1
00:00:12,860 --> 00:00:10,180
[Music]

2
00:00:15,260 --> 00:00:12,870
Thank You hall for being there so my

3
00:00:17,359 --> 00:00:15,270
name is Mohini let's blaze I'm going to

4
00:00:21,050 --> 00:00:17,369
talk about the magnetic field in earth

5
00:00:25,310 --> 00:00:21,060
and how its generated and obviously you

6
00:00:29,270 --> 00:00:25,320
may hear it from my voice I'm French

7
00:00:31,070 --> 00:00:29,280
which is why I put French here but don't

8
00:00:33,710 --> 00:00:31,080
don't worry I'm not going to speak in

9
00:00:35,990 --> 00:00:33,720
French I try to speak in English and I

10
00:00:39,200 --> 00:00:36,000
try to speak slowly to help for the

11
00:00:41,479 --> 00:00:39,210
translation and I put some Japanese text

12
00:00:43,130 --> 00:00:41,489
on my slides so I hope it's correct

13
00:00:47,149 --> 00:00:43,140
Japanese because I don't know any

14
00:00:49,130 --> 00:00:47,159
Japanese or almost and yeah so I'm going

15
00:00:53,509 --> 00:00:49,140
to talk about the Earth's core and the

16
00:00:56,689 --> 00:00:53,519
magnetic field and when I was trying to

17
00:00:59,719 --> 00:00:56,699
think about this talk I was wondering

18
00:01:02,899 --> 00:00:59,729
what people think when they hear the

19
00:01:06,320 --> 00:01:02,909
world magnetic field for me there is two

20
00:01:08,660 --> 00:01:06,330
things that are kind of amazing that

21
00:01:11,920 --> 00:01:08,670
happens on earth and that are related to

22
00:01:17,719 --> 00:01:11,930
magnetic field the first thing is that

23
00:01:21,649 --> 00:01:17,729
you all went hiking or you all use at

24
00:01:24,080 --> 00:01:21,659
least once a compass I also and we can

25
00:01:27,410 --> 00:01:24,090
see it we can decide what's north and

26
00:01:29,539 --> 00:01:27,420
what south on earth because of magnetic

27
00:01:32,270 --> 00:01:29,549
field and because it helped us with

28
00:01:34,310 --> 00:01:32,280
combusts be able to see which side is

29
00:01:37,069 --> 00:01:34,320
north which eyes which side the south

30
00:01:38,480 --> 00:01:37,079
and were not blessed whenever we have a

31
00:01:42,469 --> 00:01:38,490
compass at least for now so the house

32
00:01:45,620 --> 00:01:42,479
and the second thing is this which is

33
00:01:50,419 --> 00:01:45,630
Aurora's so that's a view from space of

34
00:01:52,789 --> 00:01:50,429
an Aurora on the South Pole and this is

35
00:01:55,340 --> 00:01:52,799
because of the interaction between the

36
00:01:58,130 --> 00:01:55,350
Sarah winds and the Earth's atmosphere

37
00:02:00,620 --> 00:01:58,140
and the reason it's only on the pole is

38
00:02:03,230 --> 00:02:00,630
because of the magnetic field and that's

39
00:02:06,020 --> 00:02:03,240
kind of crazy to think that some things

40
00:02:09,469 --> 00:02:06,030
that's created inside very center of the

41
00:02:12,950 --> 00:02:09,479
earth has so many implication for earth

42
00:02:19,179 --> 00:02:12,960
for the surface for life and for humans

43
00:02:23,420 --> 00:02:22,190
implication for life at the surface of

44
00:02:26,300 --> 00:02:23,430
the earth that you will learn about

45
00:02:28,520 --> 00:02:26,310
later this afternoon and couple of

46
00:02:31,490 --> 00:02:28,530
things that you may want to notice is

47
00:02:34,880 --> 00:02:31,500
that some animals use magnetic field to

48
00:02:38,240 --> 00:02:34,890
orientate themselves so turtles use

49
00:02:41,750 --> 00:02:38,250
magnetic field she'll be able to go back

50
00:02:44,449 --> 00:02:41,760
to the original place of burrs and some

51
