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Can something in space
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00:00:03,789 --> 00:00:06,591
cause animals to be born
with two heads?
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00:00:08,227 --> 00:00:10,495
Why were
the most fearsome warriors
4
00:00:10,596 --> 00:00:12,330
our planet has ever known
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00:00:12,431 --> 00:00:17,068
stopped by a flaming light
in the sky?
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00:00:17,136 --> 00:00:21,072
How did Columbus use
secret knowledge of the heavens
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00:00:21,140 --> 00:00:25,343
to cheat death in the New World.
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00:00:25,410 --> 00:00:29,847
Our ancestors saw a universe
filled with bad omens.
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00:00:29,948 --> 00:00:32,316
But what were they
really seeing?
10
00:00:32,417 --> 00:00:35,319
And how did fear
of these objects in the sky
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00:00:35,420 --> 00:00:38,456
change history?
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00:00:41,326 --> 00:00:43,261
Ancient mysteries,
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00:00:43,328 --> 00:00:47,098
shrouded
in the shadows of time...
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00:00:47,199 --> 00:00:49,834
Now, can they finally be solved
15
00:00:49,935 --> 00:00:53,504
by looking to the heavens?
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00:00:53,572 --> 00:00:56,207
The truth is up there,
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00:00:56,308 --> 00:00:59,377
hidden among the stars
18
00:00:59,444 --> 00:01:01,679
in a place we call...
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00:01:10,856 --> 00:01:13,357
For our ancestors,
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00:01:13,458 --> 00:01:17,228
the skies were filled
with equal parts wonder...
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00:01:19,565 --> 00:01:21,732
And terror.
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00:01:23,936 --> 00:01:27,772
Bad omens from above
changed human history...
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00:01:27,839 --> 00:01:30,408
again and again.
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00:01:35,948 --> 00:01:39,617
Four centuries
before the birth of Jesus,
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00:01:39,718 --> 00:01:42,453
it is a time of war...
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00:01:42,554 --> 00:01:45,590
Athens versus Sparta.
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00:01:45,657 --> 00:01:49,460
And this time it's for keeps.
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00:01:49,561 --> 00:01:54,332
Control of the ancient world
hangs in the balance.
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00:01:54,433 --> 00:01:57,435
Thousands of brave warriors,
30
00:01:57,536 --> 00:02:00,304
hundreds of ships at sea...
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00:02:00,372 --> 00:02:03,341
all poised for action,
32
00:02:03,442 --> 00:02:06,244
waiting for the command
from their leaders
33
00:02:06,345 --> 00:02:09,480
to unleash hell on Earth.
34
00:02:12,117 --> 00:02:13,884
And then...
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00:02:16,188 --> 00:02:19,357
An omen...
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00:02:19,458 --> 00:02:23,628
a strange light in the sky...
37
00:02:23,729 --> 00:02:26,297
a fiery object
said to be visible
38
00:02:26,365 --> 00:02:29,133
for 75 days...
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00:02:29,201 --> 00:02:33,704
as both sides nervously watch
and wait.
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00:02:36,742 --> 00:02:38,542
It's an omen.
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00:02:38,644 --> 00:02:42,913
But what does it mean,
and what is the object?
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00:02:47,185 --> 00:02:50,554
The Spartans devise a strategy.
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00:02:50,656 --> 00:02:52,823
They send an envoy
to the Greeks,
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00:02:52,924 --> 00:02:56,327
saying that with such
a bad omen overhead,
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00:02:56,428 --> 00:02:58,729
battle would have to wait.
46
00:03:01,466 --> 00:03:03,801
As days stretch into weeks,
47
00:03:03,902 --> 00:03:08,372
the Greeks grow confident
no attack is coming.
48
00:03:11,810 --> 00:03:15,479
So that is when
the Spartans strike...
49
00:03:15,547 --> 00:03:19,417
A sneak attack...
50
00:03:19,518 --> 00:03:21,552
decimating the Greeks
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00:03:21,620 --> 00:03:24,288
and marking the beginning
of the end
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00:03:24,356 --> 00:03:29,360
for the nearly 30-year-long
Peloponnesian War.
53
00:03:32,497 --> 00:03:35,566
The final toll is staggering...
54
00:03:35,634 --> 00:03:40,237
More than 3,000 Greek men
captured and killed on the spot.
55
00:03:43,408 --> 00:03:46,243
It couldn't be any clearer.
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00:03:46,345 --> 00:03:49,447
To the Greeks, the defeat
was definitive proof
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00:03:49,548 --> 00:03:53,884
the Greek Gods had sent
the sky object as a bad omen.
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00:03:55,721 --> 00:03:57,221
If you're in the middle of a war
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00:03:57,322 --> 00:03:59,123
and you see an omen
in the skies,
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00:03:59,224 --> 00:04:01,392
that's gonna mean something bad.
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00:04:01,493 --> 00:04:04,695
It's something to be
concerned about.
62
00:04:04,796 --> 00:04:07,498
But what was the object
in the sky
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00:04:07,599 --> 00:04:11,702
that brought an end
to nearly 30 years of war?
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00:04:14,873 --> 00:04:17,441
One account
of the object describes,
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00:04:17,509 --> 00:04:20,277
"A fiery body of vast size,
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00:04:20,345 --> 00:04:22,613
"as if it had been
a flaming cloud,
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00:04:22,714 --> 00:04:26,283
"not resting in one place,
but moving along
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00:04:26,351 --> 00:04:30,621
with intricate
and irregular motions."
69
00:04:30,689 --> 00:04:35,226
Could the ancient Greeks
have been describing a meteor?
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00:04:38,430 --> 00:04:40,464
Also known as shooting stars,
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00:04:40,565 --> 00:04:45,136
meteors make a fiery display
as they streak across the sky.
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00:04:46,838 --> 00:04:49,740
But since they're actually
small rocks and bits of dust
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00:04:49,841 --> 00:04:52,810
burning up as they fall
through the atmosphere,
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00:04:52,878 --> 00:04:56,313
meteors don't last very long.
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00:04:56,415 --> 00:04:58,716
They're visible
for a matter of seconds,
76
00:04:58,784 --> 00:05:03,421
not days or months,
as the Greeks described.
77
00:05:03,522 --> 00:05:07,625
Asteroids take longer
to pass through the sky,
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00:05:07,692 --> 00:05:09,427
but because they're dark,
79
00:05:09,494 --> 00:05:13,497
almost none of them are visible
to the naked eye.
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00:05:15,333 --> 00:05:18,102
What the ancient Greeks
could have seen, however,
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00:05:18,203 --> 00:05:20,371
was a comet.
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00:05:22,140 --> 00:05:26,043
Mythmakers fear comets,
because they linger in the sky
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00:05:26,111 --> 00:05:29,680
for weeks,
even months at a time.
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00:05:29,781 --> 00:05:34,285
The idea of seeing a comet
for 75 days, I could buy that.
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00:05:34,386 --> 00:05:38,088
On average, only one bright
comet is visible
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00:05:38,190 --> 00:05:40,558
to the naked eye each decade,
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00:05:40,659 --> 00:05:43,661
meaning the appearance
of one in the sky
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00:05:43,762 --> 00:05:45,796
would've been a rare
and remarkable event
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00:05:45,864 --> 00:05:49,266
to the ancients.
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00:05:49,367 --> 00:05:50,501
Comets are made of materials
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00:05:50,602 --> 00:05:52,403
that we find readily
here on Earth.
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00:05:52,504 --> 00:05:55,139
They're largely made up
of dry ice,
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00:05:55,207 --> 00:05:57,842
frozen carbon dioxide
like we exhale,
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00:05:57,943 --> 00:06:01,745
as well as water, a little bit
of organic material,
95
00:06:01,847 --> 00:06:04,782
ammonia, not too different than
what's in cleaning materials,
96
00:06:04,850 --> 00:06:09,019
and even silicates
like in sand from the beach.
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00:06:09,120 --> 00:06:11,422
When you mix all
of these ingredients together,
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00:06:11,490 --> 00:06:13,591
you have the recipe for a comet.
