1
00:00:01,560 --> 00:00:02,600
The Earth...

2
00:00:04,000 --> 00:00:05,640
..third rock from the Sun.

3
00:00:07,920 --> 00:00:09,360
And it's unique...

4
00:00:12,320 --> 00:00:13,760
..it has life.

5
00:00:16,080 --> 00:00:20,080
So how do you make
a planet like ours?

6
00:00:20,080 --> 00:00:22,400
I'm going to open up
the cosmic tool box

7
00:00:22,400 --> 00:00:23,920
and work it out.

8
00:00:23,920 --> 00:00:27,360
We're going to build
a planet, up there...

9
00:00:29,800 --> 00:00:33,040
..at the top of this
impossibly high tower.

10
00:00:37,920 --> 00:00:40,560
It gives us the perfect platform

11
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to make something really big.

12
00:00:47,480 --> 00:00:50,520
Up here, we can do in seconds

13
00:00:50,520 --> 00:00:54,360
what it takes nature millions
or billions of years to do.

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We are going to build our planet...

15
00:01:02,320 --> 00:01:04,720
brick by brick.

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00:01:18,760 --> 00:01:22,000
But to do that,
I'm going to need help.

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00:01:24,440 --> 00:01:27,760
And I'll find it in
the most unlikely places.

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Right now,
I am effectively weightless.

19
00:01:32,360 --> 00:01:34,800
I'm on the ceiling.
I am ON the ceiling.

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00:01:36,040 --> 00:01:38,640
Of course,
as with any construction work...

21
00:01:41,680 --> 00:01:43,360
..there will be hiccups.

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But out of these mistakes
will come real insights

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00:01:49,760 --> 00:01:52,920
into what makes our planet,
our solar system,

24
00:01:52,920 --> 00:01:57,080
exactly right for us - for life.

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As an engineering challenge,

26
00:01:58,960 --> 00:02:00,480
it doesn't get much bigger.

27
00:02:27,880 --> 00:02:32,680
I love it here on this hill.

28
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Feels like it was made

29
00:02:34,040 --> 00:02:36,880
for bracing Sunday walks
with the family.

30
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And indeed most weekend mornings,

31
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the place is full of parents
with their kids,

32
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including me with mine, sometimes.

33
00:02:47,760 --> 00:02:51,800
And when I was on those same
family Sunday morning walks,

34
00:02:51,800 --> 00:02:52,960
as a kid myself,

35
00:02:52,960 --> 00:02:57,680
I spent as much of my time
looking down as I did up and round.

36
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Rocks, stones, the very stuff
of the Earth -

37
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they fascinated me.

38
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And amongst my finds was one
I felt particularly important -

39
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a rock the size of your fist.

40
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A rich brown - dimpled, heavy,
glinting,

41
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somehow special.

42
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It became one of my most treasured
childhood possessions.

43
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I was convinced it was a meteorite -

44
00:03:20,840 --> 00:03:24,480
a rock that had landed here
from space.

45
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Morning.

46
00:03:33,240 --> 00:03:36,600
Like most treasured
childhood possessions,

47
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it got lost or swapped, probably
wasn't even a real meteorite anyway.

48
00:03:41,720 --> 00:03:44,600
But it didn't matter
because it had done its job -

49
00:03:44,600 --> 00:03:47,600
it sparked my interest in space,

50
00:03:47,600 --> 00:03:49,960
the idea of "out there".

51
00:03:56,800 --> 00:04:00,680
Like most kids, I suppose,
I believed that "out there"

52
00:04:00,680 --> 00:04:03,440
would be full of planets
like the Earth.

53
00:04:03,440 --> 00:04:05,920
Each of them full of life,

54
00:04:05,920 --> 00:04:08,560
even if it wasn't
quite the same as ours.

55
00:04:10,960 --> 00:04:12,840
But as it turns out,

56
00:04:12,840 --> 00:04:16,680
the planet we live on
is very, very special.

57
00:04:24,400 --> 00:04:27,400
As far as we know, our Earth

58
00:04:27,400 --> 00:04:31,120
is the only place in
the solar system with life.

59
00:04:34,360 --> 00:04:36,640
To understand why,

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00:04:36,640 --> 00:04:39,640
we are going to build
our own planet...

61
00:04:42,040 --> 00:04:44,120
..at the top of that tower.

62
00:04:59,640 --> 00:05:02,400
And to do that,

63
00:05:02,400 --> 00:05:05,360
first we have to gather up
the basic raw materials...

64
00:05:07,480 --> 00:05:12,520
..all the big ingredients we need
to start making a planet.

65
00:05:12,520 --> 00:05:13,960
All right, all right!

66
00:05:15,640 --> 00:05:17,120
And here comes my delivery now...

67
00:05:19,040 --> 00:05:20,080
..right on time.

68
00:05:32,880 --> 00:05:38,120
OK, so how much stuff do we need
to build a planet like the Earth?

69
00:05:41,400 --> 00:05:45,440
I know that the entire Earth weighs
around six septillion kilograms,

70
00:05:45,440 --> 00:05:48,880
that's a six followed by 24 zeros.

71
00:05:50,600 --> 00:05:52,600
But let's be sensible here,

72
00:05:52,600 --> 00:05:55,520
I've ordered the main planetary
raw materials

73
00:05:55,520 --> 00:05:58,200
and in the right proportions

74
00:05:58,200 --> 00:06:00,080
but I've had to scale
the delivery down...

75
00:06:01,080 --> 00:06:02,520
..a bit.

76
00:06:28,240 --> 00:06:31,760
Now, you'd think that
our living Earth

77
00:06:31,760 --> 00:06:34,400
would be made up of
countless different things.

78
00:06:34,400 --> 00:06:37,680
But actually, it's constructed
almost entirely

79
00:06:37,680 --> 00:06:40,720
out of just four
basic ingredients.

80
00:06:40,720 --> 00:06:44,160
So that's what my convoy
has delivered.

81
00:06:44,160 --> 00:06:47,640
On these trucks - girders,
iron girders.

82
00:06:47,640 --> 00:06:50,280
Like most big construction projects,

83
00:06:50,280 --> 00:06:52,120
we are going to need
a lot of iron.

84
00:06:54,600 --> 00:06:56,360
Ah, we need this...

85
00:06:59,000 --> 00:07:01,040
..oxygen.

86
00:07:01,040 --> 00:07:02,840
And over here...

87
00:07:04,280 --> 00:07:05,400
..sand...

88
00:07:09,960 --> 00:07:12,480
..that's rich in silicon.

89
00:07:15,840 --> 00:07:18,600
Magnesium,
like you find in alloy wheels.

90
00:07:21,120 --> 00:07:23,400
The convoy has brought the elements

91
00:07:23,400 --> 00:07:27,080
in exactly the same proportion
as we'd find on Earth.

92
00:07:29,880 --> 00:07:33,440
So, there are 15 trucks
laden with magnesium

93
00:07:33,440 --> 00:07:38,000
because 15% of our planet
is made from magnesium.

94
00:07:39,000 --> 00:07:43,000
There are 16 trucks
for the 16% that's silicon.

95
00:07:43,000 --> 00:07:46,120
30 trucks carrying oxygen.

96
00:07:46,120 --> 00:07:49,440
And a column of 32 trucks
with iron girders

97
00:07:49,440 --> 00:07:52,800
because almost a third of
our planet is made of iron.

98
00:07:54,720 --> 00:07:59,120
It is incredible to think that
just these four elements

99
00:07:59,120 --> 00:08:02,240
make up 93% of our planet.

100
00:08:02,240 --> 00:08:04,800
The rest is elemental seasoning.

101
00:08:04,800 --> 00:08:07,760
HORN TOOTS

102
00:08:07,760 --> 00:08:12,520
And here's Billy Bob with
some of the remaining ingredients...

103
00:08:12,520 --> 00:08:13,920
which are tiny.

104
00:08:14,960 --> 00:08:16,160
Hydrogen...

105
00:08:17,800 --> 00:08:19,240
..aluminium,

106
00:08:19,240 --> 00:08:21,040
a pinch of salt,

107
00:08:21,040 --> 00:08:23,280
calcium.

108
00:08:23,280 --> 00:08:25,480
The question now is

109
00:08:25,480 --> 00:08:29,360
how does all of this
turn into a planet?

110
00:08:36,480 --> 00:08:40,560
To find out, I need to take
these basic planetary elements

111
00:08:40,560 --> 00:08:43,400
and stick them in a blender.

112
00:08:51,440 --> 00:08:55,000
And I'm going to do
that at the top of our tower,

113
00:08:55,000 --> 00:08:58,640
where there's a sky-full of room
to break down my ingredients.

114
00:09:03,360 --> 00:09:07,160
The thing is, our planet
didn't just pop into existence.

115
00:09:07,160 --> 00:09:11,160
It started out as a swirling cloud
of elemental dust,

116
00:09:11,160 --> 00:09:13,880
floating in the great void of space.

117
00:09:13,880 --> 00:09:16,840
So that's how I am going
to have to start, as well.