00:02:47,349 --> 00:02:44,459
birds also use magnetic field to be able

52
00:02:51,020 --> 00:02:47,359
to travel very very long distance and

53
00:02:53,420 --> 00:02:51,030
some scientists even used even try to

54
00:02:58,460 --> 00:02:53,430
see if dogs may actually orientate

55
00:03:01,330 --> 00:02:58,470
themselves when they're pooping you can

56
00:03:03,890 --> 00:03:01,340
look at the paper I'm not going to and

57
00:03:09,800 --> 00:03:03,900
other things that's very important for

58
00:03:12,559 --> 00:03:09,810
life for Earth is that the magnetic

59
00:03:14,629 --> 00:03:12,569
field is actually protecting earth from

60
00:03:17,839 --> 00:03:14,639
solar winds so it's protecting the earth

61
00:03:21,259 --> 00:03:17,849
from the charged particles that are

62
00:03:25,460 --> 00:03:21,269
generated as this understand and that

63
00:03:28,030 --> 00:03:25,470
preparing over the earth and with that

64
00:03:30,589 --> 00:03:28,040
magnetic field the earth would be

65
00:03:33,099 --> 00:03:30,599
graduating with with receive radiation

66
00:03:34,939 --> 00:03:33,109
from solar winds and most of our

67
00:03:41,479 --> 00:03:34,949
telecommunication would not be walking

68
00:03:43,189 --> 00:03:41,489
now because of this charged particles so

69
00:03:45,500 --> 00:03:43,199
magnetic field is something that's very

70
00:03:47,420 --> 00:03:45,510
important for life has been important

71
00:03:51,589 --> 00:03:47,430
for life for a very long time and is

72
00:03:53,059 --> 00:03:51,599
important for humans now so when you

73
00:03:55,759 --> 00:03:53,069
look at other planets

74
00:03:57,649 --> 00:03:55,769
you could also wonder do they have also

75
00:04:00,740 --> 00:03:57,659
a magnetic field and is it something

76
00:04:04,039 --> 00:04:00,750
that only for earth or is it for all

77
00:04:06,619 --> 00:04:04,049
planets that we know and so here is a

78
00:04:09,110 --> 00:04:06,629
view of our solar system with the Sun

79
00:04:12,979 --> 00:04:09,120
here that's obviously not to scale and

80
00:04:15,559 --> 00:04:12,989
you have Mercury Venus Earth Mars which

81
00:04:18,560 --> 00:04:15,569
are the so-called rocky planets because

82
00:04:20,120 --> 00:04:18,570
their composition is very close to the

83
00:04:22,069 --> 00:04:20,130
Earth's composition so it's basically

84
00:04:24,290 --> 00:04:22,079
rocks and there is a very thin

85
00:04:26,149 --> 00:04:24,300
atmosphere but we we can have a surface

86
00:04:30,620 --> 00:04:26,159
at where we can actually stand on and

87
00:04:31,570 --> 00:04:30,630
this is a four gas giant planet and I've

88
00:04:33,939 --> 00:04:31,580
been a couple of

89
00:04:35,980 --> 00:04:33,949
missions and observation of magnetic

90
00:04:38,710 --> 00:04:35,990
field inside the solar system and

91
00:04:42,129 --> 00:04:38,720
actually most of the planets in our

92
00:04:45,700 --> 00:04:42,139
solar system have a magnetic field so

93
00:04:48,580 --> 00:04:45,710
all of the gas-giant present magnetic

94
00:04:52,420 --> 00:04:48,590
field for which the duration is slightly

95
00:04:54,999 --> 00:04:52,430
different from the rocky planet but even

96
00:04:58,629 --> 00:04:55,009
amongst the rocky planets mercury in

97
00:05:01,719 --> 00:04:58,639
Earth's of a magnetic field now and Mars

98
00:05:04,240 --> 00:05:01,729
had evidence that was a magnetic field

99
00:05:05,710 --> 00:05:04,250
in the past for Venus

100
00:05:08,260 --> 00:05:05,720
it's a little bit more tricky and

101
00:05:11,080 --> 00:05:08,270
everything related to Venice is usually

