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In the beginning,
there was darkness...
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00:00:03,962 --> 00:00:05,629
and then, bang...
3
00:00:05,672 --> 00:00:09,008
giving birth to an endless
expanding existence...
4
00:00:09,050 --> 00:00:11,593
of time, space, and matter.
5
00:00:11,636 --> 00:00:14,221
Now, see further
than we've ever imagined...
6
00:00:14,264 --> 00:00:16,265
beyond the limits
of our existence...
7
00:00:16,307 --> 00:00:21,395
in a place we call
"The Universe. "
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00:00:21,438 --> 00:00:23,939
They've intrigued man
for centuries...
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00:00:23,982 --> 00:00:28,277
captivating astronomers
and astrologers alike.
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00:00:28,319 --> 00:00:29,611
A mysterious alignment...
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00:00:29,654 --> 00:00:33,449
between the great pyramids of
Giza and the stars of Orion...
12
00:00:33,491 --> 00:00:37,036
could have been more
than a coincidence.
13
00:00:37,078 --> 00:00:40,039
And instead of 12 zodiac
constellations...
14
00:00:40,081 --> 00:00:42,124
we actually have 13.
15
00:00:42,167 --> 00:00:47,212
What is our 13th sign,
and why was it forgotten?
16
00:00:47,255 --> 00:00:49,798
The patterns that once
navigated mariners...
17
00:00:49,841 --> 00:00:51,467
across treacherous waters...
18
00:00:51,509 --> 00:00:54,803
now guide astronomers
to uncover the mysteries...
19
00:00:54,846 --> 00:01:08,984
that lie within
"The Constellations. "
20
00:01:09,027 --> 00:01:11,612
Before the Internet,
before movies...
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00:01:11,654 --> 00:01:13,655
the night sky
and the constellations...
22
00:01:13,698 --> 00:01:18,118
were the greatest show in town.
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00:01:18,161 --> 00:01:22,748
This gallery of stars forms
more than just pretty pictures.
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00:01:22,791 --> 00:01:26,877
It contains an enormous
sampling of star types.
25
00:01:26,920 --> 00:01:28,462
Through constellations...
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00:01:28,505 --> 00:01:30,589
we can learn a lot
about the galaxy...
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00:01:30,632 --> 00:01:33,509
and the universe beyond.
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00:01:33,551 --> 00:01:36,887
Before we had high-tech
navigation devices...
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00:01:36,930 --> 00:01:39,389
GPS, or even compasses...
30
00:01:39,432 --> 00:01:41,934
we had stars.
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00:01:41,976 --> 00:01:44,228
Like landmarks along the road...
32
00:01:44,521 --> 00:01:47,022
constellations can help us
find our way.
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00:01:47,065 --> 00:01:49,108
They give us
direction, distance...
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00:01:49,150 --> 00:01:52,444
and a sense of where to go.
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00:01:52,487 --> 00:01:54,613
So on Earth, when we want
to tell where something is...
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00:01:54,656 --> 00:01:58,158
we give its coordinates
in latitude and longitude.
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00:01:58,201 --> 00:01:59,618
And what that means on Earth
is a measure of...
38
00:01:59,661 --> 00:02:02,871
latitude is a measure
of the distance...
39
00:02:02,914 --> 00:02:05,582
between the North Pole
and the South Pole...
40
00:02:05,625 --> 00:02:08,877
and longitude
is the east-west distance...
41
00:02:08,920 --> 00:02:10,712
from the other direction.
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00:02:10,755 --> 00:02:14,049
Similarly, we have
a celestial coordinate system.
43
00:02:14,092 --> 00:02:15,300
But the coordinates...
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00:02:15,343 --> 00:02:17,553
they're not called
latitude and longitude.
45
00:02:17,595 --> 00:02:20,013
They're called declination
and right ascension.
46
00:02:20,056 --> 00:02:21,807
They are just
the direct extensions...
47
00:02:21,850 --> 00:02:23,642
of latitude and longitude
on Earth...
48
00:02:23,685 --> 00:02:26,311
projected out into the sky.
49
00:02:26,354 --> 00:02:29,148
Ancient navigators
used this imaginary grid...
50
00:02:29,190 --> 00:02:32,901
to plot stars and orient
themselves across the seas.
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00:02:32,944 --> 00:02:35,904
Not a precise kind
of indicator of direction...
52
00:02:35,947 --> 00:02:39,741
but certainly a cue
to keep people reminded...
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00:02:39,784 --> 00:02:44,163
of what the broad pathways
through the seas might be.
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00:02:44,205 --> 00:02:45,581
By using a sextant...
55
00:02:45,623 --> 00:02:49,084
mariners were able to use
guide stars like Polaris...
56
00:02:49,127 --> 00:02:50,544
to navigate.
57
00:02:50,587 --> 00:02:51,628
This is a sextant.
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00:02:51,671 --> 00:02:54,631
It's a tool used
in celestial navigation.
59
00:02:54,674 --> 00:02:55,841
Once a celestial body hits...
60
00:02:55,884 --> 00:02:58,594
what's called this lower limb
to the horizon...
61
00:02:58,636 --> 00:03:00,596
we mark the position.
62
00:03:00,847 --> 00:03:04,766
Using the time and the numbers
on this sextant...
63
00:03:04,809 --> 00:03:07,603
you can then use it
in fixing your position at sea.
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00:03:07,645 --> 00:03:12,524
Today's navigation uses
manmade stars: satellites.
65
00:03:12,567 --> 00:03:15,277
With the use of our manmade
stars per se...
66
00:03:15,320 --> 00:03:18,322
our GPS positions
and differential GPS...
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00:03:18,364 --> 00:03:19,615
we're able to fix
the ship's position...
68
00:03:19,657 --> 00:03:22,034
within a few yards
instantaneously...
69
00:03:22,076 --> 00:03:24,786
anywhere we are
in the world.
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00:03:24,829 --> 00:03:27,539
Now that GPS
has replaced sextants...
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00:03:27,582 --> 00:03:30,959
celestial coordinates are more
important to astronomers...
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00:03:31,002 --> 00:03:33,086
than they are to sailors.
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00:03:35,048 --> 00:03:36,548
And even though
the coordinate system...
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00:03:36,591 --> 00:03:39,593
gives them an idea of where
to point their telescopes...
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00:03:39,636 --> 00:03:42,888
the grid falls short
in a serious way.
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00:03:42,931 --> 00:03:44,973
It assumes all the stars...
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00:03:45,016 --> 00:03:47,559
are all the same distance
from us...
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00:03:47,602 --> 00:03:50,020
an assumption
that's flat-out wrong.
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00:03:52,357 --> 00:03:54,399
When you look at the stars
in the night sky...
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00:03:54,442 --> 00:03:57,486
they all appear to be
about the same distance away...
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00:03:57,528 --> 00:04:00,322
as if they were
in the same plane.
82
00:04:00,365 --> 00:04:03,242
The same happens when you look
at a city skyline...
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00:04:03,284 --> 00:04:04,701
from a distance away...
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00:04:04,744 --> 00:04:07,454
such as we are
from the Chicago skyline.
85
00:04:07,497 --> 00:04:08,914
So while those buildings...
86
00:04:08,957 --> 00:04:10,832
look like they're
the same distance...
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00:04:10,875 --> 00:04:13,418
they're really at many
different distances away.
88
00:04:13,461 --> 00:04:14,920
The same is true of the stars.
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00:04:14,963 --> 00:04:16,922
While they all look like
they're at the same distance...
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00:04:16,965 --> 00:04:20,008
some are close,
some are much further away.
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00:04:20,051 --> 00:04:22,427
So how do we know
which stars are close...
92
00:04:22,720 --> 00:04:25,180
and which are far away?
93
00:04:25,223 --> 00:04:26,306
As it turns out...
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00:04:26,391 --> 00:04:30,686
that's the most difficult
question of all.
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00:04:30,728 --> 00:04:34,106
That's been the single
greatest frustration...
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00:04:34,148 --> 00:04:37,442
in all of astronomy.
97
00:04:37,485 --> 00:04:39,903
Looking at the night sky,
even with telescopes...
98
00:04:39,946 --> 00:04:43,282
you cannot tell distances.
99
00:04:43,324 --> 00:04:47,411
That's been the holy grail
of astronomy for centuries.
100
00:04:53,126 --> 00:04:54,793
We're here in the Angeles
National Forest...
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00:04:54,836 --> 00:04:57,296
and I've got with me
a handy trail map.
102
00:04:57,338 --> 00:04:58,630
And I'd like to take a hike...
103
00:04:58,673 --> 00:05:00,966
maybe going to,
say, Switzer Falls...
104
00:05:01,009 --> 00:05:04,386
which, on my map,
looks like it's not very far...
105
00:05:04,429 --> 00:05:05,762
only maybe a mile.
106
00:05:09,517 --> 00:05:10,767
But the trouble is...
107
00:05:10,810 --> 00:05:13,395
I could badly underestimate
the difficulty of this hike...
108
00:05:13,438 --> 00:05:16,023
because my flat map here
fails to take into account...
109
00:05:16,065 --> 00:05:21,570
one very significant factor,
which is the elevation.
110
00:05:21,612 --> 00:05:25,240
So, in fact,
my simple one-mile hike...
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00:05:25,283 --> 00:05:27,868
could turn out to be
a 5,000-foot climb.
112
00:05:30,538 --> 00:05:33,123
So does my constellation map
fail to tell me...
113
00:05:33,166 --> 00:05:35,834
about the true distance
between two stars.
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00:05:35,877 --> 00:05:37,252
Even though
in a constellation...
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00:05:37,295 --> 00:05:39,338
they might look like they're
right next to each other...
116
00:05:39,380 --> 00:05:42,174
in fact, one could be much
farther away than the other...
