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SAGAN:
The sky calls to us.
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00:00:48,263 --> 00:00:50,566
If we do not destroy ourselves...
3
00:00:50,571 --> 00:00:53,592
....we will one day venture
to the stars.
4
00:00:54,503 --> 00:00:58,173
There was a time when the stars
seemed an impenetrable mystery.
5
00:00:58,178 --> 00:01:01,506
Today, we have begun
to understand them.
6
00:01:01,710 --> 00:01:06,647
In ourpersonal lives also, we
journey from ignorance to knowledge.
7
00:01:06,882 --> 00:01:11,319
Ourindividual growth reflects
the advancement of the species.
8
00:01:11,820 --> 00:01:13,956
The exploration of the cosmos is...
9
00:01:13,961 --> 00:01:16,982
....a voyage ofself-discovery.
10
00:01:27,502 --> 00:01:30,437
When I was a child, I lived here...
11
00:01:30,639 --> 00:01:35,143
....in the Bensonhurst section of
Brooklyn in the city ofNew York.
12
00:01:35,148 --> 00:01:38,413
I knew my immediate
neighborhood intimately...
13
00:01:38,418 --> 00:01:42,679
....every candy store, front stoop...
14
00:01:42,884 --> 00:01:45,148
....back yard, empty lot...
15
00:01:45,354 --> 00:01:48,448
....and wall forplaying
Chinese handball.
16
00:01:54,062 --> 00:01:56,189
It was my whole world.
17
00:02:15,283 --> 00:02:17,619
But more than a few blocks away...
18
00:02:17,624 --> 00:02:22,524
....north of the raucous traffic
and elevated railway on 86th Street...
19
00:02:22,529 --> 00:02:26,617
....was an unknown territory
off-limits to my wanderings.
20
00:02:27,129 --> 00:02:29,893
It could have been Mars
forall I knew.
21
00:02:34,002 --> 00:02:37,068
Even with an early bedtime
in the winter...
22
00:02:37,105 --> 00:02:40,097
....you could occasionally see
the stars.
23
00:02:40,609 --> 00:02:44,186
I would look up at them
and wonder what they were.
24
00:02:44,212 --> 00:02:46,976
I'd ask other kids and adults...
25
00:02:47,549 --> 00:02:49,351
....and they would answer:
26
00:02:49,356 --> 00:02:51,620
"They're lights in the sky, kid."
27
00:02:51,625 --> 00:02:55,791
Well, I could tell they were lights
in the sky, but what were they?
28
00:02:55,796 --> 00:02:59,227
There had to be some deeper answer.
29
00:03:04,633 --> 00:03:08,125
I remember I was issued
my first library card.
30
00:03:08,336 --> 00:03:13,373
It was some library on 85th Street.
Anyway, it was in alien territory.
31
00:03:13,375 --> 00:03:17,072
And I asked the librarian
for a book on stars.
32
00:03:17,512 --> 00:03:18,945
She gave me...
33
00:03:19,381 --> 00:03:22,517
....a picture book with portraits
of men and women...
34
00:03:22,522 --> 00:03:26,146
....with names like
Veronica Lake and Alan Ladd.
35
00:03:26,688 --> 00:03:30,089
I explained that wasn't what
I wanted at all.
36
00:03:30,692 --> 00:03:34,329
And for some reason,
then obscure to me, she smiled...
37
00:03:34,334 --> 00:03:37,799
....and got me another book,
the right kind of book.
38
00:03:37,804 --> 00:03:40,302
I was so excited to know
the answer...
39
00:03:40,307 --> 00:03:43,572
....l opened the book breathlessly,
right there in the library...
40
00:03:43,577 --> 00:03:46,608
....and the book said
something astonishing...
41
00:03:46,613 --> 00:03:49,099
....a very big thought.
42
00:03:49,811 --> 00:03:53,144
Stars, it said, were suns...
43
00:03:53,348 --> 00:03:55,111
....but very far away.
44
00:03:55,317 --> 00:03:59,253
The sun was a star, but close-up.
45
00:04:06,928 --> 00:04:10,866
How, I wondered, could anybody
know such things forsure?
46
00:04:10,871 --> 00:04:14,740
How did they figure it out?
Where did they even begin?
47
00:04:23,945 --> 00:04:27,011
I was ignorant of the idea
of angular size.
48
00:04:27,115 --> 00:04:31,319
I didn't know about the inverse square
law of the propagation of light.
49
00:04:31,324 --> 00:04:35,323
I didn't have any chance of
calculating the distance to the stars.
50
00:04:35,328 --> 00:04:38,627
But I could tell that if
the stars were suns...
51
00:04:38,632 --> 00:04:41,260
....they had to be awfully far away.
52
00:04:41,296 --> 00:04:45,676
Further away than 86th Street,
further away than Manhattan...
53
00:04:45,734 --> 00:04:49,101
....further away, probably,
than New Jersey.
54
00:04:49,304 --> 00:04:53,001
The universe had become
much grander...
55
00:04:53,208 --> 00:04:55,574
....than I had ever guessed.
56
00:04:58,513 --> 00:05:01,383
And then I read
another astonishing fact.
57
00:05:01,388 --> 00:05:04,682
The Earth, which includes Brooklyn...
58
00:05:04,886 --> 00:05:06,183
....was a planet.
59
00:05:06,388 --> 00:05:08,447
It went around the sun.
60
00:05:08,657 --> 00:05:10,458
There were other planets.
61
00:05:10,463 --> 00:05:12,799
They also went around the sun...
62
00:05:12,928 --> 00:05:16,464
....some closer to the sun,
some further from the sun.
63
00:05:16,469 --> 00:05:21,141
But planets didn't shine by their
own light the way the sun does.
64
00:05:21,736 --> 00:05:25,695
No, planets simply reflected
the little bit of light...
65
00:05:25,907 --> 00:05:29,502
....that shines on them
from the sun back to us.
66
00:05:29,711 --> 00:05:32,180
If you were a great distance
from the sun...
67
00:05:32,185 --> 00:05:36,151
....you wouldn't be able to see
the Earth or the other planets at all.
68
00:05:36,156 --> 00:05:39,054
Well, then, it stood
to reason, I thought...
69
00:05:39,059 --> 00:05:42,891
....that those other stars ought to
have their own planets...
70
00:05:42,896 --> 00:05:45,794
....and some of those planets
ought to have life.
71
00:05:45,799 --> 00:05:47,022
Why not?
72
00:05:47,229 --> 00:05:51,833
And that life ought to be pretty
different from life as we know it...
73
00:05:51,838 --> 00:05:53,824
....life here in Brooklyn.
74
00:05:54,035 --> 00:05:57,320
Ganymede. Look at this
amazing Ganymede stuff.
75
00:05:57,372 --> 00:05:58,613
Wait, wait, wait.
76
00:05:58,640 --> 00:06:01,243
As a child, it was
my immense good fortune...
77
00:06:01,248 --> 00:06:05,480
....to have parents and a few teachers
who encouraged my curiosity.
78
00:06:05,485 --> 00:06:07,821
This was my 6th-grade classroom.
79
00:06:08,016 --> 00:06:11,186
I came back here one day
to remember what it was like.
80
00:06:11,191 --> 00:06:14,122
I brought some of the pictures
of other worlds...
81
00:06:14,127 --> 00:06:16,958
....that were radioed back
by the Voyager spacecraft...
82
00:06:16,963 --> 00:06:19,085
....ofJupiterand its moons.
83
00:06:19,294 --> 00:06:21,062
This is Calisto which is--
84
00:06:21,067 --> 00:06:22,222
(SAGAN LAUGHS)
85
00:06:24,599 --> 00:06:26,735
What is a Calisto?
I want a Calisto.
86
00:06:26,740 --> 00:06:28,236
Now you got it.
What is it?
87
00:06:28,241 --> 00:06:31,728
It's the outermost
big moon of Jupiter.
88
00:06:32,807 --> 00:06:35,241
Who is this guy? Europa.
89
00:06:36,645 --> 00:06:38,272
Another Europa.
90
00:06:38,647 --> 00:06:42,005
A black-and-white picture
of a ring of Jupiter.
91
00:06:42,117 --> 00:06:45,143
There you go.
That's a prize for honesty.
92
00:06:45,787 --> 00:06:47,489
You didn't get a second.
93
00:06:47,494 --> 00:06:49,319
Which one would you like?
94
00:07:01,169 --> 00:07:04,439
Every one of us begins life
with an open mind...
95
00:07:04,444 --> 00:07:08,375
....a driving curiosity,
a sense of wonder.
96
00:07:09,477 --> 00:07:13,014
I thought it might be fun
if we now had some questions.
97
00:07:13,019 --> 00:07:17,545
Why is the Earth round?
Why isn't it square or any other shape?
98
00:07:17,619 --> 00:07:19,298
That's a good question.
99
00:07:19,421 --> 00:07:24,359
That's a question I've asked myself.
The answer has to do with gravity.
100
00:07:24,364 --> 00:07:26,394
The Earth has a strong gravity.
101
00:07:26,399 --> 00:07:29,164
If you were to make a mountain
very high...
102
00:07:29,169 --> 00:07:32,267
....higher than Everest,
the biggest mountain on Earth...
103
00:07:32,272 --> 00:07:34,803
....it would be crushed
by its own weight.
104
00:07:34,808 --> 00:07:37,672
Gravity pulls everything
towards the center.
105
00:07:37,677 --> 00:07:41,035
So any really big bump
on the Earth is crushed.
106
00:07:41,142 --> 00:07:44,771
But if you had a small object,
a tiny world...
107
00:07:44,980 --> 00:07:46,848
....the gravity is very low...
108
00:07:46,853 --> 00:07:50,218
....and then it can be very different
from a sphere.
109
00:07:50,223 --> 00:07:54,621
I think I have here
a world that isn't a sphere.
110
00:07:54,990 --> 00:07:56,048
Here.
111
00:07:57,258 --> 00:07:58,589
Look at this one.