102
00:05:13,420 --> 00:05:11,090
more tricky but there is no magnetic

103
00:05:15,700 --> 00:05:13,430
field and Venus now and we don't know if

104
00:05:19,120 --> 00:05:15,710
Venice add a magnetic field in the past

105
00:05:20,620 --> 00:05:19,130
it's quite interesting to see that the

106
00:05:24,279 --> 00:05:20,630
magnetic field is something that looks

107
00:05:28,740 --> 00:05:24,289
like kind of Universal for rocky planets

108
00:05:31,839 --> 00:05:28,750
and for planets in the solar system that

109
00:05:34,059 --> 00:05:31,849
at least for Earth we can observe it and

110
00:05:36,459 --> 00:05:34,069
we can have very good observations so we

111
00:05:39,459 --> 00:05:36,469
can try to look at short scale short

112
00:05:43,870 --> 00:05:39,469
time scale and long time scale evolution

113
00:05:46,439 --> 00:05:43,880
of the magnetic field on earth we can do

114
00:05:49,029 --> 00:05:46,449
ground observations so we can look at

115
00:05:51,909 --> 00:05:49,039
evolution of the magnetic field today

116
00:05:54,370 --> 00:05:51,919
from ground observation and from space

117
00:05:57,879 --> 00:05:54,380
observations and both of them will give

118
00:05:59,980 --> 00:05:57,889
us a different information but for rugs

119
00:06:02,950 --> 00:05:59,990
what's also very interesting is that

120
00:06:06,459 --> 00:06:02,960
magnetic field can be recorded in rugs

121
00:06:09,100 --> 00:06:06,469
so when a rug is formed when it reach a

122
00:06:12,309 --> 00:06:09,110
certain temperature some minerals will

123
00:06:15,370 --> 00:06:12,319
record the magnetic field as it was when

124
00:06:17,019 --> 00:06:15,380
it was formed and so we know that the

125
00:06:19,029 --> 00:06:17,029
magnetic field is something that has

126
00:06:19,360 --> 00:06:19,039
been present on earth for a very long

127
00:06:22,779 --> 00:06:19,370
time

128
00:06:25,089 --> 00:06:22,789
and I've been evolution of the magnetic

129
00:06:29,189 --> 00:06:25,099
field but basically is a global

130
00:06:32,469 --> 00:06:29,199
intensity of magnetic field has been

131
00:06:33,879 --> 00:06:32,479
stable over most of Earth's history so

132
00:06:36,010 --> 00:06:33,889
the magnetic field is something ancient

133
00:06:41,409 --> 00:06:36,020
and some things that's still going on

134
00:06:43,879 --> 00:06:41,419
right now and where does it come from so

135
00:06:45,800 --> 00:06:43,889
this is the earth and

136
00:06:48,950 --> 00:06:45,810
magnetic field is something we see at

137
00:06:52,249 --> 00:06:48,960
the surface but it comes from the very

138
00:06:55,159 --> 00:06:52,259
deep interior you may have seen this

139
00:06:58,510 --> 00:06:55,169
figure in the past you've seen it once

140
00:07:02,179 --> 00:06:58,520
in ramen stock and it's a figure of the

141
00:07:05,959 --> 00:07:02,189
structure of the earth so now we're

142
00:07:11,779 --> 00:07:05,969
standing on the crest so we're standing

143
00:07:15,140 --> 00:07:11,789
on some rocks and below us there is 6000

144
00:07:18,110 --> 00:07:15,150
kilometers between us and the very

145
00:07:21,499 --> 00:07:18,120
center of the earth and this is what's

146
00:07:23,540 --> 00:07:21,509
between us here and the center of the

147
00:07:26,089 --> 00:07:23,550
earth first

148
00:07:28,939 --> 00:07:26,099
so we're in Japan so it's very maybe

149
00:07:30,589 --> 00:07:28,949
different from other places but we're on

150
00:07:32,659 --> 00:07:30,599
this subduction zone which means that

151
00:07:34,429 --> 00:07:32,669