99
00:06:16,661 --> 00:06:18,095
When the ancient Greeks
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00:06:18,196 --> 00:06:21,432
described
a flaming cloud in the sky,
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00:06:21,533 --> 00:06:24,268
is this what they were seeing...
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00:06:24,369 --> 00:06:27,338
A comet, changing
its position in the sky
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00:06:27,439 --> 00:06:28,772
almost nightly,
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00:06:28,840 --> 00:06:32,209
faster than anything
they had ever seen?
105
00:06:34,379 --> 00:06:37,448
And what gives these icy objects
the fiery appearance
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00:06:37,549 --> 00:06:40,985
that spooked the ancients?
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00:06:41,086 --> 00:06:42,520
As comets streak
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00:06:42,621 --> 00:06:44,321
into the inner part
of the solar system,
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00:06:44,422 --> 00:06:46,824
they slowly heat up
from the Sun's heat.
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00:06:46,925 --> 00:06:49,360
As they heat up,
they grow an amazing tail
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00:06:49,461 --> 00:06:50,928
that doesn't streak out
behind them,
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00:06:51,029 --> 00:06:52,630
the way a lot of people think,
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00:06:52,731 --> 00:06:55,599
but rather it's pushed
by the Sun's radiation.
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00:06:55,700 --> 00:06:57,001
How we're able to see that tail
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00:06:57,102 --> 00:06:59,003
depends on where we are
relative to the Sun
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00:06:59,104 --> 00:07:00,538
and the comet.
117
00:07:00,639 --> 00:07:02,606
And sometimes
that tail's pushed out
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00:07:02,707 --> 00:07:05,442
such that as the comet
flies away from the Sun,
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00:07:05,544 --> 00:07:07,378
it flies into its own tail.
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00:07:11,096 --> 00:07:12,863
Comets may hold the answer
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00:07:12,964 --> 00:07:15,199
to one of the most
fundamental questions
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about our planet.
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00:07:21,473 --> 00:07:23,974
On Earth, where there is water,
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00:07:24,076 --> 00:07:25,910
there is life.
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00:07:27,245 --> 00:07:30,514
But just where did
that water come from?
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00:07:33,518 --> 00:07:36,420
Many have proposed
the water in Earth's oceans
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00:07:36,521 --> 00:07:38,823
was delivered by comets
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00:07:38,924 --> 00:07:41,258
crashing into the planet.
129
00:07:43,395 --> 00:07:46,063
Others believe the water
hitched a ride
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00:07:46,164 --> 00:07:49,467
inside rocky asteroids.
131
00:07:49,568 --> 00:07:52,103
Which theory is correct?
132
00:07:55,273 --> 00:07:57,308
Enter Rosetta...
133
00:07:57,409 --> 00:08:01,178
A mission designed to survey
then land a space probe
134
00:08:01,279 --> 00:08:03,781
on a comet.
135
00:08:03,882 --> 00:08:06,851
Rosetta and its lander,
called Philae,
136
00:08:06,952 --> 00:08:10,187
tracked down a comet
known as 67P
137
00:08:10,288 --> 00:08:15,059
after a ten-year journey
through space.
138
00:08:15,160 --> 00:08:18,162
So how do you get to a comet?
139
00:08:18,263 --> 00:08:21,332
Loop around our solar system
multiple times,
140
00:08:21,433 --> 00:08:23,968
including a daring
low-altitude skim
141
00:08:24,069 --> 00:08:28,139
less than 200 miles
above the surface of Mars.
142
00:08:28,240 --> 00:08:31,242
Then jam on the brakes.
143
00:08:33,245 --> 00:08:36,480
After establishing
a stable orbit of the comet,
144
00:08:36,581 --> 00:08:39,984
the Philae lander was deployed,
145
00:08:40,085 --> 00:08:44,088
and the world watched
and waited.
146
00:08:56,067 --> 00:08:59,336
The gravity on a comet
is so little
147
00:08:59,437 --> 00:09:02,339
that the pull on that spacecraft
was no different
148
00:09:02,440 --> 00:09:06,443
than the weight of a piece
of paper on your hand.
149
00:09:08,013 --> 00:09:10,447
The lander had to be
equipped with harpoons
150
00:09:10,549 --> 00:09:15,186
that would help attach it
to the surface of the comet.
151
00:09:15,287 --> 00:09:17,354
When those didn't deploy,
152
00:09:17,455 --> 00:09:20,024
the lander actually bounced,
153
00:09:20,125 --> 00:09:23,961
making it not just a day
for the first comet landing,
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00:09:24,062 --> 00:09:25,563
but also the second.
155
00:09:27,999 --> 00:09:32,536
Unfortunately, when Philae
finally came to est,
156
00:09:32,637 --> 00:09:36,307
it was partially
in the shade of a cliff.
157
00:09:36,408 --> 00:09:39,109
That meant that the solar panels
were only receiving
158
00:09:39,211 --> 00:09:40,945
about an hour and a half
of sunlight,
159
00:09:41,046 --> 00:09:43,214
instead of the six hours
that we were anticipating
160
00:09:43,315 --> 00:09:44,848
that they would.
161
00:09:44,950 --> 00:09:47,451
However, the Rosetta team
deployed all
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00:09:47,552 --> 00:09:49,386
of its instruments at once,
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00:09:49,487 --> 00:09:52,056
trying to get as much data
as they possibly could
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00:09:52,157 --> 00:09:55,893
before the lander
ran out of batteries.
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00:09:55,994 --> 00:09:57,494
Despite the bad luck,
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00:09:57,596 --> 00:10:02,099
the Rosetta mission was able
to make a significant discovery.
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00:10:02,200 --> 00:10:05,569
It appears unlikely
a comet like this one
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00:10:05,670 --> 00:10:08,305
brought water to our planet.
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00:10:08,406 --> 00:10:10,407
Its vapor has
a different chemical mix
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00:10:10,508 --> 00:10:12,509
than we see on Earth.
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00:10:14,546 --> 00:10:17,181
That leaves asteroids
as the most likely source
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00:10:17,282 --> 00:10:19,483
of our water...
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00:10:19,584 --> 00:10:21,952
an important finding
that could tilt
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decades of debate.
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00:10:27,626 --> 00:10:30,394
Even if comets
didn't bring water here,
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00:10:30,495 --> 00:10:33,230
they do carry with them
a set of beliefs,
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00:10:33,331 --> 00:10:35,299
superstitions, and omens
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00:10:35,400 --> 00:10:39,303
unlike anything else
in the night sky.
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00:10:41,273 --> 00:10:43,207
Were the ancients right
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00:10:43,308 --> 00:10:45,542
that there's one comet
in the solar system
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00:10:45,644 --> 00:10:48,312
with the power to cause
the birth of two-headed animals?
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00:10:50,081 --> 00:10:53,984
And could that same comet
end all life on Earth?
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00:10:55,887 --> 00:10:57,588
Dy, France,
184
00:10:57,689 --> 00:11:00,991
the year 1066...
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00:11:01,059 --> 00:11:03,927
a grand army prepares
for an invasion
186
00:11:04,029 --> 00:11:08,032
that could change
the course of history.
187
00:11:08,133 --> 00:11:11,035
They are Norman French soldiers,
188
00:11:11,136 --> 00:11:14,204
descendents of Vikings
and warriors,
189
00:11:14,306 --> 00:11:16,040
and they are led by a man
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00:11:16,141 --> 00:11:20,678
who will become known
as William the Conqueror.
191
00:11:24,215 --> 00:11:26,984
William's army is on the move,
192
00:11:27,052 --> 00:11:31,221
inspired by an omen
in the night sky.
193
00:11:31,323 --> 00:11:34,058
And what a sight it is.
194
00:11:34,159 --> 00:11:37,795
Where once there was only
the normal stars and planets,
195
00:11:37,862 --> 00:11:41,565
now on view is an object
four time larger in the sky
196
00:11:41,666 --> 00:11:42,900
than Venus
197
00:11:42,967 --> 00:11:46,303
and a quarter of the brightness
of a full moon.
198
00:11:48,139 --> 00:11:50,574
The Normans take
the comet's appearance
199
00:11:50,675 --> 00:11:52,743
and the disruption
in the heavens
200
00:11:52,844 --> 00:11:56,046
as an omen that God
is angry at their enemy...