117
00:05:42,216 --> 00:05:44,426
and I would never know it
if I just looked...
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00:05:44,469 --> 00:05:47,137
at the celestial
coordinates only.
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00:05:47,180 --> 00:05:51,099
Like hikers in the woods,
astronomers rely on clues...
120
00:05:51,142 --> 00:05:52,726
to help them gauge
the distances...
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00:05:52,769 --> 00:05:56,313
in our vast
and mysterious universe.
122
00:05:56,606 --> 00:05:57,814
So, when we're hiking
in the forest...
123
00:05:57,857 --> 00:06:00,192
even if we don't have a map
that tells us elevation...
124
00:06:00,234 --> 00:06:02,569
we can use our knowledge
of the local topography...
125
00:06:02,612 --> 00:06:03,737
and types of trees...
126
00:06:03,780 --> 00:06:06,031
to tell us something
about our altitude.
127
00:06:06,074 --> 00:06:08,825
For example, certain trees
prefer lower elevation...
128
00:06:08,868 --> 00:06:11,661
whereas other trees
prefer higher altitudes.
129
00:06:11,704 --> 00:06:12,954
Similarly, astronomers use...
130
00:06:12,997 --> 00:06:15,832
certain types of reference
stars as guideposts...
131
00:06:15,875 --> 00:06:20,670
familiar guideposts,
as a gauge of distance.
132
00:06:20,713 --> 00:06:22,964
The first tool
in the astronomer's kit...
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00:06:23,007 --> 00:06:25,967
is the phenomenon
of parallax.
134
00:06:26,010 --> 00:06:29,137
It's something we use
on a smaller scale every day...
135
00:06:29,180 --> 00:06:33,809
to see the world
in three dimensions.
136
00:06:33,851 --> 00:06:35,352
The way to think of parallax...
137
00:06:35,395 --> 00:06:39,439
is a very simple exercise
that everybody can do.
138
00:06:39,482 --> 00:06:41,483
Take a look at your finger...
139
00:06:41,526 --> 00:06:44,861
and look at something
really, really far away.
140
00:06:44,904 --> 00:06:46,196
If you use your right eye...
141
00:06:46,239 --> 00:06:49,074
and line up your finger
with a distant object...
142
00:06:49,117 --> 00:06:50,575
and then use your left eye...
143
00:06:50,618 --> 00:06:53,495
you'll see that your finger
actually appears to move...
144
00:06:53,538 --> 00:06:56,456
quite dramatically.
145
00:06:56,499 --> 00:06:58,125
This apparent shift is caused...
146
00:06:58,167 --> 00:07:02,170
by the distance
between our two eyes.
147
00:07:02,213 --> 00:07:03,630
Astronomers measure parallax...
148
00:07:03,673 --> 00:07:08,552
by looking at a star
at one position...
149
00:07:08,594 --> 00:07:12,055
and then looking at it
again six months later...
150
00:07:12,098 --> 00:07:13,807
when it's moved
as far as it could go...
151
00:07:13,850 --> 00:07:15,642
from our vantage point.
152
00:07:15,893 --> 00:07:19,020
Six months is really when
the Earth is as far away...
153
00:07:19,063 --> 00:07:21,815
from that original position
as it can be.
154
00:07:24,902 --> 00:07:30,323
The closer the star,
the greater the parallax.
155
00:07:30,366 --> 00:07:35,203
The problem is that stars
aren't very close.
156
00:07:35,246 --> 00:07:38,165
Even the parallax angle
of our closest star...
157
00:07:38,207 --> 00:07:43,795
Proxima Centauri,
is difficult to measure.
158
00:07:43,838 --> 00:07:46,089
It's less than
a second of arc.
159
00:07:46,132 --> 00:07:47,299
What's a second of arc?
160
00:07:47,341 --> 00:07:49,968
There's 360 degrees
in a circle.
161
00:07:50,011 --> 00:07:55,223
In every degree,
there is 60 minutes of arc.
162
00:07:55,266 --> 00:08:00,604
And in every minute of arc,
there are 60 seconds of arc.
163
00:08:00,646 --> 00:08:05,901
Proxima Centauri has a parallax
of 0.7 seconds of arc...
164
00:08:05,943 --> 00:08:08,862
so it's very small.
165
00:08:08,905 --> 00:08:11,239
To span the distance
to more far-flung stars...
166
00:08:11,282 --> 00:08:12,991
astronomers count on...
167
00:08:13,034 --> 00:08:16,161
a familiar guidepost
to lead them...
168
00:08:16,204 --> 00:08:21,082
much like the Coast Guard
uses a lighthouse.
169
00:08:21,125 --> 00:08:22,292
The men and women
of the Coast Guard...
170
00:08:22,335 --> 00:08:23,668
know that every lighthouse...
171
00:08:23,711 --> 00:08:26,379
has a particular
pulsation frequency.
172
00:08:26,422 --> 00:08:28,423
One might flash
two times a minute...
173
00:08:28,466 --> 00:08:29,716
another, four times.
174
00:08:29,759 --> 00:08:33,428
They can use this to determine
exactly their position...
175
00:08:33,471 --> 00:08:36,264
just based on the pattern.
176
00:08:36,307 --> 00:08:37,307
In the same way...
177
00:08:37,350 --> 00:08:39,601
astronomers can use
a cosmic lighthouse...
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00:08:39,644 --> 00:08:42,771
called a cepheid
variable star.
179
00:08:42,813 --> 00:08:44,606
The constellation Cepheus...
180
00:08:44,649 --> 00:08:47,734
named after the mythical
king of Aetheopia...
181
00:08:47,777 --> 00:08:52,155
claims 57 visible stars,
including Delta Cephei...
182
00:08:52,406 --> 00:08:54,699
a variable star
that is the prototype...
183
00:08:54,742 --> 00:08:58,453
for cepheid variables.
184
00:08:58,496 --> 00:08:59,871
By a quirk of nature...
185
00:08:59,914 --> 00:09:03,917
cepheids keep time
like a metronome.
186
00:09:03,960 --> 00:09:05,752
The bigger and brighter
the cepheid...
187
00:09:05,795 --> 00:09:08,421
the slower it will pulsate.
188
00:09:08,464 --> 00:09:11,132
So what you do is find
the cepheid variable...
189
00:09:11,175 --> 00:09:13,260
measure its pulsation period...
190
00:09:13,302 --> 00:09:15,971
it might be 10 days
or 60 days...
191
00:09:16,013 --> 00:09:19,432
and then you've got
a standard candle.
192
00:09:19,475 --> 00:09:24,312
You can determine
how far away that star is.
193
00:09:24,355 --> 00:09:27,857
A standard candle
is a basis of comparison...
194
00:09:27,900 --> 00:09:30,277
a star of known
luminosity and distance...
195
00:09:30,319 --> 00:09:34,447
that we can compare
similar stars against.
196
00:09:34,490 --> 00:09:36,950
A light bulb gives off
the amount of light.
197
00:09:36,993 --> 00:09:39,160
It gives off
a certain amount of watts.
198
00:09:39,203 --> 00:09:41,496
But that light is going
to look a lot brighter...
199
00:09:41,539 --> 00:09:43,415
if you're right up close
to that light bulb...
200
00:09:43,457 --> 00:09:46,376
than if you are
ten feet away.
201
00:09:46,419 --> 00:09:50,463
And so the luminosity
of a star doesn't change...
202
00:09:50,506 --> 00:09:52,132
you know, that is what it is.
203
00:09:52,174 --> 00:09:54,301
But apparent magnitude,
you know...
204
00:09:54,343 --> 00:09:58,179
depends on where you are,
how far away you are...
205
00:09:58,222 --> 00:10:00,098
whether you're right
up close to something...
206
00:10:00,141 --> 00:10:04,769
or you're seeing it from
the other side of the street.
207
00:10:04,812 --> 00:10:07,355
If a cepheid doesn't
appear that bright...
208
00:10:07,398 --> 00:10:10,609
then it must be far away.
209
00:10:10,651 --> 00:10:13,278
Astronomers can calculate
how far it is...
210
00:10:13,321 --> 00:10:17,365
based on how dim it appears.
211
00:10:17,408 --> 00:10:21,995
Looking at my cepheid variable
and plotting the light curve...
212
00:10:22,246 --> 00:10:24,914
how long it takes to go
from brightness to dim...
213
00:10:24,957 --> 00:10:26,666
and back to brightness again...
214
00:10:26,709 --> 00:10:31,212
tells me what the intrinsic
brightness of that star is.
215
00:10:31,255 --> 00:10:34,466
So I can calculate distance
to variable stars...
216
00:10:34,508 --> 00:10:37,969
by observing the period
of their variation.
217
00:10:38,012 --> 00:10:40,263
That's how Edwin Hubble
was able to determine...
218
00:10:40,306 --> 00:10:42,974
that Andromeda was
two million light-years...
219
00:10:43,017 --> 00:10:47,228
outside our galaxy.
220
00:10:47,271 --> 00:10:49,773
But cepheid variables
have their limits.
221
00:10:49,815 --> 00:10:52,400
To measure distances
far beyond Andromeda...
222
00:10:52,443 --> 00:10:55,278
astronomers rely
on supernovas.
223
00:11:01,535 --> 00:11:04,412
It turns out that supernovae
can also be categorized...
224
00:11:04,455 --> 00:11:06,206
as standard candles.
225
00:11:06,248 --> 00:11:09,084
Type 1 a supernovae
are all the same...
226
00:11:09,126 --> 00:11:10,168
throughout the universe.
227
00:11:10,211 --> 00:11:11,753
We know how to calibrate them...
228
00:11:11,796 --> 00:11:13,588
and that's how we determine
the distances...
229
00:11:13,631 --> 00:11:15,382
out to the Big Bang...