we're actually if you want to go from

152
00:07:36,589 --> 00:07:34,439
here towards the center of the earth

153
00:07:39,320 --> 00:07:36,599
you're actually going to cross a couple

154
00:07:42,409 --> 00:07:39,330
of crests because we are we have sub

155
00:07:46,100 --> 00:07:42,419
diction's and then you're go through the

156
00:07:49,390 --> 00:07:46,110
mantle which is also made of rocks and

157
00:07:53,420 --> 00:07:49,400
once you reach the core-mantle boundary

158
00:07:57,079 --> 00:07:53,430
you'll actually reach a big sphere of

159
00:08:00,790 --> 00:07:57,089
iren that at the very centre of our

160
00:08:03,350 --> 00:08:00,800
earth which is liquid and there is a

161
00:08:06,110 --> 00:08:03,360
central part which is called the inner

162
00:08:10,010 --> 00:08:06,120
core that's also made of iron that is

163
00:08:13,279 --> 00:08:10,020
also as that is solid you may wonder how

164
00:08:17,300 --> 00:08:13,289
we know that because we can't dig zuri

165
00:08:20,029 --> 00:08:17,310
we can't go there there is no space

166
00:08:23,269 --> 00:08:20,039
sheep or earth sheep that could go from

167
00:08:27,860 --> 00:08:23,279
the crest towards the core even if some

168
00:08:32,170 --> 00:08:27,870
movies try to do that so what we can do

169
00:08:35,420 --> 00:08:32,180
is we can actually use seismic

170
00:08:39,490 --> 00:08:35,430
observation to try to understand what is

171
00:08:44,180 --> 00:08:39,500
the structure of the earth and in Japan

172
00:08:46,400 --> 00:08:44,190
you know earthquakes and what you may

173
00:08:48,829 --> 00:08:46,410
not know is that seismologist use

174
00:08:52,699 --> 00:08:48,839
earthquake to understand what's going on

175
00:08:54,350 --> 00:08:52,709
deep inside the earth so if you think

176
00:08:54,999 --> 00:08:54,360
about an earthquake somewhere on the

177
00:08:57,429 --> 00:08:55,009
earth

178
00:09:01,569 --> 00:08:57,439
we have seismic stations that are all

179
00:09:05,379 --> 00:09:01,579
over most of the continents and that are

180
00:09:06,879 --> 00:09:05,389
recording what's going on so in Japan we

181
00:09:09,609 --> 00:09:06,889
have earthquakes we feel the surface

182
00:09:12,400 --> 00:09:09,619
waves but we have body waves that will

183
00:09:14,859 --> 00:09:12,410
travel inside ears and so if you have an

184
00:09:18,309 --> 00:09:14,869
earthquake here and you have a station

185
00:09:20,979 --> 00:09:18,319
here what you will record is a waves

186
00:09:24,009 --> 00:09:20,989
that have been traveling from here to

187
00:09:26,530 --> 00:09:24,019
here through the whole mantle and if you

188
00:09:30,869 --> 00:09:26,540
look at how fast this wave was traveling

189
00:09:33,609 --> 00:09:30,879
you can find information about the

190
00:09:36,039 --> 00:09:33,619
seismic structure of the earth and if

191
00:09:37,600 --> 00:09:36,049
you're looking at stations here you will

192
00:09:39,970 --> 00:09:37,610
actually get ways that have been

193
00:09:43,059 --> 00:09:39,980
traveler traveling through the mantle

194
00:09:46,449 --> 00:09:43,069
the core the mantle and back at the

195
00:09:49,030 --> 00:09:46,459
seismic station so that's how we can

196
00:09:52,569 --> 00:09:49,040
have information about seismic

197
00:09:55,689 --> 00:09:52,579
properties of rocks at inside the

198
00:09:59,559 --> 00:09:55,699
Earth's interior and the other thing

199
00:10:01,079 --> 00:09:59,569
that's also well used here in LC is high

200
00:10:06,039 --> 00:10:01,089
pressure and high temperature

201
00:10:08,499 --> 00:10:06,049
