1
00:00:21,745 --> 00:00:23,096
I want to ask you something:

2
00:00:23,096 --> 00:00:25,578
When was the last time 
you watched the stars?

3
00:00:25,578 --> 00:00:27,861
I know most people forget they exist

4
00:00:27,861 --> 00:00:30,061
specially in this polluted city

5
00:00:30,061 --> 00:00:32,598
which is sometimes foggy,

6
00:00:32,598 --> 00:00:34,092
we never see them.

7
00:00:34,092 --> 00:00:36,436
But since I was a kid, 
maybe not that young,

8
00:00:36,436 --> 00:00:38,120
maybe 12 or 13 years,

9
00:00:38,120 --> 00:00:41,481
I've been captivated by stars
and would watch them whenever possible.

10
00:00:41,481 --> 00:00:43,808
My dad gave me a small telescope

11
00:00:43,808 --> 00:00:46,806
by the time I was 14 and I spent hours

12
00:00:46,806 --> 00:00:48,965
watching planets and stars

13
00:00:48,965 --> 00:00:50,349
and always wondering:

14
00:00:50,349 --> 00:00:51,773
What is out there?

15
00:00:51,773 --> 00:00:54,747
Is there someone watching me back

16
00:00:54,747 --> 00:00:56,936
with a telescope, wondering 
what is out here?

17
00:00:57,508 --> 00:00:59,966
This allure went on for years

18
00:00:59,966 --> 00:01:02,388
and at some point 
I decided to be an astronomer.

19
00:01:03,102 --> 00:01:05,820
In Mexico, in order to be an astronomer
you need to be a physicist.

20
00:01:05,820 --> 00:01:07,724
So I studied physics.

21
00:01:07,724 --> 00:01:10,618
I never got to be an astronomer,
now I'm something in between,

22
00:01:10,893 --> 00:01:13,203
half an astrophysicist, half a physicist

23
00:01:13,203 --> 00:01:14,837
but this idea of stars

24
00:01:14,837 --> 00:01:16,848
and the possibility of reaching them

25
00:01:16,848 --> 00:01:18,251
remained with me.

26
00:01:18,584 --> 00:01:20,692
When I started my major in physics

27
00:01:20,692 --> 00:01:23,232
I realized something many of you

28
00:01:23,232 --> 00:01:26,065
have heard of, even if you are not 
totally clear about it:

29
00:01:26,555 --> 00:01:30,564
that more than 100 years ago, in 1905,

30
00:01:30,564 --> 00:01:32,432
this guy named Albert Einstein,

31
00:01:32,432 --> 00:01:35,155
discovered that light speed

32
00:01:35,155 --> 00:01:37,792
is the fastest in the universe.

33
00:01:37,792 --> 00:01:39,187
That might not say you a lot

34
00:01:39,187 --> 00:01:41,400
because light speed is huge.

35
00:01:41,400 --> 00:01:44,583
Light moves up to 186,000 mi/s

36
00:01:44,583 --> 00:01:47,657
so high a speed that we can phone call

37
00:01:47,657 --> 00:01:49,837
someone in India or Japan

38
00:01:49,837 --> 00:01:52,389
with no problem at all.

39
00:01:52,389 --> 00:01:55,795
Even astronauts who went 
to the moon 40 years ago

40
00:01:56,825 --> 00:02:00,556
were interviewed and
the President could talk to them

41
00:02:00,556 --> 00:02:03,834
with no evident delay

42
00:02:03,834 --> 00:02:06,331
even though the astronauts 
were in the moon,

43
00:02:06,331 --> 00:02:09,473
thing is that light speed is huge

44
00:02:09,473 --> 00:02:12,592
and the universe gigantic.

45
00:02:13,759 --> 00:02:16,376
We cannot travel faster than light speed

46
00:02:16,376 --> 00:02:18,231
and that is a severe problem

47
00:02:18,231 --> 00:02:20,589
to reach for the stars.

48
00:02:20,589 --> 00:02:23,354
Sun is 8 light-minutes away,

49
00:02:23,354 --> 00:02:25,707
that is, it takes 8 minutes for light

50
00:02:25,707 --> 00:02:28,382
to get here from the Sun,
from the Sun to us.

51
00:02:28,382 --> 00:02:29,988
If the Sun exploded right now,

52
00:02:29,988 --> 00:02:32,273
nobody would notice 
up until eight minutes later.