112
00:07:59,794 --> 00:08:01,284
See? It's lumpy.
113
00:08:03,064 --> 00:08:04,451
It's a lumpy world.
114
00:08:05,333 --> 00:08:07,012
It looks like a potato.
115
00:08:07,435 --> 00:08:10,805
There's a large potato
orbiting the planet Mars.
116
00:08:10,810 --> 00:08:13,219
This is one of the moons of Mars.
117
00:08:13,241 --> 00:08:15,471
That's a perfect example.
118
00:08:15,677 --> 00:08:19,881
You can have big departures from
a sphere if your gravity is low.
119
00:08:19,886 --> 00:08:21,983
Now the question in the front.
120
00:08:21,988 --> 00:08:25,420
Is the sun considered part
of the Milky Way galaxy?
121
00:08:25,425 --> 00:08:28,990
Sure, you're considered part
of the Milky Way galaxy.
122
00:08:28,995 --> 00:08:33,495
Everything except other galaxies is
part of the Milky Way galaxy.
123
00:08:33,500 --> 00:08:35,053
The sun is one star.
124
00:08:35,263 --> 00:08:40,200
There is a few hundred billion stars
in the Milky Way.
125
00:08:40,502 --> 00:08:44,105
Around each star, maybe,
is a whole bunch of planets.
126
00:08:44,110 --> 00:08:47,336
And on one of those planets is life...
127
00:08:47,542 --> 00:08:51,410
....and one of the life forms
on that planet is you.
128
00:08:51,613 --> 00:08:54,606
You're a part of
the Milky Way galaxy too.
129
00:09:04,459 --> 00:09:09,396
Sometimes I think, how lucky we are
to live in this time...
130
00:09:09,597 --> 00:09:13,468
....the first moment in human history
when we are, in fact...
131
00:09:13,473 --> 00:09:15,270
....visiting other worlds...
132
00:09:15,275 --> 00:09:19,502
....and engaging in a deep
reconnaissance of the cosmos.
133
00:09:19,874 --> 00:09:22,710
But if we had been born
in a much earlierage...
134
00:09:22,715 --> 00:09:26,014
....no matterhow great our dedication,
we couldn't have understood...
135
00:09:26,019 --> 00:09:28,574
....what the stars and planets are.
136
00:09:37,826 --> 00:09:42,644
We would not have known that there
were othersuns and other worlds.
137
00:09:45,667 --> 00:09:49,626
This is one of the great secrets
wrested from nature...
138
00:09:49,838 --> 00:09:55,167
....through a million years ofpatient
observation and courageous thinking.
139
00:09:57,779 --> 00:10:01,783
Human beings have always asked
questions about the stars.
140
00:10:01,788 --> 00:10:04,843
It's as natural as breathing.
141
00:10:05,086 --> 00:10:09,124
But imagine a time before science
had found out the answers.
142
00:10:09,129 --> 00:10:11,718
Imagine what it was like, say...
143
00:10:11,926 --> 00:10:15,453
....hundreds of thousands
of years ago...
144
00:10:15,663 --> 00:10:19,258
....soon after the discovery of fire.
145
00:10:19,467 --> 00:10:23,062
We were just as smart
and just as curious then...
146
00:10:23,271 --> 00:10:24,932
....as we are now.
147
00:10:25,140 --> 00:10:27,208
Sometimes it seems to me that...
148
00:10:27,213 --> 00:10:30,717
....there were people then
who thought like this:
149
00:10:32,614 --> 00:10:36,175
We are wandering hunter folk.
150
00:10:36,384 --> 00:10:38,045
Fire keeps us warm.
151
00:10:38,253 --> 00:10:41,484
Its light makes holes in the darkness.
152
00:10:41,689 --> 00:10:43,953
It keeps hungry animals away.
153
00:10:44,392 --> 00:10:47,884
In the darkness,
we can see each otherand talk.
154
00:10:49,063 --> 00:10:51,054
We take care of the flame.
155
00:10:51,266 --> 00:10:54,258
The flame takes care of us.
156
00:10:55,170 --> 00:10:57,468
The stars are not near to us.
157
00:10:57,672 --> 00:11:01,369
When we climb a hill ora tree,
they are no closer.
158
00:11:01,576 --> 00:11:05,512
They flicker with
a strange, cold, white...
159
00:11:06,314 --> 00:11:07,628
....faraway light.
160
00:11:08,316 --> 00:11:12,616
Many of them, all over the sky,
but only at night.
161
00:11:12,987 --> 00:11:15,080
I wonder what they are.
162
00:11:15,890 --> 00:11:19,417
One night I thought
the stars are flames.
163
00:11:19,627 --> 00:11:22,985
They give a little light
at night as fire does.
164
00:11:23,031 --> 00:11:25,300
Maybe the stars are campfires...
165
00:11:25,305 --> 00:11:28,463
....which other wanderers
light at night.
166
00:11:29,170 --> 00:11:32,707
The stars give a much
smallerlight than campfires...
167
00:11:32,712 --> 00:11:35,505
....so they must be very faraway.
168
00:11:36,077 --> 00:11:38,739
I wonderif our campfires...
169
00:11:38,947 --> 00:11:42,116
....look like stars to the people
in the sky.
170
00:11:42,121 --> 00:11:46,720
But why don't those campfires
and the wanderers who made them...
171
00:11:46,821 --> 00:11:48,719
....fall down at our feet?
172
00:11:48,856 --> 00:11:53,054
Why don't strange tribes
drop from the sky?
173
00:11:54,862 --> 00:11:59,629
Those beings in the sky
must have greatpowers.
174
00:12:06,641 --> 00:12:09,477
I don't suppose
that every hunter-gatherer...
175
00:12:09,482 --> 00:12:12,256
....had such thoughts about the stars.
176
00:12:12,413 --> 00:12:16,050
But we know from contemporary
hunter-gatherer communities...
177
00:12:16,055 --> 00:12:19,781
....that very imaginative ideas arise.
178
00:12:20,221 --> 00:12:22,746
The Kung Bushmen...
179
00:12:22,957 --> 00:12:26,227
....of the Kalahari Desert
in the Republic of Botswana...
180
00:12:26,232 --> 00:12:29,152
....have an explanation
of the Milky Way.
181
00:12:29,163 --> 00:12:32,132
At their latitude,
it's often overhead.
182
00:12:32,333 --> 00:12:36,360
They call it the "backbone of night."
183
00:12:36,571 --> 00:12:39,199
They believe it holds the sky up.
184
00:12:39,407 --> 00:12:41,943
They believe that if not
for the Milky Way...
185
00:12:41,948 --> 00:12:45,780
....pieces of sky would come crashing
down at our feet.
186
00:12:45,785 --> 00:12:49,617
So the Milky Way, in their view,
has some practical value.
187
00:12:49,622 --> 00:12:52,142
The backbone of night.
188
00:12:54,989 --> 00:12:57,685
Later on, metaphors about...
189
00:12:57,959 --> 00:13:00,450
....campfires or backbones...
190
00:13:00,662 --> 00:13:04,165
....or holes through which
the flame could be seen...
191
00:13:04,170 --> 00:13:08,534
....were replaced in most human
communities by another idea.
192
00:13:09,003 --> 00:13:13,872
The powerful beings in the sky
were promoted to gods.
193
00:13:14,509 --> 00:13:17,603
They were given names and relatives...
194
00:13:17,812 --> 00:13:19,947
....and special responsibilities...
195
00:13:19,952 --> 00:13:23,518
....for the cosmic services they were
expected to perform.
196
00:13:23,523 --> 00:13:27,386
There was a god
for every human concern.
197
00:13:27,588 --> 00:13:28,756
Gods ran nature.
198
00:13:28,856 --> 00:13:33,293
Nothing happened without the direct
intervention of some god.
199
00:13:33,594 --> 00:13:37,244
If the gods were happy,
there was plenty of food...
200
00:13:37,265 --> 00:13:39,163
....and humans were happy.
201
00:13:40,635 --> 00:13:43,409
But if something
displeased the gods...
202
00:13:43,604 --> 00:13:47,904
....and it didn't take much,
the consequences were awesome:
203
00:13:48,109 --> 00:13:51,340
Droughts, floods, storms, wars...
204
00:13:51,546 --> 00:13:55,175
....earthquakes, volcanic eruptions,
epidemics.
205
00:13:56,084 --> 00:13:59,110
The gods had to be propitiated.
206
00:13:59,320 --> 00:14:02,094
And a vast industry
of priests arose...
207
00:14:02,190 --> 00:14:04,715
....to make the gods less angry.
208
00:14:05,326 --> 00:14:08,386
But because the gods
were capricious...
209
00:14:08,596 --> 00:14:11,299
....you couldn't be sure
what they would do.
210
00:14:11,304 --> 00:14:13,733
Nature was a mystery.
211
00:14:14,001 --> 00:14:16,629
It was hard to understand the world.
212
00:14:19,574 --> 00:14:22,737
Ourancestors groped in darkness...
213
00:14:22,944 --> 00:14:25,446
....to make sense
of theirsurroundings.
214
00:14:25,451 --> 00:14:27,349
Powerless before nature...
215
00:14:27,615 --> 00:14:30,385
....they invented rituals and myths...
216
00:14:30,390 --> 00:14:32,945
....some desperate and cruel...
217
00:14:33,154 --> 00:14:36,817
....others imaginative and benign.
218
00:14:37,158 --> 00:14:39,421
The ancient Greeks explained...
219
00:14:39,594 --> 00:14:43,264
....that diffuse band ofbrightness
in the night sky...
220
00:14:43,269 --> 00:14:46,043
....as the milk of the goddess Hera...
221
00:14:46,134 --> 00:14:49,303
....squirted from herbreast
across the heavens.
222
00:14:49,308 --> 00:14:52,739
We still call it the Milky Way.
223
00:14:59,247 --> 00:15:02,450
In gratitude for the many gifts
of the gods...
224
00:15:02,455 --> 00:15:06,580
....ourancestors created works
ofsurpassing beauty.