230
00:11:15,424 --> 00:11:19,969
and the very edges
of the universe.
231
00:11:20,012 --> 00:11:21,930
Peering into the Big Bang...
232
00:11:21,972 --> 00:11:26,810
scientists can nearly see
the beginning of time...
233
00:11:26,852 --> 00:11:31,106
300,000 years
after the Big Bang.
234
00:11:31,148 --> 00:11:33,274
Even our most
familiar constellations...
235
00:11:33,317 --> 00:11:36,653
have a lot to teach us
about the cosmos.
236
00:11:39,198 --> 00:11:41,574
Orion,
which is Greek for hunter...
237
00:11:41,617 --> 00:11:45,495
has 77 visible stars.
238
00:11:45,538 --> 00:11:49,290
Alnitak, Alnilam, and Mintaka...
239
00:11:49,333 --> 00:11:53,378
make up the three stars
in Orion's belt.
240
00:11:53,421 --> 00:11:56,464
In modern times,
astronomers have hunted Orion...
241
00:11:56,507 --> 00:12:02,804
finding a variety
of astonishing objects.
242
00:12:03,097 --> 00:12:04,097
When I see Orion...
243
00:12:04,140 --> 00:12:08,059
I also see the life
and death of stars.
244
00:12:08,102 --> 00:12:09,269
Just below the belt...
245
00:12:09,311 --> 00:12:12,021
there's a little smudge
called the Orion Nebula.
246
00:12:12,064 --> 00:12:15,650
Now, that's a nursery,
a nursery for baby stars...
247
00:12:15,693 --> 00:12:19,529
and you can actually see that
with the naked eye.
248
00:12:19,572 --> 00:12:24,909
Orion has also bagged
a pair of stellar gems.
249
00:12:24,952 --> 00:12:26,995
If you look at the upper
left-hand shoulder of Orion...
250
00:12:27,037 --> 00:12:29,372
you see the red giant
Betelgeuse.
251
00:12:29,415 --> 00:12:30,999
And if you immediately look
right down...
252
00:12:31,041 --> 00:12:32,834
to the lower right star...
253
00:12:32,877 --> 00:12:34,711
the star that's sort
of his leg...
254
00:12:34,754 --> 00:12:38,173
you'll see the blue
supergiant Rigel.
255
00:12:38,215 --> 00:12:41,009
Betelgeuse,
as a red supergiant...
256
00:12:41,051 --> 00:12:45,722
is a star in its death throes.
257
00:12:45,765 --> 00:12:47,849
A red supergiant is a star...
258
00:12:47,892 --> 00:12:50,226
that is actually quite a bit
cooler than our Sun...
259
00:12:50,269 --> 00:12:51,603
but much, much larger.
260
00:12:51,645 --> 00:12:56,441
Betelgeuse is 14 times
more massive than our Sun.
261
00:12:56,484 --> 00:12:58,526
When it runs out
of nuclear fuel...
262
00:12:58,569 --> 00:13:00,487
Betelgeuse
will become unstable...
263
00:13:00,529 --> 00:13:04,365
and implode
in a colossal supernova.
264
00:13:04,408 --> 00:13:07,202
It can detonate at any time.
265
00:13:07,244 --> 00:13:08,703
And when it explodes...
266
00:13:08,746 --> 00:13:11,498
it will light up
the entire night sky...
267
00:13:11,540 --> 00:13:15,668
and it will even be visible
during daytime.
268
00:13:15,711 --> 00:13:17,504
And maybe it's already
blown up.
269
00:13:17,546 --> 00:13:20,673
It's 427 light-years
from Earth...
270
00:13:20,716 --> 00:13:24,177
which means that perhaps
it has already exploded...
271
00:13:24,220 --> 00:13:28,431
but light hasn't had time
to reach us yet.
272
00:13:28,724 --> 00:13:31,392
The supernova will draw
more attention to a sky...
273
00:13:31,435 --> 00:13:36,147
that's been captivating us
for thousands of years.
274
00:13:36,190 --> 00:13:39,484
The ancient Egyptians
consulted the heavens...
275
00:13:39,527 --> 00:13:43,238
to tell them when to plant
and when to harvest.
276
00:13:43,280 --> 00:13:46,407
Every star possessed
a sacred meaning.
277
00:13:46,450 --> 00:13:47,951
They called Sirius...
278
00:13:47,993 --> 00:13:49,994
in the constellation
Canis Major...
279
00:13:50,037 --> 00:13:52,330
the Star of Isis.
280
00:13:52,373 --> 00:13:56,334
Sirius' appearance before dawn
during the summer solstice...
281
00:13:56,377 --> 00:14:00,338
forecasted the annual rise
of the Nile river.
282
00:14:00,381 --> 00:14:02,715
Other constellations,
like Orion...
283
00:14:02,758 --> 00:14:07,554
might have had a certain
architectural significance.
284
00:14:07,596 --> 00:14:10,431
Egyptologists have often
asked the question...
285
00:14:10,474 --> 00:14:13,768
why did the ancient Egyptians
build three great pyramids...
286
00:14:13,811 --> 00:14:15,687
that are slightly misaligned?
287
00:14:15,729 --> 00:14:18,731
Did they have bad ruler sticks
thousands of years ago?
288
00:14:18,774 --> 00:14:21,067
The three pyramids
seem to be aligned...
289
00:14:21,110 --> 00:14:25,446
to the three constellation
stars of Orion.
290
00:14:25,489 --> 00:14:28,283
What does this alignment mean?
291
00:14:28,325 --> 00:14:31,536
Was it a coincidence,
or were the pyramids...
292
00:14:31,579 --> 00:14:34,372
intentionally engineered
this way?
293
00:14:36,876 --> 00:14:41,254
The pyramids of Giza seduce us
with archeological mystery...
294
00:14:41,297 --> 00:14:44,299
and historical intrigue.
295
00:14:44,341 --> 00:14:46,718
Some scientists
think the pyramids...
296
00:14:46,760 --> 00:14:49,888
have a certain
astronomical importance.
297
00:14:49,930 --> 00:14:52,140
It has been claimed
that the layout...
298
00:14:52,182 --> 00:14:55,310
of the three major pyramids
on the Giza plateau...
299
00:14:55,352 --> 00:14:56,978
including the great pyramid...
300
00:14:57,021 --> 00:14:58,897
are set on the ground...
301
00:14:58,939 --> 00:15:03,151
to mimic the three stars
in Orion's belt.
302
00:15:03,402 --> 00:15:04,444
It's one of
my favorite connections...
303
00:15:04,486 --> 00:15:07,906
between events on Earth
and events in the sky.
304
00:15:07,948 --> 00:15:09,490
But the ancient Egyptians...
305
00:15:09,533 --> 00:15:12,660
didn't see a hunter in Orion
like we do.
306
00:15:12,703 --> 00:15:17,332
They saw Osiris,
God of Rebirth.
307
00:15:17,374 --> 00:15:20,668
Some speculate that air shafts
within the great pyramids...
308
00:15:20,711 --> 00:15:22,337
were specifically designed...
309
00:15:22,379 --> 00:15:26,633
to catapult the souls
of pharaohs to the heavens.
310
00:15:26,675 --> 00:15:29,177
In those pyramids,
we have two different shafts.
311
00:15:29,219 --> 00:15:30,303
And those shafts...
312
00:15:30,346 --> 00:15:33,389
one points north
and one points south.
313
00:15:33,432 --> 00:15:36,309
The south shaft
points toward Orion.
314
00:15:36,352 --> 00:15:37,393
So the soul of the pharaoh...
315
00:15:37,436 --> 00:15:39,687
would be launched
through that shaft...
316
00:15:39,730 --> 00:15:43,983
in order to be connected
to Osiris, Orion...
317
00:15:44,026 --> 00:15:47,987
and be resurrected again,
enjoying eternal life.
318
00:15:48,030 --> 00:15:50,531
But others are
a bit more skeptical.
319
00:15:50,574 --> 00:15:52,617
In order to make it
match correctly...
320
00:15:52,660 --> 00:15:55,954
you have to flip it
upside down on the ground...
321
00:15:55,996 --> 00:15:57,163
or in the sky...
322
00:15:57,206 --> 00:16:00,041
but the Egyptians
did place an importance...
323
00:16:00,084 --> 00:16:02,627
on north and on south
in the pyramid.
324
00:16:02,670 --> 00:16:05,046
And it doesn't make
any sense to say...
325
00:16:05,089 --> 00:16:07,215
well, yes, they lined
the stars up right...
326
00:16:07,257 --> 00:16:09,676
but then when it came
to mapping on the ground...
327
00:16:09,718 --> 00:16:12,095
it was perfectly okay
to flip everything around...
328
00:16:12,137 --> 00:16:14,305
and make it upside down.
329
00:16:14,348 --> 00:16:18,601
The north shaft points
toward one specific star.
330
00:16:18,644 --> 00:16:19,727
The one pointing north...
331
00:16:19,770 --> 00:16:21,562
points to the pole star
at the time...
332
00:16:21,814 --> 00:16:26,401
2,000 years before Christ,
2000 B.C., 3000 B.C.
333
00:16:26,443 --> 00:16:28,861
And that pole star
was Thuban.
334
00:16:28,904 --> 00:16:32,407
Thuban is located
in the constellation Draco...
335
00:16:32,449 --> 00:16:33,574
or the dragon.
336
00:16:33,617 --> 00:16:37,704
Draco has 79 visible stars.
337
00:16:37,746 --> 00:16:39,497
Thuban has been replaced...
338
00:16:39,540 --> 00:16:42,959
by our generation's pole star,
Polaris.
339
00:16:43,002 --> 00:16:45,586
Polaris illuminates
the arctic...
340
00:16:45,629 --> 00:16:50,758
governing our sky as a beacon
over the North Pole.