experiments so what people what say

202
00:10:10,569 --> 00:10:08,509
scientists do is they use diamond under

203
00:10:13,869 --> 00:10:10,579
cells which are actually very tiny

204
00:10:16,809 --> 00:10:13,879
diamonds and you put a very very very

205
00:10:21,150 --> 00:10:16,819
small sample between the two up X of the

206
00:10:24,789 --> 00:10:21,160
diamonds and you push right here and

207
00:10:26,980 --> 00:10:24,799
because this here is a very very small

208
00:10:30,280 --> 00:10:26,990
surface you actually managed to get very

209
00:10:32,139 --> 00:10:30,290
high pressures so if you know what you

210
00:10:34,780 --> 00:10:32,149
think should be the composition of the

211
00:10:37,960 --> 00:10:34,790
core and you put it inside two diamonds

212
00:10:40,689 --> 00:10:37,970
you can actually manage to see what

213
00:10:43,150 --> 00:10:40,699
would be the properties of material that

214
00:10:46,509 --> 00:10:43,160
is supposed to be at the very centre of

215
00:10:49,389 --> 00:10:46,519
the earth so that's how we know so

216
00:10:52,569 --> 00:10:49,399
combining these two kind of observation

217
00:10:55,449 --> 00:10:52,579
we know that the core is mostly liquid

218
00:10:58,419 --> 00:10:55,459
and is made of iron and we have a

219
00:11:03,489 --> 00:10:58,429
central inner core that is most that is

220
00:11:07,350 --> 00:11:03,499
solid and this liquid outer core is

221
00:11:09,040 --> 00:11:07,360
where the magnetic field is generated so

222
00:11:11,829 --> 00:11:09,050
let's go to

223
00:11:14,050 --> 00:11:11,839
how to generate a magnetic field so what

224
00:11:17,530 --> 00:11:14,060
you need is you need an electrically

225
00:11:20,860 --> 00:11:17,540
conductive fluid which is Iran's liquid

226
00:11:24,100 --> 00:11:20,870
iron inside the core and you need some

227
00:11:27,430 --> 00:11:24,110
energy to start pushing them as a fluid

228
00:11:30,250 --> 00:11:27,440
and what's called a dynamo effect is

229
00:11:33,460 --> 00:11:30,260
when you start pushing a fluid you will

230
00:11:35,500 --> 00:11:33,470
induce a flow this flow because it's a

231
00:11:38,009 --> 00:11:35,510
flow inside an electrically conductive

232
00:11:41,380 --> 00:11:38,019
fluid will induce a magnetic field and

233
00:11:42,850 --> 00:11:41,390
if you choose carefully your flow if you

234
00:11:45,220 --> 00:11:42,860
choose carefully the geometry of the

235
00:11:49,000 --> 00:11:45,230
flow this magnetic field that was

236
00:11:50,949 --> 00:11:49,010
generated by flow will also induce

237
00:11:54,069 --> 00:11:50,959
another flow that we didn't do smack

238
00:11:56,350 --> 00:11:54,079
netic field and you'll get a loop that

239
00:11:58,750 --> 00:11:56,360
will basically increase the magnetic

240
00:12:01,780 --> 00:11:58,760
field up to a point where you get a

241
00:12:05,440 --> 00:12:01,790
dynamo so it's basically self self

242
00:12:07,630 --> 00:12:05,450
sustained a flow and magnetic field but

243
00:12:09,400 --> 00:12:07,640
for that you need some energy you need

244
00:12:11,860 --> 00:12:09,410
some energy available to actually

245
00:12:14,530 --> 00:12:11,870
generate this magnetic field so what's

246
00:12:16,150 --> 00:12:14,540
the energy available in the earth that's

247
00:12:18,760 --> 00:12:16,160
actually driving what we call the

248
00:12:21,940 --> 00:12:18,770
geodynamo so geo for Earth's and dynamo

249
00:12:25,860 --> 00:12:21,950
for this effect we're talking about

250
00:12:29,440 --> 00:12:25,870
liquid flowing and so the density

251