225
00:15:09,524 --> 00:15:12,015
This is all that remains...
226
00:15:12,226 --> 00:15:15,730
....of the ancient temple ofHera,
queen ofheaven:
227
00:15:15,997 --> 00:15:20,866
A single marble column standing
in a vast field ofruins...
228
00:15:21,569 --> 00:15:23,771
....on the Greek island of Samos.
229
00:15:23,776 --> 00:15:26,207
It was one of the wonders
of the world...
230
00:15:26,212 --> 00:15:30,667
....built bypeople with
an extraordinary eye for clarity...
231
00:15:30,878 --> 00:15:32,436
....and symmetry.
232
00:15:39,821 --> 00:15:42,356
Those who thronged to that temple...
233
00:15:42,361 --> 00:15:45,159
....were also the architects
ofa bridge...
234
00:15:45,164 --> 00:15:47,957
....from their world to ours.
235
00:15:50,565 --> 00:15:55,059
We were moving once again
in our voyage ofself-discovery...
236
00:15:55,336 --> 00:15:57,964
....on ourjourney to the stars.
237
00:16:02,910 --> 00:16:06,607
Here, 25 centuries ago...
238
00:16:07,248 --> 00:16:10,818
....on the island of Samos
and in the other Greek colonies...
239
00:16:10,823 --> 00:16:13,588
....which had grown up
in the busy Aegean Sea...
240
00:16:13,593 --> 00:16:16,182
....there was a glorious awakening.
241
00:16:16,390 --> 00:16:20,161
Suddenly, people believed
that everything was made of atoms...
242
00:16:20,166 --> 00:16:24,632
....that human beings and other animals
had evolved from simpler forms...
243
00:16:24,637 --> 00:16:29,262
....that diseases were not caused by
demons or the gods...
244
00:16:29,470 --> 00:16:33,770
....that the Earth was only
a planet going around a sun...
245
00:16:33,975 --> 00:16:36,341
....which was very far away.
246
00:16:39,914 --> 00:16:44,010
This revolution made cosmos
out of chaos.
247
00:16:44,418 --> 00:16:47,955
Here, in the sixth century B.C.,
a new idea developed...
248
00:16:47,960 --> 00:16:50,825
....one of the great ideas
of the human species.
249
00:16:50,830 --> 00:16:54,886
It was argued that the universe
was knowable.
250
00:16:55,196 --> 00:16:57,858
Why? Because it was ordered.
251
00:16:58,065 --> 00:17:00,835
Because there are regularities
in nature...
252
00:17:00,840 --> 00:17:03,979
....which permitted secrets
to be uncovered.
253
00:17:05,907 --> 00:17:09,308
Nature was not entirely unpredictable.
254
00:17:09,510 --> 00:17:13,241
There were rules which even
she had to obey.
255
00:17:15,783 --> 00:17:20,447
This ordered and admirable character
of the universe...
256
00:17:20,655 --> 00:17:22,646
....was called cosmos.
257
00:17:23,824 --> 00:17:26,671
And it was set
in stark contradiction...
258
00:17:26,761 --> 00:17:28,991
....to the idea of chaos.
259
00:17:29,864 --> 00:17:34,130
This was the first conflict
of which we know...
260
00:17:34,569 --> 00:17:37,197
....between science and mysticism...
261
00:17:37,605 --> 00:17:40,335
....between nature and the gods.
262
00:17:46,147 --> 00:17:48,115
But why here?
263
00:17:48,716 --> 00:17:53,354
Why in these remote islands and inlets
of the eastern Mediterranean?
264
00:17:53,359 --> 00:17:55,768
Why not in the great cities of...
265
00:17:55,856 --> 00:18:00,520
....lndia or Egypt, Babylon,
China, Mesoamerica?
266
00:18:03,197 --> 00:18:06,847
Because they were all
at the center of old empires.
267
00:18:09,070 --> 00:18:12,647
They were set in their ways,
hostile to new ideas.
268
00:18:12,807 --> 00:18:14,570
But here in lonia...
269
00:18:14,775 --> 00:18:18,879
....were a multitude ofnewly colonized
islands and city-states.
270
00:18:18,884 --> 00:18:23,213
Isolation, even ifincomplete,
promotes diversity.
271
00:18:23,417 --> 00:18:27,581
No single concentration ofpower
could enforce conformity.
272
00:18:27,788 --> 00:18:30,723
Free inquiry became possible.
273
00:18:31,626 --> 00:18:34,959
They were beyond the frontiers
of the empires.
274
00:18:35,162 --> 00:18:38,739
The merchants and tourists
and sailors ofAfrica...
275
00:18:38,866 --> 00:18:42,370
....Asia and Europe
met in the harbors oflonia...
276
00:18:42,803 --> 00:18:46,603
....to exchange goods
and stories and ideas.
277
00:18:46,807 --> 00:18:50,072
There was a vigorous and heady
interaction...
278
00:18:50,277 --> 00:18:55,078
....ofmany traditions, prejudices,
languages and gods.
279
00:19:04,925 --> 00:19:08,326
These people were ready to experiment.
280
00:19:08,896 --> 00:19:11,990
Once you are open to
questioning rituals...
281
00:19:12,199 --> 00:19:14,368
....and time-honored practices...
282
00:19:14,373 --> 00:19:18,771
....you find that one question
leads to another.
283
00:19:28,482 --> 00:19:31,819
What do you do when you're faced
with several different gods...
284
00:19:31,824 --> 00:19:34,422
....each claiming the same territory?
285
00:19:34,427 --> 00:19:37,191
The Babylonian Marduk
and the Greek Zeus...
286
00:19:37,196 --> 00:19:40,649
....were each considered
king of the gods...
287
00:19:40,861 --> 00:19:42,795
....master of the sky.
288
00:19:43,264 --> 00:19:46,834
You might decide, since they otherwise
had different attributes...
289
00:19:46,839 --> 00:19:49,804
....that one of them was merely
invented by the priests.
290
00:19:49,809 --> 00:19:52,466
But if one, why not both?
291
00:19:58,245 --> 00:20:01,457
And so it was here
that the great idea arose:
292
00:20:01,482 --> 00:20:03,718
The realization that there
might be a way...
293
00:20:03,723 --> 00:20:06,520
....to know the world
without the god hypothesis.
294
00:20:06,525 --> 00:20:11,287
That there be principles,
forces, laws of nature...
295
00:20:11,492 --> 00:20:15,196
....through which the world might be
understood without attributing...
296
00:20:15,201 --> 00:20:19,667
....the fall of every sparrow to
the direct intervention of Zeus.
297
00:20:19,672 --> 00:20:22,864
This is the place
where science was born.
298
00:20:23,237 --> 00:20:25,068
That's why we're here.
299
00:20:26,607 --> 00:20:31,544
This Greek revolution happened
between 600 and 400 B.C.
300
00:20:32,213 --> 00:20:35,583
It was accomplished by the same
practical and productive people...
301
00:20:35,588 --> 00:20:37,618
....who made the society function.
302
00:20:37,623 --> 00:20:40,921
Political power was in the hands
of the merchants...
303
00:20:40,926 --> 00:20:44,558
....who promoted the technology
on which theirprosperity depended.
304
00:20:44,563 --> 00:20:46,927
The earliestpioneers
ofscience were...
305
00:20:46,932 --> 00:20:50,217
....merchants and artisans
and their children.
306
00:20:56,270 --> 00:20:59,671
The first lonian scientist was
named Thales.
307
00:21:00,141 --> 00:21:03,110
He was born over there
in the city of Miletus...
308
00:21:03,115 --> 00:21:05,408
....across this narrow strait.
309
00:21:05,613 --> 00:21:07,581
He had traveled in Egypt...
310
00:21:07,586 --> 00:21:10,851
....and was conversant
with the knowledge of Babylon.
311
00:21:10,856 --> 00:21:15,990
Like the Babylonians, he believed
that the world had once all been water.
312
00:21:15,995 --> 00:21:18,083
To explain the dry land...
313
00:21:18,292 --> 00:21:21,662
....the Babylonians added
that their god, Marduk...
314
00:21:21,667 --> 00:21:25,257
....had placed a mat on the face
of the waters...
315
00:21:25,466 --> 00:21:27,802
....and piled dirt on top of it.
316
00:21:29,270 --> 00:21:31,172
Thales had a similar view...
317
00:21:31,177 --> 00:21:34,073
....but he left Marduk out.
318
00:21:34,875 --> 00:21:38,174
Yes, the world had once been
mostly water...
319
00:21:38,679 --> 00:21:43,207
....but it was a natural process
which explained the dry land.
320
00:21:43,417 --> 00:21:47,855
Thales thought it was similar to
the silting up he had observed...
321
00:21:47,860 --> 00:21:50,415
....at the delta of the river Nile.
322
00:21:51,592 --> 00:21:55,255
Whether Thales' conclusions
were right or wrong...
323
00:21:55,462 --> 00:21:58,920
....is not nearly as important
as his approach.
324
00:21:59,133 --> 00:22:02,660
The world was not made by the gods...
325
00:22:02,870 --> 00:22:06,240
....but instead was the result
of material forces...
326
00:22:06,245 --> 00:22:08,143
....interacting in nature.
327
00:22:08,742 --> 00:22:12,576
Thales brought back from
Babylon and Egypt...
328
00:22:12,780 --> 00:22:16,011
....the seeds of new sciences:
329
00:22:16,250 --> 00:22:18,650
Astronomy and geometry...
330
00:22:18,853 --> 00:22:21,856
....sciences which would
sprout and grow...
331
00:22:21,861 --> 00:22:24,882
....in the fertile soil of lonia.
332
00:22:26,460 --> 00:22:30,362
Anaximander of Miletus, over there...
333
00:22:30,798 --> 00:22:33,267
....was a friend and colleague
of Thales...
334
00:22:33,272 --> 00:22:35,636
....one of the first people
that we know of...
335
00:22:35,641 --> 00:22:38,072
....to have actually done
an experiment.