341
00:16:50,801 --> 00:16:53,594
Lying in the constellation
Ursa Minor...
342
00:16:53,637 --> 00:16:57,598
it's 2,500 times brighter
than the Sun...
343
00:16:57,641 --> 00:17:03,730
outshining its companion stars
Polaris AB and B.
344
00:17:03,772 --> 00:17:07,191
Although it's ruled the heavens
as our north star...
345
00:17:07,234 --> 00:17:09,110
for as long
as we can remember...
346
00:17:09,153 --> 00:17:12,613
its reign won't last forever.
347
00:17:12,656 --> 00:17:16,951
As Earth orbits the Sun,
it teeters back and forth.
348
00:17:16,994 --> 00:17:20,371
This wobbling is called
precession.
349
00:17:20,414 --> 00:17:24,417
If Earth was a perfect sphere,
it wouldn't precess...
350
00:17:24,460 --> 00:17:27,837
but the gravitational pulls
of the Moon and Sun...
351
00:17:27,880 --> 00:17:32,592
tug at the bulging equator,
upsetting Earth's spin.
352
00:17:32,634 --> 00:17:36,471
Now, the Earth is like
a gyroscope or a spinning top.
353
00:17:36,513 --> 00:17:38,973
Notice that if I spin this
very rapidly...
354
00:17:39,016 --> 00:17:40,767
and then I move the axis...
355
00:17:40,809 --> 00:17:42,977
it points
in the same direction.
356
00:17:43,020 --> 00:17:45,396
This is the Earth
pointing toward Polaris...
357
00:17:45,439 --> 00:17:47,607
that as the Earth
goes around the Sun...
358
00:17:47,649 --> 00:17:49,859
it always points
in the same direction.
359
00:17:49,902 --> 00:17:52,070
However,
precession is caused...
360
00:17:52,112 --> 00:17:53,738
by gravitational
interference...
361
00:17:54,031 --> 00:17:55,990
so the Earth
begins to wobble.
362
00:17:56,033 --> 00:17:57,909
As Earth wobbles...
363
00:17:57,951 --> 00:18:01,162
its axis draws a circle
in the sky.
364
00:18:01,205 --> 00:18:06,584
It takes 26,000 years
to make one complete circle.
365
00:18:06,627 --> 00:18:07,835
The north celestial pole...
366
00:18:07,878 --> 00:18:09,504
will move further
and further away...
367
00:18:09,546 --> 00:18:11,839
from the position of Polaris.
368
00:18:11,882 --> 00:18:15,551
In about 14,000 years
from now...
369
00:18:15,594 --> 00:18:18,346
about halfway
around its circle...
370
00:18:18,388 --> 00:18:21,390
it will be very close
to the bright star Vega.
371
00:18:21,433 --> 00:18:23,351
But because Vega
is so much brighter...
372
00:18:23,393 --> 00:18:25,686
than any other star
in that part of the sky...
373
00:18:25,729 --> 00:18:32,735
it will be a very significant
north polar star.
374
00:18:32,778 --> 00:18:37,198
In 26,000 years, Earth's axis,
centered on the North Pole...
375
00:18:37,241 --> 00:18:39,534
will make one complete circle...
376
00:18:39,576 --> 00:18:43,788
and it will point back
to where it is today.
377
00:18:43,831 --> 00:18:45,998
And Polaris
will overthrow Vega...
378
00:18:46,041 --> 00:18:50,044
and reclaim its title
as our north star.
379
00:18:50,087 --> 00:18:53,047
The closer a star is
to one of Earth's poles...
380
00:18:53,090 --> 00:18:56,968
the more its position
remains fixed in the sky.
381
00:18:57,010 --> 00:19:00,179
Astronomers call
these stars circumpolar...
382
00:19:00,222 --> 00:19:05,143
meaning that they're
visible all year long.
383
00:19:05,185 --> 00:19:07,186
In fact, all
of the constellations...
384
00:19:07,229 --> 00:19:09,063
of northern stars...
385
00:19:09,106 --> 00:19:11,357
such as the Little Dipper
and the Big Dipper...
386
00:19:11,400 --> 00:19:14,193
just go around
in a fairly small circle.
387
00:19:14,236 --> 00:19:15,403
So the result of that...
388
00:19:15,445 --> 00:19:19,031
they go around Polaris
without ever rising and setting.
389
00:19:19,074 --> 00:19:20,241
The further south you go...
390
00:19:20,284 --> 00:19:23,161
the more constellations
actually rise, say...
391
00:19:23,203 --> 00:19:24,245
at the beginning
of the night...
392
00:19:24,496 --> 00:19:25,913
and set at the end
of the night...
393
00:19:25,956 --> 00:19:30,918
and so they don't have
that magical property.
394
00:19:30,961 --> 00:19:36,174
Stars vary in size, density
and also brightness.
395
00:19:36,216 --> 00:19:37,884
Instead of shining
with a steady glow...
396
00:19:37,926 --> 00:19:39,427
like most stars...
397
00:19:39,469 --> 00:19:41,262
variable stars pulsate...
398
00:19:41,305 --> 00:19:45,391
brightening and dimming
in a hypnotic pattern.
399
00:19:45,434 --> 00:19:48,936
A variable star
is like a pot of tea.
400
00:19:48,979 --> 00:19:52,523
You take a kettle
and put it on a burner...
401
00:19:52,566 --> 00:19:53,900
and it starts to expand...
402
00:19:53,942 --> 00:19:56,277
and then it releases
its excess energy...
403
00:19:56,320 --> 00:19:57,486
and then drops.
404
00:19:57,529 --> 00:19:59,530
And then it starts
to build up pressure...
405
00:19:59,573 --> 00:20:01,282
and then it drops again.
406
00:20:01,325 --> 00:20:02,742
So kind of in the same way...
407
00:20:02,784 --> 00:20:04,660
the variable stars'
atmospheres...
408
00:20:04,703 --> 00:20:06,954
expand and shrink
with time...
409
00:20:06,997 --> 00:20:10,291
and this makes the star appear
to get brighter and dimmer.
410
00:20:10,334 --> 00:20:12,210
Sometimes this happens
over a matter of hours.
411
00:20:12,252 --> 00:20:16,088
Sometimes it can be
days or even months.
412
00:20:16,131 --> 00:20:18,424
A special class
of variable stars...
413
00:20:18,467 --> 00:20:20,468
called T-Tauri stars...
414
00:20:20,510 --> 00:20:23,429
pulsate because they're young
and unstable.
415
00:20:23,472 --> 00:20:26,474
Like stubborn teenagers,
T-Tauri stars...
416
00:20:26,516 --> 00:20:28,768
have erratic outbursts...
417
00:20:28,810 --> 00:20:33,814
except their tantrums involve
a struggle with gravity.
418
00:20:33,857 --> 00:20:38,319
As the nuclear forces
push it outward...
419
00:20:38,362 --> 00:20:39,862
gravity pulls it back in...
420
00:20:39,905 --> 00:20:42,073
and it misses
that equilibrium position...
421
00:20:42,115 --> 00:20:43,115
sort of like a pendulum...
422
00:20:43,367 --> 00:20:44,951
and it oscillates
back and forth.
423
00:20:48,914 --> 00:20:52,166
T-Tauris will outgrow
their pulsations.
424
00:20:52,209 --> 00:20:54,543
As they age,
they'll reach equilibrium...
425
00:20:54,586 --> 00:20:57,505
becoming stable stars.
426
00:20:57,547 --> 00:21:00,007
In fact,
before our Sun matured...
427
00:21:00,050 --> 00:21:04,512
scientists think
that it used to be a T-Tauri.
428
00:21:04,554 --> 00:21:06,847
This probably gives us
our best look...
429
00:21:06,890 --> 00:21:10,226
at what our solar system
and our Sun looked like...
430
00:21:10,269 --> 00:21:14,188
when it had just formed
in its earliest evolution.
431
00:21:14,231 --> 00:21:16,691
And we know that,
for example...
432
00:21:16,733 --> 00:21:19,485
that the clouds of dust and gas
around these stars...
433
00:21:19,528 --> 00:21:20,736
are very messy...
434
00:21:20,779 --> 00:21:24,198
and it must have been
a pretty violent scene...
435
00:21:24,241 --> 00:21:27,702
with many lunks
and chunks of rock...
436
00:21:27,744 --> 00:21:31,497
colliding into each other
and bombarding each other.
437
00:21:31,540 --> 00:21:34,709
The first T-Tauri stars
were identified...
438
00:21:34,751 --> 00:21:37,712
in the constellation Taurus.
439
00:21:37,754 --> 00:21:43,801
Taurus, the bull,
possesses 98 visible stars.
440
00:21:43,844 --> 00:21:50,224
Aldebaran, a red giant star,
is the bull's bloodshot eye.
441
00:21:50,267 --> 00:21:53,394
Taurus is one of the
zodiac constellations...
442
00:21:53,437 --> 00:21:56,564
that lie near the plane
of the ecliptic.
443
00:21:56,606 --> 00:21:58,607
It's called
the ecliptic plane...
444
00:21:58,650 --> 00:22:01,610
because that's the only circle
around the sky...
445
00:22:01,653 --> 00:22:03,779
where eclipses can occur.
446
00:22:03,822 --> 00:22:07,408
The Moon has to pass through
the ecliptic, for example...
447
00:22:07,451 --> 00:22:10,995
in order to give us
an eclipse of the Sun.
448
00:22:11,038 --> 00:22:13,998
It's also the path
that our Earth travels along...
449
00:22:14,041 --> 00:22:17,209
as we orbit the Sun.
450
00:22:17,252 --> 00:22:20,671
Eight degrees above
and below the ecliptic...
451
00:22:20,714 --> 00:22:23,632
lies a region
called the zodiac.