201
00:11:56,147 --> 00:11:59,183
The English king Harold.
202
00:11:59,284 --> 00:12:02,052
Comets have been associated
with the death of kings,
203
00:12:02,153 --> 00:12:04,755
because comets linger
in the heavens.
204
00:12:04,856 --> 00:12:06,990
Meteors, they just come and go,
205
00:12:07,058 --> 00:12:09,193
but comets linger in
the heavens,
206
00:12:09,294 --> 00:12:13,063
signaling that the gods
are angry at the king
207
00:12:13,131 --> 00:12:15,766
and the king must die.
208
00:12:18,670 --> 00:12:22,172
October 14, 1066...
209
00:12:22,273 --> 00:12:25,042
The Normans have crossed
the English Channel
210
00:12:25,143 --> 00:12:27,945
and engaged King Harold
and his forces
211
00:12:28,046 --> 00:12:30,647
at the Battle of Hastings.
212
00:12:30,749 --> 00:12:35,018
It's time to fight
and, for thousands of men,
213
00:12:35,120 --> 00:12:37,287
time to die.
214
00:12:42,026 --> 00:12:43,861
When the battle finally ends,
215
00:12:43,962 --> 00:12:48,632
6,000 men are dead,
more English than Norman.
216
00:12:48,733 --> 00:12:50,868
That includes King Harold,
217
00:12:50,935 --> 00:12:55,706
whose advisors had warned him
the object was a bad omen.
218
00:12:55,774 --> 00:12:57,741
And it works.
The Normans won.
219
00:12:57,842 --> 00:12:59,109
The Anglo-Saxons lost.
220
00:12:59,210 --> 00:13:01,078
The history
of the English-speaking world
221
00:13:01,179 --> 00:13:02,913
changed forever.
222
00:13:03,014 --> 00:13:05,516
The battle and the omen
223
00:13:05,583 --> 00:13:09,086
live on in a famous work of art.
224
00:13:09,187 --> 00:13:11,688
The Bayeux Tapestry is
an incredible work of art.
225
00:13:11,756 --> 00:13:13,223
It's 230 feet long,
226
00:13:13,291 --> 00:13:16,026
and it tells the whole story
of the invasion.
227
00:13:16,127 --> 00:13:18,529
It shows them crossing
the English Channel.
228
00:13:18,630 --> 00:13:19,863
It shows them in battle.
229
00:13:19,931 --> 00:13:21,698
It shows
the Anglo-Saxon shield wall.
230
00:13:21,800 --> 00:13:24,067
It even shows
the Anglo-Saxon king dying
231
00:13:24,169 --> 00:13:26,470
with an arrow in his eye.
232
00:13:26,571 --> 00:13:29,139
And there, hovering over it all,
233
00:13:29,207 --> 00:13:31,875
is the omen that set
it all in motion...
234
00:13:31,943 --> 00:13:33,877
Not just any comet,
235
00:13:33,978 --> 00:13:35,846
it's Halley's Comet.
236
00:13:37,816 --> 00:13:39,716
Halley's Comet has been recorded
237
00:13:39,818 --> 00:13:43,720
by Chinese astronomers
and on ancient stone tablets,
238
00:13:43,822 --> 00:13:48,225
dating back thousands of years.
239
00:13:48,293 --> 00:13:50,227
The comet swings by the Sun
240
00:13:50,295 --> 00:13:53,897
once every 75 or 76 years,
241
00:13:53,998 --> 00:13:56,900
making it the only comet
visible to the naked eye
242
00:13:57,001 --> 00:14:00,671
that you can see
twice in a lifetime.
243
00:14:01,330 --> 00:14:05,667
It seems nearly every time
Halley's Comet swings by Earth,
244
00:14:05,768 --> 00:14:08,336
it shakes up our history.
245
00:14:11,874 --> 00:14:14,276
The ancient Swiss thought
of Halley's Comet
246
00:14:14,377 --> 00:14:16,111
as such a bad omen,
247
00:14:16,212 --> 00:14:19,314
they blamed it for everything
from earthquakes
248
00:14:19,415 --> 00:14:21,283
to the birth
of two-headed animals.
249
00:14:23,519 --> 00:14:26,788
Following its appearance
in 1456,
250
00:14:26,856 --> 00:14:30,125
it is said the Pope
excommunicated the comet,
251
00:14:30,226 --> 00:14:33,228
thinking it was a bad omen
for Christian soldiers
252
00:14:33,329 --> 00:14:35,730
battling the Ottoman Empire.
253
00:14:35,832 --> 00:14:40,635
But is fear of Halley's Comet
just superstition,
254
00:14:40,736 --> 00:14:45,407
or could it really cause
earthly Armageddon?
255
00:14:47,410 --> 00:14:49,578
Imagine...
256
00:14:49,679 --> 00:14:53,515
November 27, 2061...
257
00:14:53,583 --> 00:14:57,786
As amateur astronomers gather
for a look at Halley's Comet,
258
00:14:57,854 --> 00:14:59,788
stunning news is confirmed.
259
00:14:59,856 --> 00:15:02,824
There has been a change
in Halley's orbit,
260
00:15:02,925 --> 00:15:07,462
and it's headed straight
for Earth.
261
00:15:07,563 --> 00:15:10,232
If a giant comet were
to crash into the Earth,
262
00:15:10,299 --> 00:15:13,068
it would really ruin your day.
263
00:15:13,136 --> 00:15:16,271
First of all, there would be
a blinding flash of heat
264
00:15:16,372 --> 00:15:18,473
traveling at the speed of light,
265
00:15:18,574 --> 00:15:21,543
infrared radiation,
heat radiation coming out.
266
00:15:21,644 --> 00:15:24,779
Then a few seconds later,
the shockwave.
267
00:15:24,847 --> 00:15:28,283
The shockwave traveling
near the speed of sound,
268
00:15:28,384 --> 00:15:31,419
pulverizing everything
in its wake.
269
00:15:31,487 --> 00:15:35,323
And then after that,
perhaps we would have a tsunami
270
00:15:35,391 --> 00:15:37,659
coming at you.
271
00:15:37,760 --> 00:15:41,062
Remember that Halley's Comet
is about 20 miles across,
272
00:15:41,130 --> 00:15:43,165
about the size of Manhattan,
273
00:15:43,266 --> 00:15:45,800
but the object which destroyed
the dinosaurs
274
00:15:45,902 --> 00:15:49,437
65 million years ago
was only 6 miles across.
275
00:15:49,539 --> 00:15:52,607
And so, if we had Halley's Comet
276
00:15:52,708 --> 00:15:53,808
hit the planet Earth,
277
00:15:53,910 --> 00:15:56,311
it would be
not just a city buster,
278
00:15:56,379 --> 00:15:59,214
it would be a planet buster.
279
00:16:01,350 --> 00:16:03,718
Even today
we have the technology
280
00:16:03,819 --> 00:16:06,288
to track and photograph
Halley's Comet
281
00:16:06,389 --> 00:16:08,223
at every point in its orbit.
282
00:16:08,291 --> 00:16:11,593
In the future, there is time
to develop a plan
283
00:16:11,661 --> 00:16:14,429
to save humanity.
284
00:16:14,530 --> 00:16:17,766
If we have a comet and we've
been following its orbit,
285
00:16:17,833 --> 00:16:20,235
for many, many years
and we know it very accurately
286
00:16:20,336 --> 00:16:23,538
and we can predict
the collision with Earth
287
00:16:23,639 --> 00:16:24,773
decades ahead of time,
288
00:16:24,840 --> 00:16:27,075
then we might be able
to do something
289
00:16:27,176 --> 00:16:30,445
about that comet
before it hits the Earth.
290
00:16:30,546 --> 00:16:33,615
You can send a spacecraft up
there and tug it a little bit
291
00:16:33,716 --> 00:16:36,785
so that a bit at a time
we pull it away
292
00:16:36,886 --> 00:16:40,789
in such a way
that it doesn't hit the Earth.