00:12:32,380 --> 00:12:29,450
variations in a liquid will induce flows

252
00:12:34,090 --> 00:12:32,390
so that's what we're usually thinking

253
00:12:37,360 --> 00:12:34,100
when we're thinking about driving the

254
00:12:40,720 --> 00:12:37,370
Dynamo so by NZ effects are basically

255
00:12:43,510 --> 00:12:40,730
when you take a V per set of fluid and

256
00:12:45,130 --> 00:12:43,520
you put it in water it will go down so

257
00:12:47,590 --> 00:12:45,140
if you put milk in water it's slightly

258
00:12:49,990 --> 00:12:47,600
heavier than water so the milk will go

259
00:12:54,100 --> 00:12:50,000
at the bottom of your cap or if you have

260
00:12:56,380 --> 00:12:54,110
a light fluid in a overall fridge that's

261
00:12:59,680 --> 00:12:56,390
slightly heavier it will go up just

262
00:13:02,710 --> 00:12:59,690
because of density variation and if you

263
00:13:05,699 --> 00:13:02,720
manage to get a way to get light or evie

264
00:13:08,860 --> 00:13:05,709
fluids you will in juice flow and that's

265
00:13:11,970 --> 00:13:08,870
what we call conviction and for example

266
00:13:16,240 --> 00:13:11,980
in the ocean it's something that's very

267
00:13:19,870 --> 00:13:16,250
important so you have the freezing of

268
00:13:21,750 --> 00:13:19,880
ice at the pole that will create salty

269
00:13:25,680 --> 00:13:21,760
and cold water the

270
00:13:30,240 --> 00:13:25,690
salty encode water will go down and will

271
00:13:33,600 --> 00:13:30,250
be warmed at the equator and it will you

272
00:13:35,520 --> 00:13:33,610
will get liquid that's warm and not too

273
00:13:38,280 --> 00:13:35,530
salty so it would be slightly lighter

274
00:13:41,640 --> 00:13:38,290
and so this will induce an overall

275
00:13:43,670 --> 00:13:41,650
circulation that's called thermo aligned

276
00:13:46,470 --> 00:13:43,680
circulations that for example

277
00:13:49,260 --> 00:13:46,480
represented here where you have a

278
00:13:52,920 --> 00:13:49,270
formation of deep water at the pores

279
00:13:54,710 --> 00:13:52,930
that will actually roll and do this kind

280
00:13:59,070 --> 00:13:54,720
of very very large-scale circulation

281
00:14:00,780 --> 00:13:59,080
into the ocean and in France it's some

282
00:14:03,120 --> 00:14:00,790
things that people are very happy about

283
00:14:07,320 --> 00:14:03,130
it because I don't know if you notice

284
00:14:09,960 --> 00:14:07,330
here but there is a warm water coming

285
00:14:12,840 --> 00:14:09,970
from the equator that goes up to France

286
00:14:17,040 --> 00:14:12,850
to the French coast and that actually is

287
00:14:18,540 --> 00:14:17,050
why we can swim here so it should go to

288
00:14:19,980 --> 00:14:18,550
France and you go to the ocean and

289
00:14:22,200 --> 00:14:19,990
you're actually managed to swim because

290
00:14:23,730 --> 00:14:22,210
the water will be not too cold but if

291
00:14:26,130 --> 00:14:23,740
you go at the same place here in Canada

292
00:14:28,560 --> 00:14:26,140
or in the u.s. if you're at the same

293
00:14:30,840 --> 00:14:28,570
latitude you're not going to go in the

294
00:14:36,630 --> 00:14:30,850
water it's going to be way too cold so

295
00:14:39,720 --> 00:14:36,640
if you want vacation go to France so

296
00:14:41,850 --> 00:14:39,730
let's go back to the earth and we're

297
00:14:44,190 --> 00:14:41,860
looking at the outer core here and

298
00:14:48,510 --> 00:14:44,200
what's actually driving density

299
00:14:53,040 --> 00:14:48,520
variation in two years first the Earth's

300
00:14:55,230 --> 00:14:53,050