336
00:22:38,077 --> 00:22:42,600
By examining the moving shadow
cast by a vertical stick...
337
00:22:42,810 --> 00:22:47,482
....he determined accurately
the lengths of the year and seasons.
338
00:22:47,548 --> 00:22:50,779
For ages, men had used sticks...
339
00:22:50,985 --> 00:22:53,254
....to club and spear each other.
340
00:22:53,259 --> 00:22:56,781
Anaximander used a stick
to measure time.
341
00:23:01,262 --> 00:23:05,858
In 540 B.C., or thereabouts,
on this island of Samos...
342
00:23:06,066 --> 00:23:10,594
....there came to power a tyrant
named Polycrates.
343
00:23:10,871 --> 00:23:13,107
He seems to have started
as a caterer...
344
00:23:13,112 --> 00:23:16,324
....and then went on to
international piracy.
345
00:23:16,343 --> 00:23:20,871
His loot was unloaded
on this very breakwater.
346
00:23:21,081 --> 00:23:23,572
(DRUM BEATS)
347
00:23:29,456 --> 00:23:33,727
But he oppressed his own people,
he made war on his neighbors.
348
00:23:33,732 --> 00:23:36,063
He quite rightly feared invasion.
349
00:23:36,068 --> 00:23:40,966
So Polycrates surrounded his capital
city with an impressive wall...
350
00:23:41,168 --> 00:23:44,103
....whose remains stand till this day.
351
00:23:53,514 --> 00:23:57,685
To carry water from a distant spring
through the fortifications...
352
00:23:57,690 --> 00:24:00,537
....he ordered this great tunnel built.
353
00:24:00,688 --> 00:24:04,180
A kilometerlong,
itpierces a mountain.
354
00:24:04,458 --> 00:24:06,994
Two cuttings were dug
from eitherside...
355
00:24:06,999 --> 00:24:09,463
....which met almostperfectly
in the middle.
356
00:24:09,468 --> 00:24:12,694
The project took some 15 years
to complete.
357
00:24:13,634 --> 00:24:17,284
It is a token of the civil engineering
ofits day...
358
00:24:17,404 --> 00:24:21,442
....and an indication of the
extraordinarypractical capability...
359
00:24:21,447 --> 00:24:22,834
....of the lonians.
360
00:24:25,646 --> 00:24:28,148
The enduring legacy of the lonians...
361
00:24:28,153 --> 00:24:30,784
....is the tools and techniques
they developed...
362
00:24:30,789 --> 00:24:34,147
....which remain the basis
ofmodern technology.
363
00:24:38,225 --> 00:24:41,456
This was the time of Theodorus...
364
00:24:41,662 --> 00:24:44,392
....the master engineer of the age...
365
00:24:44,598 --> 00:24:48,591
....a man who is credited with
the invention of...
366
00:24:48,802 --> 00:24:52,761
....the key, the ruler,
the carpenter's square...
367
00:24:52,973 --> 00:24:55,893
....the level, the lathe,
bronze casting.
368
00:24:56,343 --> 00:24:59,312
Why are there no monuments
to this man?
369
00:25:00,314 --> 00:25:03,806
Those who dreamt and speculated...
370
00:25:04,018 --> 00:25:06,620
....and deduced about
the laws of nature...
371
00:25:06,625 --> 00:25:09,289
....talked to the engineers
and the technologists.
372
00:25:09,294 --> 00:25:11,630
They were often the same people.
373
00:25:11,692 --> 00:25:15,651
The practical and the theoretical
were one.
374
00:25:16,697 --> 00:25:21,634
(DRUM BEATS)
375
00:25:22,503 --> 00:25:26,166
This new hybrid ofabstract thought...
376
00:25:26,373 --> 00:25:30,023
....and everyday experience
blossomed into science.
377
00:25:31,145 --> 00:25:35,482
When these practical men turned
theirattention to the natural world...
378
00:25:35,487 --> 00:25:38,553
....they began to uncover
hidden wonders...
379
00:25:38,585 --> 00:25:41,145
....and breathtaking possibilities.
380
00:25:41,789 --> 00:25:45,439
Anaximanderstudied the profusion
ofliving things...
381
00:25:45,459 --> 00:25:48,087
....and saw theirinterrelationships.
382
00:25:48,195 --> 00:25:52,325
He concluded that life had originated
in waterand mud...
383
00:25:52,800 --> 00:25:55,530
....and then colonized the dry land.
384
00:25:56,370 --> 00:25:58,268
"Human beings," he said...
385
00:25:58,405 --> 00:26:01,398
"...must have evolved
from simpler forms."
386
00:26:01,809 --> 00:26:07,065
This insight had to wait 24 centuries
until its truth was demonstrated...
387
00:26:07,347 --> 00:26:09,110
....by Charles Darwin.
388
00:26:17,724 --> 00:26:22,129
Nothing was excluded from the
investigations of the first scientists.
389
00:26:22,134 --> 00:26:26,429
Even the airbecame the subject
of close examination...
390
00:26:26,633 --> 00:26:30,626
....by a Greek from Sicily
named Empedocles.
391
00:26:32,272 --> 00:26:34,832
He made an astonishing discovery...
392
00:26:35,042 --> 00:26:39,787
....with a household implement
that people had used for centuries.
393
00:26:39,813 --> 00:26:42,976
This is the so-called
water thief.
394
00:26:43,183 --> 00:26:47,381
It's a brazen sphere with a neck
and a hole at the top...
395
00:26:47,588 --> 00:26:50,357
....and a set of little holes
at the bottom.
396
00:26:50,362 --> 00:26:52,559
It was used as a kitchen ladle.
397
00:26:52,564 --> 00:26:56,256
You fill it by immersing it in water.
398
00:26:58,765 --> 00:27:01,268
If, after it's been in there
a little bit...
399
00:27:01,273 --> 00:27:04,558
....you pull it out
with the neck uncovered...
400
00:27:05,706 --> 00:27:10,644
....then the water trickles out
the little holes making a small shower.
401
00:27:10,649 --> 00:27:14,372
Instead, if you pull it out
with the neck covered...
402
00:27:15,048 --> 00:27:16,946
....the water is retained.
403
00:27:28,495 --> 00:27:30,588
Now try to fill it...
404
00:27:30,831 --> 00:27:34,289
....with the neck covered
with my thumb.
405
00:27:38,405 --> 00:27:39,573
Nothing happens.
406
00:27:40,407 --> 00:27:41,533
Why not?
407
00:27:42,109 --> 00:27:44,111
There's something in the way.
408
00:27:44,116 --> 00:27:49,048
Some material is blocking the access
of the water into the sphere.
409
00:27:49,383 --> 00:27:51,578
I can't see any such material.
410
00:27:52,452 --> 00:27:54,079
What could it be?
411
00:27:54,821 --> 00:27:57,312
Empedocles identified it...
412
00:27:57,524 --> 00:27:58,923
....as air.
413
00:27:59,560 --> 00:28:01,323
What else could it be?
414
00:28:01,695 --> 00:28:04,823
A thing you can't see
can exert pressure...
415
00:28:05,032 --> 00:28:09,036
....can frustrate my wish to fill
this vessel with water...
416
00:28:09,041 --> 00:28:13,302
....if I were dumb enough to
leave my thumb on the neck.
417
00:28:14,141 --> 00:28:17,804
Empedocles had discovered...
418
00:28:19,146 --> 00:28:20,636
....the invisible.
419
00:28:21,248 --> 00:28:24,240
Air, he thought, must be matter...
420
00:28:24,451 --> 00:28:27,818
....in a form so finely divided...
421
00:28:28,689 --> 00:28:30,806
....that it couldn't be seen.
422
00:28:31,525 --> 00:28:35,928
This hint, this whiff
of the existence ofatoms...
423
00:28:36,129 --> 00:28:40,655
....was carried much furtherby
a contemporary named Democritus.
424
00:28:40,968 --> 00:28:45,439
Ofall the ancient scientists, it is
he who speaks most clearly to us...
425
00:28:45,444 --> 00:28:47,174
....across the centuries.
426
00:28:47,179 --> 00:28:50,611
The few surviving fragments
ofhis scientific writings...
427
00:28:50,616 --> 00:28:54,448
....reveal a mind of the highest
logical and intuitive powers.
428
00:28:54,453 --> 00:28:59,453
He believed that a large number of
other worlds wander through space...
429
00:28:59,458 --> 00:29:01,955
....that worlds are born and die...
430
00:29:01,960 --> 00:29:04,157
....that some are
rich and living creatures...
431
00:29:04,162 --> 00:29:07,388
....and others are dry and barren.
432
00:29:08,762 --> 00:29:11,798
He was the first to understand
that the Milky Way...
433
00:29:11,803 --> 00:29:15,602
....is an aggregate of the light
ofinnumerable faint stars.
434
00:29:15,607 --> 00:29:19,476
Beyond campfires in the sky,
beyond the milk ofHera...
435
00:29:19,673 --> 00:29:24,610
....beyond the backbone ofnight,
the mind ofDemocritus soared.
436
00:29:29,883 --> 00:29:33,720
He saw deep connections between
the heavens and the Earth.
437
00:29:33,725 --> 00:29:36,655
"Man," he said, "is a microcosm...
438
00:29:37,090 --> 00:29:38,682
....a little cosmos."
439
00:30:02,516 --> 00:30:06,452
Democritus came from
the lonian town ofAbdera...
440
00:30:06,653 --> 00:30:09,062
....on the northern Aegean shore.
441
00:30:12,292 --> 00:30:16,626
In those days, Abdera was
the butt ofjokes.
442
00:30:17,531 --> 00:30:19,648
If, around the year400 B.C...
443
00:30:19,833 --> 00:30:22,869
....in the equivalent
ofa restaurant like this...
444
00:30:22,874 --> 00:30:25,706
....you told a story about
someone from Abdera...
445
00:30:25,711 --> 00:30:28,047
....you were guaranteed a laugh.