293
00:16:40,890 --> 00:16:42,457
The truly dangerous comets
294
00:16:42,558 --> 00:16:45,627
are the ones
we've never seen before...
295
00:16:45,728 --> 00:16:47,629
Objects with orbits so long
296
00:16:47,730 --> 00:16:49,631
that they come in
once every thousand
297
00:16:49,732 --> 00:16:52,467
or ten thousand years.
298
00:16:52,568 --> 00:16:54,836
For a comet coming in
for the first time
299
00:16:54,904 --> 00:16:56,438
in recorded history,
300
00:16:56,539 --> 00:16:58,840
there's essentially nothing
we can do
301
00:16:58,908 --> 00:17:00,742
with today's technology.
302
00:17:00,810 --> 00:17:04,813
We have a few months' warning,
maybe one year at maximum.
303
00:17:04,914 --> 00:17:06,748
We don't know the trajectory
very well.
304
00:17:06,816 --> 00:17:10,018
We can't send up the spacecraft.
305
00:17:10,086 --> 00:17:13,021
So I'm sorry to say
that if there's a giant comet
306
00:17:13,089 --> 00:17:14,489
with Earth's name written on it
307
00:17:14,557 --> 00:17:17,192
heading toward us
for the first time,
308
00:17:17,260 --> 00:17:18,493
it's good-bye, cruel world.
309
00:17:18,594 --> 00:17:20,395
I'm sorry.
310
00:17:20,463 --> 00:17:24,366
A really bad omen
that actually comes to pass.
311
00:17:27,436 --> 00:17:30,372
If a new comet is approaching
Earth for the first time
312
00:17:30,439 --> 00:17:32,274
in recorded history,
313
00:17:32,375 --> 00:17:36,111
it's definitely coming in fast.
314
00:17:36,178 --> 00:17:38,647
Visualizing the motion
of a comet in its orbit
315
00:17:38,714 --> 00:17:42,217
is kind of like visualizing
the motion of a ball
316
00:17:42,318 --> 00:17:43,485
being tossed into the air.
317
00:17:43,586 --> 00:17:45,687
It starts out
moving fairly quickly,
318
00:17:45,788 --> 00:17:47,756
slows at the apex,
319
00:17:47,857 --> 00:17:50,125
and accelerates back
towards the ground.
320
00:17:50,226 --> 00:17:53,461
This is, in fact,
a partial orbit.
321
00:17:53,529 --> 00:17:56,231
Let's look at one full orbit.
322
00:17:58,167 --> 00:18:00,368
So, as a comet moves
away from the Sun,
323
00:18:00,436 --> 00:18:02,170
it's moving fairly quickly
324
00:18:02,271 --> 00:18:04,739
until, under the Sun's
gravitational influence,
325
00:18:04,807 --> 00:18:07,309
it slows, reaching the apex,
326
00:18:07,410 --> 00:18:09,144
a point we call the aphelion.
327
00:18:09,245 --> 00:18:10,545
From that point on,
328
00:18:10,613 --> 00:18:14,749
it accelerates
back towards the Sun, coming...
329
00:18:14,850 --> 00:18:17,719
back to its original position.
330
00:18:20,156 --> 00:18:23,391
With our newfound understanding
of the dangers that lurk
331
00:18:23,492 --> 00:18:25,093
in the solar system,
332
00:18:25,161 --> 00:18:29,431
we do have to be aware
that some of these bad omens
333
00:18:29,532 --> 00:18:33,768
indeed do turn out
to have terrible effects
334
00:18:33,869 --> 00:18:37,105
on humans on Earth.
335
00:18:37,206 --> 00:18:40,141
While our ancestors
feared comets,
336
00:18:40,242 --> 00:18:44,612
they were even more frightened
of another bad omen in the sky...
337
00:18:44,714 --> 00:18:48,450
One that arrives with
a sudden shadow and the terror
338
00:18:48,517 --> 00:18:53,221
of daytime turned into
a potentially endless night.
339
00:18:56,826 --> 00:18:58,560
In the tenth century,
340
00:18:58,661 --> 00:19:03,264
a group of Vikings
are on top of the world.
341
00:19:03,366 --> 00:19:06,368
They've set sail from what
we would now call Norway
342
00:19:06,469 --> 00:19:09,137
and are bound
for the Shetland Islands
343
00:19:09,238 --> 00:19:13,375
off the coast
of modern-day Scotland.
344
00:19:13,476 --> 00:19:15,143
And while they may be ready
345
00:19:15,244 --> 00:19:17,278
for anything the North Sea
can throw at them,
346
00:19:17,380 --> 00:19:20,081
nothing can prepare them
for what is happening
347
00:19:20,182 --> 00:19:22,550
in the northern sky.
348
00:19:22,651 --> 00:19:27,088
One minute, bright sunlight.
349
00:19:27,189 --> 00:19:31,693
Then suddenly, a shadow starts
to blot out the Sun.
350
00:19:31,794 --> 00:19:35,063
What's going on?
351
00:19:35,164 --> 00:19:38,099
Norse mythology tells
of twin wolves
352
00:19:38,167 --> 00:19:40,268
who track the Sun and moon.
353
00:19:40,369 --> 00:19:43,505
When they catch them
and devour them,
354
00:19:43,606 --> 00:19:47,342
that will signal
the beginning of Ragnarok...
355
00:19:47,443 --> 00:19:49,611
The end of all things.
356
00:19:51,680 --> 00:19:55,350
For a Viking, the question
he must face is simple
357
00:19:55,451 --> 00:19:56,684
yet chilling...
358
00:19:56,786 --> 00:19:58,653
is this it?
359
00:19:58,721 --> 00:20:02,056
With the midday sun
getting darker by the second,
360
00:20:02,158 --> 00:20:05,193
is this the end of the world?
361
00:20:05,294 --> 00:20:07,462
This is the bad omen
362
00:20:07,563 --> 00:20:11,399
that is a solar eclipse.
363
00:20:11,500 --> 00:20:13,134
Historically, in China,
364
00:20:13,235 --> 00:20:15,970
people would go outside
and bang pots,
365
00:20:16,071 --> 00:20:18,039
because they perceived
the solar eclipse
366
00:20:18,140 --> 00:20:22,510
as a bad omen of a dragon
consuming the Sun,
367
00:20:22,611 --> 00:20:26,581
and by banging the pots, they
were scaring away the dragon.
368
00:20:28,417 --> 00:20:31,486
In the case
of a total solar eclipse,
369
00:20:31,587 --> 00:20:33,588
it actually gets
reasonably dark.
370
00:20:33,689 --> 00:20:36,658
It can last several minutes.
371
00:20:36,759 --> 00:20:40,929
You don't know that the Sun's
gonna come back.
372
00:20:41,030 --> 00:20:43,097
You could go wild
373
00:20:43,199 --> 00:20:45,200
with uncertainty
about your future, and, indeed,
374
00:20:45,301 --> 00:20:48,937
ancient cultures
would sometimes react
375
00:20:49,038 --> 00:20:51,906
in very, very negative ways
to an eclipse.
376
00:20:52,007 --> 00:20:54,909
There would be mass murders.
377
00:20:55,010 --> 00:20:56,478
All sorts of things
could happen.
378
00:20:56,579 --> 00:20:58,379
Mayhem would break loose.
379
00:21:03,085 --> 00:21:06,254
In 585 BC,
380
00:21:06,355 --> 00:21:08,456
a six-year conflict
381
00:21:08,557 --> 00:21:11,593
near present-day Turkey
382
00:21:11,694 --> 00:21:16,564
is thrown into turmoil
when the day becomes night.
383
00:21:19,134 --> 00:21:22,470
There's some evidence
that on May 28, 585,
384
00:21:22,571 --> 00:21:25,573
a battle between
the Lydians and the Medes
385
00:21:25,674 --> 00:21:29,143
was stopped because
of a solar eclipse.
386
00:21:29,245 --> 00:21:31,980
They were into the sixth year
battling each other,
387
00:21:32,081 --> 00:21:35,650
and near sunset,
a solar eclipse occurred.
388
00:21:35,751 --> 00:21:38,286
The battlefield goes quiet,
389
00:21:38,387 --> 00:21:42,290
as all involved
look to the heavens.