53
00:02:33,269 --> 00:02:35,677
The closest star after the Sun

54
00:02:35,677 --> 00:02:37,779
is Alfa Centauri,

55
00:02:37,779 --> 00:02:40,138
it takes four years for light to travel

56
00:02:40,138 --> 00:02:41,626
and it's right besides the Sun.

57
00:02:42,057 --> 00:02:43,483
We live in a galaxy

58
00:02:43,493 --> 00:02:46,487
that is a star spiral called Milky Way.

59
00:02:46,487 --> 00:02:49,662
The center of our galaxy 
was 30,000 light years away,

60
00:02:49,662 --> 00:02:52,160
it takes 30,000 light years 
for light to travel

61
00:02:52,160 --> 00:02:54,765
from the center of the galaxy to us,

62
00:02:54,765 --> 00:02:56,582
and two million years

63
00:02:56,582 --> 00:02:58,495
in traveling from Andromeda galaxy

64
00:02:58,495 --> 00:03:01,464
that is one of our neighbor galaxies.

65
00:03:01,624 --> 00:03:04,254
The universe is huge, vast,

66
00:03:04,254 --> 00:03:06,732
if we ever want to reach the stars

67
00:03:06,732 --> 00:03:09,583
the light limit is very serious,

68
00:03:09,583 --> 00:03:11,973
a very serious problem, but why?

69
00:03:12,620 --> 00:03:14,913
Why we cannot travel faster than light?

70
00:03:14,923 --> 00:03:16,901
And it's not because Einstein said so,

71
00:03:16,901 --> 00:03:18,767
that is no how science works.

72
00:03:18,767 --> 00:03:21,053
In science 
there is no authority principle;

73
00:03:21,053 --> 00:03:23,116
it's not because some famous guy says so.

74
00:03:23,623 --> 00:03:25,635
There are reasons, theoretical reasons,

75
00:03:25,635 --> 00:03:27,715
observational reasons,

76
00:03:27,715 --> 00:03:29,413
experiments show it,

77
00:03:29,413 --> 00:03:32,592
it is a verified fact,

78
00:03:32,592 --> 00:03:33,971
but why?

79
00:03:34,285 --> 00:03:38,384
Basically, the answer is that 
theory of relativity prevents it,

80
00:03:38,384 --> 00:03:40,179
so I will tell you a bit,

81
00:03:40,179 --> 00:03:42,489
a very quick course:

82
00:03:42,489 --> 00:03:45,612
Relativity in a couple of minutes.

83
00:03:45,612 --> 00:03:48,625
Don't be afraid, 
I'll give a general overview,

84
00:03:48,625 --> 00:03:51,992
normally it takes six months to teach this

85
00:03:51,992 --> 00:03:54,561
to sixth and seventh graders 
of physics major.

86
00:03:54,561 --> 00:03:56,854
So right now I will explain it

87
00:03:56,854 --> 00:03:59,276
in two minutes and for non-physicists.

88
00:03:59,276 --> 00:04:01,036
So, don't worry.

89
00:04:02,639 --> 00:04:05,036
Relativity is an old concept

90
00:04:05,036 --> 00:04:07,428
though it wasn't called like that.

91
00:04:07,428 --> 00:04:10,951
The concept can be traced 
back from Galileo Galilei

92
00:04:10,951 --> 00:04:14,252
around 1620, in the 17th century.

93
00:04:14,667 --> 00:04:17,939
Galileo was the first one 
to realize something interesting,

94
00:04:17,939 --> 00:04:20,224
when it comes to movement, when I move,

95
00:04:20,224 --> 00:04:23,342
my movement is always relative 
to something else.

96
00:04:23,342 --> 00:04:25,491
Movement is said to be relative,

97
00:04:25,491 --> 00:04:28,834
here on the stage,
my movement is relative to the floor.

98
00:04:29,088 --> 00:04:32,401
The measurement of your car speed 
is relative to the street,

99
00:04:33,221 --> 00:04:35,433
actually planes speed measurement

100
00:04:35,433 --> 00:04:37,648
is made relative to the air, 
not the floor.

101
00:04:37,648 --> 00:04:40,349
You might have noticed this
while watching a movie.

102
00:04:40,349 --> 00:04:42,781
A plane speed measurement 
is relative to the air,

103
00:04:42,781 --> 00:04:45,579
and the Earth spins around the Sun, etc.