446
00:30:30,510 --> 00:30:32,478
It was, in a way...
447
00:30:32,679 --> 00:30:35,079
....the Brooklyn ofits time.
448
00:30:37,584 --> 00:30:41,964
For Democritus, all of life was to be
enjoyed and understood.
449
00:30:41,988 --> 00:30:44,491
For him, understanding and enjoyment...
450
00:30:44,496 --> 00:30:46,993
....were pretty much the same thing.
451
00:30:46,998 --> 00:30:51,743
He said, "A life without festivity is
a long road without an inn."
452
00:30:51,832 --> 00:30:55,993
Democritus may have come from Abdera,
but he was no dummy.
453
00:30:59,339 --> 00:31:02,542
Democritus understood
that the complex forms...
454
00:31:02,547 --> 00:31:05,978
....changes and motions
of the material world...
455
00:31:06,146 --> 00:31:10,818
....all derived from the interaction
of very simple moving parts.
456
00:31:10,917 --> 00:31:13,613
He called these parts atoms.
457
00:31:18,592 --> 00:31:22,289
All material objects are
collections ofatoms...
458
00:31:22,829 --> 00:31:24,464
....intricately assembled...
459
00:31:24,469 --> 00:31:25,761
....even we.
460
00:31:25,999 --> 00:31:28,263
When I cut this apple...
461
00:31:28,535 --> 00:31:30,837
....the knife must be
passing through...
462
00:31:30,842 --> 00:31:34,541
....empty spaces between the atoms,
Democritus argued.
463
00:31:34,546 --> 00:31:37,977
If there were no such empty spaces,
no void...
464
00:31:38,178 --> 00:31:42,740
....then the knife would encounter
some impenetrable atom...
465
00:31:42,949 --> 00:31:45,085
....and the apple wouldn't be cut.
466
00:31:45,090 --> 00:31:48,388
Let's compare the cross sections
of the two pieces.
467
00:31:48,393 --> 00:31:51,021
Are the exposed areas exactly equal?
468
00:31:51,191 --> 00:31:54,127
No, said Democritus,
the curvature of the apple...
469
00:31:54,132 --> 00:31:59,315
....forces this slice to be slightly
shorter than the rest of the apple.
470
00:31:59,332 --> 00:32:02,699
If they were equally tall,
then we'd have...
471
00:32:02,903 --> 00:32:05,205
....a cylinder and not an apple.
472
00:32:05,210 --> 00:32:07,541
No matter how sharp the knife...
473
00:32:07,546 --> 00:32:10,610
....these two pieces have
unequal cross sections.
474
00:32:10,615 --> 00:32:11,975
But why?
475
00:32:12,179 --> 00:32:15,205
Because on the scale
of the very small...
476
00:32:15,415 --> 00:32:18,885
....matter exhibits some
irreducible roughness...
477
00:32:18,890 --> 00:32:22,889
....and this fine scale of roughness
Democritus of Abdera identified...
478
00:32:22,894 --> 00:32:25,025
....with the world of the atoms.
479
00:32:25,030 --> 00:32:27,394
His arguments are not those
we use today.
480
00:32:27,399 --> 00:32:31,898
But they're elegant and subtle
and derived from everyday experience.
481
00:32:31,903 --> 00:32:35,334
And his conclusions were
fundamentally right.
482
00:32:40,607 --> 00:32:43,910
Democritus believed that nothing
happens at random...
483
00:32:43,915 --> 00:32:47,175
....that everything has
a material cause.
484
00:32:48,515 --> 00:32:52,451
He said, "I would rather understand
one cause...
485
00:32:52,652 --> 00:32:54,916
....than be king of Persia."
486
00:32:55,121 --> 00:32:58,558
He believed that poverty
in a democracy was far better...
487
00:32:58,563 --> 00:33:00,393
....than wealth in a tyranny.
488
00:33:00,398 --> 00:33:04,097
He believed that the prevailing
religions of his time were evil...
489
00:33:04,102 --> 00:33:08,124
....and that neither souls
nor immortal gods existed.
490
00:33:08,735 --> 00:33:13,672
There is no evidence that Democritus
was persecuted for his beliefs.
491
00:33:14,241 --> 00:33:17,233
But then again, he came from Abdera.
492
00:33:19,513 --> 00:33:21,047
However, in his time...
493
00:33:21,052 --> 00:33:24,684
....the brief tradition of tolerance
for unconventional views...
494
00:33:24,689 --> 00:33:26,660
....was beginning to erode.
495
00:33:27,153 --> 00:33:29,890
Forinstance,
the prevailing belief was...
496
00:33:29,895 --> 00:33:32,742
....that the moon and the sun
were gods.
497
00:33:33,293 --> 00:33:37,264
Another contemporary of Democritus,
named Anaxagoras, taught...
498
00:33:37,269 --> 00:33:41,234
....that the moon was a place
made of ordinary matter...
499
00:33:41,239 --> 00:33:45,619
....and that the sun was a red-hot stone
far away in the sky.
500
00:33:45,705 --> 00:33:48,799
For this, Anaxagoras was condemned...
501
00:33:49,009 --> 00:33:52,604
....convicted and imprisoned
for impiety...
502
00:33:52,812 --> 00:33:54,575
....a religious crime.
503
00:33:54,781 --> 00:33:58,376
People began to be persecuted
for their ideas.
504
00:33:58,685 --> 00:34:01,347
A portrait of Democritus is now...
505
00:34:01,555 --> 00:34:04,251
....on the Greek 1 00-drachma note.
506
00:34:05,125 --> 00:34:07,461
But his ideas were suppressed...
507
00:34:07,494 --> 00:34:09,896
....and his influence on history
made minor.
508
00:34:09,901 --> 00:34:12,592
The mystics were beginning to win.
509
00:34:12,799 --> 00:34:16,929
(DRUM BEATS)
510
00:34:19,406 --> 00:34:22,000
You see, lonia was also the home...
511
00:34:22,208 --> 00:34:25,245
....ofanother quite different
intellectual tradition.
512
00:34:25,250 --> 00:34:27,873
Its founder was Pythagoras...
513
00:34:28,081 --> 00:34:31,731
....who lived here on Samos
in the 6th century B.C.
514
00:34:32,686 --> 00:34:34,984
According to local legend...
515
00:34:35,188 --> 00:34:38,749
....this cave was once his abode.
516
00:34:39,092 --> 00:34:41,720
Maybe that was once his living room.
517
00:34:41,828 --> 00:34:43,796
Many centuries later...
518
00:34:44,064 --> 00:34:48,034
....this small Greek Orthodox shrine
was erected on his front porch.
519
00:34:48,039 --> 00:34:52,971
There's a continuity of tradition
from Pythagoras to Christianity.
520
00:34:53,206 --> 00:34:57,077
Pythagoras was the first person
in the history of the world...
521
00:34:57,082 --> 00:35:00,205
....to decide that the Earth
was a sphere.
522
00:35:00,447 --> 00:35:04,645
Perhaps he argued by analogy
with the moon or the sun...
523
00:35:04,851 --> 00:35:08,088
....maybe he noticed the curved shadow
of the Earth on the moon...
524
00:35:08,093 --> 00:35:09,889
....during a lunar eclipse.
525
00:35:09,894 --> 00:35:12,892
Or maybe he recognized
that when ships leave Samos...
526
00:35:12,897 --> 00:35:15,326
....their masts disappear last.
527
00:35:20,600 --> 00:35:24,177
Pythagoras believed that
a mathematical harmony...
528
00:35:24,304 --> 00:35:26,275
....underlies all ofnature.
529
00:35:26,373 --> 00:35:28,842
The modern tradition
ofmathematical argument...
530
00:35:28,847 --> 00:35:32,278
....essential in all ofscience
owes much to him.
531
00:35:32,412 --> 00:35:36,383
And the notion that the heavenly bodies
move to a kind of...
532
00:35:36,388 --> 00:35:38,613
....music of the spheres...
533
00:35:38,918 --> 00:35:41,619
....was also derived from Pythagoras.
534
00:35:42,055 --> 00:35:45,121
It was he who first used
the word cosmos...
535
00:35:45,125 --> 00:35:48,161
....to mean a well-ordered
and harmonious universe...
536
00:35:48,166 --> 00:35:51,653
....a world amenable
to human understanding.
537
00:35:56,036 --> 00:35:59,673
For this great idea,
we are indebted to Pythagoras.
538
00:35:59,678 --> 00:36:04,204
But there were deep ironies
and contradictions in his thoughts.
539
00:36:04,678 --> 00:36:06,780
Many of the lonians believed...
540
00:36:06,785 --> 00:36:11,484
....that the underlying harmony and
unity of the universe was accessible...
541
00:36:11,489 --> 00:36:14,387
....through observation
and experiment...
542
00:36:14,392 --> 00:36:17,123
....the method which dominates
science today.
543
00:36:17,128 --> 00:36:20,093
However, Pythagoras had
a very different method.
544
00:36:20,098 --> 00:36:25,030
He believed that the laws of nature
can be deduced by pure thought.
545
00:36:25,432 --> 00:36:28,702
He and his followers were not
basically experimentalists...
546
00:36:28,707 --> 00:36:30,704
....they were mathematicians...
547
00:36:30,709 --> 00:36:33,571
....and they were
thoroughgoing mystics.
548
00:36:34,474 --> 00:36:38,410
They were fascinated by these
five regularsolids...
549
00:36:38,611 --> 00:36:41,910
....bodies whose faces
are all polygons:
550
00:36:42,115 --> 00:36:44,743
Triangles orsquares...
551
00:36:44,951 --> 00:36:46,350
....orpentagons.
552
00:36:46,553 --> 00:36:49,522
There can be an infinite number
ofpolygons...
553
00:36:49,527 --> 00:36:52,548
....but only five regularsolids.
554
00:36:55,128 --> 00:37:00,065
Four of the solids were associated
with earth, fire, airand water.
555
00:37:00,734 --> 00:37:04,329
The cube, for example,
represented earth.