390
00:21:42,391 --> 00:21:44,359
And they said,
"The gods are giving us a sign.
391
00:21:44,460 --> 00:21:46,361
We shouldn't be fighting."
392
00:21:46,462 --> 00:21:48,997
So they made a truce
and even offered
393
00:21:49,098 --> 00:21:52,133
their own sons and daughters
to the other side for marriage.
394
00:21:52,234 --> 00:21:54,469
That was a good thing,
395
00:21:54,570 --> 00:21:58,439
even though it was initially
thought of as a bad omen.
396
00:21:58,541 --> 00:22:02,944
So what's really going on
during a solar eclipse?
397
00:22:03,045 --> 00:22:05,280
A solar eclipse occurs
398
00:22:05,381 --> 00:22:08,416
when the moon goes exactly,
399
00:22:08,517 --> 00:22:12,287
or nearly exactly,
between Earth and the Sun.
400
00:22:12,388 --> 00:22:14,222
So the moon's disc
401
00:22:14,323 --> 00:22:17,625
blocks part
or all of the Sun's disc.
402
00:22:17,726 --> 00:22:21,462
And the Sun is so important
in our lives that the idea
403
00:22:21,564 --> 00:22:24,666
of something going in front
of it and blotting it out
404
00:22:24,767 --> 00:22:27,635
would be just
a remarkable event.
405
00:22:27,736 --> 00:22:30,939
So you can imagine
this would create fear,
406
00:22:31,040 --> 00:22:33,141
or perhaps
it would be interpreted
407
00:22:33,242 --> 00:22:37,045
as a sign
of something terrible to happen.
408
00:22:37,146 --> 00:22:38,646
But none of this would matter.
409
00:22:38,747 --> 00:22:41,082
Eclipses on Earth
wouldn't be possible
410
00:22:41,183 --> 00:22:44,085
without an amazing coincidence.
411
00:22:44,186 --> 00:22:46,588
One that isn't duplicated
anywhere else
412
00:22:46,689 --> 00:22:49,257
in our solar system.
413
00:22:49,358 --> 00:22:51,593
The sun and the moon
just happen to be
414
00:22:51,694 --> 00:22:56,431
the same apparent size
in our sky.
415
00:22:56,532 --> 00:22:59,133
That's because,
while the moon's diameter
416
00:22:59,234 --> 00:23:02,604
is about 400 times smaller
than the Sun's,
417
00:23:02,705 --> 00:23:07,442
the moon itself
is 400 times closer to us.
418
00:23:07,543 --> 00:23:10,945
It's a celestial accident
that the disc of the moon
419
00:23:11,046 --> 00:23:13,982
just covers the disc of the Sun.
420
00:23:14,083 --> 00:23:18,119
And so these eclipses
have fascinated astronomers
421
00:23:18,220 --> 00:23:19,954
for thousands of years.
422
00:23:20,055 --> 00:23:22,290
The perfect fit of Earth's moon
423
00:23:22,391 --> 00:23:24,626
makes eclipses possible.
424
00:23:24,727 --> 00:23:27,228
But will that
always be the case?
425
00:23:30,265 --> 00:23:33,167
Year by year, inch by inch,
426
00:23:33,268 --> 00:23:37,572
the moon is moving
further away from Earth.
427
00:23:37,673 --> 00:23:40,341
Someday in the distant future,
428
00:23:40,442 --> 00:23:44,078
the moon will no longer
completely block the Sun.
429
00:23:44,179 --> 00:23:46,581
The moon continues to go away
from the Earth,
430
00:23:46,682 --> 00:23:49,083
appearing smaller and smaller
in the sky.
431
00:23:49,184 --> 00:23:52,086
That means that
in about half a billion years,
432
00:23:52,187 --> 00:23:55,490
total solar eclipses
will no longer be possible.
433
00:23:55,591 --> 00:23:57,859
So we've lived in a special time
434
00:23:57,960 --> 00:24:01,262
where we can enjoy the beauty
435
00:24:01,363 --> 00:24:03,631
of what the ancients thought
were bad omens,
436
00:24:03,732 --> 00:24:05,566
and we now understand them
437
00:24:05,668 --> 00:24:08,603
and can appreciate them
for how beautiful and rare
438
00:24:08,704 --> 00:24:11,539
they really are.
439
00:24:11,640 --> 00:24:16,377
Our ancestors also saw
lunar eclipses as a bad omen.
440
00:24:18,414 --> 00:24:21,282
A lunar eclipse foretold
famine and disease,
441
00:24:21,383 --> 00:24:24,952
according to the Chinese.
442
00:24:25,054 --> 00:24:29,624
In Japan, lunar eclipses
were associated with earthquakes
443
00:24:29,725 --> 00:24:33,461
and meant disaster
was on the way.
444
00:24:33,562 --> 00:24:37,899
But does science support
this superstition?
445
00:24:38,000 --> 00:24:42,637
If the sky turns dark,
will the ground roll and roar?
446
00:24:46,975 --> 00:24:50,445
The ancients looked warily
on the night sky,
447
00:24:50,546 --> 00:24:55,316
where sudden changes
might foretell impending doom.
448
00:24:55,384 --> 00:24:59,387
The disappearance of the moon
in a total lunar eclipse
449
00:24:59,455 --> 00:25:03,558
struck fear into our ancestors.
450
00:25:03,659 --> 00:25:06,227
But did it also,
as some believed,
451
00:25:06,295 --> 00:25:09,564
cause earthquakes.
452
00:25:09,665 --> 00:25:11,599
Some people in Japan,
in particular,
453
00:25:11,700 --> 00:25:15,403
have thought that
total lunar eclipses cause
454
00:25:15,471 --> 00:25:18,039
bigger or more frequent
earthquakes.
455
00:25:18,107 --> 00:25:22,176
So lunar eclipses
were bad omens for that reason.
456
00:25:24,012 --> 00:25:27,248
December 21, 2010...
457
00:25:27,349 --> 00:25:30,852
For only the second time
in the last two millennia,
458
00:25:30,919 --> 00:25:32,854
a lunar eclipse takes place
459
00:25:32,921 --> 00:25:36,524
on the day
of the winter solstice.
460
00:25:36,625 --> 00:25:40,194
In Japan, a massive
7.4 earthquake
461
00:25:40,262 --> 00:25:44,866
triggers tsunami warnings
along the coast.
462
00:25:44,967 --> 00:25:48,202
30 years prior,
a 7.7 quake
463
00:25:48,270 --> 00:25:51,539
killed 25,000 people in Iran,
464
00:25:51,640 --> 00:25:53,875
just a few hours
before the start
465
00:25:53,976 --> 00:25:56,911
of a total lunar eclipse.
466
00:25:57,012 --> 00:25:59,213
Could it be that when
the Sun and moon
467
00:25:59,314 --> 00:26:01,215
are in perfect alignment,
468
00:26:01,316 --> 00:26:05,052
their combined gravity has
enough influence on the Earth
469
00:26:05,154 --> 00:26:08,890
to trigger killer quakes?
470
00:26:08,991 --> 00:26:11,492
The truth is that if you look
at long-term statistics,
471
00:26:11,593 --> 00:26:13,861
you don't see this.
472
00:26:13,962 --> 00:26:16,964
And physically, we can't think
of a reason why
473
00:26:17,065 --> 00:26:19,567
a total lunar eclipse
or a partial lunar eclipse
474
00:26:19,635 --> 00:26:21,569
would lead to more earthquakes.
475
00:26:21,637 --> 00:26:24,539
It's bunk, basically.
476
00:26:24,640 --> 00:26:26,407
A lunar eclipse happens
477
00:26:26,508 --> 00:26:29,443
when the Earth's shadow
covers the moon.
478
00:26:30,979 --> 00:26:32,513
If the disappearance of the moon
479
00:26:32,614 --> 00:26:34,916
wasn't frightening enough
to ancient eyes,
480
00:26:34,983 --> 00:26:36,851
during some eclipses,
481
00:26:36,952 --> 00:26:40,788
the moon actually changes color.