452
00:22:23,925 --> 00:22:26,302
Every constellation
that falls within this band...
453
00:22:26,345 --> 00:22:29,347
is referred to
as a zodiac constellation.
454
00:22:29,389 --> 00:22:31,015
At any given time...
455
00:22:31,058 --> 00:22:32,391
the Sun is in a constellation
of the zodiac.
456
00:22:32,434 --> 00:22:36,771
The Sun lies
between us on the Earth...
457
00:22:36,813 --> 00:22:39,190
and a certain constellation.
458
00:22:39,232 --> 00:22:41,442
Because we orbit our Sun...
459
00:22:41,485 --> 00:22:44,779
the Sun appears to move
through zodiac constellations...
460
00:22:44,821 --> 00:22:46,655
that are fixed in the sky.
461
00:22:46,698 --> 00:22:50,034
During nighttime, the opposite
portion of our sky...
462
00:22:50,077 --> 00:22:53,954
is lit by the Sun.
463
00:22:53,997 --> 00:22:57,792
Astrologers linked each of
the 12 zodiac constellations...
464
00:22:57,834 --> 00:23:01,295
to the month that the Sun
passes through.
465
00:23:01,338 --> 00:23:04,715
So in June, the Sun
sweeps through Cancer...
466
00:23:04,758 --> 00:23:08,594
and in July,
it glides across Leo.
467
00:23:08,637 --> 00:23:10,638
But you see,
there's a problem with that.
468
00:23:10,680 --> 00:23:13,140
Each constellation
is of different sizes.
469
00:23:13,183 --> 00:23:16,685
Some are small,
some are big.
470
00:23:16,728 --> 00:23:19,772
It takes the Sun seven days
to pass through Scorpius...
471
00:23:19,815 --> 00:23:22,316
the smallest
zodiac constellation...
472
00:23:22,359 --> 00:23:26,779
and 44 days to clear
Virgo, the largest.
473
00:23:26,822 --> 00:23:30,866
So you cannot divide the year
into 12 equal pieces...
474
00:23:30,909 --> 00:23:32,910
with 12 equally shaped
constellations.
475
00:23:36,873 --> 00:23:39,625
A lot of people put
a great deal of significance...
476
00:23:39,668 --> 00:23:43,504
on their zodiac sign,
their Sun sign.
477
00:23:43,547 --> 00:23:46,799
But in reality,
since the Earth is precessing...
478
00:23:46,842 --> 00:23:49,635
the constellation in which
the Sun appears today...
479
00:23:49,678 --> 00:23:51,178
is different
from the constellation...
480
00:23:51,221 --> 00:23:53,139
in which it appeared
2,000 years ago.
481
00:23:53,181 --> 00:23:54,473
So the next time
someone tells you...
482
00:23:54,766 --> 00:23:57,268
that you're competitive
because you're a Scorpio...
483
00:23:57,310 --> 00:23:58,978
tell him, "Well, you know...
484
00:23:59,020 --> 00:24:02,648
today I'm really not
a Scorpio anymore. "
485
00:24:02,691 --> 00:24:06,444
From the infamous
"What's your sign?" line...
486
00:24:06,486 --> 00:24:09,947
to predicting fortunes and
defining personality traits...
487
00:24:09,990 --> 00:24:12,116
the 12 signs of the zodiac
488
00:24:12,159 --> 00:24:15,327
have played a substantial role
in pop culture.
489
00:24:15,370 --> 00:24:17,997
But where do these signs
come from...
490
00:24:18,039 --> 00:24:20,499
and who named the stars?
491
00:24:24,379 --> 00:24:27,298
We have original names
for stars in some cases...
492
00:24:27,340 --> 00:24:29,258
that came to us
from Mesopotamia.
493
00:24:29,301 --> 00:24:31,552
Some names
were added to the stars...
494
00:24:31,595 --> 00:24:32,928
by the Greeks
and the Romans.
495
00:24:32,971 --> 00:24:35,306
Some of those survived,
some of them did not.
496
00:24:35,348 --> 00:24:38,142
With the collapse
of the Roman empire...
497
00:24:38,185 --> 00:24:40,102
in about 450 A.D...
498
00:24:40,145 --> 00:24:42,146
much of this knowledge
was lost.
499
00:24:42,189 --> 00:24:44,482
However, it was preserved
by the Arabs.
500
00:24:44,524 --> 00:24:47,485
And, in fact, much of
astronomy survives today...
501
00:24:47,527 --> 00:24:49,111
because of the Arabic
astronomers...
502
00:24:49,154 --> 00:24:52,406
preserving and augmenting
the calculations and work...
503
00:24:52,449 --> 00:24:54,074
of the Greek and Roman
astronomers.
504
00:24:54,117 --> 00:24:58,871
In 150 A.D., Greek scientist
Claudius Ptolemy...
505
00:24:58,914 --> 00:25:01,957
merged his own observations
with historical writings...
506
00:25:02,000 --> 00:25:05,669
labeling more than 1,000 stars.
507
00:25:05,712 --> 00:25:08,380
And out of all
the constellations...
508
00:25:08,423 --> 00:25:09,798
that cover our skies...
509
00:25:09,841 --> 00:25:13,677
we've learned that 12
are zodiac constellations...
510
00:25:13,720 --> 00:25:17,306
but in reality, there are 13.
511
00:25:23,355 --> 00:25:25,314
Even if we're not
followers of astrology...
512
00:25:25,357 --> 00:25:28,901
most of us know what
our astrological sign is.
513
00:25:28,944 --> 00:25:30,569
What most of us don't know...
514
00:25:30,612 --> 00:25:34,823
is that instead of having
12 zodiac constellations...
515
00:25:34,866 --> 00:25:38,035
there are actually 13.
516
00:25:38,078 --> 00:25:41,747
Ophiuchus, which is Greek
for the serpent bearer...
517
00:25:41,790 --> 00:25:43,958
is our forgotten sign.
518
00:25:44,000 --> 00:25:46,794
It has 55 visible stars...
519
00:25:46,836 --> 00:25:49,255
and is home
to Barnard's star...
520
00:25:49,297 --> 00:25:54,885
which is the fastest moving star
through our night sky.
521
00:25:54,928 --> 00:25:58,097
Nestled between Scorpius
and Sagittarius...
522
00:25:58,139 --> 00:26:02,685
Ophiuchus dwarfs
the constellations it surrounds.
523
00:26:02,727 --> 00:26:05,187
Although it was one
of the original...
524
00:26:05,230 --> 00:26:08,482
48-star patterns
that Ptolemy catalogued...
525
00:26:08,525 --> 00:26:09,984
some scientists speculate...
526
00:26:10,026 --> 00:26:12,194
that it might have been
dropped as a zodiac sign...
527
00:26:12,237 --> 00:26:16,156
to keep an even number of 12.
528
00:26:16,199 --> 00:26:18,158
Others think that precession...
529
00:26:18,201 --> 00:26:21,370
could have nudged Ophiuchus
off the zodiac...
530
00:26:21,413 --> 00:26:26,000
but the real answer
remains a mystery.
531
00:26:26,042 --> 00:26:27,876
The only star in the universe...
532
00:26:27,919 --> 00:26:30,546
that doesn't belong
to a specific constellation...
533
00:26:30,589 --> 00:26:31,839
is our Sun.
534
00:26:31,881 --> 00:26:33,424
Comparatively speaking...
535
00:26:33,466 --> 00:26:39,305
the Sun is a typical aging star
with an average mass.
536
00:26:39,347 --> 00:26:42,683
But stars that have
about 50 to 100 times...
537
00:26:42,726 --> 00:26:44,143
the mass of our Sun...
538
00:26:44,185 --> 00:26:46,812
are called Wolf-Rayet stars.
539
00:26:46,855 --> 00:26:48,897
The brightest observable
Wolf-Rayet...
540
00:26:48,940 --> 00:26:54,153
is called Gamma Velorum,
in the constellation Vela.
541
00:26:54,195 --> 00:26:57,531
These massive stars
are incredibly luminous...
542
00:26:57,866 --> 00:27:01,535
and are in their final
stages of evolution.
543
00:27:01,578 --> 00:27:03,787
The reason
they get so luminous...
544
00:27:03,830 --> 00:27:07,916
that they are pouring out energy
and radiation so furiously...
545
00:27:07,959 --> 00:27:10,085
it's actually powerful enough...
546
00:27:10,128 --> 00:27:13,672
to push off the outer layers
of the star's atmosphere.
547
00:27:13,715 --> 00:27:15,883
These stars literally
evaporate themselves...
548
00:27:15,925 --> 00:27:18,802
from all the heat and radiation
that they're generating...
549
00:27:18,845 --> 00:27:23,307
leaving behind just a very,
very hot central core.
550
00:27:23,350 --> 00:27:25,684
Although scientists
haven't directly observed...
551
00:27:25,727 --> 00:27:27,311
the death of any...
552
00:27:27,354 --> 00:27:29,563
they speculate
that Wolf-Rayet stars...
553
00:27:29,606 --> 00:27:30,856
will end their lives...
554
00:27:30,899 --> 00:27:33,859
in colossal supernova
explosions...
555
00:27:33,902 --> 00:27:38,405
or possibly collapse
into massive black holes.
556
00:27:38,448 --> 00:27:39,740
But before they do...
557
00:27:39,783 --> 00:27:41,450
they put on
a very spectacular show...
558
00:27:41,493 --> 00:27:45,245
of blowing out all
of their outer layers of gas...
559
00:27:45,288 --> 00:27:47,706
into the interstellar medium.
560
00:27:47,749 --> 00:27:51,710
Today, our network of ground-
and space-based telescopes...
561
00:27:51,753 --> 00:27:55,547
allows astronomers to see
any point in the sky...