118
00:10:05,840 --> 00:10:07,480
In case you're wondering,

119
00:10:07,480 --> 00:10:09,080
yes, I am...

120
00:10:10,560 --> 00:10:12,160
..scared of heights, that is.

121
00:10:12,160 --> 00:10:15,800
High...really high.

122
00:10:29,640 --> 00:10:34,920
4.5 billion years ago,
before the Earth began to form,

123
00:10:34,920 --> 00:10:38,720
this dust and gas was all there was.

124
00:11:03,600 --> 00:11:07,400
So, how do we get from
this cloud of dust

125
00:11:07,400 --> 00:11:09,640
to a planet like the Earth?

126
00:11:09,640 --> 00:11:11,920
We need something to bind
it all together,

127
00:11:11,920 --> 00:11:14,080
a sort of cosmic superglue.

128
00:11:14,080 --> 00:11:17,480
Now, you might think
that'd be gravity. Right?

129
00:11:17,480 --> 00:11:18,560
Wrong.

130
00:11:36,400 --> 00:11:41,400
The best way to find out what
this super-strong planetary glue is

131
00:11:41,400 --> 00:11:43,560
is to discover its power

132
00:11:43,560 --> 00:11:47,120
in the weightless
environment of space.

133
00:11:50,480 --> 00:11:53,120
It's why I've come
to this Air Force base,

134
00:11:53,120 --> 00:11:55,120
where astronauts are trained.

135
00:11:59,040 --> 00:12:01,520
I'll be honest,
I am pretty thrilled right now

136
00:12:01,520 --> 00:12:03,440
because I'm about to boldly go

137
00:12:03,440 --> 00:12:06,840
where quite few have gone before.

138
00:12:06,840 --> 00:12:08,480
I'm not actually going into space.

139
00:12:08,480 --> 00:12:10,160
There were budgetary issues
with that.

140
00:12:10,160 --> 00:12:12,600
But never mind because
we have come up with

141
00:12:12,600 --> 00:12:14,640
the very next best thing
for our purposes.

142
00:12:14,640 --> 00:12:16,800
Where I'm headed is over there.

143
00:12:27,240 --> 00:12:30,880
This plane offers thrill-seekers
something unique -

144
00:12:30,880 --> 00:12:33,360
it can cancel out
the Earth's gravity.

145
00:12:36,200 --> 00:12:40,480
For me, it means I can recreate
the conditions in which

146
00:12:40,480 --> 00:12:43,680
that elemental dust began
to make a planet.

147
00:12:45,120 --> 00:12:48,080
Hi, how are you doing? Richard, hey.
Good to see you. Welcome aboard.

148
00:12:48,080 --> 00:12:50,680
Are you ready...? I'm ready!
Ready for a unique experience?

149
00:12:50,680 --> 00:12:54,160
I don't know, I've never tried it,
obviously. Let's see.

150
00:12:54,160 --> 00:12:58,920
'On today's flight, my chaperone
is Dan Durda...' Thank you.

151
00:12:58,920 --> 00:13:01,960
'..an expert on space dust.'

152
00:13:01,960 --> 00:13:03,400
All right, Richard. I think...

153
00:13:03,400 --> 00:13:05,720
Which seat are you here?
I'm 2F. I'm just...

154
00:13:05,720 --> 00:13:08,760
In the context, having this
conversation is hilarious.

155
00:13:08,760 --> 00:13:12,320
I should imagine
all astronauts do this.

156
00:13:12,320 --> 00:13:14,160
The attendant service
on the space flights

157
00:13:14,160 --> 00:13:16,720
is not quite up to par, though.
I was wondering about that.

158
00:13:16,720 --> 00:13:19,440
Do they have, like, a trolley
with all the space food on it?

159
00:13:19,440 --> 00:13:21,920
I've got a window seat
but there is no window.

160
00:13:21,920 --> 00:13:24,360
That's on purpose.
I don't doubt it.

161
00:13:33,640 --> 00:13:35,040
A lack of windows

162
00:13:35,040 --> 00:13:38,120
isn't the only strange thing
about this plane.

163
00:13:38,120 --> 00:13:40,680
It's also got a padded interior,

164
00:13:40,680 --> 00:13:43,200
sort of like a flying asylum.

165
00:13:44,600 --> 00:13:47,680
That's because, within 15 minutes,

166
00:13:47,680 --> 00:13:50,360
we are going to experience
weightlessness.

167
00:13:53,360 --> 00:13:55,600
And those zero gravity conditions

168
00:13:55,600 --> 00:13:59,640
will allow Dan to show me
a fascinating experiment.

169
00:13:59,640 --> 00:14:02,000
Inside this Perspex box

170
00:14:02,000 --> 00:14:04,400
is the next step
to building a planet.

171
00:14:05,880 --> 00:14:08,320
We're going to simulate
the way the planets formed

172
00:14:08,320 --> 00:14:10,640
in the very earliest days
of the solar system.

173
00:14:10,640 --> 00:14:13,080
Instead of microscopic
dust particles,

174
00:14:13,080 --> 00:14:15,320
I've got coffee - ordinary coffee.

175
00:14:15,320 --> 00:14:18,120
So in this little box,
we're going to see exhibited

176
00:14:18,120 --> 00:14:20,200
what it was that
brought stuff together?

177
00:14:20,200 --> 00:14:23,720
Absolutely. So this is what
kick-starts the whole process?

178
00:14:23,720 --> 00:14:25,640
Big things have small beginnings.

179
00:14:25,640 --> 00:14:27,280
So it all starts with a coffee?

180
00:14:27,280 --> 00:14:29,640
It all starts with early coffee.
Just like my day.

181
00:14:29,640 --> 00:14:31,760
It does all start with a coffee.
Even the solar system.

182
00:14:31,760 --> 00:14:33,480
As it turns out! We shall see.

183
00:14:33,480 --> 00:14:35,280
Right, switch the gravity off, then.

184
00:14:35,280 --> 00:14:37,000
That's right!

185
00:14:37,000 --> 00:14:38,640
It doesn't work, it's broken.

186
00:14:39,680 --> 00:14:43,320
The plane is now climbing
to 34,000 feet.

187
00:14:44,560 --> 00:14:48,600
Once there, it'll throttle back
down to Earth in a steep arc,

188
00:14:48,600 --> 00:14:51,080
perfectly judged so that inside,

189
00:14:51,080 --> 00:14:55,120
we're falling at the same rate
as the plane drops.

190
00:14:55,120 --> 00:14:57,000
The result -

191
00:14:57,000 --> 00:15:00,880
a few moments of weightlessness.

192
00:15:00,880 --> 00:15:02,240
Oh, yeah!

193
00:15:02,240 --> 00:15:04,440
Oh, I swam, I did swim.

194
00:15:04,440 --> 00:15:05,920
Oh, that's peculiar.

195
00:15:05,920 --> 00:15:08,120
Oh, look at that! Beautiful.
Oh, we got it!

196
00:15:08,120 --> 00:15:10,800
Look at! See, that's what
I was trying to show you.

197
00:15:10,800 --> 00:15:12,400
Unfortunately, I'm upside down.

198
00:15:12,400 --> 00:15:15,600
I can't! I can't...it's over there.
Here we go.

199
00:15:15,600 --> 00:15:16,640
Hang on, it's...

200
00:15:16,640 --> 00:15:19,000
You come here to do
these experiments all the time.

201
00:15:19,000 --> 00:15:21,880
Right, I'm going to watch
but I'm going to do it upside down.

202
00:15:21,880 --> 00:15:23,760
Why are you better at this
than I am?

203
00:15:23,760 --> 00:15:26,520
I'm really struggling. I'm...

204
00:15:26,520 --> 00:15:28,600
Gravity, there it is.
DAN LAUGHS

205
00:15:31,720 --> 00:15:33,320
What are we looking for?

206
00:15:33,320 --> 00:15:36,160
We're now weightless.
That's how our planet started.

207
00:15:36,160 --> 00:15:38,480
So these clumps,
what's bringing them together?

208
00:15:38,480 --> 00:15:40,400
Electrostatic forces.

209
00:15:40,400 --> 00:15:42,560
Electrostatic's clumping
this coffee together.

210
00:15:42,560 --> 00:15:45,680
So this is the effect,
this is what starts it all off.

211
00:15:45,680 --> 00:15:48,240
It's hard to concentrate
when I'm floating.

212
00:15:48,240 --> 00:15:50,200
That's not gravity causing
that clumping.

213
00:15:50,200 --> 00:15:52,000
That's electrostatics.
I'm on the roof!

214
00:15:52,000 --> 00:15:54,000
How did I get on the roof?
And now I'm on the floor.

215
00:15:56,080 --> 00:15:59,760
Now gravity is coming back into
play... And it's all gone.
..and it doesn't work.

216
00:15:59,760 --> 00:16:01,240
That's why we're weightless,

217
00:16:01,240 --> 00:16:03,560
to see phenomena that we can't
normally see

218
00:16:03,560 --> 00:16:04,680
when gravity's turned on.