556
00:37:04,537 --> 00:37:08,990
These four elements, they thought,
make up terrestrial matter.
557
00:37:10,009 --> 00:37:11,806
So the fifth solid...
558
00:37:12,011 --> 00:37:15,369
....they mystically associated
with the cosmos.
559
00:37:15,448 --> 00:37:18,551
Perhaps it was the substance
of the heavens.
560
00:37:18,556 --> 00:37:21,111
This fifth solid was called...
561
00:37:21,321 --> 00:37:23,789
....the dodecahedron.
562
00:37:24,157 --> 00:37:27,649
Its faces are pentagons, 12 of them.
563
00:37:28,261 --> 00:37:30,196
Knowledge of the dodecahedron...
564
00:37:30,201 --> 00:37:33,632
....was considered too dangerous
for the public.
565
00:37:35,702 --> 00:37:40,162
Ordinary people were to be
kept ignorant of the dodecahedron.
566
00:37:40,406 --> 00:37:43,443
In love with whole numbers,
the Pythagoreans believed...
567
00:37:43,448 --> 00:37:45,812
....that all things could be
derived from them...
568
00:37:45,817 --> 00:37:48,014
....certainly all other numbers.
569
00:37:48,019 --> 00:37:51,251
So a crisis in doctrine occurred
when they discovered...
570
00:37:51,256 --> 00:37:53,887
....that the square root of two
was irrational.
571
00:37:53,892 --> 00:37:57,223
The square root of two could
not be represented as the ratio...
572
00:37:57,228 --> 00:38:00,293
....of two whole numbers
no matter how big they were.
573
00:38:00,298 --> 00:38:03,145
Irrational originally meant
only that...
574
00:38:03,196 --> 00:38:06,366
....that you can't express a number
as a ratio.
575
00:38:06,371 --> 00:38:09,769
But for the Pythagoreans,
it came to mean something else...
576
00:38:09,774 --> 00:38:11,818
....something threatening...
577
00:38:11,871 --> 00:38:15,967
....a hint that their world-view
might not make sense...
578
00:38:16,176 --> 00:38:19,009
....the other meaning of irrational.
579
00:38:19,913 --> 00:38:24,784
Instead of wanting everyone to share
and know of their discoveries...
580
00:38:24,789 --> 00:38:28,188
....the Pythagoreans suppressed
the square root of two...
581
00:38:28,193 --> 00:38:30,018
....and the dodecahedron.
582
00:38:30,056 --> 00:38:32,547
The outside world was not to know.
583
00:38:38,464 --> 00:38:40,934
The Pythagoreans had discovered...
584
00:38:40,939 --> 00:38:43,770
....in the mathematical underpinnings
ofnature...
585
00:38:43,775 --> 00:38:46,606
....one of the two most
powerful scientific tools.
586
00:38:46,611 --> 00:38:49,700
The other, of course, is experiment.
587
00:38:50,009 --> 00:38:52,779
But instead of using theirinsight
to advance...
588
00:38:52,784 --> 00:38:55,648
....the collective voyage
ofhuman discovery...
589
00:38:55,653 --> 00:39:00,420
....they made ofit little more
than the hocus-pocus ofa mystery cult.
590
00:39:00,425 --> 00:39:03,723
Science and mathematics were to be
removed from the hands...
591
00:39:03,728 --> 00:39:05,845
....ofmerchants and artisans.
592
00:39:06,292 --> 00:39:09,429
This tendency found its most
effective advocate...
593
00:39:09,434 --> 00:39:12,796
....in a follower ofPythagoras
named Plato.
594
00:39:13,066 --> 00:39:17,765
He preferred the perfection
of these mathematical abstractions...
595
00:39:17,971 --> 00:39:21,099
....to the imperfections
of everyday life.
596
00:39:21,307 --> 00:39:25,845
He believed that ideas were farmore
real than the natural world.
597
00:39:25,850 --> 00:39:28,681
He advised the astronomers
not to waste their time...
598
00:39:28,686 --> 00:39:30,617
....observing stars and planets.
599
00:39:30,622 --> 00:39:34,418
It was better, he believed,
just to think about them.
600
00:39:35,021 --> 00:39:38,825
Plato expressed hostility to
observation and experiment.
601
00:39:38,830 --> 00:39:41,461
He taught contempt
for the real world...
602
00:39:41,466 --> 00:39:46,430
....and disdain for the practical
application ofscientific knowledge.
603
00:39:47,133 --> 00:39:51,070
Plato's followers succeeded
in extinguishing the light...
604
00:39:51,075 --> 00:39:53,106
....ofscience and experiment...
605
00:39:53,111 --> 00:39:57,491
....that had been kindled
by Democritus and the otherlonians.
606
00:40:00,246 --> 00:40:03,850
Plato's unease with the world
as revealed by oursenses...
607
00:40:03,855 --> 00:40:08,583
....was to dominate
and stifle Western philosophy.
608
00:40:11,024 --> 00:40:12,821
Even as late as 1600...
609
00:40:13,026 --> 00:40:16,596
....Johannes Kepler was still
struggling to interpret...
610
00:40:16,601 --> 00:40:18,898
....the structure of
the cosmos in terms of...
611
00:40:18,903 --> 00:40:23,335
....Pythagorean solids
and Platonic perfection.
612
00:40:23,536 --> 00:40:27,674
Ironically, it was Kepler who helped
re-establish the old lonian method...
613
00:40:27,679 --> 00:40:30,643
....of testing ideas
against observations.
614
00:40:30,648 --> 00:40:33,680
But why had science lost its way
in the firstplace?
615
00:40:33,685 --> 00:40:36,816
What appeal did Pythagoras'
and Plato's teachings...
616
00:40:36,821 --> 00:40:38,885
....have for their contemporaries?
617
00:40:38,890 --> 00:40:40,720
Theyprovided, I believe...
618
00:40:40,725 --> 00:40:43,856
....an intellectually
respectablejustification...
619
00:40:43,861 --> 00:40:46,723
....fora corrupt social order.
620
00:40:50,296 --> 00:40:53,700
The mercantile tradition which had
led to lonian science...
621
00:40:53,705 --> 00:40:56,041
....also led to a slave economy.
622
00:40:56,836 --> 00:40:58,827
You could get richer...
623
00:40:59,038 --> 00:41:01,598
....if you owned a lot of slaves.
624
00:41:01,975 --> 00:41:05,178
Athens, in the time
of Plato and Aristotle...
625
00:41:05,183 --> 00:41:07,942
....had a vast slave population.
626
00:41:08,147 --> 00:41:12,049
All of that brave Athenian talk
about democracy...
627
00:41:12,251 --> 00:41:15,152
....applied only to a privileged few.
628
00:41:15,755 --> 00:41:20,089
Plato and Aristotle were comfortable
in a slave society.
629
00:41:20,293 --> 00:41:23,387
They offered justifications
for oppression.
630
00:41:24,030 --> 00:41:25,998
They served tyrants.
631
00:41:26,199 --> 00:41:29,569
They taught the alienation
of the body from the mind...
632
00:41:29,574 --> 00:41:33,662
....a natural enough idea, I suppose,
in a slave society.
633
00:41:33,806 --> 00:41:36,361
They separated thought from matter.
634
00:41:36,542 --> 00:41:39,112
They divorced the Earth
from the heavens.
635
00:41:39,117 --> 00:41:42,980
Divisions which were to dominate
Western thinking...
636
00:41:43,182 --> 00:41:45,445
....for more than 20 centuries.
637
00:41:45,485 --> 00:41:47,919
The Pythagoreans had won.
638
00:41:54,093 --> 00:41:57,305
In the recognition by
Pythagoras and Plato...
639
00:41:57,330 --> 00:41:59,499
....that the cosmos is knowable...
640
00:41:59,504 --> 00:42:02,802
....that there is a mathematical
underpinning to nature...
641
00:42:02,807 --> 00:42:06,092
....they greatly advanced
the cause ofscience.
642
00:42:06,506 --> 00:42:10,567
But in the suppression
of disquieting facts...
643
00:42:10,777 --> 00:42:15,476
....the sense that science should be
kept fora small elite...
644
00:42:15,681 --> 00:42:19,915
....the distaste for experiment,
the embrace ofmysticism...
645
00:42:20,386 --> 00:42:23,719
....the easy acceptance
ofslave societies...
646
00:42:23,923 --> 00:42:27,791
....theirinfluence has
significantly set back...
647
00:42:27,994 --> 00:42:29,673
....the human endeavor.
648
00:42:30,997 --> 00:42:35,934
The books of the lonian scientists
are entirely lost.
649
00:42:36,836 --> 00:42:41,569
Their views were suppressed,
ridiculed and forgotten...
650
00:42:42,341 --> 00:42:45,211
....by the Platonists
and by the Christians...
651
00:42:45,216 --> 00:42:48,703
....who adopted much of
the philosophy of Plato.
652
00:42:49,482 --> 00:42:54,215
Finally, aftera long,
mystical sleep...
653
00:42:54,487 --> 00:42:59,083
....in which the tools of
scientific inquiry lay moldering...
654
00:42:59,292 --> 00:43:02,212
....the lonian approach was
rediscovered.
655
00:43:07,066 --> 00:43:09,762
The Western world reawakened.
656
00:43:09,969 --> 00:43:13,427
Experiment and open inquiry...
657
00:43:13,639 --> 00:43:17,040
....slowly became respectable
once again.
658
00:43:17,743 --> 00:43:21,804
Forgotten books and fragments were
read once more.
659
00:43:22,181 --> 00:43:26,242
Leonardo and Copernicus
and Columbus...
660
00:43:26,452 --> 00:43:29,615
....were inspired by
the lonian tradition.
661
00:43:41,868 --> 00:43:45,668
The Pythagoreans
and theirsuccessors...
662
00:43:45,872 --> 00:43:48,864
....held the peculiarnotion that...
663
00:43:49,075 --> 00:43:51,339
....the Earth was tainted...