482
00:26:40,889 --> 00:26:43,391
When our moon passes through
Earth's shadow,
483
00:26:43,492 --> 00:26:46,127
it can turn blood red.
484
00:26:46,228 --> 00:26:49,497
To the ancients,
that was a bad omen.
485
00:26:49,598 --> 00:26:52,500
From the moon's perspective,
during a total lunar eclipse,
486
00:26:52,601 --> 00:26:55,336
the moon is receiving
the Sunlight
487
00:26:55,437 --> 00:26:59,307
of all the Sunrises
and sunsets on Earth.
488
00:26:59,408 --> 00:27:03,044
And that light is predominantly
orange or red,
489
00:27:03,145 --> 00:27:06,247
having traveled
through all of that air
490
00:27:06,348 --> 00:27:09,317
and dust and whatnot
in the atmosphere.
491
00:27:12,254 --> 00:27:14,422
As frightening as they were,
492
00:27:14,523 --> 00:27:17,024
some sky watchers
eventually realized
493
00:27:17,125 --> 00:27:20,995
that eclipses were predictable.
494
00:27:21,063 --> 00:27:24,398
Omens in the sky are something
that you can make use of.
495
00:27:24,499 --> 00:27:28,903
If you have superior knowledge
of eclipses, you can use it.
496
00:27:28,971 --> 00:27:32,073
One person to take advantage
of that knowledge,
497
00:27:32,140 --> 00:27:36,410
the famed explorer
Christopher Columbus.
498
00:27:36,511 --> 00:27:39,914
In 1502, Columbus and his crew
499
00:27:40,015 --> 00:27:42,850
were stranded in Jamaica
and running out of food.
500
00:27:42,951 --> 00:27:46,020
And the natives, basically,
were no longer thinking
501
00:27:46,121 --> 00:27:49,090
that there is something
special and God-like,
502
00:27:49,191 --> 00:27:52,426
you know?
They were losing their oomph.
503
00:27:52,494 --> 00:27:57,064
Columbus is said to have access
to a perpetual almanac
504
00:27:57,132 --> 00:27:59,467
that contained
more than 300 pages
505
00:27:59,568 --> 00:28:01,903
of sky tables, charts,
506
00:28:02,004 --> 00:28:05,006
and eclipse forecasts.
507
00:28:05,107 --> 00:28:08,843
Columbus happened to know that
there was a total lunar eclipse
508
00:28:08,944 --> 00:28:10,378
coming up the next night,
509
00:28:10,479 --> 00:28:13,147
and he told the natives
that if they don't continue
510
00:28:13,215 --> 00:28:17,084
to provide food,
the moon will go away.
511
00:28:17,185 --> 00:28:21,022
Sure enough, the next night,
a lunar eclipse did occur,
512
00:28:21,123 --> 00:28:22,323
as predicted by Columbus.
513
00:28:22,391 --> 00:28:24,458
And so this raised him,
514
00:28:24,559 --> 00:28:26,394
his stature, in their eyes,
515
00:28:26,495 --> 00:28:29,597
and the next day they started
providing goods and services
516
00:28:29,665 --> 00:28:33,034
once again.
517
00:28:33,135 --> 00:28:38,506
It's been said that all warfare
is based on deception.
518
00:28:38,573 --> 00:28:41,842
And some of the world's
greatest military leaders
519
00:28:41,944 --> 00:28:47,281
have used deceptions
based on lunar eclipses.
520
00:28:47,382 --> 00:28:49,450
The famed T.E. Lawrence,
521
00:28:49,551 --> 00:28:52,253
better known as
"Lawrence of Arabia,"
522
00:28:52,354 --> 00:28:55,289
is said to have timed his
assault on Aqaba
523
00:28:55,390 --> 00:28:58,125
to a lunar eclipse.
524
00:28:58,226 --> 00:29:00,494
Muslims Turks holding the town
525
00:29:00,562 --> 00:29:04,165
were distracted on
the night of the eclipse.
526
00:29:04,266 --> 00:29:08,202
As was their tradition,
they were busy making noises,
527
00:29:08,303 --> 00:29:10,905
firing rifles and banging pots
528
00:29:11,006 --> 00:29:15,142
in an effort to rescue the moon.
529
00:29:15,210 --> 00:29:19,080
Using his knowledge of science
and superstition,
530
00:29:19,181 --> 00:29:22,383
Lawrence and his Arab fighters
were victorious,
531
00:29:22,484 --> 00:29:25,720
taking the town without losing
a single man.
532
00:29:29,024 --> 00:29:32,526
September 20, 331 B.C.
533
00:29:32,627 --> 00:29:35,129
Alexander the Great
is outnumbered
534
00:29:35,197 --> 00:29:36,564
and headed for defeat
535
00:29:36,665 --> 00:29:40,568
at the hands of Emperor Darius
of Persia.
536
00:29:40,669 --> 00:29:42,837
Alexander the Great
was very smart.
537
00:29:42,938 --> 00:29:44,305
There's a lunar eclipse.
538
00:29:44,373 --> 00:29:46,273
You know it's an omen
of something.
539
00:29:46,375 --> 00:29:49,276
You don't want your own army
to become disheartened,
540
00:29:49,378 --> 00:29:53,280
so he used it as
a propaganda coup.
541
00:29:53,382 --> 00:29:56,017
As the moon glows blood red,
542
00:29:56,118 --> 00:29:59,353
Alexander's secret weapon
goes to work
543
00:29:59,454 --> 00:30:02,023
and the great leader
launches a desperate plan
544
00:30:02,090 --> 00:30:04,925
to save himself, his men
545
00:30:05,027 --> 00:30:07,461
and his empire.
546
00:30:12,334 --> 00:30:15,836
In the ancient world,
bad omens from the heavens
547
00:30:15,904 --> 00:30:19,840
were exploited
to change history.
548
00:30:19,908 --> 00:30:22,243
On a battlefield in Mesopotamia,
549
00:30:22,344 --> 00:30:26,414
Alexander the Great
turns a lunar eclipse
550
00:30:26,515 --> 00:30:29,216
into a weapon of fear.
551
00:30:29,284 --> 00:30:33,054
Alexander the Great spread word
via his astrologers
552
00:30:33,155 --> 00:30:35,956
that the lunar eclipse meant
that the Persians
553
00:30:36,058 --> 00:30:38,759
were going to lose.
554
00:30:38,827 --> 00:30:40,061
His men take heart,
555
00:30:40,162 --> 00:30:41,429
they make sure they spread
this message
556
00:30:41,530 --> 00:30:42,963
to the enemy army...
557
00:30:45,367 --> 00:30:47,935
They lose heart.
It's a fantastic coup
558
00:30:48,003 --> 00:30:50,438
in terms of undermining
the enemy morale.
559
00:30:50,539 --> 00:30:54,175
Of course it helps them
win the battle.
560
00:30:54,276 --> 00:30:56,243
The bad omen, paired with
561
00:30:56,344 --> 00:30:59,346
Alexander's tactical superiority
562
00:30:59,448 --> 00:31:02,450
is a devastating blow
against the Persians
563
00:31:02,551 --> 00:31:05,019
as Alexander romps to victory
564
00:31:05,087 --> 00:31:07,221
and into history.
565
00:31:10,358 --> 00:31:12,493
Nearly 300 years later,
566
00:31:12,594 --> 00:31:14,462
another omen would play a part
567
00:31:14,529 --> 00:31:17,498
in history's
most notorious betrayal
568
00:31:17,599 --> 00:31:20,868
and assassination.
569
00:31:21,615 --> 00:31:24,851
From a hilltop
in the mountains north of Rome,
570
00:31:24,952 --> 00:31:28,054
observers gather and watch
with trepidation
571
00:31:28,155 --> 00:31:32,825
as an unblinking red dot
rises in the night sky.
572
00:31:36,130 --> 00:31:40,867
The date, March 15, 44 B.C.
573
00:31:40,968 --> 00:31:42,135
The Ides of March.
574
00:31:48,675 --> 00:31:51,344
Julius Caesar is dead.
575
00:31:51,411 --> 00:31:56,048
And now, it appears
Mars is angry.