219
00:16:06,720 --> 00:16:08,440
So what's happening here?

220
00:16:09,520 --> 00:16:13,320
These coffee grains,
like that first cosmic dust,

221
00:16:13,320 --> 00:16:15,560
rub together as they float.

222
00:16:18,360 --> 00:16:20,840
This means individual grains

223
00:16:20,840 --> 00:16:24,000
get either negatively
or positively charged.

224
00:16:26,480 --> 00:16:30,200
And this static charge
means they stick together...

225
00:16:34,000 --> 00:16:37,080
..just like the fledgling
particles of the Earth

226
00:16:37,080 --> 00:16:39,080
4.5 billion years ago.

227
00:16:44,360 --> 00:16:46,880
This is as near as
we're going to get

228
00:16:46,880 --> 00:16:50,280
to being out there with
those particles without gravity.

229
00:16:50,280 --> 00:16:51,760
How cool is that?!

230
00:16:52,840 --> 00:16:55,040
Oh!
HE LAUGHS

231
00:17:01,520 --> 00:17:03,480
Congratulations! Thank you for that.

232
00:17:03,480 --> 00:17:05,160
I enjoyed it, thank you.

233
00:17:05,160 --> 00:17:07,200
I need you to know
that I did that

234
00:17:07,200 --> 00:17:09,400
only because it was the best way
of demonstrating

235
00:17:09,400 --> 00:17:11,880
an essential principle
in building a planet

236
00:17:11,880 --> 00:17:13,840
and not because
I had any fun at all.

237
00:17:13,840 --> 00:17:15,680
It was...yeah, it's quite boring.

238
00:17:15,680 --> 00:17:16,880
I loved that!

239
00:17:24,240 --> 00:17:26,640
So, around
our planet-building tower,

240
00:17:26,640 --> 00:17:30,040
we've bound together those
first clumps of dust

241
00:17:30,040 --> 00:17:31,840
without gravity present.

242
00:17:32,920 --> 00:17:34,240
But there is a problem.

243
00:17:36,800 --> 00:17:39,840
Electrostatic forces
are very strong

244
00:17:39,840 --> 00:17:43,120
but are only effective
over tiny distances.

245
00:17:47,840 --> 00:17:49,760
Beyond a certain point,

246
00:17:49,760 --> 00:17:51,960
about the size of gravel,

247
00:17:51,960 --> 00:17:54,080
the dust stops growing.

248
00:17:58,320 --> 00:18:02,600
So our planet-building plans
have ground to a halt

249
00:18:02,600 --> 00:18:05,840
with nothing to show
beyond bigger bits of dust.

250
00:18:05,840 --> 00:18:07,880
We need another force

251
00:18:07,880 --> 00:18:10,720
to somehow grow them more.

252
00:18:10,720 --> 00:18:14,400
I think it's time to introduce
a little gravity to the situation.

253
00:18:25,440 --> 00:18:30,840
How, then, does gravity take those
bigger bits of dust and gravel,

254
00:18:30,840 --> 00:18:33,680
and turn them into rocks

255
00:18:33,680 --> 00:18:35,800
or even an entire planet?

256
00:18:42,080 --> 00:18:44,840
At a concealed
underground laboratory,

257
00:18:44,840 --> 00:18:48,480
I'm told there's a secret device

258
00:18:48,480 --> 00:18:50,520
that will help me find the answer.

259
00:18:57,840 --> 00:19:01,320
Until 2001, this was a gold mine.

260
00:19:01,320 --> 00:19:04,440
Now, it's at the cutting edge
of scientific research.

261
00:19:16,600 --> 00:19:18,600
My goal lies

262
00:19:18,600 --> 00:19:21,800
nearly a kilometre and a half
straight down.

263
00:19:23,240 --> 00:19:26,920
I'm going deeper underground
than I've ever been before.

264
00:19:28,920 --> 00:19:30,360
You know in disaster movies...

265
00:19:31,760 --> 00:19:33,200
..when things go wrong

266
00:19:33,200 --> 00:19:36,880
in things like giant lifts
going a mile underground -

267
00:19:36,880 --> 00:19:40,000
the short guy never
lasts very long, does he?

268
00:19:40,000 --> 00:19:42,240
Just thinking that out loud.

269
00:19:46,600 --> 00:19:48,600
More and more rock flashing past.

270
00:19:48,600 --> 00:19:50,040
Still plunging.

271
00:19:52,280 --> 00:19:54,720
Still, plunging is better
than plummeting.

272
00:19:56,960 --> 00:19:59,800
At the bottom of this shaft
is an instrument

273
00:19:59,800 --> 00:20:03,040
that's part of a global
gravity research experiment.

274
00:20:03,040 --> 00:20:05,600
Apparently, it's going to
help us understand

275
00:20:05,600 --> 00:20:08,120
how gravity can grow
a planet from gravel.

276
00:20:21,960 --> 00:20:25,520
In the tunnels of these,
the Sandford Labs,

277
00:20:25,520 --> 00:20:29,440
scientists are unravelling
the workings of the universe.

278
00:20:29,440 --> 00:20:32,400
ALARM BLARES

279
00:20:34,520 --> 00:20:37,920
I might not look it
but I feel a bit like James Bond -

280
00:20:37,920 --> 00:20:41,840
summoned to the underground lair
of an international super-baddie.

281
00:20:45,280 --> 00:20:47,760
And here is what I've come to see.

282
00:20:47,760 --> 00:20:50,600
Meet Dr Gnome.

283
00:20:50,600 --> 00:20:54,120
Now the good doctor here
is no common or garden gnome.

284
00:20:54,120 --> 00:20:57,320
He is a precision
instrument of science.

285
00:20:57,320 --> 00:21:00,440
He's special because he has
a super-tough coating

286
00:21:00,440 --> 00:21:03,160
that means he can't be chipped
or damaged easily.

287
00:21:03,160 --> 00:21:05,240
So you would think that
wherever he went,

288
00:21:05,240 --> 00:21:08,040
he remained exactly the same.

289
00:21:08,040 --> 00:21:09,720
Looks the same.

290
00:21:09,720 --> 00:21:11,080
Same expression -

291
00:21:11,080 --> 00:21:13,080
slightly puzzled.

292
00:21:15,680 --> 00:21:19,640
Well, scientists have taken
Dr Gnome all over the world.

293
00:21:22,120 --> 00:21:23,680
And wherever he's been,

294
00:21:23,680 --> 00:21:27,800
he's been weighed
with high precision scales.

295
00:21:27,800 --> 00:21:31,000
And it's his weight that
helps explain

296
00:21:31,000 --> 00:21:35,280
how gravity can turn gravel
into a planet.

297
00:21:37,280 --> 00:21:40,280
It's my job now to weigh him
down here,

298
00:21:40,280 --> 00:21:42,800
a mile down beneath the surface,

299
00:21:42,800 --> 00:21:45,000
in laboratory conditions.

300
00:21:45,000 --> 00:21:48,320
So let's zero the machine,
pop him on.

301
00:21:51,640 --> 00:21:54,960
And as you can see,
the doctor tipping the scales

302
00:21:54,960 --> 00:21:57,960
at 330.95g.

303
00:21:57,960 --> 00:21:59,440
In the interest of thoroughness,

304
00:21:59,440 --> 00:22:02,880
he has been weighed in a number
of other locations down here.

305
00:22:04,320 --> 00:22:07,600
And in all of them,
we got the same reading.

306
00:22:07,600 --> 00:22:10,160
A kilometre and a half under
the surface,

307
00:22:10,160 --> 00:22:13,840
he weighs 330.95g.

308
00:22:15,880 --> 00:22:18,240
And now we must travel back up
to the surface

309
00:22:18,240 --> 00:22:21,080
where we shall finish
this experiment.

310
00:22:21,080 --> 00:22:25,000
Right then, Doctor, you just
sit there. I'll do all the walking.

311
00:22:29,280 --> 00:22:32,240
The doctor has to travel
first class.

312
00:22:36,920 --> 00:22:40,880
It's vitally important that
he isn't damaged on the way up,

313
00:22:40,880 --> 00:22:44,520
or picks up any dirt that
might interfere with readings.

314
00:22:57,320 --> 00:22:59,560
OK, Doctor,

315
00:22:59,560 --> 00:23:03,000
time to weigh you
up here, on the surface.

316
00:23:03,000 --> 00:23:05,120
Zero the machine,

317
00:23:05,120 --> 00:23:06,280
let it calm down...

318
00:23:07,680 --> 00:23:08,720
..and here we go.

319
00:23:11,240 --> 00:23:12,720
Look at that!

320
00:23:12,720 --> 00:23:16,200
You are 0.06g heavier up here

321
00:23:16,200 --> 00:23:18,120
than you were down there.

322
00:23:18,120 --> 00:23:20,080
I honestly didn't expect that.

323
00:23:20,080 --> 00:23:21,720
But just to be sure,

324
00:23:21,720 --> 00:23:24,560
he needs to be weighed
in some other places.

