electrostatic induction Modification in the distribution of electric charge on one material under the influence of an electric charge on a nearby object. It occurs whenever any object is placed in an electric field. When a negatively charged object is brought near a neutral object, it induces a positive charge on the near side of the object and a negative charge on the far side. If the negative side of the original object is momen¬ tarily grounded, the negative charge may escape, so that the object becomes positively charged by induction.
electroweak theory Theory that describes both the electromagnetic force and the weak force. Though the forces appeal' to be different, they are actually different facets of a more fundamental force. This theory, for¬ mulated in the 1960s by Sheldon Glashow (bom 1932), Steven Weinberg (born 1933), and Abdus Salam (born 1926), represents a 20th-century sci¬ entific landmark and won its authors a 1979 Nobel Prize. It was validated in the 1980s with the discovery of the W particle and Z particle, which it had predicted. See also fundamental interaction, unified field theory.
electrum Natural or artificial alloy of gold with at least 20% silver, used to make the first known coins in the Western world. Most natural elec- trum also contains copper, iron, palladium, bismuth, and perhaps other
metals. The colour varies from white-gold to brassy, depending on the percentages of the major constituents and copper. The first Western coin¬ age, possibly begun by King Gyges of Lydia (7th century bc), consisted of irregular ingots of electrum bearing his stamp as a guarantee of nego¬ tiability at a predetermined value. See also coinage.
elegy Ve-l9-je\ Meditative lyric poem. The classical elegy was any poem written in elegiac metre (alternating lines of dactylic hexameter and pen¬ tameter). Today the term may refer to this metre rather than to content, but in English literature since the 16th century it has meant a lament in any metre. A distinct variety with a formal pattern is the pastoral elegy, such as John Milton’s “Lycidas” (1638). Poets of the 18th-century Grave¬ yard School reflected on death and immortality in elegies, most famously Thomas Gray’s “An Elegy Written in a Country Church Yard” (1751).
element, chemical One of the more than 110 presently known kinds of substances that constitute all matter at and above the level of atoms (the smallest units of any element). All atoms of an element are identical in nuclear charge (number of protons) and number of electrons (see atomic number), but their mass (atomic weight) may differ if they have different numbers of neutrons (see isotope). Each permanently named element has a one- or two-letter chemical symbol. Elements combine to form a wide variety of compounds. All elements with atomic numbers greater than 83 (bismuth), and some isotopes of lighter elements, are unstable and radio¬ active (see radioactivity). The transuranium elements, with atomic numbers greater than 92 (see uranium), artificially created by bombardment of other elements with neutrons or other particles, were discovered beginning in 1940. The most common elements (by weight) in Earth’s crust are oxy¬ gen, 49%; silicon, 26%; aluminum, 8%; and iron, 5%. Of the known ele¬ ments, 11 (hydrogen, nitrogen, oxygen, fluorine, chlorine, and the six noble gases) are GASes under ordinary conditions, two (bromine and mer¬ cury) are liquids (two more, cesium and gallium, melt at about or just above room temperature), and the rest are solids. See also periodic table. See illustration and table on following pages.
elementary education or primary education Traditionally, the first stage of formal education, beginning at age 5-7 and ending at age 11-13. Often preceded by some form of preschool, it usually includes middle school, or junior high school (ages 11-13), though this is some¬ times regarded as part of secondary education. Nearly all nations are com¬ mitted to some form of elementary education, though in many developing countries many children are unable to continue full-time studies past the age of 10 or 11. The elementary curriculum usually emphasizes reading and writing, arithmetic, social studies, and science. A basic teaching strat¬ egy involves moving the student from the immediate and familiar to the distant and unfamiliar, an approach first formulated by Johann Heinrich Pestalozzi.
elementary particle See subatomic particle
elephant Any of three ungulate species in the order Proboscidea (fam¬ ily Elephantidae), characterized by their large size, long trunk, tusks, massive legs, large ears, and huge head. All species are grayish to brown, with sparse, coarse body hair.
The trunk is used for breathing, drinking, and reaching for food.
Elephants eat grasses, leaves, and fruit. The African savanna, or bush elephant (Loxodonta africana ), of sub-Saharan Africa, is the largest liv¬ ing land animal, weighing up to 16,500 lbs (7,500 kg) and standing Asian elephant [Elephas maximus).
10-13 ft (3-4 m) tall at the shoulder. ES ROSS _
The African forest elephant (L.
cyclotis) is smaller. The Indian elephant (Elephas maximus ), of South and Southeast Asia, weighs about 12,000 lbs (5,500 kg) and stands about 10 ft (3 m) tall. Elephants live in habitats ranging from thick jungle to savanna, in small family groups led by old cows. Most bulls live in bach¬ elor herds. Elephants migrate seasonally. They may eat more than 500 lbs (225 kg) of vegetation daily. All species are considered endangered by the International Union for Conservation of Nature and Natural Resources (IUCN).
elephant bird See aepyornis
© 2006 Encyclopaedia Britannica, Inc.
Elephant Man ► elevator I 611
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PERIODIC TABLE OF THE ELEMENTS
18
0
1
2
□
alkali metals
[” | other nonmetals 0 noble gases
13
14
15
16
17
2
H
1 la
■
alkaline earth metals
0 halogens
| actinide elements
Ilia
IVa
Va
Via
Vila
He
3
4
□
transition metals Q rare earth elements (21,39, 57-71)
5
6
7
8
9
10
Li
Be
B
other metals
lanthanide elements (57-71 only)
B
C
N
O
F
Ne
11
12
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Na
Mg
nib
IVb
Vb
Vlb
Vllb
-Vlllb-
lb
lib
Al
Si
P
S
Cl
Ar
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
1
Xe
55
56
57
72
73
74
75
76
77
78
79
80
81
82
83
85
86
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg