TED2012
Terry Moore: Why is 'x' the unknown?
Filmed:
Readability: 5.1
3,872,013 views
Why is 'x' the symbol for an unknown? In this short and funny talk, Terry Moore gives the surprising answer.
Terry Moore - Thinker
Terry Moore is the director of the Radius Foundation, a forum for exploring and gaining insight from different worldviews. Full bio
Terry Moore is the director of the Radius Foundation, a forum for exploring and gaining insight from different worldviews. Full bio
Double-click the English transcript below to play the video.
00:16
I have the answer to a question that we've all asked.
0
611
3601
00:20
The question is,
1
4212
1117
00:21
Why is it that the letter X
2
5329
2284
00:23
represents the unknown?
3
7613
1998
00:25
Now I know we learned that in math class,
4
9611
2967
00:28
but now it's everywhere in the culture --
5
12578
1751
00:30
The X prize, the X-Files,
6
14329
2801
00:33
Project X, TEDx.
7
17130
3923
00:36
Where'd that come from?
8
21053
1995
00:38
About six years ago
9
23048
1218
00:40
I decided that I would learn Arabic,
10
24266
2716
00:42
which turns out to be a supremely logical language.
11
26982
3952
00:46
To write a word or a phrase
12
30934
2317
00:49
or a sentence in Arabic
13
33251
1681
00:50
is like crafting an equation,
14
34932
2233
00:53
because every part is extremely precise
15
37165
2366
00:55
and carries a lot of information.
16
39531
2852
00:58
That's one of the reasons
17
42383
1350
00:59
so much of what we've come to think of
18
43733
1515
01:01
as Western science and mathematics and engineering
19
45248
3819
01:04
was really worked out in the first few centuries of the Common Era
20
49067
3322
01:08
by the Persians and the Arabs and the Turks.
21
52389
3316
01:11
This includes the little system in Arabic
22
55705
2317
01:13
called al-jebra.
23
58022
1716
01:15
And al-jebr roughly translates to
24
59738
3168
01:18
"the system for reconciling disparate parts."
25
62906
3699
01:22
Al-jebr finally came into English as algebra.
26
66605
4050
01:26
One example among many.
27
70655
2167
01:28
The Arabic texts containing this mathematical wisdom
28
72822
3966
01:32
finally made their way to Europe --
29
76788
1783
01:34
which is to say Spain --
30
78571
1286
01:35
in the 11th and 12th centuries.
31
79857
2465
01:38
And when they arrived
32
82322
1150
01:39
there was tremendous interest
33
83472
1883
01:41
in translating this wisdom
34
85355
1734
01:42
into a European language.
35
87089
1649
01:44
But there were problems.
36
88738
2018
01:46
One problem
37
90756
1717
01:48
is there are some sounds in Arabic
38
92473
2633
01:51
that just don't make it through a European voice box
39
95106
2999
01:54
without lots of practice.
40
98105
2267
01:56
Trust me on that one.
41
100372
1734
01:58
Also, those very sounds
42
102106
2217
02:00
tend not to be represented
43
104323
1914
02:02
by the characters that are available in European languages.
44
106237
3588
02:05
Here's one of the culprits.
45
109825
1814
02:07
This is the letter SHeen,
46
111639
1884
02:09
and it makes the sound we think of as SH -- "sh."
47
113523
3599
02:13
It's also the very first letter
48
117122
2602
02:15
of the word shalan,
49
119724
2432
02:18
which means "something"
50
122156
1794
02:19
just like the the English word "something" --
51
123950
1848
02:21
some undefined, unknown thing.
52
125798
3286
02:24
Now in Arabic,
53
129084
1165
02:26
we can make this definite
54
130249
1201
02:27
by adding the definite article "al."
55
131450
2148
02:29
So this is al-shalan --
56
133598
2602
02:32
the unknown thing.
57
136200
1650
02:33
And this is a word that appears throughout early mathematics,
58
137850
3303
02:37
such as this 10th century derivation of proofs.
59
141153
7200
02:44
The problem for the Medieval Spanish scholars
60
148353
2510
02:46
who were tasked with translating this material
61
150863
2568
02:49
is that the letter SHeen and the word shalan
62
153431
4482
02:53
can't be rendered into Spanish
63
157913
1950
02:55
because Spanish doesn't have that SH,
64
159863
2586
02:58
that "sh" sound.
65
162449
1297
02:59
So by convention,
66
163746
1582
03:01
they created a rule in which
67
165328
1666
03:02
they borrowed the CK sound, "ck" sound,
68
166994
4218
03:07
from the classical Greek
69
171212
1748
03:08
in the form of the letter Kai.
70
172960
2681
03:11
Later when this material was translated
71
175641
2719
03:14
into a common European language,
72
178360
2348
03:16
which is to say Latin,
73
180708
2050
03:18
they simply replaced the Greek Kai
74
182758
2033
03:20
with the Latin X.
75
184791
2350
03:23
And once that happened,
76
187141
1269
03:24
once this material was in Latin,
77
188410
2465
03:26
it formed the basis for mathematics textbooks
78
190875
3583
03:30
for almost 600 years.
79
194458
2083
03:32
But now we have the answer to our question.
80
196541
2018
03:34
Why is it that X is the unknown?
81
198559
2781
03:37
X is the unknown
82
201340
1823
03:39
because you can't say "sh" in Spanish.
83
203163
3782
03:42
(Laughter)
84
206945
2384
03:45
And I thought that was worth sharing.
85
209329
2317
03:47
(Applause)
86
211646
3117
ABOUT THE SPEAKER
Terry Moore - ThinkerTerry Moore is the director of the Radius Foundation, a forum for exploring and gaining insight from different worldviews.
Why you should listen
Terry Moore directs the Radius Foundation in New York, which, as its website says, "seeks new ways of exploring and understanding dissimilar conceptual systems or paradigms -- scientific, religious, philosophical, and aesthetic -- with the aim to find a world view of more complete insight and innovation. The Radius Foundation is a forum for different views."
The foundation has published several works that examine the intersection of religion and metaphysics with science and social action.
Terry Moore | Speaker | TED.com