562
00:27:55,590 --> 00:27:58,425
but ancient astronomers
in the northern hemisphere...
563
00:27:58,468 --> 00:28:00,594
couldn't see
that the southern hemisphere...
564
00:28:00,637 --> 00:28:05,849
looks out on an entirely
different view.
565
00:28:05,892 --> 00:28:06,934
If you're in the southern
hemisphere...
566
00:28:06,976 --> 00:28:09,269
the most prominent feature
in the night sky...
567
00:28:09,312 --> 00:28:10,521
is the Milky Way.
568
00:28:10,563 --> 00:28:11,897
And in the Milky Way...
569
00:28:11,940 --> 00:28:14,233
you have these zones
that are dark.
570
00:28:14,275 --> 00:28:15,401
They are dust clouds.
571
00:28:15,652 --> 00:28:16,568
But when you look
at them from Earth...
572
00:28:16,611 --> 00:28:17,903
they're just dark...
573
00:28:17,946 --> 00:28:21,573
against the backdrop
of a very bright Milky Way...
574
00:28:21,616 --> 00:28:22,741
and all the stars.
575
00:28:22,784 --> 00:28:25,244
It's the most noticeable thing.
576
00:28:25,286 --> 00:28:27,663
These dark clouds
appear as holes...
577
00:28:27,706 --> 00:28:31,166
within the Milky Way's
starry swath.
578
00:28:31,209 --> 00:28:34,002
There is such a distinctive
pattern, these holes...
579
00:28:34,045 --> 00:28:35,462
that some civilizations...
580
00:28:35,505 --> 00:28:37,881
in particular,
the Incas in South America...
581
00:28:37,924 --> 00:28:40,634
identified
these black splotches...
582
00:28:40,677 --> 00:28:45,389
these absorptions,
as constellations themselves.
583
00:28:45,432 --> 00:28:47,141
These dense patches of dust...
584
00:28:47,183 --> 00:28:51,145
are known as
dark cloud constellations.
585
00:28:51,187 --> 00:28:55,315
There is an amazing,
complete blackout of stars...
586
00:28:55,358 --> 00:28:57,234
in a region near the center...
587
00:28:57,277 --> 00:28:59,778
the direction near the center
of the galaxy...
588
00:28:59,821 --> 00:29:01,071
and it's called
the Coal Sack.
589
00:29:01,114 --> 00:29:04,032
It's just such
a dense cloud of dust...
590
00:29:04,075 --> 00:29:07,995
it just blocks out all the light
from the stars behind it.
591
00:29:08,037 --> 00:29:12,541
Today, the Coal Sack lies
in the constellation Crux.
592
00:29:12,584 --> 00:29:15,627
Crux, commonly called
the Southern Cross...
593
00:29:15,670 --> 00:29:17,713
is the smallest
constellation...
594
00:29:17,756 --> 00:29:20,340
and 20 stars are visible.
595
00:29:20,383 --> 00:29:23,343
Sailors relied on
Alpha and Gamma Crux...
596
00:29:23,386 --> 00:29:24,803
to locate the South Pole...
597
00:29:24,846 --> 00:29:27,306
since there is no pole star
like Polaris...
598
00:29:27,348 --> 00:29:31,185
in the southern hemisphere.
599
00:29:31,227 --> 00:29:32,853
As astronomy developed...
600
00:29:32,896 --> 00:29:34,480
the scientific community
realized...
601
00:29:34,522 --> 00:29:37,149
it needed to unify
the names and shapes...
602
00:29:37,192 --> 00:29:39,985
of the constellations.
603
00:29:40,028 --> 00:29:42,154
In 1922, a group formed...
604
00:29:42,197 --> 00:29:45,157
called the International
Astronomical Union.
605
00:29:45,200 --> 00:29:47,868
They were sort of the political
body of scientists...
606
00:29:47,911 --> 00:29:51,455
assigned to divide up the sky
and set up boundaries...
607
00:29:51,498 --> 00:29:54,333
so that everybody could agree
here are the boundaries.
608
00:29:54,375 --> 00:29:58,587
Those boundaries were based
on historic constellations.
609
00:29:58,630 --> 00:30:01,757
The IAU adopted
most of Ptolemy's...
610
00:30:01,800 --> 00:30:05,052
original constellations
and added more...
611
00:30:05,094 --> 00:30:10,057
to include every visible star
with no overlaps.
612
00:30:10,099 --> 00:30:11,934
Some of them were named
more recently...
613
00:30:11,976 --> 00:30:13,811
in the southern hemisphere...
614
00:30:13,853 --> 00:30:18,398
when Western Europeans
had got a really good look...
615
00:30:18,441 --> 00:30:20,234
at the southern skies.
616
00:30:20,276 --> 00:30:22,402
In all,
88 official constellations...
617
00:30:22,445 --> 00:30:24,279
cover the night sky.
618
00:30:24,322 --> 00:30:26,657
But there are other
small collections of stars...
619
00:30:26,699 --> 00:30:29,952
that form obvious patterns
called asterisms...
620
00:30:29,994 --> 00:30:32,329
like the Little Dipper
and Big Dipper.
621
00:30:32,372 --> 00:30:37,125
The Big Dipper is made out of
Ursa Major's brightest stars.
622
00:30:37,377 --> 00:30:43,507
Ursa Major, or the great bear,
has 71 visible stars.
623
00:30:43,550 --> 00:30:47,928
The Big Dipper is recognized
by its resemblance to a ladle.
624
00:30:47,971 --> 00:30:49,805
The Big Dipper is probably...
625
00:30:49,848 --> 00:30:52,349
the easiest object
in the sky to find...
626
00:30:52,392 --> 00:30:55,227
even if you don't know
anything else.
627
00:30:55,270 --> 00:30:57,437
For being such
a familiar asterism...
628
00:30:57,480 --> 00:31:00,691
the Big Dipper
is still full of surprises.
629
00:31:00,733 --> 00:31:03,777
The second star in its handle,
named Mizar...
630
00:31:03,820 --> 00:31:06,405
looks like a single point
of light...
631
00:31:06,447 --> 00:31:12,494
but a closer look reveals
that it's five blazing stars.
632
00:31:12,745 --> 00:31:17,499
Cygnus, the swan,
claims 79 visible stars.
633
00:31:17,542 --> 00:31:21,712
A star named Deneb
is a thermonuclear powerhouse...
634
00:31:21,754 --> 00:31:24,298
that forms the swan's tail.
635
00:31:24,340 --> 00:31:27,259
At 200 times the diameter
of our Sun...
636
00:31:27,302 --> 00:31:31,471
and as much as 250,000 times
as bright...
637
00:31:31,514 --> 00:31:33,724
Deneb is one
of the largest examples...
638
00:31:33,766 --> 00:31:37,102
of a white supergiant star.
639
00:31:37,145 --> 00:31:40,981
It's a star in a very unusual
phase of its evolution.
640
00:31:41,024 --> 00:31:43,442
There's very few stars
like that...
641
00:31:43,484 --> 00:31:46,111
and they don't spend very much
time of their lives...
642
00:31:46,154 --> 00:31:49,656
in such a high luminosity state.
643
00:31:49,699 --> 00:31:51,575
White supergiants are rare...
644
00:31:51,618 --> 00:31:53,577
because the star
is transitioning...
645
00:31:53,620 --> 00:31:56,496
from a red
to a blue supergiant...
646
00:31:56,539 --> 00:32:00,918
a phase that only lasts
a few million years.
647
00:32:00,960 --> 00:32:04,338
This may sound like a long time
by human standards...
648
00:32:04,380 --> 00:32:05,505
but for a star...
649
00:32:05,548 --> 00:32:10,427
it's less than one percent
of its lifetime.
650
00:32:10,470 --> 00:32:13,513
For a constellation
named after a graceful bird...
651
00:32:13,556 --> 00:32:18,352
Cygnus bears the scars
of a violent past.
652
00:32:18,394 --> 00:32:19,937
So Cygnus is also home...
653
00:32:19,979 --> 00:32:21,897
to something called
the Cygnus Loop...
654
00:32:21,940 --> 00:32:24,191
which is a supernova
remnant.
655
00:32:24,233 --> 00:32:28,403
There was a star that blew
itself to bits, basically.
656
00:32:28,446 --> 00:32:31,531
A gaping black hole,
called Cygnus X1...
657
00:32:31,574 --> 00:32:34,242
lies in the swan's heart.
658
00:32:34,285 --> 00:32:37,496
Cygnus X1 is an 8.7
solar mass black hole...
659
00:32:37,538 --> 00:32:40,374
so that's 8.7 times
the mass of our Sun...
660
00:32:40,416 --> 00:32:43,627
that's orbiting another star.
661
00:32:43,670 --> 00:32:49,633
Cygnus X1 was the first
black hole to ever be recorded.
662
00:32:49,676 --> 00:32:51,885
In fact, we first
detected Cygnus X1...
663
00:32:51,928 --> 00:32:53,553
not so much
because of the black hole...
664
00:32:53,596 --> 00:32:55,931
because it's black-
it's very hard to see...
665
00:32:55,974 --> 00:32:58,976
but because of its effect
on its companion...
666
00:32:59,018 --> 00:33:00,894
which is this giant star.
667
00:33:00,937 --> 00:33:01,937
And in fact, the black hole...
668
00:33:01,980 --> 00:33:04,815
is slowly devouring
the companion...
669
00:33:04,857 --> 00:33:07,192
and eventually it will
probably swallow it up.
670
00:33:07,235 --> 00:33:08,318
And when it does...
671
00:33:08,361 --> 00:33:11,071
a constellation
will lose a star...
672
00:33:11,114 --> 00:33:13,490
and our perception
of the night sky...
673
00:33:13,533 --> 00:33:15,826
will change forever.
674
00:33:20,039 --> 00:33:23,625
Our night sky
is in constant change.