325
00:23:26,360 --> 00:23:28,000
And sure enough -

326
00:23:28,000 --> 00:23:31,360
331.01g.

327
00:23:31,360 --> 00:23:34,200
The doctor is showing a consistent
weight gain

328
00:23:34,200 --> 00:23:35,960
of six hundredths of a gram

329
00:23:35,960 --> 00:23:39,680
up here on the surface,
compared to when he was down below.

330
00:23:43,840 --> 00:23:46,840
Have you been secretly snacking?!

331
00:23:46,840 --> 00:23:50,320
I can assure you that Dr Gnome
hasn't grown on the way up.

332
00:23:50,320 --> 00:23:52,960
His weight gain can be explained

333
00:23:52,960 --> 00:23:54,600
by Earth's gravity.

334
00:23:56,440 --> 00:23:59,480
Gravity is THE universal force

335
00:23:59,480 --> 00:24:01,720
that attracts one thing to another.

336
00:24:05,720 --> 00:24:07,840
When we measure something's weight,

337
00:24:07,840 --> 00:24:11,680
we are actually measuring
the Earth's gravitational pull.

338
00:24:13,720 --> 00:24:17,040
So why has the doctor's
weight changed?

339
00:24:18,200 --> 00:24:20,840
Well, it's largely to do
with differences

340
00:24:20,840 --> 00:24:23,240
in the amount of rock underfoot.

341
00:24:25,080 --> 00:24:28,960
Up here on the surface, there is
a good mile more rock

342
00:24:28,960 --> 00:24:30,760
beneath me and Dr Gnome

343
00:24:30,760 --> 00:24:33,200
than there is
in the lab down there,

344
00:24:33,200 --> 00:24:36,240
meaning more planetary bulk
pulling down on us,

345
00:24:36,240 --> 00:24:38,680
making for a heavier Dr Gnome
up here

346
00:24:38,680 --> 00:24:39,840
than down there.

347
00:24:39,840 --> 00:24:41,920
Nothing's changed about the gnome.

348
00:24:41,920 --> 00:24:43,560
What's changed is gravity.

349
00:24:45,760 --> 00:24:49,680
Our experiment shows that
the more massive something is,

350
00:24:49,680 --> 00:24:52,280
the stronger
its gravitational pull.

351
00:24:53,720 --> 00:24:57,560
So in space, around
4.5 billion years ago,

352
00:24:57,560 --> 00:25:00,920
when there were no planets,
just those elemental clumps,

353
00:25:00,920 --> 00:25:03,720
any difference in the size
of those clumps

354
00:25:03,720 --> 00:25:06,440
would have mattered,
because of gravity.

355
00:25:15,880 --> 00:25:19,840
If we add gravity to
our orbiting swarm of dust,

356
00:25:19,840 --> 00:25:24,360
we start to see the larger bits
attracting the smaller bits.

357
00:25:25,800 --> 00:25:27,680
Because they are bigger,

358
00:25:27,680 --> 00:25:31,520
they have a stronger
gravitational pull.

359
00:25:31,520 --> 00:25:33,720
The bigger they are,

360
00:25:33,720 --> 00:25:35,720
the bigger they get.

361
00:25:35,720 --> 00:25:37,600
They start to become rocks.

362
00:25:38,840 --> 00:25:40,440
And the larger rocks

363
00:25:40,440 --> 00:25:42,440
draw in the smaller ones.

364
00:25:43,520 --> 00:25:47,200
In space, a rock
just a kilometre wide

365
00:25:47,200 --> 00:25:50,240
can grow to a near
Earth-sized planet

366
00:25:50,240 --> 00:25:52,240
in just a few million years.

367
00:25:54,040 --> 00:25:55,680
Around our tower,

368
00:25:55,680 --> 00:25:57,480
we can do it in seconds.

369
00:25:59,120 --> 00:26:02,120
And we're seeing something
really promising.

370
00:26:06,360 --> 00:26:09,920
The exciting thing is
that even though that process

371
00:26:09,920 --> 00:26:12,320
began 4.5 billion years ago -

372
00:26:12,320 --> 00:26:14,560
on Earth, it hasn't finished.

373
00:26:14,560 --> 00:26:16,200
Because if you know where to look,

374
00:26:16,200 --> 00:26:19,840
you can see where gravity
is still shaping our planet, today.

375
00:26:29,000 --> 00:26:31,520
Out in Arizona's Badlands,

376
00:26:31,520 --> 00:26:34,480
there is breathtaking evidence

377
00:26:34,480 --> 00:26:37,320
of how gravity
is still building the Earth.

378
00:26:48,480 --> 00:26:51,320
This is the Barringer Crater.

379
00:26:53,240 --> 00:26:56,840
When this vast crater was
first discovered,

380
00:26:56,840 --> 00:26:59,440
many believed it to be
an extinct volcano.

381
00:27:01,280 --> 00:27:02,560
But in fact,

382
00:27:02,560 --> 00:27:05,480
it was created by a meteorite.

383
00:27:09,600 --> 00:27:12,720
This 1.2km wide hole

384
00:27:12,720 --> 00:27:14,480
is an impact crater.

385
00:27:16,880 --> 00:27:20,600
And it's given scientists
like Matt Genge

386
00:27:20,600 --> 00:27:24,240
a unique insight
into how planets are built.

387
00:27:39,480 --> 00:27:43,440
Matt, how are you? Hello, mate.
Sorry about the dust. Wow!

388
00:27:43,440 --> 00:27:45,600
This crater is the scar

389
00:27:45,600 --> 00:27:49,000
left by an incredibly
violent impact.

390
00:27:49,000 --> 00:27:53,440
If you look at the crater wall,
you can see the strata...

391
00:27:54,840 --> 00:27:57,960
..beds of rock,
running across the crater. Yes.

392
00:27:57,960 --> 00:28:01,040
There's this nice red layer
of rocks.

393
00:28:01,040 --> 00:28:04,080
Above and below, there's some
lighter coloured rocks

394
00:28:04,080 --> 00:28:06,680
and they're actually
the same band of rocks.

395
00:28:06,680 --> 00:28:10,560
That layer has been folded
over the red layer, red layers,

396
00:28:10,560 --> 00:28:12,320
like the cheese in a sandwich.

397
00:28:12,320 --> 00:28:15,240
But they've been folded over
all the way round the crater,

398
00:28:15,240 --> 00:28:19,680
like they've been thrown outwards
and have collapsed back.

399
00:28:19,680 --> 00:28:22,680
How big was it?
Cos it's a really big crater.

400
00:28:22,680 --> 00:28:27,040
We think the object itself was
probably only about 30m in size.

401
00:28:27,040 --> 00:28:30,680
So a couple of double-decker buses
back-to-back.

402
00:28:30,680 --> 00:28:33,920
And it made a hole that big?
It made a hole that big. Why?

403
00:28:33,920 --> 00:28:36,760
Simply because of how
fast it was moving.

404
00:28:36,760 --> 00:28:39,000
So by the time it fell towards
the Earth,

405
00:28:39,000 --> 00:28:41,680
it gets faster and faster as it
falls towards the Earth,

406
00:28:41,680 --> 00:28:46,920
hits the ground maybe at 26,000mph.

407
00:28:46,920 --> 00:28:48,600
And the energy...

408
00:28:50,080 --> 00:28:54,120
..the kinetic energy
associated with that speed

409
00:28:54,120 --> 00:28:57,480
is so huge, it's around two megatons,

410
00:28:57,480 --> 00:29:00,600
that it blew all that material
outwards.

411
00:29:00,600 --> 00:29:05,000
The rocks actually flowed
like water out of the crater.

412
00:29:05,000 --> 00:29:07,200
So this whole...
all this area has been affected?

413
00:29:07,200 --> 00:29:08,840
It's not just the big hole, then,

414
00:29:08,840 --> 00:29:11,120
it's everything around
that we're on. Absolutely, yeah.

415
00:29:11,120 --> 00:29:13,920
All of this. In fact, if you were
here before the crater was formed,

416
00:29:13,920 --> 00:29:15,960
you'd have had all that rock
on top of your head,

417
00:29:15,960 --> 00:29:18,720
so you wouldn't have been very happy.
No, that would have been bad.

418
00:29:22,880 --> 00:29:26,240
The meteorite was just 30m wide

419
00:29:26,240 --> 00:29:29,680
but the shockwave of its impact
would have been enough

420
00:29:29,680 --> 00:29:33,640
to obliterate a brick wall
60km away.

421
00:29:41,480 --> 00:29:43,640
The Barringer Crater is evidence

422
00:29:43,640 --> 00:29:45,760
of how gravity builds a planet.

423
00:29:47,080 --> 00:29:50,600
Because every meteorite
that plummets to the ground

424
00:29:50,600 --> 00:29:54,600
is drawn in by
the Earth's gravitational pull.

425
00:29:56,040 --> 00:29:59,280
So when did all this happen, then?
How old is that?

426
00:29:59,280 --> 00:30:04,520
So the crater itself is
about 50,000 years old.

