30 (
thirty) is the
natural number following
29 and preceding
31.
In mathematics
30 is the sum of the first four squares, which makes it a
square pyramidal number.
It is a
primorial and is the smallest
Giuga number.
30 is the smallest
sphenic number,
and the smallest of the form 2\cdot 3\cdot r where r is a prime
greater than 3. 30 has an
aliquot sum of
42; the second
sphenic
number and all
sphenic numbers
of this form have an
aliquot sum 12
greater than themselves. The
aliquot
sequence of 30 is 16 members long, it comprises (
30,
42,
54,
66,
90,
144,
259,
45,
33,
15,
9,
4,
3,
1,0)
Thirty has but one number for which it is the
aliquot sum the
square
number 841.
Adding up some subsets of its divisors (e.g., 5, 10 and 15) gives
30, hence 30 is a
semiperfect
number.
30 is the largest number such that
coprimes
smaller than itself are also prime.
A
polygon with thirty sides is called a
tricontagon. Both an
icosahedron and a
dodecahedron have 30 edges.
E_{8} has
Coxeter number 30.
30 is a
Harshad number.
Since any group G such that |G| = p
^{n}m, where p does not
divide m, has a subgroup of order p
^{n}, and 30 is the only
number less than 60 that is not either a prime or of the above
form, it is the only candidate for the order of a
simple group less than 60 that one needs other
methods to reject.
In science
Astronomy
In other fields
Thirty is:
Historical years
30 A.D.,
30
B.C.,
1930,
2030,
etc.
History and Literature
- At age 30 (according to most biblical scholars) Jesus of Nazareth was baptized by John the Baptist, at
the beginning of his public ministry of teaching and healing.
- One of the rallying-cries of the 1960s student/youth protest
movement was the slogan, 'Don't trust anyone over thirty'.
- In 'The Myth of Sisyphus' the French existentialist Albert Camus comments that the age of thirty is
a crucial period in the life of a man, for at that age he gains a
new awareness of the meaning of time.
- In Franz Kafka's novel 'The Trial'
Joseph wakes up on the morning of his thirtieth birthday to find
himself under arrest for an unspecified crime. After making many
futile attempts to find the nature of the crime or the name of his
accuser, Joseph dies on the eve of his thirty-first birthday.
- The
number of uprights that formed the Sarsen
Circle at Stonehenge, also the supposed number of holes forming the
arrays of Y and Z Holes at
Stonehenge.
- Western Christianity's most prolific 20th century essayist,
F. W.
Boreham in 'Life at Thirty' ('Cliffs
of Opal') mentions that in addition to Jesus commencing ministry at
30 (Luke 3:23), Joseph was 30 when he stood before Pharaoh, King of
Egypt (Genesis 41:46), King David was 30 when he began to reign (2
Samuel 5:4), and the Levites were numbered from the age of 30 and
upward (1 Chronicles 23:3). Also in that essay Boreham writes 'It
was said of [the English poet] Keats, that "he ensphered himself in
thirty perfect years and died, not young".'
Sports
- In tennis, the number 30 represents the second point gained in
a game.
- The California
Angels (now Los Angeles Angels) baseball team retired the
number in honor of its most notable wearer, Nolan Ryan, on June 16, 1992. (Ryan is the only
major league player to have his number retired by three different
teams, though the other two teams retired number 34 for him rather
than 30). The San Francisco
Giants extended the same honor to Orlando Cepeda. Nick
Swisher of the Chicago White
Sox wears the number 30 and is known as "The Dirty 30".
- 30 is one of the more common numbers worn by hockey goaltenders
(along with 31).
- The number of New Jersey
Devils goalie, Martin
Brodeur
Music
References