BA
D. E. Edwards BSc, MSc Brian Stratton BSc, MSc
A. J. H. Goddard PhD, MIMechE, Elizabeth Tootill BSc, MSc
FInstNucE, FInstP, MSRP David Eric Ward BSc, MSc, PhD
William Gould BA Edmund Wright DPhil
Contents
Preface vii
Credits viii
A Dictionary of Science 1
Atomic Theory Chronology 63
The Big-Bang Theory (Feature) 86
Biochemistry Chronology 90
Cell Biology Chronology 144
Cosmology Chronology 200
Crystal Defects (Feature) 210
Electronics Chronology 275
El Niño (Feature) 284
Explosives Chronology 308
Genetically Modified Organisms (Feature) 352
Learning in Animals (Feature) 470
Microscopy Chronology 528
Moon Exploration Chronology 541
Magnetic Resonance Imaging (Feature) 569
Plastics Chronology 638
Polymers (Feature) 648
Refrigeration (Feature) 702
Solar System (Feature) 766
Optical Astronomical Telescopes (Feature) 809
Vitamins Chronology 863
Appendices
SI units 893
Fundamental constants 895
The solar system 895
Geological time scale 896
Simplified classification of land plants 897
Simplified classification of the animal kingdom 898
The periodic table 899
Useful websites 900
A
aa See. tion. The angular displacement α=v/c,
AAR See . wherevis the earth’s orbital velocity and cis
the speed of light.
AAS See .
abiogenesis The origin of living from
ab- A preÜx attached to the name of a prac- nonliving matter, as by *biopoiesis. See also
tical electrical unit to provide a name for a .
unit in the electromagnetic system of units
(see ), e.g. abampere, abiotic factor Any of the nonliving factors
abcoulomb, abvolt. The preÜx is an abbrevi- that make up the abiotic environment in
which living organisms occur. They include
ation of the word ‘absolute’ as this system is
all the aspects of climate, geology, and at-
also known as the absolute system.Compare
-. In modern practice both absolute and mosphere that may affect the biotic environ-
ment.Compare .
electrostatic units have been replaced by *SI
units. abomasum The fourth andÜnal chamber
abdomen The posterior region of the body of the stomach of ruminants. It leads from
trunk of animals. In vertebrates it contains the *omasum and empties into the small in-
the stomach and intestines and the organs of testine. The abomasum is referred to as the
excretion and reproduction. It is particularly ‘true stomach’ as it is in this chamber that
well deÜned in mammals, being separated protein digestion occurs, in acidic condi-
from the *thorax by the *diaphragm. In tions.SeeR.
many arthropods, such as insects and spi- ABO system One of the most important
ders, it may be segmented. human *blood group systems. The system is
Abelian group See. based on the presence or absence of *anti-
gens A and B on the surface of red blood cells
aberration 1.(in optics) A defect in the and of *antibodies against these in blood
image formed by a lens or curved mirror. In serum. A person whose blood contains ei-
chromatic aberration the image formed by a ther or both these antibodies cannot receive
lens (but not a mirror) has coloured fringes a transfusion of blood containing the corre-
as a result of the different extent to which sponding antigens as this would cause the
light of different colours is refracted by glass. red cells to clump (see). The
It is corrected by using an *achromatic lens. table overleaf illustrates the basis of the sys-
Inspherical aberration, the rays from the tem: people of blood group O are described
object come to a focus in slightly different as ‘universal donors’ as they can give blood
positions as a result of the curvature of the to those of any of the other groups. See also
lens or mirror. For a mirror receiving light .
strictly parallel with its axis, this can be cor-
rected by using a parabolic surface rather abscisic acid A naturally occurring plant
than a spherical surface. Spherical aberra- hormone that appears to be involved pri-
tion in lenses is minimized by making both marily in seed maturation, stress responses
surfaces contribute equally to the ray devia- (e.g. to heat and waterlogging), and in regu-
tions, and can be lessened (though with re- lating closure of leaf pores (stomata). In
duced image brightness) by the use of seeds, it promotes the synthesis of storage
diaphragms to let light pass only through the protein and prevents premature germina-
centre part of the lens. See also ; tion. In leaves, abscisic acid is produced in
. 2.(in astronomy) The apparent dis- large amounts when the plant lacks sufÜ-
placement in the position of a star as a result cient water, promoting closure of stomata
of the earth’s motion round the sun. Light and hence reducing further water losses. It
appears to come from a point that is slightly was formerly believed to play a central role
displaced in the direction of the earth’s mo- in *abscission, hence the name.