576
00:31:56,150 --> 00:31:58,785
The Roman had
whole colleges of priests
577
00:31:58,852 --> 00:32:01,587
who were responsible
for interpreting the omens.
578
00:32:01,688 --> 00:32:03,756
Omens in the sky,
omens from the birds,
579
00:32:03,857 --> 00:32:06,359
omens everywhere.
They were the guys you went to.
580
00:32:06,460 --> 00:32:08,895
What does it mean?
581
00:32:08,996 --> 00:32:12,765
On the night of Caesar's death,
582
00:32:12,866 --> 00:32:16,502
it was said that Mars was
especially bright and red,
583
00:32:16,570 --> 00:32:21,574
as though marking a triumph
over the emperor.
584
00:32:21,675 --> 00:32:24,010
More than 2,000 years later,
585
00:32:24,111 --> 00:32:28,548
we know Mars isn't red
because it's angry.
586
00:32:28,649 --> 00:32:31,551
Mars is red, literally,
587
00:32:31,652 --> 00:32:34,687
because it is rusty.
588
00:32:34,755 --> 00:32:37,590
There's leftover water on
the surface of Mars
589
00:32:37,658 --> 00:32:39,358
and below the surface.
590
00:32:39,459 --> 00:32:41,928
Leftover from when Mars formed.
591
00:32:42,029 --> 00:32:44,831
And it rusts or oxidizes
592
00:32:44,898 --> 00:32:47,834
the iron in the surface.
593
00:32:49,803 --> 00:32:53,072
But why would Mars be brighter
on certain nights,
594
00:32:53,173 --> 00:32:57,043
giving it extra power
as an omen?
595
00:32:57,110 --> 00:33:00,446
The distance between Earth
and Mars varies
596
00:33:00,547 --> 00:33:03,649
as the two planets orbit
the Sun.
597
00:33:03,750 --> 00:33:05,051
Earth circles the Sun
598
00:33:05,118 --> 00:33:08,988
once every 365 days.
599
00:33:09,089 --> 00:33:12,925
Mars takes 687 days,
600
00:33:13,026 --> 00:33:16,362
meaning that at some times
during their orbits,
601
00:33:16,463 --> 00:33:20,533
Earth is getting closer
and closer to Mars.
602
00:33:20,634 --> 00:33:22,969
Finally, the planets reach
the phase
603
00:33:23,070 --> 00:33:25,571
astronomers call opposition.
604
00:33:25,639 --> 00:33:30,409
That's when Mars and the Sun are
on opposite sides of the Earth.
605
00:33:30,477 --> 00:33:34,480
It is during opposition
that Mars is closest to Earth
606
00:33:34,548 --> 00:33:37,683
and shines its brightest.
607
00:33:37,751 --> 00:33:40,820
When the Sun is directly
between Mars and Earth,
608
00:33:40,921 --> 00:33:43,723
the planets are
farthest away from each other,
609
00:33:43,824 --> 00:33:45,858
about seven times farther
610
00:33:45,926 --> 00:33:47,994
than they were
during opposition.
611
00:33:51,632 --> 00:33:54,433
Ancient observers
often saw omens
612
00:33:54,534 --> 00:33:56,435
in the bright celestial objects
613
00:33:56,536 --> 00:34:00,873
we know today as planets.
614
00:34:00,974 --> 00:34:03,009
But could a planet be
responsible for
615
00:34:03,110 --> 00:34:04,543
an ancient mystery
616
00:34:04,645 --> 00:34:05,645
buried in the jungles
617
00:34:05,746 --> 00:34:09,048
of Mexico's Yucatan Peninsula?
618
00:34:09,149 --> 00:34:12,485
For years, archaeologists
studying the Mayan ruins
619
00:34:12,552 --> 00:34:14,587
at Chichen Itza
620
00:34:14,688 --> 00:34:17,924
wondered why twin staircases
on one of the buildings
621
00:34:17,991 --> 00:34:20,559
are out of alignment.
622
00:34:20,627 --> 00:34:23,796
Could it be somehow connected
to the astronomer priests
623
00:34:23,897 --> 00:34:28,834
who wielded tremendous power
in Mayan culture?
624
00:34:28,936 --> 00:34:30,870
By offsetting the stairs,
625
00:34:30,971 --> 00:34:35,041
what message were they trying to
send across the centuries?
626
00:34:35,142 --> 00:34:38,277
We do know this...
627
00:34:38,345 --> 00:34:43,316
the Mayans called Venus
"the great star."
628
00:34:43,417 --> 00:34:45,618
Mayan leaders would
always account for
629
00:34:45,719 --> 00:34:47,053
the position of Venus
630
00:34:47,154 --> 00:34:51,324
in their calculations for
battles and raids.
631
00:34:51,425 --> 00:34:53,693
When Venus is close
to the horizon,
632
00:34:53,794 --> 00:34:56,295
it can shimmer,
it can change colors.
633
00:34:56,363 --> 00:34:59,365
Venus has been reported as a UFO
634
00:34:59,433 --> 00:35:02,735
more times than any
other object in the universe.
635
00:35:02,803 --> 00:35:04,870
You can imagine, to the
ancients, when it was doing
636
00:35:04,972 --> 00:35:07,773
those weird things, those
twinkling and changing colors,
637
00:35:07,874 --> 00:35:11,544
that could be seen
as a bad omen.
638
00:35:11,611 --> 00:35:14,046
The Mayans would
actually block their chimneys,
639
00:35:14,147 --> 00:35:18,017
so what they feared as
the evil light from Venus
640
00:35:18,118 --> 00:35:20,453
couldn't get into their homes.
641
00:35:20,520 --> 00:35:22,822
If you look at Venus,
orbit after orbit,
642
00:35:22,889 --> 00:35:24,824
month after month,
you'll notice that
643
00:35:24,891 --> 00:35:27,760
it traces out a pattern
in the sky.
644
00:35:27,861 --> 00:35:29,996
These different patterns are
actually reflected
645
00:35:30,063 --> 00:35:33,265
in Mayan architecture.
646
00:35:33,333 --> 00:35:36,002
And so, the mysterious message
647
00:35:36,069 --> 00:35:38,771
is revealed.
648
00:35:38,872 --> 00:35:41,374
The misalignment of
the grand staircase
649
00:35:41,475 --> 00:35:43,442
at El Caracol,
650
00:35:43,510 --> 00:35:46,545
an ancient Mayan observatory,
651
00:35:46,613 --> 00:35:48,981
actually matches perfectly
652
00:35:49,049 --> 00:35:51,984
with Venus's most northern
appearance in the sky.
653
00:35:56,490 --> 00:35:59,825
Bright lights in the sky
always attracted the attention
654
00:35:59,926 --> 00:36:02,828
of our ancient ancestors.
655
00:36:02,929 --> 00:36:05,698
And while some were
merely ominous,
656
00:36:05,799 --> 00:36:10,036
others crackled with the threat
657
00:36:10,137 --> 00:36:12,605
of imminent attack.
658
00:36:20,847 --> 00:36:23,916
Darkness reigns.
659
00:36:23,984 --> 00:36:26,786
Polar bears are common here.
660
00:36:26,887 --> 00:36:28,554
So, too, are elk
661
00:36:28,622 --> 00:36:30,556
and other dangerous creatures
662
00:36:30,624 --> 00:36:33,926
that serve as
both predator and prey
663
00:36:34,027 --> 00:36:38,964
for the hearty few who make
this land their home.
664
00:36:39,066 --> 00:36:41,967
It is dark and scary
665
00:36:42,069 --> 00:36:47,640
and potentially deadly.
666
00:36:47,707 --> 00:36:53,045
Suddenly, a man out hunting
sees it,
667
00:36:53,146 --> 00:36:57,149
a threat known to his people
since ancient times.
668
00:36:59,519 --> 00:37:01,554
So he does what comes naturally,
669
00:37:01,655 --> 00:37:07,393
what generations of native
Alaskans have done before him.
670
00:37:07,461 --> 00:37:08,761
He draws his weapon
671
00:37:08,862 --> 00:37:10,996
and prepares to defend himself
672
00:37:11,064 --> 00:37:13,365
from the swirling
electrical madness
673
00:37:13,467 --> 00:37:17,403
he sees in the skies.