core is very warm it's very hot it has

301
00:14:57,780 --> 00:14:55,240
been hot since the formation of the

302
00:15:01,520 --> 00:14:57,790
Earth's because of all this energy that

303
00:15:04,350 --> 00:15:01,530
was accreted or this energy that was

304
00:15:07,830 --> 00:15:04,360
that somehow during the accretion and

305
00:15:10,500 --> 00:15:07,840
this heat wants to go out and the mantle

306
00:15:14,250 --> 00:15:10,510
is actually pumping heat from the outer

307
00:15:17,640 --> 00:15:14,260
core and this induce a density variation

308
00:15:19,680 --> 00:15:17,650
at the top of the outer core and the

309
00:15:22,260 --> 00:15:19,690
second important thing that will create

310
00:15:25,560 --> 00:15:22,270
density variation is the freezing of the

311
00:15:28,170 --> 00:15:25,570
inner core so I told you in our Korea

312
00:15:29,560 --> 00:15:28,180
solid an inner core is actually made of

313
00:15:33,580 --> 00:15:29,570
the same

314
00:15:36,580 --> 00:15:33,590
allow that the article but since the

315
00:15:39,930 --> 00:15:36,590
temperature in the core decrease it's

316
00:15:42,910 --> 00:15:39,940
like eyes formed in your freezer it's

317
00:15:45,490 --> 00:15:42,920
freezing of the solid area of the liquid

318
00:15:47,020 --> 00:15:45,500
iron from the outer core and so at the

319
00:15:49,690 --> 00:15:47,030
surface of the inner core you will

320
00:15:52,180 --> 00:15:49,700
believe late and eat because of this

321
00:15:55,020 --> 00:15:52,190
freezing and you will also release light

322
00:15:58,990 --> 00:15:55,030
elements because the same way the eyes

323
00:16:02,140 --> 00:15:59,000
in the ocean as less salt and the water

324
00:16:05,590 --> 00:16:02,150
then here is a solid inner core is

325
00:16:08,170 --> 00:16:05,600
actually Foreman of an iron that has

326
00:16:11,770 --> 00:16:08,180
less impurities what we got light

327
00:16:13,930 --> 00:16:11,780
elements than the global outer core so

328
00:16:16,660 --> 00:16:13,940
at the surface of the inner core you're

329
00:16:19,780 --> 00:16:16,670
releasing a liquid that's lighter

330
00:16:24,940 --> 00:16:19,790
because it has more impurities and it's

331
00:16:27,430 --> 00:16:24,950
also hotter so due to this density

332
00:16:32,920 --> 00:16:27,440
variation you're inducing flows inside

333
00:16:35,110 --> 00:16:32,930
the outer core that drives a dynamo here

334
00:16:37,450 --> 00:16:35,120
I draw this kind of flows because it's

335
00:16:39,870 --> 00:16:37,460
how we usually see conviction it's like

336
00:16:43,330 --> 00:16:39,880
nice prunes and it goes up and goes down

337
00:16:45,910 --> 00:16:43,340
but for the core of the earth it's a lot

338
00:16:48,670 --> 00:16:45,920
more complicated and the Earth's core is

339
00:16:52,090 --> 00:16:48,680
rotating very fastly it's also very and

340
00:16:55,930 --> 00:16:52,100
viscous and what it means it means that

341
00:16:58,660 --> 00:16:55,940
the Earth's core actually the flows

342
00:17:02,410 --> 00:16:58,670
inside it looks like the ocean it looks

343
00:17:07,510 --> 00:17:02,420
like water so it see it means that it's

344
00:17:10,120 --> 00:17:07,520
very turbulent and now people manage to

345
00:17:12,579 --> 00:17:10,130
do simulations to actually model this

346
00:17:14,860 --> 00:17:12,589
kind of flows and we get this kind of

347
00:17:17,199 --> 00:17:14,870
pictures and which does not look like

348
00:17:18,520 --> 00:17:17,209
what I showed you just before was just

349
00:17:20,860 --> 00:17:18,530
like nice plumes

350