abscissa 2
a Group Antigens on red Antibodies Blood group of Blood group of
cell surface in serum people donor can people donor can
receive blood from give blood to
A A anti-B A, O A, AB
B B anti-A B, O B, AB
AB A and B none A, B, AB, O AB
O neither A nor B anti-A and O A, B, AB, O
anti-B
ABO system.
abscissa SeeC . tral carbon atom is at the centre of a tetrahe-
dron with the four groups at the corners and
abscission The separation of a leaf, fruit,
that the –H and –OH come out of the paper
or other part from the body of a plant. It in-
volves the formation of an abscission zone, and the –CHO and –CH2OH groups go into
the paper. The resulting three-dimensional
at the base of the part, within which a layer
structure was taken to be that of d-glycer-
of cells (abscission layer) breaks down. This
process is suppressed so long as sufÜcient aldehyde and called D-glyceraldehyde. Any
amounts of *auxin, a plant hormone,Ûow cboomn patooumn dh athvaint gc othnitsa cinosn aÜng uarsaytmiomn ebterlioc ncgasr-
from the part through the abscission zone.
However, if the auxinÛow declines, for ex- tcoo nthÜeg uDr-asteiorine sb. eOlonneg hsa tvoi nthge t hLe-s oepripeos.s iItte is
ample due to injury or ageing, abscission is important to note that the preÜxes D- and L-
activated. Ethylene (*ethene) acts as the pri-
do not stand for dextrorotatory and laevoro-
mary trigger for abscission, inducing cells in
tatory (they are not the same as d- and l-). In
the abscission zone to produce cellulase en- fact the arbitrary conÜguration assigned to
zymes that degrade cell walls.
D-glyceraldehyde is now known to be the
absolute 1.Not dependent on or relative correct one for the dextrorotatory form, al-
to anything else, e.g. *absolute zero. 2.De- though this was not known at the time.
noting a temperature measured on an ab- However, all D-compounds are not dextro-
solute scale, a scale of temperature based on rotatory. For instance, the acid obtained by
absolute zero. The usual absolute scale now oxidizing the –CHO group of glyceraldehyde
is that of thermodynamic *temperature; its is glyceric acid (1,2-dihydroxypropanoic
unit, the kelvin, was formerly called the de- acid). By convention, this belongs to the
gree absolute (°A) and is the same size as the D-series, but it is in fact laevorotatory; i.e.
degree Celsius. In British engineering prac- its name can be written as D-glyceric acid
tice an absolute scale with Fahrenheit-size orl-glyceric acid. To avoid confusion it is
degrees has been used: this is the Rankine better to use + (for dextrorotatory) and – (for
scale. laevorotatory), as in D-(+)-glyceraldehyde
and D-(–)-glyceric acid.
absolute alcohol See.
The D–L convention can also be used with
absolute conÜguration A way of denot- alpha amino acids (compounds with the
ing the absolute structure of an optical iso- –NH2group on the same carbon as the
mer (see ). Two conventions –COOH group). In this case the molecule is
are in use: The D–L convention relates the imagined as being viewed along the H–C
structure of the molecule to some reference bond between the hydrogen and the asym-
molecule. In the case of sugars and similar metric carbon atom. If the clockwise order of
compounds, the dextrorotatory form of the other three groups is –COOH, –R, –NH2,
glyceraldehyde (HOCH2CH(OH)CHO), 2,3- the amino acid belongs to the D-series; oth-
dihydroxypropanal) was used. The rule is as erwise it belongs to the L-series. This is
follows. Write the structure of this molecule known as the CORN rule.