675
00:33:23,668 --> 00:33:26,962
Within each constellation,
stars are born...
676
00:33:27,005 --> 00:33:31,591
while others are swallowed
by black holes.
677
00:33:31,634 --> 00:33:35,846
Every supernova explosion,
exotic star, and nebula...
678
00:33:35,888 --> 00:33:38,390
has one thing in common...
679
00:33:38,433 --> 00:33:39,474
they are identified...
680
00:33:39,517 --> 00:33:42,644
by the constellation
they're located in.
681
00:33:42,687 --> 00:33:44,271
But even before we invented...
682
00:33:44,564 --> 00:33:46,898
high-powered telescopes
to see them...
683
00:33:46,941 --> 00:33:50,861
constellations served
an important purpose...
684
00:33:50,903 --> 00:33:51,945
they brought people...
685
00:33:51,988 --> 00:33:57,576
the nightly news
that they dared not ignore.
686
00:33:57,618 --> 00:34:00,037
It was a question
of life and death.
687
00:34:00,079 --> 00:34:03,123
You see, the night sky
is a calendar.
688
00:34:03,166 --> 00:34:05,792
That was the very first
scientific invention...
689
00:34:05,835 --> 00:34:09,796
of us humans,
the calendar in the sky.
690
00:34:09,839 --> 00:34:11,757
The rising and setting
of the Sun...
691
00:34:11,799 --> 00:34:13,592
the changing phases
of the Moon...
692
00:34:13,843 --> 00:34:15,343
the seasonal reappearances...
693
00:34:15,386 --> 00:34:17,637
and disappearances
of the stars...
694
00:34:17,680 --> 00:34:21,266
people see that there is,
in fact...
695
00:34:21,309 --> 00:34:22,809
an order to the world.
696
00:34:22,852 --> 00:34:25,645
They, in fact,
see order in the sky...
697
00:34:25,688 --> 00:34:27,230
that is useful for them...
698
00:34:27,273 --> 00:34:29,983
to anticipate
what's happening on the Earth.
699
00:34:30,026 --> 00:34:32,527
That's a tool for survival.
700
00:34:32,570 --> 00:34:33,737
When you look at the sky...
701
00:34:33,780 --> 00:34:36,156
you see these
groups of stars...
702
00:34:36,199 --> 00:34:38,658
that are connected
to important events...
703
00:34:38,701 --> 00:34:41,161
that would prompt you
to behave in certain ways...
704
00:34:41,204 --> 00:34:42,537
or to move in certain ways...
705
00:34:42,580 --> 00:34:44,247
or to plant or harvest.
706
00:34:49,545 --> 00:34:50,796
Besides seeing
the pattern of stars...
707
00:34:50,838 --> 00:34:53,215
changing with the seasons...
708
00:34:53,257 --> 00:34:56,343
the ancients made
another crucial observation...
709
00:34:56,385 --> 00:35:02,224
the shifting stellar canopy
shaped their world.
710
00:35:02,266 --> 00:35:05,185
Travelers who went
a long way south...
711
00:35:05,228 --> 00:35:07,020
for example, from Greece...
712
00:35:07,063 --> 00:35:09,731
started being able to see
different constellations...
713
00:35:09,774 --> 00:35:11,191
from any
of the constellations...
714
00:35:11,234 --> 00:35:12,609
that had been visible
in their hometown.
715
00:35:12,652 --> 00:35:13,819
So it's telling you...
716
00:35:13,861 --> 00:35:15,654
that you're really moving
on a curved surface...
717
00:35:15,696 --> 00:35:19,366
and changing your perspective.
718
00:35:19,408 --> 00:35:21,535
Today we understand
the shape of the Earth...
719
00:35:21,577 --> 00:35:23,870
and the parade of the seasons.
720
00:35:23,913 --> 00:35:27,207
But constellations haven't
outlived their usefulness.
721
00:35:27,250 --> 00:35:29,334
Instead of telling us
about the Earth...
722
00:35:29,377 --> 00:35:33,880
they're helping us
make sense of the stars.
723
00:35:33,923 --> 00:35:37,217
A constellation is a lot
like an art museum.
724
00:35:37,260 --> 00:35:39,136
In an art museum,
you will see artists...
725
00:35:39,178 --> 00:35:41,471
who have used different
kinds of materials...
726
00:35:41,514 --> 00:35:45,559
paintings, photographs,
and ordinary objects.
727
00:35:45,601 --> 00:35:48,603
A constellation
also has similar objects...
728
00:35:48,646 --> 00:35:50,522
but made of different
materials.
729
00:35:50,565 --> 00:35:52,691
Some of them have more
helium or hydrogen...
730
00:35:52,733 --> 00:35:54,568
or carbon, silicon, iron...
731
00:35:54,610 --> 00:35:56,778
and yet we can group them
together.
732
00:35:56,821 --> 00:35:57,946
In both cases...
733
00:35:57,989 --> 00:36:00,490
the objects that are gathered
in an art museum...
734
00:36:00,533 --> 00:36:01,741
or a constellation...
735
00:36:01,784 --> 00:36:03,160
they're artificial collections...
736
00:36:03,202 --> 00:36:05,662
that we've put together
for some reason.
737
00:36:05,705 --> 00:36:11,918
Like countries, constellations
divide the sky into territories.
738
00:36:11,961 --> 00:36:13,753
When you say "Orion,"
I know exactly...
739
00:36:13,796 --> 00:36:15,755
what part of the sky
you're talking about.
740
00:36:15,798 --> 00:36:16,923
So to an astronomer...
741
00:36:16,966 --> 00:36:19,092
a constellation really
is kind of a handy map.
742
00:36:19,135 --> 00:36:20,635
It's just a way
of organizing things...
743
00:36:20,928 --> 00:36:23,430
so we kind of know
where stuff is.
744
00:36:23,472 --> 00:36:25,932
And even though the night sky
is infinite...
745
00:36:25,975 --> 00:36:28,768
we can see only
a sampling of stars...
746
00:36:28,811 --> 00:36:32,606
before dust and distance
blocks our view.
747
00:36:32,648 --> 00:36:34,441
You will probably see
on a very dark night...
748
00:36:34,483 --> 00:36:38,445
maybe 1,500 to 2,000 stars
with your naked eye...
749
00:36:38,487 --> 00:36:40,322
if you're not using binoculars
or anything.
750
00:36:45,203 --> 00:36:47,162
So what we're seeing is
only a tiny, tiny fraction...
751
00:36:47,205 --> 00:36:48,955
of what's really out there.
752
00:36:49,207 --> 00:36:50,123
That would be sort of
like looking...
753
00:36:50,166 --> 00:36:52,500
at the whole population
of the United States...
754
00:36:52,543 --> 00:36:54,252
350 million Americans...
755
00:36:54,295 --> 00:36:57,297
and seeing five people.
756
00:36:57,340 --> 00:37:03,637
Centaurus, or the centaur,
contains 101 visible stars.
757
00:37:03,679 --> 00:37:06,473
Two of its stars,
Alpha and Beta Centauri...
758
00:37:06,515 --> 00:37:10,685
are the brightest stars
in our night sky.
759
00:37:10,728 --> 00:37:13,271
Centaurus holds
Alpha Centauri...
760
00:37:13,314 --> 00:37:17,317
the star nearest to the Earth
after our own Sun.
761
00:37:17,360 --> 00:37:20,237
And a closer look reveals
that Alpha Centauri...
762
00:37:20,279 --> 00:37:25,700
is actually
a triple star system.
763
00:37:25,743 --> 00:37:28,745
It's not unusual for stars
to share the spotlight...
764
00:37:28,788 --> 00:37:31,706
with one or two
orbiting co-stars.
765
00:37:31,749 --> 00:37:34,501
In fact, it's the norm.
766
00:37:34,543 --> 00:37:37,712
Over 60 percent of the stars
you see in the heavens...
767
00:37:37,755 --> 00:37:41,424
are actually double stars,
triple stars, quadruple stars.
768
00:37:41,467 --> 00:37:43,802
Our Sun is an exception.
769
00:37:43,844 --> 00:37:47,222
Our Sun apparently
has no companion.
770
00:37:47,265 --> 00:37:50,642
While our Sun makes its
lonely voyage through space...
771
00:37:50,685 --> 00:37:55,563
the stars of Omega Centauri
never lack company.
772
00:37:55,606 --> 00:37:58,108
It is the brightest
globular star cluster...
773
00:37:58,150 --> 00:38:01,152
that you can see
without a telescope...
774
00:38:01,195 --> 00:38:02,696
just with the naked eye...
775
00:38:02,738 --> 00:38:06,449
because it is a giant cluster
of about 10 million stars.
776
00:38:06,492 --> 00:38:10,662
Omega Centauri is the largest
star cluster in our galaxy.
777
00:38:10,705 --> 00:38:12,539
These tightly bound stars...
778
00:38:12,581 --> 00:38:15,709
all have different,
complicated orbits...
779
00:38:15,751 --> 00:38:19,838
but they still manage to move
together as a single group.
780
00:38:19,880 --> 00:38:25,051
Where the cluster comes from
is anyone's guess.
781
00:38:25,094 --> 00:38:26,594
It's an unusual object...
782
00:38:26,637 --> 00:38:29,389
and a lot of astronomers
suspect...
783
00:38:29,432 --> 00:38:32,600
that this might be
the center of a galaxy...
784
00:38:32,643 --> 00:38:36,354
which got eaten or consumed
by the Milky Way...
785
00:38:36,397 --> 00:38:37,564
when it fell in.
786
00:38:37,606 --> 00:38:39,816
That certainly happens
fairly often...
787
00:38:39,859 --> 00:38:42,402
that big galaxies
are cannibals...