664
00:43:51,544 --> 00:43:53,978
....somehow nasty...
665
00:43:54,180 --> 00:43:58,810
....while the heavens were
pristine and divine.
666
00:43:59,485 --> 00:44:02,421
So the fundamental idea
that the Earth is a planet...
667
00:44:02,426 --> 00:44:05,358
....that we're citizens
of the universe...
668
00:44:05,363 --> 00:44:08,088
....was rejected and forgotten.
669
00:44:11,497 --> 00:44:15,297
This idea was first argued
byAristarchus...
670
00:44:15,501 --> 00:44:19,516
....born here on Samos,
three centuries afterPythagoras.
671
00:44:19,672 --> 00:44:22,708
He held that the Earth moves
around the sun.
672
00:44:22,713 --> 00:44:26,145
He correctly located ourplace
in the solarsystem.
673
00:44:26,150 --> 00:44:30,013
Forhis trouble,
he was accused ofheresy.
674
00:44:31,784 --> 00:44:36,322
From the size of the Earth's shadow
on the moon during a lunar eclipse...
675
00:44:36,327 --> 00:44:40,520
....he deduced that the sun
had to be much, much larger...
676
00:44:40,726 --> 00:44:43,820
....than the Earth,
and also very far away.
677
00:44:44,230 --> 00:44:47,033
From this he may have argued
that it was absurd...
678
00:44:47,038 --> 00:44:50,269
....for so large an object as the sun
to be going around...
679
00:44:50,274 --> 00:44:53,363
....so small an object as the Earth.
680
00:44:53,573 --> 00:44:58,644
So he put the sun rather than the Earth
at the center of the solar system.
681
00:44:58,649 --> 00:45:02,381
And he had the Earth and the other
planets going around the sun.
682
00:45:02,386 --> 00:45:05,952
He also had the Earth rotating
on its axis once a day.
683
00:45:05,957 --> 00:45:10,323
These are ideas that we ordinarily
associate with the name Copernicus.
684
00:45:10,328 --> 00:45:14,026
But Copernicus seems to have gotten
some hint of these ideas...
685
00:45:14,031 --> 00:45:16,654
....by reading about Aristarchus.
686
00:45:17,129 --> 00:45:20,066
In fact, in the manuscript
of Copernicus' book...
687
00:45:20,071 --> 00:45:23,703
....he referred to Aristarchus,
but in the final version...
688
00:45:23,708 --> 00:45:26,399
....he suppressed the citation.
689
00:45:27,106 --> 00:45:29,973
Resistance to Aristarchus,
a kind of...
690
00:45:30,610 --> 00:45:33,312
....geocentrism in everyday life,
is with us still.
691
00:45:33,317 --> 00:45:36,247
We still talk about a sun rising...
692
00:45:36,449 --> 00:45:38,917
....and the sun setting.
693
00:45:39,619 --> 00:45:42,247
It's 2200 years since Aristarchus...
694
00:45:42,421 --> 00:45:47,290
....and the language still pretends
that the Earth does not turn...
695
00:45:48,127 --> 00:45:52,215
....that the sun is not at the center
of the solarsystem.
696
00:45:55,268 --> 00:45:59,238
Aristarchus understood the basic
scheme of the solarsystem...
697
00:45:59,243 --> 00:46:01,001
....but not its scale.
698
00:46:03,609 --> 00:46:07,480
He knew that the planets move
in concentric orbits about the sun...
699
00:46:07,485 --> 00:46:11,135
....and he probably knew their order
out to Saturn.
700
00:46:12,251 --> 00:46:14,687
But he was much too modest
in his estimates...
701
00:46:14,692 --> 00:46:17,247
....ofhow farapart the planets are.
702
00:46:17,523 --> 00:46:21,093
In order to calculate the true scale
of the solarsystem...
703
00:46:21,098 --> 00:46:22,923
....you need a telescope.
704
00:46:23,129 --> 00:46:26,832
It wasn't until the 17th century
that astronomers were able to get...
705
00:46:26,837 --> 00:46:30,633
....even a rough estimate
of the distance to the sun.
706
00:46:32,538 --> 00:46:35,241
And once you knew
the distance to the sun...
707
00:46:35,246 --> 00:46:37,009
....what about the stars?
708
00:46:37,014 --> 00:46:39,443
How faraway are they?
709
00:46:43,349 --> 00:46:47,053
There is a way to measure
the distance to the stars...
710
00:46:47,058 --> 00:46:49,989
....and the lonians were
fully capable of discovering it.
711
00:46:49,994 --> 00:46:53,789
Aristarchus had toyed
with the daring idea...
712
00:46:53,993 --> 00:46:56,723
....that the stars were distant suns.
713
00:46:56,929 --> 00:46:59,598
Now, if a star were as near
as the sun...
714
00:46:59,603 --> 00:47:03,035
....it should appear as big
and as bright as the sun.
715
00:47:03,040 --> 00:47:07,006
Everyone knows that the farther away
an object is, the smaller it seems.
716
00:47:07,011 --> 00:47:10,676
This inverse proportionality between
apparent size and distance...
717
00:47:10,681 --> 00:47:14,580
....is the basis of perspective
in art and photography.
718
00:47:14,585 --> 00:47:17,483
So the further away we are
from the sun...
719
00:47:17,488 --> 00:47:20,384
....the smaller and dimmer it appears.
720
00:47:20,586 --> 00:47:23,989
How far from the sun would we
have to be for it to appear...
721
00:47:23,994 --> 00:47:26,257
....as small and dim as a star?
722
00:47:26,459 --> 00:47:29,598
Or equivalently,
how small a piece of sun...
723
00:47:29,628 --> 00:47:32,037
....would be as bright as a star?
724
00:47:32,231 --> 00:47:36,936
An experiment to answer this question
was performed in 1 7th-century Holland...
725
00:47:36,941 --> 00:47:41,771
....by Christiaan Huygens and is
very much in the lonian tradition.
726
00:47:41,974 --> 00:47:46,911
Huygens drilled a number of holes
in a brass plate...
727
00:47:47,346 --> 00:47:49,949
....and held the plate up to the sun.
728
00:47:49,954 --> 00:47:54,750
He asked himself,
which hole seemed as bright...
729
00:47:54,954 --> 00:47:59,425
....as he remembered the star Sirius
to have been the previous evening.
730
00:47:59,430 --> 00:48:02,661
Well, the hole that matched was
effectively...
731
00:48:02,666 --> 00:48:07,394
....1l28,000th the apparent size
of the sun.
732
00:48:07,666 --> 00:48:11,727
So Sirius, he reasoned,
must be 28,000 times...
733
00:48:11,937 --> 00:48:16,463
....further away than the sun,
or about half a light-year away.
734
00:48:16,842 --> 00:48:19,812
It's hard to remember
just how bright a star is...
735
00:48:19,817 --> 00:48:23,849
....hours after you've looked at it,
but Huygens remembered very well.
736
00:48:23,854 --> 00:48:28,087
If he had known that Sirius was
intrinsically brighter than the sun...
737
00:48:28,092 --> 00:48:30,689
....he would've gotten
the answer exactly right.
738
00:48:30,694 --> 00:48:34,750
Sirius is 8.8 light-years
away from us.
739
00:48:35,728 --> 00:48:38,595
Between Aristarchus and Huygens...
740
00:48:38,798 --> 00:48:42,234
....people had answered that question
which had so excited me...
741
00:48:42,239 --> 00:48:44,303
....as a young boy growing up
in Brooklyn:
742
00:48:44,308 --> 00:48:46,863
The question, "What are the stars?"
743
00:48:50,109 --> 00:48:55,073
And the answer is that the stars are
mighty suns, light-years away...
744
00:48:55,247 --> 00:48:58,094
....in the depths
of interstellar space.
745
00:49:03,456 --> 00:49:07,790
And around those suns,
are there otherplanets?
746
00:49:08,861 --> 00:49:10,905
And on those other worlds...
747
00:49:11,030 --> 00:49:13,999
....are there beings
who wonderas we do?
748
00:49:18,370 --> 00:49:20,770
Here is a light bulb...
749
00:49:20,973 --> 00:49:23,742
....which is supposed to represent
a nearby star.
750
00:49:23,747 --> 00:49:27,413
Next to it, and very hard to see
because of the bright light...
751
00:49:27,418 --> 00:49:28,778
....is a planet.
752
00:49:28,981 --> 00:49:33,142
We'll need a volunteer.
Who would like to come up, please?
753
00:49:33,185 --> 00:49:35,988
Ordinarily, it's hard to
see the planet...
754
00:49:35,993 --> 00:49:40,159
....because it's so close that the star
washes out the planet.
755
00:49:40,164 --> 00:49:44,596
But if we're able to put something
in front of the star...
756
00:49:44,797 --> 00:49:48,534
....to make an artificial eclipse,
then we might be able to see the planet.
757
00:49:48,539 --> 00:49:52,800
I'm gonna stand over here.
Imagine that I'm a telescope...
758
00:49:53,005 --> 00:49:54,640
....somewhere near the Earth.
759
00:49:54,645 --> 00:49:58,542
And, Tab, if you'd slowly move
the disc across.
760
00:49:58,744 --> 00:50:00,946
Good. A little faster would be nice.
761
00:50:00,951 --> 00:50:03,782
Now you're just beginning to cover
over the star.
762
00:50:03,787 --> 00:50:07,019
I really can't see the planet at all.
Keep going.
763
00:50:07,024 --> 00:50:08,486
Now, right there...
764
00:50:08,687 --> 00:50:11,169
....l can't see the star at all...
765
00:50:11,257 --> 00:50:15,159
....and I see the planet lit
by the light of the star.
766
00:50:15,361 --> 00:50:18,792
Now, that is a method for looking
for planets...
767
00:50:18,898 --> 00:50:20,729
....around nearby stars.
768
00:50:20,933 --> 00:50:25,870
And that method uses a spacecraft
to hold the disc...
769
00:50:26,405 --> 00:50:29,074
....and scan the sky
for another telescope...