00:17:25,660 --> 00:17:20,870
it's very turbulent it has lots of very

351
00:17:29,590 --> 00:17:25,670
small scale it is and it's a lot more

352
00:17:33,730 --> 00:17:29,600
complicated but that was simplest view

353
00:17:35,410 --> 00:17:33,740
to see it so here is a simulation of the

354
00:17:38,800 --> 00:17:35,420
best thing we can do to model the

355
00:17:40,530 --> 00:17:38,810
Earth's core which is very tricky to do

356
00:17:45,900 --> 00:17:40,540
because of the turbulence and

357
00:17:49,140 --> 00:17:45,910
highly rotating fluid and you see a

358
00:17:52,770 --> 00:17:49,150
small circle like small plumes of light

359
00:17:55,410 --> 00:17:52,780
fluid that goes up here and every fluid

360
00:18:00,690 --> 00:17:55,420
that goes down so that's what's actually

361
00:18:05,040 --> 00:18:00,700
generating the Dynamo and now there is a

362
00:18:07,500 --> 00:18:05,050
question of the Dynamo history so here

363
00:18:09,960 --> 00:18:07,510
is a simplest view of the Earth's

364
00:18:12,090 --> 00:18:09,970
formation so it looks like what we see

365
00:18:15,750 --> 00:18:12,100
in the tolls before so you start with

366
00:18:18,270 --> 00:18:15,760
small planets you build you build a

367
00:18:21,060 --> 00:18:18,280
bigger planets the planetesimals and

368
00:18:23,240 --> 00:18:21,070
protoplanets and then the Earth's but

369
00:18:26,250 --> 00:18:23,250
here I should use a structure inside

370
00:18:29,550 --> 00:18:26,260
because in green you have the mantle in

371
00:18:32,760 --> 00:18:29,560
red is a core and at first the planet is

372
00:18:34,440 --> 00:18:32,770
so hot that there is no inner core but

373
00:18:36,330 --> 00:18:34,450
for now we think that the inner core is

374
00:18:39,300 --> 00:18:36,340
driving the Dynamo in okok

375
00:18:42,000 --> 00:18:39,310
crystallization is driving the Dynamo so

376
00:18:43,710 --> 00:18:42,010
a big question now for research is

377
00:18:48,660 --> 00:18:43,720
trying to understand what was happening

378
00:18:51,240 --> 00:18:48,670
before this inner core first crystal so

379
00:18:54,900 --> 00:18:51,250
before we add any inner core how can we

380
00:18:57,060 --> 00:18:54,910
still have a dynamo people here in LCE

381
00:18:59,580 --> 00:18:57,070
are working on a different hypothesis

382
00:19:02,550 --> 00:18:59,590
one of the main one recently has been

383
00:19:04,830 --> 00:19:02,560
the publication of sio2 crystallization

384
00:19:07,260 --> 00:19:04,840
inside the Earth's core which is

385
00:19:11,400 --> 00:19:07,270
basically instead of crystallizing the

386
00:19:13,350 --> 00:19:11,410
inner core which is dance solid made

387
00:19:15,630 --> 00:19:13,360
mostly of iron you would crystallize

388
00:19:19,670 --> 00:19:15,640
something that's very light that will go

389
00:19:24,180 --> 00:19:19,680
up and goes up to the commenter boundary

390
00:19:28,200 --> 00:19:24,190
but I think now what's interesting is

391
00:19:31,050 --> 00:19:28,210
that we can also have a look at other

392
00:19:33,600 --> 00:19:31,060
planets and so another thing we're

393
00:19:37,740 --> 00:19:33,610
thinking here at LC is trying to see

394
00:19:39,960 --> 00:19:37,750
what is universal in planetary dynamos

395
00:19:42,420 --> 00:19:39,970
and can we actually try to understand

396
00:19:44,310 --> 00:19:42,430
better the earth and here's magnetic

397
00:19:47,580 --> 00:19:44,320
field by looking at other planets and

398
00:19:53,670 --> 00:19:47,590
even at looking at other exoplanets so

399
00:19:53,680 --> 00:20:26,860
[Music]