down with the asymmetric carbon in the The R–S convention is a convention based
centre, the –CHO group at the top, the –OH on priority of groups attached to the chiral
on the right, the –CH2OH at the bottom, and carbon atom. The order of priority is I, Br, Cl,
the –H on the left. Now imagine that the cen- SO3H, OCOCH3, OCH3, OH, NO2, NH2,
3 absolute value
(cid:1)(cid:2)(cid:3) (cid:1)(cid:2)(cid:3) (cid:1)(cid:2)(cid:3) a
(cid:2) (cid:1) (cid:3)(cid:2) (cid:1) (cid:2)(cid:1)(cid:3)(cid:2)
(cid:2) (cid:3)(cid:2)
(cid:1)(cid:2)(cid:3)(cid:2) (cid:1)(cid:2)(cid:3)(cid:2) (cid:1)(cid:2)(cid:3)(cid:2)
(cid:4) (cid:4) (cid:4)
(cid:5)(cid:6)(cid:7)(cid:8)(cid:7)(cid:9)(cid:10)(cid:11)(cid:12)(cid:9)(cid:13)(cid:14)(cid:6)(cid:7) (cid:15)(cid:16)(cid:9)(cid:14)(cid:17)(cid:16)(cid:14)(cid:9)(cid:18)(cid:10)(cid:19)(cid:8)(cid:10)(cid:20) (cid:22)(cid:19)(cid:15)(cid:17)(cid:23)(cid:18)(cid:9)(cid:10)(cid:5)(cid:9)(cid:12)(cid:24)(cid:18)(cid:17)(cid:16)(cid:19)(cid:12)(cid:8)
(cid:21)(cid:19)(cid:13)(cid:18)(cid:8)(cid:15)(cid:19)(cid:12)(cid:8)(cid:15)
(cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:2)(cid:6)(cid:7)(cid:8)(cid:9)(cid:10)(cid:11)(cid:12)(cid:7)(cid:13)(cid:10)(cid:14)(cid:8)(cid:13)(cid:10)(cid:15)(cid:3)(cid:16)(cid:17)(cid:18)(cid:2)(cid:13)(cid:19)(cid:14)(cid:8)(cid:13)(cid:11)(cid:20)(cid:21)(cid:8)(cid:22)(cid:11)(cid:20)(cid:22)(cid:12)(cid:23)(cid:12)(cid:7)(cid:1)
(cid:2) (cid:1)(cid:3)(cid:3)(cid:2)
(cid:1) (cid:2)
(cid:1)(cid:2)(cid:20) (cid:1)(cid:3)(cid:3)(cid:2) (cid:1)(cid:2)(cid:20) (cid:25)(cid:2)(cid:4)
(cid:25)(cid:2)
(cid:4)
(cid:1)(cid:2)(cid:12)(cid:7)(cid:12)(cid:23)(cid:19)(cid:23)(cid:10)(cid:15)(cid:3)(cid:24)(cid:15)(cid:19)(cid:25)(cid:15)(cid:26)(cid:27)(cid:16)(cid:15)(cid:19)(cid:23)(cid:15)(cid:28)(cid:14)(cid:10)(cid:15)(cid:26)(cid:29)(cid:24)(cid:30)(cid:15)(cid:11)(cid:31)(cid:7)(cid:10)(cid:5) (cid:15)!(cid:14)(cid:10)(cid:15)"(cid:20)(cid:7)(cid:10)(cid:9)(cid:31)(cid:7)(cid:10)(cid:15)(cid:19)(cid:25)(cid:15)#(cid:19)(cid:10)$(cid:10)(cid:13)(cid:15)$(cid:19)(cid:28)(cid:14)(cid:15)(cid:27)(cid:15)(cid:20)(cid:23)(cid:15)(cid:28)(cid:20)(cid:22)
(cid:26) (cid:26)
(cid:1) (cid:1)
(cid:20) (cid:4) (cid:4) (cid:20)
(cid:27)(cid:28)(cid:17)(cid:12)(cid:8)(cid:11)(cid:19)(cid:29)(cid:14)(cid:9)(cid:7)(cid:16)(cid:19)(cid:12)(cid:8) (cid:30)(cid:28)(cid:17)(cid:12)(cid:8)(cid:11)(cid:19)(cid:29)(cid:14)(cid:9)(cid:7)(cid:16)(cid:19)(cid:12)(cid:8)
(cid:24)%&(cid:15)(cid:25)(cid:8)(cid:25)(cid:28)(cid:10)" (cid:15)!(cid:14)(cid:10)(cid:15)(cid:7)(cid:20)$(cid:10)(cid:25)(cid:28)(cid:15)(cid:22)(cid:11)(cid:19)(cid:20)(cid:11)(cid:19)(cid:28)(cid:8)(cid:15)(cid:6)(cid:11)(cid:20)(cid:31)(cid:22)(cid:15)(cid:19)(cid:25)(cid:15)’(cid:10)(cid:14)(cid:19)(cid:23)(cid:13)(cid:15)(cid:28)(cid:14)(cid:10)(cid:15)(cid:9)(cid:14)(cid:19)(cid:11)(cid:12)(cid:7)(cid:15)(cid:9)(cid:12)(cid:11)’(cid:20)(cid:23)(cid:15)(cid:12)(cid:28)(cid:20)"
Absolute configuration.
COOCH3, CONH2, COCH3, CHO, CH2OH, without reference to a tuned musical instru-
C6H5, C2H5, CH3, H, with hydrogen lowest. ment.