770
00:50:29,079 --> 00:50:31,804
....to see if there are any planets.
771
00:50:32,011 --> 00:50:36,549
Tab, you accomplished your mission
to look for planets around other stars.
772
00:50:36,554 --> 00:50:39,919
Thank you for being
our interplanetary spacecraft.
773
00:50:39,924 --> 00:50:42,513
So this is one way.
774
00:50:42,721 --> 00:50:46,325
And there are spaceships
that will be able to do this...
775
00:50:46,330 --> 00:50:48,294
....in the next 1 0 years or so.
776
00:50:48,299 --> 00:50:49,962
And there's another way.
777
00:50:49,967 --> 00:50:52,698
This has already been tried
from the Earth.
778
00:50:52,703 --> 00:50:56,794
Imagine that there's a nearby star
that you can see.
779
00:50:57,002 --> 00:51:00,995
It's bright and it has
a dark companion, a planet...
780
00:51:01,206 --> 00:51:04,810
....shining only by reflected light
near it, so dim you can't see it.
781
00:51:04,815 --> 00:51:09,577
But imagine that this planet
and its star...
782
00:51:09,782 --> 00:51:12,118
....are going around each other.
783
00:51:12,785 --> 00:51:14,116
Like that:
784
00:51:14,320 --> 00:51:17,122
You can see the star,
you can't see the planet.
785
00:51:17,127 --> 00:51:19,828
So now I'm gonna need two volunteers.
786
00:51:21,694 --> 00:51:22,718
You two.
787
00:51:24,063 --> 00:51:27,132
Just to save time
because they're in the front row.
788
00:51:27,137 --> 00:51:30,369
I need one of you to turn
the star and the planet...
789
00:51:30,374 --> 00:51:34,462
....and another person to pull
the star and planet along.
790
00:51:34,540 --> 00:51:36,208
And what you will see...
791
00:51:36,213 --> 00:51:39,541
....is that the star
you can make out...
792
00:51:39,745 --> 00:51:42,581
....will be moving
in a funny, wiggly pattern...
793
00:51:42,586 --> 00:51:44,917
....which will be the clue,
the evidence...
794
00:51:44,922 --> 00:51:47,386
....for the existence
of the dark planet.
795
00:51:47,391 --> 00:51:50,583
Okay, let's have a spin. Good.
And a pull.
796
00:51:50,789 --> 00:51:52,658
And you see this funny motion...
797
00:51:52,663 --> 00:51:57,322
....that the star makes
because of the planet. Thank you.
798
00:51:57,529 --> 00:52:00,933
That's another way of finding out
the existence of a planet...
799
00:52:00,938 --> 00:52:03,834
....that you couldn't see directly.
800
00:52:04,036 --> 00:52:07,164
Well, both of these methods are
being used.
801
00:52:07,473 --> 00:52:12,137
And by the time that you people are...
802
00:52:12,344 --> 00:52:14,141
....as old as I am...
803
00:52:14,346 --> 00:52:17,777
....we should know,
for all the nearest stars...
804
00:52:17,916 --> 00:52:20,552
....if they have planets
going around them.
805
00:52:20,557 --> 00:52:25,124
We might know dozens or even hundreds
of other planetary systems...
806
00:52:25,129 --> 00:52:28,627
....and see if they're like our own
or very different...
807
00:52:28,632 --> 00:52:32,431
....or no other planets
going around other stars at all.
808
00:52:32,436 --> 00:52:34,900
That will happen in your lifetime.
809
00:52:34,905 --> 00:52:40,088
It'll be the first time in the world's
history that anybody found out...
810
00:52:40,305 --> 00:52:43,242
....if there are planets
around the other stars.
811
00:52:43,247 --> 00:52:48,179
Now, the nearby stars, the ones
you can see with the naked eye...
812
00:52:48,480 --> 00:52:50,949
....those are all
in the solar neighborhood.
813
00:52:50,954 --> 00:52:53,652
That's what astronomers call it:
The neighborhood.
814
00:52:53,657 --> 00:52:58,248
But it's a very tiny place
in the Milky Way galaxy.
815
00:52:59,191 --> 00:53:01,527
The Milky Way is that band of light...
816
00:53:01,532 --> 00:53:04,830
....that you see across the sky
on a clear night.
817
00:53:04,835 --> 00:53:08,167
I can't tell if there are any more
clear nights in Brooklyn.
818
00:53:08,172 --> 00:53:12,037
You must've seen the Milky Way,
a faint band of light at night.
819
00:53:12,042 --> 00:53:16,667
Well, that's just 1 00 billion stars...
820
00:53:16,875 --> 00:53:18,809
....all seen together...
821
00:53:19,011 --> 00:53:21,605
....edge on, as in this picture.
822
00:53:21,814 --> 00:53:25,350
If you could get out of
the Milky Way and look down on it...
823
00:53:25,355 --> 00:53:27,453
....it would look like that picture.
824
00:53:27,458 --> 00:53:29,822
If we did look down
on the Milky Way...
825
00:53:29,827 --> 00:53:32,725
....where would the sun
and nearby stars be?
826
00:53:32,730 --> 00:53:36,095
Would it be in the center where things
look important...
827
00:53:36,100 --> 00:53:37,925
....or at least well-lit?
828
00:53:38,297 --> 00:53:41,630
No. We would be way out here...
829
00:53:41,834 --> 00:53:45,827
....in the suburbs,
in the countryside of the galaxy.
830
00:53:46,038 --> 00:53:47,906
We're not in any important place.
831
00:53:47,911 --> 00:53:51,877
All the stars you could see would be
in a little place like that.
832
00:53:51,882 --> 00:53:55,280
And the Milky Way would be
this band of light...
833
00:53:55,285 --> 00:53:57,913
....1 00 billion stars all together.
834
00:53:58,317 --> 00:54:01,453
The fact that we live
in the outskirts of the galaxy...
835
00:54:01,458 --> 00:54:04,945
....was discovered a long time ago...
836
00:54:05,157 --> 00:54:07,926
....towards the end
of the First World War...
837
00:54:07,931 --> 00:54:10,429
....by a man named Harlow Shapley...
838
00:54:10,434 --> 00:54:14,741
....who was mapping the position
of these clusters of stars.
839
00:54:14,867 --> 00:54:17,568
See, every one of these is a bunch...
840
00:54:17,569 --> 00:54:20,239
....of maybe 1 0,000 stars all together.
841
00:54:20,244 --> 00:54:22,441
It's called a globular cluster.
842
00:54:22,446 --> 00:54:25,944
And you can see that they are
centered around the middle...
843
00:54:25,949 --> 00:54:28,046
....the center of the galaxy.
844
00:54:28,051 --> 00:54:32,017
People used to think that the sun was
at the center of the galaxy...
845
00:54:32,022 --> 00:54:36,588
....something important about our
position. That turns out to be wrong.
846
00:54:36,593 --> 00:54:38,818
We live in the outskirts...
847
00:54:39,024 --> 00:54:41,960
....the globular clusters are
centered around...
848
00:54:41,965 --> 00:54:45,623
....the marvelous middle
of the Milky Way galaxy.
849
00:54:45,831 --> 00:54:49,773
And then it turned out
that this isn't the only galaxy.
850
00:54:49,868 --> 00:54:52,302
We live in this one...
851
00:54:52,905 --> 00:54:55,040
....but there are many others.
852
00:54:55,045 --> 00:54:58,032
And as this picture reminds us...
853
00:54:58,744 --> 00:55:01,380
....there are many different kinds
of galaxies...
854
00:55:01,385 --> 00:55:03,982
....of which ours might be
just this one.
855
00:55:03,987 --> 00:55:08,544
There are, in fact,
1 00 billion other galaxies...
856
00:55:08,754 --> 00:55:13,691
....each of which contains
something like 1 00 billion stars.
857
00:55:14,426 --> 00:55:19,390
Think of how many stars and planets
and kinds of life there may be...
858
00:55:20,165 --> 00:55:24,329
....in this vast and awesome universe.
859
00:55:27,139 --> 00:55:29,508
As long as there have been humans...
860
00:55:29,513 --> 00:55:32,944
....we have searched
for ourplace in the cosmos.
861
00:55:33,111 --> 00:55:35,909
Where are we? Who are we?
862
00:55:38,016 --> 00:55:42,316
We find that we live
on an insignificantplanet...
863
00:55:42,521 --> 00:55:44,489
....ofa humdrum star...
864
00:55:44,690 --> 00:55:47,853
....lost in a galaxy
tucked away in some...
865
00:55:48,060 --> 00:55:51,463
....forgotten corner ofa universe
in which there are...
866
00:55:51,468 --> 00:55:54,728
....farmore galaxies than people.
867
00:55:57,970 --> 00:56:02,174
We make our world significant by
the courage of our questions...
868
00:56:02,179 --> 00:56:04,802
....and by the depth of ouranswers.
869
00:56:06,378 --> 00:56:09,472
We embarked on ourjourney
to the stars...
870
00:56:10,082 --> 00:56:12,676
....with a question first framed...
871
00:56:12,885 --> 00:56:15,586
....in the childhood of ourspecies...
872
00:56:15,854 --> 00:56:20,120
....and in each generation
asked anew...
873
00:56:20,392 --> 00:56:22,553
....with undiminished wonder:
874
00:56:22,928 --> 00:56:25,089
"What are the stars?"
875
00:56:43,181 --> 00:56:46,048
Exploration is in ournature.
876
00:56:46,652 --> 00:56:48,950
We began as wanderers...
877
00:56:49,254 --> 00:56:52,121
....and we are wanderers still.
878
00:57:03,402 --> 00:57:06,098
We have lingered long enough...
879
00:57:06,305 --> 00:57:09,103
....on the shores of the cosmic ocean.
880
00:57:09,341 --> 00:57:11,138
We are ready at last...
881
00:57:11,343 --> 00:57:14,574
....to set sail for the stars.
9999
00:00:0,500 --> 00:00:2,00
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