427
00:30:04,520 --> 00:30:08,160
But we actually know that
meteorites like this

428
00:30:08,160 --> 00:30:10,160
have been falling on Earth

429
00:30:10,160 --> 00:30:13,240
throughout the Earth's history,
for the last 4.5 billion years.

430
00:30:13,240 --> 00:30:15,280
In fact, in the past,

431
00:30:15,280 --> 00:30:17,000
they were much more frequent.

432
00:30:17,000 --> 00:30:19,520
So back when the Earth was forming,

433
00:30:19,520 --> 00:30:23,600
that bombardment was continual.

434
00:30:23,600 --> 00:30:27,720
There was probably one of them
every few minutes.

435
00:30:27,720 --> 00:30:30,280
These were the objects that
were making the Earth.

436
00:30:34,960 --> 00:30:36,720
Billions of years later,

437
00:30:36,720 --> 00:30:40,320
meteorite fragments that
survived the initial impact

438
00:30:40,320 --> 00:30:43,280
offer a glimpse
into the earliest moments

439
00:30:43,280 --> 00:30:44,920
of a planet's formation.

440
00:30:50,640 --> 00:30:52,520
This is rather a special meteorite.

441
00:30:53,680 --> 00:30:56,480
It fell in Mexico

442
00:30:56,480 --> 00:30:59,360
in 1969

443
00:30:59,360 --> 00:31:02,200
and it's called Allende.

444
00:31:02,200 --> 00:31:04,040
We give meteorites names.

445
00:31:04,040 --> 00:31:07,640
And what's special
about this meteorite is

446
00:31:07,640 --> 00:31:11,520
it's perhaps
the oldest material on Earth.

447
00:31:11,520 --> 00:31:14,480
So it's around 4.5 billion years old.

448
00:31:14,480 --> 00:31:17,000
So that right there

449
00:31:17,000 --> 00:31:19,640
is the oldest thing on Earth?

450
00:31:19,640 --> 00:31:21,680
Yeah.

451
00:31:21,680 --> 00:31:23,280
Wow.

452
00:31:23,280 --> 00:31:24,320
Can I hold it?

453
00:31:25,400 --> 00:31:28,000
Er...no. OK.

454
00:31:28,000 --> 00:31:29,640
But you can touch it, if you like.

455
00:31:29,640 --> 00:31:31,840
Just touch the oldest thing
on Earth. Yeah.

456
00:31:31,840 --> 00:31:33,680
Oh, come on.

457
00:31:33,680 --> 00:31:34,880
Wow.

458
00:31:35,920 --> 00:31:38,960
It is kind of a goose-bump moment

459
00:31:38,960 --> 00:31:42,800
because of the significance
of a little piece of rock that,

460
00:31:42,800 --> 00:31:46,040
well, frankly,
I'd walk straight past.

461
00:31:46,040 --> 00:31:48,080
Well, most people probably would.

462
00:31:48,080 --> 00:31:50,240
But although they're quite rare,

463
00:31:50,240 --> 00:31:52,960
you can find them everywhere.

464
00:31:52,960 --> 00:31:55,000
They fall all over the world.

465
00:31:55,000 --> 00:31:58,240
But not always quite as
spectacularly as here!

466
00:31:58,240 --> 00:32:01,160
Yeah, you'd notice that.
You'd certainly notice.

467
00:32:01,160 --> 00:32:05,640
But to imagine that some of us
are walking past lumps of rock

468
00:32:05,640 --> 00:32:09,000
that contain all the elements
you need to build a planet...

469
00:32:09,000 --> 00:32:11,680
You know, you've got the magnesium
and the silicon

470
00:32:11,680 --> 00:32:13,080
and the iron and the oxygen.

471
00:32:13,080 --> 00:32:16,160
It's just incredible that this
is how we started

472
00:32:16,160 --> 00:32:18,360
and they're just scattered

473
00:32:18,360 --> 00:32:19,440
all over the world.

474
00:32:23,440 --> 00:32:26,880
If you or I were to find
an actual meteorite,

475
00:32:26,880 --> 00:32:29,280
and - who knows? - we might,

476
00:32:29,280 --> 00:32:32,120
it's, I don't know,
almost a haunting thought

477
00:32:32,120 --> 00:32:34,680
to consider that what
you had in your hand

478
00:32:34,680 --> 00:32:37,640
might be 4.5 billion years old

479
00:32:37,640 --> 00:32:41,520
and one of the fundamental
building blocks of our planet,

480
00:32:41,520 --> 00:32:42,720
our world,

481
00:32:42,720 --> 00:32:44,360
of our existence.

482
00:32:44,360 --> 00:32:46,200
But the meteorite that you found

483
00:32:46,200 --> 00:32:49,040
might not have landed
billions of years ago.

484
00:32:49,040 --> 00:32:51,320
It might have landed
the day before you found it.

485
00:32:51,320 --> 00:32:52,720
And that's quite exciting -

486
00:32:52,720 --> 00:32:56,160
they're still arriving.
the process is still going on.

487
00:32:56,160 --> 00:32:58,760
It's just that they're
late gatecrashers

488
00:32:58,760 --> 00:33:00,920
to some giant planetary party.

489
00:33:04,040 --> 00:33:09,520
Astonishingly, today,
40,000 tonnes worth of meteorites

490
00:33:09,520 --> 00:33:12,200
fall to Earth every year -

491
00:33:12,200 --> 00:33:15,640
the equivalent of 30,000
transit vans

492
00:33:15,640 --> 00:33:17,760
dropping out of the sky -

493
00:33:17,760 --> 00:33:20,160
mostly arriving as dust.

494
00:33:21,520 --> 00:33:23,280
But very occasionally,

495
00:33:23,280 --> 00:33:25,200
as something much bigger.

496
00:33:29,640 --> 00:33:31,880
Early in 2013,

497
00:33:31,880 --> 00:33:36,160
a meteorite fell near
the Russian town of Chelyabinsk

498
00:33:36,160 --> 00:33:38,600
that was the largest in a century...

499
00:33:40,000 --> 00:33:43,800
..nearly 10,000 tonnes,
before breaking up.

500
00:33:45,320 --> 00:33:48,960
But such spectacular events
are incredibly rare.

501
00:33:52,640 --> 00:33:56,160
In fact, you're more likely
to die from falling out of bed

502
00:33:56,160 --> 00:33:58,440
than from being struck
by a meteorite.

503
00:34:02,320 --> 00:34:04,600
GLASS SMASHES

504
00:34:04,600 --> 00:34:06,640
Back when the Earth was forming,
though,

505
00:34:06,640 --> 00:34:09,280
huge meteorite strikes
were constant,

506
00:34:09,280 --> 00:34:12,080
with tens of millions hitting
a year.

507
00:34:21,440 --> 00:34:24,840
The thing is,
rather than destroying it,

508
00:34:24,840 --> 00:34:27,120
the onslaught built our planet.

509
00:34:28,760 --> 00:34:31,800
Starting 4.5 billion years ago,

510
00:34:31,800 --> 00:34:36,800
it took just 100 million years
to reach almost full size.

511
00:34:44,360 --> 00:34:48,160
So now we have a planet that's
roughly the same size as Earth

512
00:34:48,160 --> 00:34:50,000
and the same shape.

513
00:34:50,000 --> 00:34:52,600
But at the moment, the surface
of our planet

514
00:34:52,600 --> 00:34:56,080
is a molten, fiery vision of hell,

515
00:34:56,080 --> 00:34:58,000
which is going to be inconvenient.

516
00:35:10,240 --> 00:35:13,240
For starters,
there's nothing to stand on -

517
00:35:13,240 --> 00:35:14,880
no solid rock.

518
00:35:16,520 --> 00:35:19,600
It's just a fiery,
molten sea of magma.

519
00:35:21,720 --> 00:35:24,400
And there's no way life could start

520
00:35:24,400 --> 00:35:26,640
in this volcanic environment.

521
00:35:32,960 --> 00:35:36,600
So how are we going to get
a solid surface for our planet?

522
00:35:49,200 --> 00:35:51,040
Back on the desert floor,

523
00:35:51,040 --> 00:35:53,480
Professor Jeff Karlson
and his team

524
00:35:53,480 --> 00:35:56,040
are setting up a unique experiment.

525
00:35:58,760 --> 00:36:00,360
They reckon they can show me

526
00:36:00,360 --> 00:36:02,600
how to make land for our planet.

527
00:36:05,640 --> 00:36:07,840
The first step in their challenge -

528
00:36:07,840 --> 00:36:10,560
recreating that early, molten Earth.

529
00:36:12,400 --> 00:36:17,240
And that means constructing
what is basically a mobile volcano.

530
00:36:22,320 --> 00:36:25,160
And now we're going to see
if we can make it erupt.

531
00:36:28,600 --> 00:36:30,240
All right, Richard? Yeah.

532
00:36:30,240 --> 00:36:31,720
Let's get the helmet on. Yeah.