104
00:04:45,859 --> 00:04:48,206
If you were somewhere in space

105
00:04:48,206 --> 00:04:51,663
in the middle of nowhere 
it would be useless

106
00:04:51,663 --> 00:04:53,914
to ask if you are moving or not

107
00:04:53,914 --> 00:04:57,681
because there is no reference 
to compare your position,

108
00:04:57,681 --> 00:05:00,071
so movement is relative,
speeds are relative,

109
00:05:00,071 --> 00:05:03,163
because they are always measured
in relation to something else.

110
00:05:03,163 --> 00:05:06,461
This was discovered
by Galileo 400 years ago.

111
00:05:06,461 --> 00:05:08,341
That was an interesting fact

112
00:05:08,341 --> 00:05:10,859
for all physic studies made after Galileo.

113
00:05:10,859 --> 00:05:14,679
Newton and all great advances 
of the 18th and 19th centuries

114
00:05:14,679 --> 00:05:16,626
agreed with Galileo.

115
00:05:16,626 --> 00:05:19,695
Speed is relative, that's fine,

116
00:05:19,695 --> 00:05:22,092
speeds aren't absolute.

117
00:05:22,092 --> 00:05:25,091
But by the end of 19th century 
something strange happened,

118
00:05:25,091 --> 00:05:28,323
many physicists studying light

119
00:05:28,323 --> 00:05:30,738
discovered that light is quite weird,

120
00:05:30,738 --> 00:05:33,653
light speed is indeed absolute

121
00:05:33,653 --> 00:05:36,078
and though Galileo stated
that speeds were relative,

122
00:05:36,078 --> 00:05:38,984
that's not the case of light,
it's always the same number

123
00:05:38,984 --> 00:05:40,488
no matter who measures it,

124
00:05:40,488 --> 00:05:43,477
or how fast is going whoever is measuring,

125
00:05:43,477 --> 00:05:46,644
no matter how fast the lightbulb 
sending out the light is moving.

126
00:05:46,644 --> 00:05:49,080
The measurement always 
yields the same number

127
00:05:49,080 --> 00:05:51,115
and this was a problem.

128
00:05:51,115 --> 00:05:53,221
This might not seem interesting to you

129
00:05:53,221 --> 00:05:56,556
but physicists of the 19th 
century were going crazy.

130
00:05:56,983 --> 00:06:00,577
Problem was: either Galileo was wrong

131
00:06:00,577 --> 00:06:02,718
and speeds were indeed absolute,

132
00:06:02,718 --> 00:06:04,583
which was apparently nonsense;

133
00:06:04,583 --> 00:06:06,877
or those who were measuring light speed

134
00:06:06,877 --> 00:06:08,896
were wrong and didn't know how to measure.

135
00:06:08,896 --> 00:06:10,890
But nobody was wrong

136
00:06:10,890 --> 00:06:13,340
which was even worst.

137
00:06:13,340 --> 00:06:16,658
Decades went by,

138
00:06:16,658 --> 00:06:20,151
until in 1905 this guy appeared,

139
00:06:20,151 --> 00:06:22,028
a man called Albert Einstein,

140
00:06:22,028 --> 00:06:24,705
who devoted his life to bringing together

141
00:06:24,705 --> 00:06:27,981
Galileo's idea that speeds were relative

142
00:06:27,981 --> 00:06:31,215
and the apparently real fact

143
00:06:31,215 --> 00:06:34,380
shown by the experiments, 
that there was an absolute speed,

144
00:06:34,380 --> 00:06:36,011
light speed.

145
00:06:36,011 --> 00:06:37,822
Long story short,

146
00:06:37,822 --> 00:06:39,558
because math is complicated,

147
00:06:39,558 --> 00:06:41,321
part of Einstein genius

148
00:06:41,321 --> 00:06:43,954
was realizing there was a solution.

149
00:06:44,641 --> 00:06:47,193
There was a logical solution 
to the problem

150
00:06:48,276 --> 00:06:51,292
and that logical solution 
derived in what we now know

151
00:06:51,292 --> 00:06:54,388
as Einstein's theory of relativity.

152
00:06:54,388 --> 00:06:56,787
It's a very interesting theory 
that changes

153
00:06:56,787 --> 00:06:59,337
what we understand by space and time,

154
00:06:59,337 --> 00:07:02,469
for instance, nobody tells us 
that space is relative

155
00:07:02,469 --> 00:07:04,809
distances, object lengths

156
00:07:04,809 --> 00:07:08,200
depend on their movement;
if an object moves fast, they shrink.