674
00:37:17,504 --> 00:37:19,538
Blazing lights.
675
00:37:19,606 --> 00:37:23,609
A mysterious and
ever-changing symphony of color.
676
00:37:26,580 --> 00:37:31,684
Today, we know this phenomenon
as the aurora borealis,
677
00:37:31,785 --> 00:37:35,387
the Northern Lights.
678
00:37:35,489 --> 00:37:38,324
And for many cultures,
like the Eskimos
679
00:37:38,425 --> 00:37:41,527
living near Barrow, Alaska,
680
00:37:41,595 --> 00:37:46,899
the aurora is a bad omen.
681
00:37:46,967 --> 00:37:49,435
Auroras, the northern
or southern lights,
682
00:37:49,503 --> 00:37:52,004
have often been seen as
bad omens because
683
00:37:52,105 --> 00:37:54,373
there are these
ghostly lights in the sky
684
00:37:54,474 --> 00:37:57,443
and they're flickering
and they're of unknown origin
685
00:37:57,544 --> 00:37:58,944
to the people watching them.
686
00:37:59,045 --> 00:38:01,981
Are the gods angry or something?
687
00:38:02,048 --> 00:38:07,353
So what causes
this sparkling show in the sky?
688
00:38:07,454 --> 00:38:09,488
Aurorae are fascinating examples
689
00:38:09,589 --> 00:38:11,490
of the interaction between
690
00:38:11,591 --> 00:38:14,894
the Sun and us here on Earth.
691
00:38:14,995 --> 00:38:17,463
The sun has what we call
space weather.
692
00:38:17,564 --> 00:38:21,333
These are solar flares or other
phenomena associated with
693
00:38:21,401 --> 00:38:23,068
the Sun's magnetic activity
694
00:38:23,136 --> 00:38:26,972
that shower our planet with
not only high energy radiation
695
00:38:27,040 --> 00:38:29,808
but also energetic particles.
696
00:38:29,910 --> 00:38:32,778
Earth has a magnetic field.
697
00:38:32,846 --> 00:38:35,047
Now, if that magnetic field
was in isolation,
698
00:38:35,115 --> 00:38:37,349
it would look sort of
like a cored apple.
699
00:38:37,450 --> 00:38:39,418
But it's not in isolation.
700
00:38:39,486 --> 00:38:42,521
The solar wind charged particles
streaming out of the Sun
701
00:38:42,622 --> 00:38:44,356
impinges upon Earth,
702
00:38:44,457 --> 00:38:47,626
flattening the nearside
and extending the farside
703
00:38:47,727 --> 00:38:48,928
of that field.
704
00:38:49,029 --> 00:38:50,696
It also has holes at
705
00:38:50,764 --> 00:38:52,364
the north and the south
706
00:38:52,465 --> 00:38:53,933
called polar cusps.
707
00:38:54,034 --> 00:38:56,769
Solar wind can flow into
the polar cusps,
708
00:38:56,836 --> 00:38:59,338
creating the aurora borealis
709
00:38:59,439 --> 00:39:01,807
and the aurora australis.
710
00:39:01,908 --> 00:39:04,677
As they excite the gases
in our atmosphere,
711
00:39:04,744 --> 00:39:06,645
depending upon the gases
that get excited,
712
00:39:06,746 --> 00:39:08,714
you get different colors.
713
00:39:08,815 --> 00:39:11,917
These different gases are
exactly what are used to make
714
00:39:12,018 --> 00:39:14,453
the neon signs that we see
down at the deli.
715
00:39:14,554 --> 00:39:18,724
When you see that green palm
tree or that red open sign,
716
00:39:18,825 --> 00:39:21,527
those are different gases
being energized
717
00:39:21,628 --> 00:39:23,462
and it's the light escaping
718
00:39:23,563 --> 00:39:25,898
as the electrons
change energy levels
719
00:39:25,999 --> 00:39:29,501
that we perceive
as these different colors.
720
00:39:29,569 --> 00:39:32,805
The spectacular light show
an aurora provides
721
00:39:32,906 --> 00:39:36,041
isn't the only way
to experience one.
722
00:39:36,109 --> 00:39:41,647
As it turns out, you can
actually hear an aurora too.
723
00:39:41,748 --> 00:39:44,583
There have always been stories
of people hearing sounds
724
00:39:44,651 --> 00:39:46,518
associated with the aurora.
725
00:39:46,620 --> 00:39:49,054
Popping and whistling noises.
726
00:39:49,155 --> 00:39:52,558
But it was unclear
if these were just stories
727
00:39:52,659 --> 00:39:55,060
or real, until recently
728
00:39:55,161 --> 00:39:57,529
when scientists were
finally able to record
729
00:39:57,631 --> 00:39:59,632
that, under very certain
circumstances,
730
00:39:59,733 --> 00:40:02,001
you can hear whistling
and popping noises
731
00:40:02,102 --> 00:40:04,737
associated with the Sun's energy
interacting with
732
00:40:04,838 --> 00:40:06,839
our own Earth's atmosphere.
733
00:40:06,906 --> 00:40:11,076
What causes the sound is still
a bit of a mystery.
734
00:40:11,177 --> 00:40:14,380
Researchers think the same
solar energy waves
735
00:40:14,447 --> 00:40:17,449
that generate the spectacular
lights in the sky
736
00:40:17,550 --> 00:40:22,721
are also responsible for
the sounds closer to the ground.
737
00:40:22,822 --> 00:40:26,425
The phenomenon of auroras
is an ancient mystery
738
00:40:26,526 --> 00:40:30,329
that stretches across
the cosmos.
739
00:40:30,430 --> 00:40:34,033
Jupiter has amazing aurorae that
we see on a regular basis.
740
00:40:34,134 --> 00:40:35,801
Saturn has aurorae.
741
00:40:35,902 --> 00:40:38,871
And even Venus.
742
00:40:38,972 --> 00:40:42,508
Omens, portents, and signs
743
00:40:42,609 --> 00:40:46,812
are how ancient people
made sense of their universe.
744
00:40:46,913 --> 00:40:50,949
Today, astronomers are making
remarkable discoveries
745
00:40:51,051 --> 00:40:53,619
that help explain
the science behind
746
00:40:53,720 --> 00:40:56,355
these once terrifying events.
747
00:40:56,456 --> 00:40:58,090
One of the things that's
really amazing about
748
00:40:58,158 --> 00:41:01,360
the time that we live in,
is that all of these things
749
00:41:01,428 --> 00:41:03,929
that were very scary
for our ancestors
750
00:41:03,997 --> 00:41:07,499
we now understand
through the lens of science.
751
00:41:07,600 --> 00:41:10,736
Humans always want to know
about the future.
752
00:41:10,804 --> 00:41:14,707
Whether you're an ancient Roman,
an ancient Chinese,
753
00:41:14,808 --> 00:41:17,509
a person living in America
in the 21st century,
754
00:41:17,610 --> 00:41:21,413
we want to look for signs
in nature, signs in the heavens,
755
00:41:21,514 --> 00:41:23,749
that can help us
understand things,
756
00:41:23,850 --> 00:41:25,718
can reassure us that we know
757
00:41:25,785 --> 00:41:28,287
what will happen in the future.
758
00:41:28,388 --> 00:41:30,055
As we learn more about
the universe,
759
00:41:30,156 --> 00:41:32,791
knowledge is replacing fear.
760
00:41:32,892 --> 00:41:35,627
People go north
to see the aurora.
761
00:41:35,695 --> 00:41:37,396
They take eclipse cruises.
762
00:41:37,497 --> 00:41:42,301
Yesterday's bad omens
are today's tourist attractions.
763
00:41:42,402 --> 00:41:47,373
This, then, is humanity
at the dawn of the 21st century,
764
00:41:47,474 --> 00:41:49,975
striving to understand
and experience first hand
765
00:41:50,076 --> 00:41:52,978
what men and women
through the millennia
766
00:41:53,046 --> 00:41:56,048
formerly saw as bad omens.
58382
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