533
00:36:33,480 --> 00:36:36,520
I'm guessing what we've got in here
is not lunch, is it?

534
00:36:36,520 --> 00:36:38,360
It isn't.

535
00:36:38,360 --> 00:36:41,400
Whoa! That's really hot!

536
00:36:41,400 --> 00:36:45,680
So what Bob is stirring there isn't
something that looks like lava...

537
00:36:45,680 --> 00:36:50,160
No, it's... ..it's actual lava.

538
00:36:50,160 --> 00:36:52,920
We just put in the ingredients,
just like a recipe,

539
00:36:52,920 --> 00:36:56,640
and cook up this primordial,
primitive material

540
00:36:56,640 --> 00:36:58,120
that makes up our Earth.

541
00:36:58,120 --> 00:37:00,160
It's amazing and exhilarating

542
00:37:00,160 --> 00:37:02,920
but also quite incredibly hot
up here. Can I get down?

543
00:37:02,920 --> 00:37:04,920
It's very hot. Yeah. And you can see,

544
00:37:04,920 --> 00:37:08,160
we have to get it that hot so it
will flow in a very viscous form.

545
00:37:10,400 --> 00:37:14,120
The recipe for lava that
Jeff's team are using

546
00:37:14,120 --> 00:37:17,000
includes the essential
planetary ingredients -

547
00:37:17,000 --> 00:37:19,800
iron, magnesium and silicon.

548
00:37:21,200 --> 00:37:24,080
But before this turns to solid land,

549
00:37:24,080 --> 00:37:26,280
we need to make the lava flow.

550
00:37:27,680 --> 00:37:30,080
The spout, here. I see it.
Here it comes, here it comes.

551
00:37:52,600 --> 00:37:53,800
The temperatures

552
00:37:53,800 --> 00:37:56,480
reached by
this lava are extraordinary.

553
00:37:59,320 --> 00:38:02,000
We know from using
our infrared camera,

554
00:38:02,000 --> 00:38:06,000
where it's incandescent orange,
there, it's about 1,100 degrees
centigrade.

555
00:38:06,000 --> 00:38:09,160
Where it starts to get dark grey,
like down at the toe here,

556
00:38:09,160 --> 00:38:12,000
it's about 850 degrees centigrade,
now.

557
00:38:12,000 --> 00:38:13,240
Wow!

558
00:38:13,240 --> 00:38:15,880
And now it's coming out here
at 1,100 degrees again,

559
00:38:15,880 --> 00:38:18,320
just like the temperature
that we're pouring in.

560
00:38:18,320 --> 00:38:21,640
So this is much hotter
than that stuff on top? It is.

561
00:38:21,640 --> 00:38:24,000
Looking at what happens here
on a small scale

562
00:38:24,000 --> 00:38:26,200
but with the same materials
and the same temperatures

563
00:38:26,200 --> 00:38:27,840
and the same behaviours,

564
00:38:27,840 --> 00:38:31,960
you can look back and work out
what happened on the early Earth.

565
00:38:31,960 --> 00:38:36,560
Exactly. We're sort of replicating
those conditions of the early Earth,

566
00:38:36,560 --> 00:38:38,120
in miniature.

567
00:38:38,120 --> 00:38:39,120
Imagine the whole planet

568
00:38:39,120 --> 00:38:41,640
covered with glowing,
incandescent orange lava -

569
00:38:41,640 --> 00:38:43,080
magma oceans.

570
00:38:44,400 --> 00:38:46,120
That is intense.

571
00:38:46,120 --> 00:38:48,560
You can see the little
wrinkles and folds

572
00:38:48,560 --> 00:38:50,280
starting to form on the surface

573
00:38:50,280 --> 00:38:53,000
as the surface cools
and a crust starts to form.

574
00:38:53,000 --> 00:38:56,080
I can feel wrinkles and folds
forming on my face, watching.

575
00:38:58,600 --> 00:39:01,680
So, in order to
create land from lava,

576
00:39:01,680 --> 00:39:06,040
we need to cool it down
until it turns into a crust.

577
00:39:06,040 --> 00:39:07,440
Simple.

578
00:39:07,440 --> 00:39:09,800
But there's a wrinkle in our plan.

579
00:39:13,840 --> 00:39:15,600
On the early Earth,

580
00:39:15,600 --> 00:39:18,000
the lava didn't cool
in the way you'd expect.

581
00:39:19,840 --> 00:39:22,680
There was a reason
the surface stayed molten.

582
00:39:26,320 --> 00:39:30,160
Jeff has a, well, slightly
unusual demonstration

583
00:39:30,160 --> 00:39:32,800
of what that was.

584
00:39:32,800 --> 00:39:34,280
Site up on the target...

585
00:39:35,840 --> 00:39:37,000
Shooters, fire.

586
00:39:52,960 --> 00:39:54,680
We're going in there?
Let's go have a look.

587
00:39:54,680 --> 00:39:56,720
That was quite exhilarating,
I'll be honest.

588
00:39:56,720 --> 00:39:58,960
Oh, my God! I can't see the target.
OK, what am I doing?

589
00:39:58,960 --> 00:40:02,080
OK, look here, Richard.
Here's where all the bullets hit.

590
00:40:02,080 --> 00:40:04,200
Feel how hot it is there, still.

591
00:40:04,200 --> 00:40:06,840
It is, yes. Yes,
there's definite heat in there.

592
00:40:06,840 --> 00:40:09,200
Ow, they're really...
You could think of these as...

593
00:40:09,200 --> 00:40:11,840
each one of these like a tiny
meteorite that struck the Earth

594
00:40:11,840 --> 00:40:15,880
and transferred its kinetic energy
to heat energy,

595
00:40:15,880 --> 00:40:17,520
keeping the planet warm.

596
00:40:17,520 --> 00:40:19,560
I think I see where
you're going with this

597
00:40:19,560 --> 00:40:21,000
cos I did wonder for a moment.

598
00:40:21,000 --> 00:40:22,840
So these are like meteors.

599
00:40:22,840 --> 00:40:25,880
Right. So, the planet was
under bombardment at a time. Right.

600
00:40:25,880 --> 00:40:28,280
And those were going in like these
and when they hit,

601
00:40:28,280 --> 00:40:30,520
this is kinetic energy
converting into heat.

602
00:40:30,520 --> 00:40:32,480
And what, a meteorite hitting
is enough,

603
00:40:32,480 --> 00:40:33,960
is going to make it hot? It is.

604
00:40:33,960 --> 00:40:35,840
It keeps it hot and
that's one of the reasons

605
00:40:35,840 --> 00:40:37,440
your planet's not cooling down.

606
00:40:37,440 --> 00:40:39,480
And these meteorites
are a lot bigger.

607
00:40:39,480 --> 00:40:42,320
The meteorites are much bigger
than our little bullets, of course,

608
00:40:42,320 --> 00:40:44,440
and they're travelling
about ten times as fast.

609
00:40:44,440 --> 00:40:47,200
I'd love to get a better idea,
a better sense of that moment

610
00:40:47,200 --> 00:40:49,840
when that energy is converted
from kinetic into heat.

611
00:40:49,840 --> 00:40:52,080
But to do that, they'd have to
shoot through my hand

612
00:40:52,080 --> 00:40:53,480
and that's going to hurt, so...

613
00:40:53,480 --> 00:40:55,200
Well, we have a safer way to do that.

614
00:40:55,200 --> 00:40:58,400
A thermal infrared camera's been
filming the entire experiment here

615
00:40:58,400 --> 00:41:01,000
and we can show you
the images created by that.

616
00:41:07,080 --> 00:41:09,720
In here? Yeah.

617
00:41:09,720 --> 00:41:12,400
So this is a thermal camera
looking at what we've just seen.

618
00:41:12,400 --> 00:41:13,600
Right. There's the plate.

619
00:41:13,600 --> 00:41:16,040
Hot areas are going to show up red

620
00:41:16,040 --> 00:41:19,120
and little cooler areas will
show up in a bluer, cooler colour

621
00:41:19,120 --> 00:41:21,920
as each one of these bullets
strikes the metal.

622
00:41:21,920 --> 00:41:25,280
And there they go, look!
I mean, it's really pronounced.

623
00:41:25,280 --> 00:41:27,800
Look at the pieces being
blasted off, there.

624
00:41:27,800 --> 00:41:30,040
Watching them go in like that,

625
00:41:30,040 --> 00:41:32,280
I can imagine they were meteorites.

626
00:41:32,280 --> 00:41:35,720
Exactly, much bigger
and ten times faster.

627
00:41:35,720 --> 00:41:37,760
And this effect is one
of the reasons

628
00:41:37,760 --> 00:41:39,600
why my Planet Earth won't set...

629
00:41:39,600 --> 00:41:42,160
That's right. ..remains molten.

630
00:41:58,280 --> 00:42:02,320
So, to stand a chance of creating
a solid surface for our planet,

631
00:42:02,320 --> 00:42:08,040
we need to stop this constant
barrage of meteors and asteroids.