788
00:38:42,445 --> 00:38:43,737
and they eat little galaxies.
789
00:38:43,779 --> 00:38:49,034
And Omega Centauri may be
a remnant of this process.
790
00:38:49,076 --> 00:38:50,410
The light from Alpha Centauri...
791
00:38:50,453 --> 00:38:54,080
takes about 4.2 years
to reach us...
792
00:38:54,123 --> 00:38:55,999
but when we look
at Omega Centauri...
793
00:38:56,042 --> 00:39:00,211
we're seeing light
that's traveled 16,000 years.
794
00:39:00,254 --> 00:39:05,008
That's some indication of how
large Centaurus really is.
795
00:39:05,051 --> 00:39:07,761
It also shows
that a constellation exists...
796
00:39:07,803 --> 00:39:12,515
only in our mind's eye.
797
00:39:12,558 --> 00:39:15,685
And each star,
like every piece of art...
798
00:39:15,728 --> 00:39:17,854
begs to be explored.
799
00:39:22,943 --> 00:39:25,945
The constellations
organize the night sky
800
00:39:25,988 --> 00:39:29,282
and make it
almost comprehensible.
801
00:39:29,325 --> 00:39:31,534
As we gaze
at the twinkling lights...
802
00:39:31,827 --> 00:39:32,869
it's easy to forget...
803
00:39:32,912 --> 00:39:36,915
that each is one of billions
of blazing suns...
804
00:39:36,957 --> 00:39:41,252
fusing elements and possibly
creating new worlds.
805
00:39:41,295 --> 00:39:46,841
Our distance gives us
no sense of the stars' power.
806
00:39:46,884 --> 00:39:48,468
It also gives us no sense...
807
00:39:48,511 --> 00:39:52,138
of the endless depth of space
we're peering into.
808
00:39:52,181 --> 00:39:54,724
The flat planes
of the constellations...
809
00:39:54,767 --> 00:39:56,893
are an illusion.
810
00:39:56,936 --> 00:40:00,063
As you start getting away
from the Sun...
811
00:40:00,106 --> 00:40:03,108
by several light-years...
812
00:40:03,359 --> 00:40:06,194
the nearby stars
begin shifting...
813
00:40:06,237 --> 00:40:09,948
relative to the more distant
background stars.
814
00:40:09,990 --> 00:40:12,659
So the constellations
start distorting.
815
00:40:12,701 --> 00:40:15,412
By the time you are out
at 10, 20, 30 light-years...
816
00:40:15,454 --> 00:40:18,790
you probably wouldn't recognize
few of the constellations.
817
00:40:18,833 --> 00:40:24,170
So if you lived on a planet
going around Vega, let's say...
818
00:40:24,213 --> 00:40:26,047
that's 25 light-years
away from here...
819
00:40:26,090 --> 00:40:30,385
you'd have a different set
of constellations in your sky.
820
00:40:34,390 --> 00:40:37,976
Millennia of stargazing
have made the grand sweep...
821
00:40:38,018 --> 00:40:40,353
of the constellations
predictable.
822
00:40:40,396 --> 00:40:42,439
Our rotation around the Sun...
823
00:40:42,481 --> 00:40:46,568
carries us through
their annual cycle.
824
00:40:46,610 --> 00:40:50,447
The stars in the constellations
are in constant motion...
825
00:40:50,489 --> 00:40:52,699
not just as the galaxy spins...
826
00:40:52,741 --> 00:40:58,204
but also as each star's gravity
tugs and pulls on its neighbors.
827
00:40:58,247 --> 00:41:03,626
The fastest motion of the stars
is 150 miles per second.
828
00:41:03,669 --> 00:41:08,756
We don't have any manmade object
that can go that fast.
829
00:41:08,799 --> 00:41:10,675
The random motions
of these stars...
830
00:41:10,718 --> 00:41:12,218
with respect to each other...
831
00:41:12,261 --> 00:41:15,096
are more like
10 or 20 miles a second...
832
00:41:15,139 --> 00:41:17,765
and that is comparable
to the speed...
833
00:41:17,808 --> 00:41:20,560
of our fastest spacecraft.
834
00:41:20,603 --> 00:41:22,604
That's, of course,
way, way faster...
835
00:41:22,646 --> 00:41:25,982
than a high-speed bullet.
836
00:41:26,025 --> 00:41:28,109
The stars are always moving...
837
00:41:28,152 --> 00:41:32,489
and their distance from us
masks their enormous speed.
838
00:41:32,531 --> 00:41:35,325
It's like looking out the window
of a speeding automobile.
839
00:41:35,367 --> 00:41:37,744
The fence posts and trees
closest to the highway...
840
00:41:37,786 --> 00:41:46,336
whiz by, while the distant
landscape creeps slowly past.
841
00:41:46,378 --> 00:41:49,881
Over our lifetime-in fact,
close to a thousand lifetimes...
842
00:41:49,924 --> 00:41:54,552
most stars don't appear
to move at all.
843
00:41:54,595 --> 00:41:55,762
It just intrigues me to think...
844
00:41:55,804 --> 00:42:00,683
that if I could find one
of our recent relatives...
845
00:42:00,726 --> 00:42:03,102
the Cro-Magnon man,
for example...
846
00:42:03,145 --> 00:42:04,395
he would probably correct me...
847
00:42:04,438 --> 00:42:07,023
because he would be
more familiar with the sky...
848
00:42:07,066 --> 00:42:08,274
and he would know
the constellations...
849
00:42:08,317 --> 00:42:11,110
a little bit better
than the people do today.
850
00:42:11,153 --> 00:42:12,654
But little by little...
851
00:42:12,696 --> 00:42:16,491
our star maps are reaching
their expiration dates.
852
00:42:16,534 --> 00:42:18,493
In 10,000 years, the stars...
853
00:42:18,536 --> 00:42:19,827
would be noticeably different.
854
00:42:19,870 --> 00:42:21,496
The constellations would be
noticeably different...
855
00:42:21,539 --> 00:42:23,289
than what we see now.
856
00:42:23,332 --> 00:42:26,751
In 500,000 years,
they will be unrecognizable.
857
00:42:26,794 --> 00:42:29,045
And if you truly could see
a time-lapse photo...
858
00:42:29,088 --> 00:42:31,589
over a period
of a million years...
859
00:42:31,632 --> 00:42:36,803
you would, in fact, see
stars racing around the sky.
860
00:42:36,845 --> 00:42:39,222
The constellations
are a snapshot...
861
00:42:39,265 --> 00:42:42,141
a flattened portrait
of the night sky.
862
00:42:42,434 --> 00:42:44,811
And like a portrait,
it's a good likeness...
863
00:42:44,853 --> 00:42:46,938
but not the whole story.
864
00:42:46,981 --> 00:42:48,398
If we could fly into space...
865
00:42:48,440 --> 00:42:50,149
and see them
from another angle...
866
00:42:50,192 --> 00:42:52,735
these old, familiar
star formations...
867
00:42:52,778 --> 00:42:55,863
would be unidentifiable.
868
00:42:55,906 --> 00:42:57,615
But right here, right now...
869
00:42:57,658 --> 00:43:01,661
the 88 constellations
provide reassuring guideposts...
870
00:43:01,704 --> 00:43:05,331
while reminding us of our past.
871
00:43:05,374 --> 00:43:08,835
The constellations really
don't fulfill the functions...
872
00:43:09,128 --> 00:43:10,336
that they fulfilled
originally...
873
00:43:10,379 --> 00:43:12,505
for the people
that devised them.
874
00:43:12,548 --> 00:43:16,676
For them, there was a direct
cause-and-effect connection...
875
00:43:16,719 --> 00:43:19,512
between something that was
of interest to them...
876
00:43:19,555 --> 00:43:20,847
and their lives.
877
00:43:20,889 --> 00:43:25,351
They watched Sirius because
it was a seasonal indicator.
878
00:43:25,394 --> 00:43:27,854
We don't use the sky
that way anymore.
879
00:43:27,896 --> 00:43:29,856
But the stories are resilient...
880
00:43:29,898 --> 00:43:31,899
and the images are resilient.
881
00:43:31,942 --> 00:43:33,693
We hold onto those
constellations...
882
00:43:33,736 --> 00:43:37,196
and frankly,
I'm delighted we do.
883
00:43:37,239 --> 00:43:39,657
Instead of telling
stories of the past...
884
00:43:39,700 --> 00:43:43,453
modern astronomy compels us
to look at constellations...
885
00:43:43,495 --> 00:43:47,081
as a grouping of possibilities.
886
00:43:47,124 --> 00:43:48,207
Most of the constellations...
887
00:43:48,250 --> 00:43:51,002
have three to five planets
inside them.
888
00:43:51,045 --> 00:43:52,879
And in a few more years...
889
00:43:52,921 --> 00:43:53,921
we're gonna identify...
890
00:43:53,964 --> 00:43:56,716
perhaps hundreds
of Earth-like planets...
891
00:43:56,759 --> 00:43:58,635
orbiting other stars.
892
00:43:58,677 --> 00:44:01,262
So we will have this epiphany
every night...
893
00:44:01,305 --> 00:44:03,723
realizing that when we look
at the constellations...
894
00:44:03,766 --> 00:44:06,893
somebody may be looking back.
895
00:44:06,935 --> 00:44:08,603
In a space so vast...
896
00:44:08,646 --> 00:44:09,729
that we can only see...
897
00:44:09,772 --> 00:44:12,565
a small fraction
of our universe...
898
00:44:12,608 --> 00:44:16,402
we look to the stars,
wondering what it all means...
899
00:44:16,445 --> 00:44:19,238
making patterns,
inventing stories...
900
00:44:19,281 --> 00:44:21,324
attempting to solve
the mysteries...
901
00:44:21,367 --> 00:44:24,118
that our constellations hold.
71499
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