The molecule is viewed with the group of absolute space Space that exists as a
lowest priority behind the chiral atom. If the
background to events and processes and is
clockwise arrangement of the other three not affected by objects or other entities in
groups is in descending priority, the com- the universe. The idea underpins Newtonian
pound belongs to the R-series; if the de- physics, although many physicists have al-
scending order is anticlockwise it is in the ways regarded absolute space as an undesir-
S-series. D-(+)-glyceraldehyde is R-(+)-glyc- able concept and suggested, as in *Mach’s
Aeraldehyde. See illustration. principle, that fundamental physics should
be described by *relational theories.
• Information about IUPAC nomenclature for the absolute temperature See;
R–S system .
absolute expansivity See. absolute time Time that exists indepen-
absolute humidity See. dently of any events or processes in the uni-
verse. Like *absolute space, absolute time is
absolute permittivity See. a basic concept in Newtonian physics.
absolute pitch (perfect pitch) The ability absolute value (modulus) The square
of a person to identify and reproduce a note root of the sum of the squares of the real
absolute zero 4
a numbers in a *complex number, i.e. the ab- the total mass of the earth’s crust, often ex-
solute value of the complex number z=x+ iy pressed as a percentage. For example, the
is |z| = √(x2+y2). abundance of aluminium in the earth’s crust
is about 8%. 2.The ratio of the number of
absolute zero Zero of thermodynamic
atoms of a particular isotope of an element
*temperature (0 kelvin) and the lowest tem-
to the total number of atoms of all the iso-
perature theoretically attainable. It is the
topes present, often expressed as a percent-
temperature at which the kinetic energy of
age. For example, the abundance of
atoms and molecules is minimal. It is equiv-
alent to –273.15°C or –459.67°F.See also uranium–235 in natural uranium is 0.71%.
- ;. This is the natural abundance, i.e. the abun-
dance as found in nature before any enrich-
absorbed dose See. ment has taken place.
absorptance Symbolα. The ratio of the abyssal zone The lower depths of the
radiant or luminousÛux absorbed by a body ocean (below approximately 2000 metres),
to theÛux falling on it. Formerly called ab- where there is effectively no light penetra-
sorptivity, the absorptance of a *black body tion. Abyssal organisms are adapted for liv-
is by deÜnition 1. ing under high pressures in cold dark
absorption 1.(in chemistry) The take up conditions.See also .
of a gas by a solid or liquid, or the take up of a.c. See .
a liquid by a solid. Absorption differs from
*adsorption in that the absorbed substance acac The symbol for the *acetylacetonato
permeates the bulk of the absorbing sub- ligand, used in formulae.
stance. 2.(in physics) The conversion of the accelerant AÛammable material used to
energy of electromagnetic radiation, sound, start and spread aÜre in cases of arson.
streams of particles, etc., into other forms of Petrol and parafÜn are the substances com-
energy on passing through a medium. A monly used. Traces of accelerant are de-
beam of light, for instance, passing through a tectable by gas chromatography in forensic
medium, may lose intensity because of two work.
effects: scattering of light out of the beam,
and absorption of photons by atoms or mol- acceleration Symbola. The rate of in-
ecules in the medium. When a photon is ab- crease of speed or velocity. It is measured in
sorbed, there is a transition to an excited ms–2. For a body moving linearly with con-
state. 3.(in biology) The movement ofÛuid stant acceleration afrom a speed uto a
or a dissolved substance across a plasma speedv,
membrane. In many animals, for example, a=(v–u)/t=(v2–u2)/2s
soluble food material is absorbed into cells wheretis the time taken and sthe distance
lining the alimentary canal and thence into covered.
the blood. In plants, water and mineral salts If the acceleration is not constant it is
are absorbed from the soil by the *roots. See given by dv/dt= d2s/dt2. If the motion is not
; . linear the vector character of displacement,
absorption coefÜcient 1.(in physics) velocity, and acceleration must be consid-
SeeL’ . 2.(in chemistry) The ered.See also .
volume of a given gas, measured at standard acceleration of free fall Symbolg. The
temperature and pressure, that will dissolve
acceleration experienced by any massive ob-
in unit volume of a given liquid.
ject falling freely in the earth’s gravitational
absorption indicator See - Üeld. Experimentally this is almost constant
. for all positions near the earth’s surface, in-
absorption spectrum See. dependent of the nature of the falling body
(provided air resistance is eliminated). This
absorptivity See. is taken to indicate the strict proportionality
of *weight (the force causing the accelera-
ABS plastic Any of a class of plastics based
tion) and inertial *mass, on the basis of
on acrylonitrile–butadiene–styrene copoly-
Newton’s second law of motion (see
mers. N’ ). There is some
abundance 1.The ratio of the total mass variation of gwith latitude, because of the
of a speciÜed element in the earth’s crust to earth’s rotation and because the earth is