632
00:42:20,640 --> 00:42:22,680
On the actual Earth,

633
00:42:22,680 --> 00:42:26,920
this bombardment petered out
around four billion years ago.

634
00:42:26,920 --> 00:42:29,160
On the planet we're building,

635
00:42:29,160 --> 00:42:31,000
it can be done in a jiffy.

636
00:42:33,400 --> 00:42:37,400
And reducing the impacts from space
helps the surface to cool

637
00:42:37,400 --> 00:42:39,200
so that lava...

638
00:42:40,120 --> 00:42:41,360
..turns to rock.

639
00:42:46,400 --> 00:42:47,640
Perfect!

640
00:42:47,640 --> 00:42:52,120
We now have a planet
we can stand on without being burnt.

641
00:42:52,120 --> 00:42:55,560
But there is something
pretty important missing.

642
00:42:55,560 --> 00:42:58,320
If we're going to have life
on this planet of ours,

643
00:42:58,320 --> 00:43:00,400
we are going to need water.

644
00:43:05,320 --> 00:43:08,360
Incredibly, some water has been
with us

645
00:43:08,360 --> 00:43:11,000
from the very birth of our planet,

646
00:43:11,000 --> 00:43:15,200
trapped in dust and rock,
and then locked inside of the Earth.

647
00:43:18,200 --> 00:43:22,000
Volcanic activity released this
water as steam,

648
00:43:22,000 --> 00:43:25,840
forming rain clouds that then
filled the first oceans.

649
00:43:33,560 --> 00:43:37,000
A lot more water arrived from space,

650
00:43:37,000 --> 00:43:40,960
because asteroids and comets
actually carried ice inside them,

651
00:43:40,960 --> 00:43:43,280
adding to our already wet planet.

652
00:43:43,280 --> 00:43:45,720
So, we've got water.

653
00:43:45,720 --> 00:43:47,760
We've also got land.

654
00:43:48,800 --> 00:43:50,240
But it doesn't look right.

655
00:43:54,800 --> 00:43:58,280
All that volcanic activity
hasn't just pumped steam

656
00:43:58,280 --> 00:44:03,760
into the atmosphere, it's
produced a toxic cocktail of gasses.

657
00:44:05,040 --> 00:44:08,000
This isn't a planet for us yet.

658
00:44:12,360 --> 00:44:16,000
So, how do we clean up this
poisonous atmosphere?

659
00:44:16,000 --> 00:44:19,720
Well, the answer lies with the
oldest living thing on the planet.

660
00:44:26,760 --> 00:44:32,440
On these rocks, there's a thin film
of bacteria called a stromatolite.

661
00:44:34,680 --> 00:44:37,720
These ones today are in Australia,

662
00:44:37,720 --> 00:44:41,200
but three billion years ago
they were everywhere.

663
00:44:42,200 --> 00:44:46,320
They live on sunlight,
and carbon dioxide in water,

664
00:44:46,320 --> 00:44:50,720
and as a waste product,
they release oxygen.

665
00:44:57,680 --> 00:45:02,720
For more than a billion years, these
bacteria pumped the stuff out

666
00:45:02,720 --> 00:45:06,400
until the air was right
for the evolution of complex life...

667
00:45:08,080 --> 00:45:09,640
..including us.

668
00:45:16,120 --> 00:45:20,600
To build our planet, we started
with truckloads of raw materials.

669
00:45:28,920 --> 00:45:32,880
And we mixed them together...

670
00:45:35,000 --> 00:45:37,360
..into a cosmic cloud of dust.

671
00:45:41,440 --> 00:45:44,560
We got it to stick together
with static electricity.

672
00:45:48,960 --> 00:45:51,000
And then we added gravity.

673
00:46:00,000 --> 00:46:01,760
We bulked the planet up.

674
00:46:05,640 --> 00:46:10,160
Then we stopped the onslaught
to cool it down, and make land.

675
00:46:14,000 --> 00:46:17,360
And then we sourced water

676
00:46:17,360 --> 00:46:19,480
and a breathable atmosphere.

677
00:46:27,240 --> 00:46:29,680
But hang on. This isn't right.

678
00:46:34,480 --> 00:46:37,480
There's something seriously amiss
with our planet.

679
00:46:40,840 --> 00:46:44,280
This is definitely not how
things should be looking.

680
00:46:44,280 --> 00:46:46,520
It's a bad case of the wobbles.

681
00:46:51,400 --> 00:46:55,840
A wobble this big, even slowed down
over millions of years,

682
00:46:55,840 --> 00:46:57,640
would be catastrophic.

683
00:46:59,040 --> 00:47:03,160
Without stability,
seasonal changes are extreme,

684
00:47:03,160 --> 00:47:05,240
ice ages are frequent,

685
00:47:05,240 --> 00:47:08,920
and the surface is
scoured by hurricane-force winds.

686
00:47:13,560 --> 00:47:19,000
It's no good! Our planet has
conditions completely hostile
to life.

687
00:47:19,000 --> 00:47:21,440
But don't worry,
because to stabilise things,

688
00:47:21,440 --> 00:47:23,600
we don't actually have to
look too far.

689
00:47:26,240 --> 00:47:29,360
The solution is a moon.

690
00:47:44,040 --> 00:47:47,880
To find out how a moon can stop
a planet's wobble,

691
00:47:47,880 --> 00:47:50,480
I've come to NASA in Texas...

692
00:47:56,600 --> 00:48:00,440
..where the answer is kept
in a bomb-proof vault...

693
00:48:03,680 --> 00:48:05,120
..wrapped in foil.

694
00:48:12,200 --> 00:48:14,280
And if that isn't enough,

695
00:48:14,280 --> 00:48:18,320
this entire facility
demands OCD levels of hygiene.

696
00:48:30,520 --> 00:48:34,160
One man who knows a lot about this
object is Harrison Schmitt.

697
00:48:35,600 --> 00:48:39,640
And that's because he found it...
on the moon.

698
00:48:42,920 --> 00:48:46,200
Four decades ago,
Harrison was an astronaut.

699
00:48:46,200 --> 00:48:49,200
December 6th, 1972.

700
00:48:49,200 --> 00:48:52,320
Dr Harrison Schmitt, better known
as Jack.

701
00:48:52,320 --> 00:48:56,080
He would be the first geologist to
set foot on an alien world.

702
00:48:57,720 --> 00:49:00,720
We have liftoff at 2.13...

703
00:49:05,200 --> 00:49:11,160
I'm going to meet Harrison, after
a final zap in the NASA microwave.

704
00:49:11,160 --> 00:49:13,120
SHRILL BEEP

705
00:49:16,360 --> 00:49:18,880
Harrison. Hey. Hello. Welcome.

706
00:49:18,880 --> 00:49:21,680
I so wanted to shake your hand
but it's in there!

707
00:49:21,680 --> 00:49:23,520
A little bit later maybe.

708
00:49:23,520 --> 00:49:26,600
It's great to meet you,
and what have you've got in here?

709
00:49:26,600 --> 00:49:29,560
We have one of the Apollo 17
samples.

710
00:49:29,560 --> 00:49:32,800
It's one collected near
the lunar module challenger.

711
00:49:32,800 --> 00:49:36,520
And it is a...

712
00:49:36,520 --> 00:49:40,800
..er, really quite a unique
type of rock.

713
00:49:41,840 --> 00:49:46,640
That rock formed about 3.8 billion
years ago.

714
00:49:46,640 --> 00:49:48,560
That's with a B!

715
00:49:48,560 --> 00:49:53,840
So it's extremely old, it's part
of a mass of magma that partially

716
00:49:53,840 --> 00:49:59,160
filled the valley of Tarse Littoral
where we landed on Apollo 17.

717
00:49:59,160 --> 00:50:03,080
So let's just get this into context
because, for mere mortals like me

718
00:50:03,080 --> 00:50:07,000
to understand, you are standing
there as the only geologist ever

719
00:50:07,000 --> 00:50:09,240
to have walked on the moon?
That's correct.

720
00:50:09,240 --> 00:50:12,440
And therefore, when you saw these
rocks on the moon, they would have

721
00:50:12,440 --> 00:50:15,720
meant more to you anyway because of
your training and knowledge.
I hope so.

722
00:50:15,720 --> 00:50:18,480
Your brain must have been
just screaming!

723
00:50:18,480 --> 00:50:20,080
You were looking at that rock.

724
00:50:20,080 --> 00:50:23,040
Well, you can't believe where this
geologic setting was.

725
00:50:23,040 --> 00:50:25,960
It's a valley deeper than
the Grand Canyon of the Colorado

726
00:50:25,960 --> 00:50:27,760
here in the United States.

727
00:50:29,120 --> 00:50:32,800
The mountains on either side
are 6,000-7,000 feet

728
00:50:32,800 --> 00:50:34,720
above the valley floor.

729
00:50:34,720 --> 00:50:36,440
This was off the valley floor.

730
00:50:39,840 --> 00:50:43,440
It's the moon that saves the real
Earth from the disastrous

731
00:50:43,440 --> 00:50:45,200
climatic effects of wobbling.

732
00:50:46,600 --> 00:50:49,640
But how exactly the moon
keeps us stable

733
00:50:49,640 --> 00:50:52,280
is tied into its mysterious origins.

734
00:50:57,240 --> 00:50:59,160
Until the Apollo programme,

735
00:50:59,160 --> 00:51:02,960
we had no real idea of how
the Earth got its moon.

736
00:51:04,680 --> 00:51:08,760
Finding out was an important
goal for Harrison Schmitt

737
00:51:08,760 --> 00:51:15,040
when his Apollo 17 module touched
down on December 11th, 1972.

738
00:51:15,040 --> 00:51:17,760
Feels good, stand by for touchdown.

739
00:51:17,760 --> 00:51:20,120
Stand by, down at two.

740
00:51:20,120 --> 00:51:23,040
Feels good. Ten feet.

741
00:51:23,040 --> 00:51:25,000
That's contact!

742
00:51:27,040 --> 00:51:29,120
Harrison had just three days

743
00:51:29,120 --> 00:51:31,960
to collect as many lunar samples
as possible.

744
00:51:33,520 --> 00:51:36,800
Late in the mission,
things got a little tense.

745
00:51:36,800 --> 00:51:39,840
Harrison had just
half an hour of oxygen left

746
00:51:39,840 --> 00:51:43,080
and he was getting a bit carried
away with his work.

747
00:51:44,400 --> 00:51:46,320
I've got to dig a trench, Houston.

748
00:51:48,680 --> 00:51:51,480
Fantastic, sports fans!

749
00:51:51,480 --> 00:51:53,800
It's trench time!

750
00:51:53,800 --> 00:51:55,280
They got to leave at a certain time,

751
00:51:55,280 --> 00:51:56,720
regardless of what they got.

752
00:51:56,720 --> 00:52:00,440
There isn't enough time to do it, no
matter which way we want to do it.

753
00:52:00,440 --> 00:52:02,520
We need more time.

754
00:52:02,520 --> 00:52:06,200
We need to make it clear,
we've got to pull out.

755
00:52:06,200 --> 00:52:09,080
We'd like you to
leave immediately.

756
00:52:09,080 --> 00:52:10,920
OK.

757
00:52:10,920 --> 00:52:13,200
By golly, this time goes fast!

758
00:52:13,200 --> 00:52:15,200
We're on our way, Houston.

759
00:52:20,680 --> 00:52:24,320
Once Harrison and NASA were able
to examine the rocks,

760
00:52:24,320 --> 00:52:29,000
they began to understand fully just
how the moon had formed,

761
00:52:29,000 --> 00:52:32,240
and the massive stabilising effect
it brought.

762
00:52:36,600 --> 00:52:40,360
What the scientists discovered was
an extraordinary connection.

763
00:52:41,920 --> 00:52:46,040
It seems this moon rock was
made of pretty much the same stuff

764
00:52:46,040 --> 00:52:47,280
as Earth rock.

765
00:52:49,320 --> 00:52:53,200
The oxygen isotope ratios
in the rocks are identical

766
00:52:53,200 --> 00:52:55,600
to those ratios that we have here
on Earth

767
00:52:55,600 --> 00:52:59,880
and it tells you that the Earth
and the moon formed in, basically,

768
00:52:59,880 --> 00:53:02,720
almost identically the same
part of the solar system.

769
00:53:02,720 --> 00:53:05,360
And this information that you
brought back has helped

770
00:53:05,360 --> 00:53:09,600
people narrow down the theories
as to how the moon came to be

771
00:53:09,600 --> 00:53:12,800
where it is and like it is.
No question about that.

772
00:53:12,800 --> 00:53:15,960
The primary hypothesis right now
is giant impact.

773
00:53:21,800 --> 00:53:24,040
Soon after the Earth formed,

774
00:53:24,040 --> 00:53:26,880
another planet-sized rock
crashed into it.

775
00:53:28,680 --> 00:53:31,720
The impact threw huge chunks
into orbit.

776
00:53:32,880 --> 00:53:36,440
And these clumped together
to make the moon.

777
00:53:38,840 --> 00:53:43,600
When first formed, it was much,
much closer than it is now.

778
00:53:50,040 --> 00:53:54,320
One of the primary reasons that we
still are here on this planet

779
00:53:54,320 --> 00:53:59,360
is that the Earth is a stable planet
and it's been stabilised by the moon.

780
00:53:59,360 --> 00:54:03,280
With the moon there, there's
a gravitational stabilisation

781
00:54:03,280 --> 00:54:08,560
that occurs that keeps the Earth
wobble down to an absolute minimum

782
00:54:08,560 --> 00:54:11,280
and that makes a big
difference for us, because

783
00:54:11,280 --> 00:54:15,920
if you wanted to have major climate
change on Earth, introduce a wobble.

784
00:54:15,920 --> 00:54:18,280
It doesn't mean that
life wouldn't be here

785
00:54:18,280 --> 00:54:22,720
but it would be a very difficult
and different kind of life that we

786
00:54:22,720 --> 00:54:23,960
would have to deal with

787
00:54:23,960 --> 00:54:26,800
with this wobble over fairly long
periods of time.

788
00:54:31,360 --> 00:54:35,480
So, let's see what happens
to our planet when we add a moon.

789
00:54:39,360 --> 00:54:43,240
Our planet and its new moon
are two dancers

790
00:54:43,240 --> 00:54:47,040
locked in a gravitational embrace,

791
00:54:47,040 --> 00:54:51,400
steadying themselves
as they swirl round and round.

792
00:54:54,160 --> 00:54:57,360
Having a moon has one other
vital effect.

793
00:54:57,360 --> 00:55:02,120
Tiny variations in its gravitational
pull on our planet's oceans

794
00:55:02,120 --> 00:55:04,560
have given it tides,

795
00:55:04,560 --> 00:55:07,360
and that's more important
than you might think.

796
00:55:10,080 --> 00:55:15,560
Without the tides, early life on
Earth may never have left the sea,

797
00:55:15,560 --> 00:55:19,400
because the tides created
damp strips along the coast

798
00:55:19,400 --> 00:55:21,960
that tempted life onto land.

799
00:55:24,000 --> 00:55:27,120
And the actual positioning of
the moon is crucial.

800
00:55:27,120 --> 00:55:31,400
Ever since its formation, it's been
drifting away from the Earth.

801
00:55:31,400 --> 00:55:35,520
But when it was closer,
it generated immense tides.

802
00:55:39,120 --> 00:55:43,800
If we had them today, every few
hours, New York and London

803
00:55:43,800 --> 00:55:47,080
would disappear under
tens of metres of water.

804
00:55:49,680 --> 00:55:53,680
And if the moon was further away,
the planet's spin would slow

805
00:55:53,680 --> 00:55:55,760
and the days would be longer.

806
00:55:55,760 --> 00:55:58,280
But put it at just the right
distance, which in reality

807
00:55:58,280 --> 00:56:03,880
is about 239,000 miles, and
we have the stability we need.

808
00:56:03,880 --> 00:56:07,560
So, there it is - the perfect
planetary relationship.

809
00:56:12,600 --> 00:56:17,480
After trial and error, I have
built my planet and its moon...

810
00:56:19,120 --> 00:56:21,600
..and got them working just right.

811
00:56:27,440 --> 00:56:32,520
In reality, this whole process
took four and a half billion years.

812
00:56:34,880 --> 00:56:39,240
The sheer scale of it all
is understandably mind-blowing,

813
00:56:39,240 --> 00:56:43,080
especially when you realise
that with just one element

814
00:56:43,080 --> 00:56:44,400
out of place...

815
00:56:46,560 --> 00:56:50,000
..nothing works, and life stops.

816
00:56:56,080 --> 00:56:59,560
So what holds the Earth
and moon in place?

817
00:57:02,200 --> 00:57:05,440
They need a sun to orbit around,

818
00:57:05,440 --> 00:57:08,440
and other planets
to make our solar system...

819
00:57:10,480 --> 00:57:14,400
..all of which is just a tiny
part of a Milky Way galaxy

820
00:57:14,400 --> 00:57:17,240
with 300 billion stars.

821
00:57:24,160 --> 00:57:29,400
And that galaxy is just one amongst
half a trillion other galaxies.

822
00:57:36,520 --> 00:57:41,600
So, to keep it all working, we're
going to have to build a universe.

823
00:57:51,920 --> 00:57:53,880
And to build a universe,

824
00:57:53,880 --> 00:57:55,200
I'm going to need

825
00:57:55,200 --> 00:57:56,400
a lot of help.

826
00:57:57,440 --> 00:57:59,880
Oh, this is really difficult!

827
00:58:03,920 --> 00:58:05,360
Oh, my God, it's beautiful!

828
00:58:11,440 --> 00:58:14,000
Do I look faintly ridiculous? Yes!

829
00:58:24,360 --> 00:58:26,400
I'll be honest.
I'm faintly nervous.

830
00:58:56,040 --> 00:58:58,840
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