157
00:07:08,200 --> 00:07:10,128
Time is also relative,

158
00:07:10,128 --> 00:07:13,086
any watch ticking relative 
to my movement, would delay

159
00:07:13,086 --> 00:07:15,245
this we have measured many times,

160
00:07:15,245 --> 00:07:19,190
even worst: simultaneity is relative;

161
00:07:19,190 --> 00:07:21,896
when I say two things 
happen exactly at once,

162
00:07:21,896 --> 00:07:24,445
someone moving in relation to me
would disagree.

163
00:07:24,635 --> 00:07:27,834
One of us sees something first
and worst:

164
00:07:27,834 --> 00:07:30,011
we might be moving on opposed directions

165
00:07:30,011 --> 00:07:31,403
and watch things backwards:

166
00:07:31,403 --> 00:07:33,097
first this one, then that one.

167
00:07:33,097 --> 00:07:35,228
So the conclusion is that sometimes,

168
00:07:35,228 --> 00:07:37,805
the order in time of different things

169
00:07:37,805 --> 00:07:40,387
is not absolute, the order 
of time can change,

170
00:07:40,387 --> 00:07:42,721
one thing before, other thing after

171
00:07:42,721 --> 00:07:44,780
but this brings up another huge problem,

172
00:07:44,780 --> 00:07:48,235
if time order is not well defined,
what about causality?

173
00:07:48,235 --> 00:07:50,352
If something causes something else

174
00:07:50,352 --> 00:07:52,312
that something should had happened first,

175
00:07:52,312 --> 00:07:54,977
but if we disagree on what happened first,

176
00:07:54,977 --> 00:07:57,695
where does that leaves causality?

177
00:07:57,695 --> 00:07:59,600
Another crisis.

178
00:07:59,600 --> 00:08:01,643
Part of what Einstein did

179
00:08:01,643 --> 00:08:03,714
was realizing that there was solution,

180
00:08:03,714 --> 00:08:06,512
a solution to protect causality

181
00:08:06,512 --> 00:08:09,545
was thinking that light speed 
is not absolute,

182
00:08:10,378 --> 00:08:14,915
but the maximum speed of universe.

183
00:08:14,915 --> 00:08:18,373
If nothing can travel faster than light
we protect causality.

184
00:08:18,663 --> 00:08:21,186
If something could travel 
faster than light

185
00:08:21,186 --> 00:08:24,340
then we could travel to the past,

186
00:08:24,340 --> 00:08:28,142
we would be able to see 
the effect before the cause,

187
00:08:28,142 --> 00:08:30,163
which is not the proper way.

188
00:08:30,163 --> 00:08:32,744
So light speed is the maximum speed

189
00:08:32,744 --> 00:08:35,001
and that is to protect causality.

190
00:08:35,302 --> 00:08:38,793
So far as of the beginning 
of the 20th century,

191
00:08:38,793 --> 00:08:40,467
light speed was the fastest

192
00:08:40,467 --> 00:08:43,207
and if that was all left to say,
my talk would be done

193
00:08:43,207 --> 00:08:44,910
and off we go.

194
00:08:44,910 --> 00:08:47,100
But, fortunately that's not the case.

195
00:08:47,100 --> 00:08:50,028
In 1916, Einstein developed 
a second theory,

196
00:08:50,028 --> 00:08:52,904
also called relativity and that's 
why people get confused

197
00:08:52,904 --> 00:08:55,208
this one is called general relativity,

198
00:08:55,208 --> 00:08:57,031
and it's a theory about gravity.

199
00:08:57,031 --> 00:08:59,228
Einstein tried to understand gravity,

200
00:08:59,228 --> 00:09:01,469
which we already understood 
a bit since Newton;

201
00:09:01,469 --> 00:09:03,125
but he noticed some problems,

202
00:09:03,125 --> 00:09:06,579
gravity was thought of 
by Newton as instantaneous,

203
00:09:06,579 --> 00:09:09,930
if someone moved the Sun,
Earth would immediately react,

204
00:09:09,930 --> 00:09:14,271
this would go against the fact that 
nothing can travel faster than light,

205
00:09:14,271 --> 00:09:17,649
so Einstein began to develop 
a new gravity theory,

206
00:09:17,649 --> 00:09:18,919
it took him 10 years,

207
00:09:18,919 --> 00:09:22,522
an amazing achievement 
for someone as smart of Einstein,

208
00:09:22,522 --> 00:09:24,046
was based on a beautiful thing:

209
00:09:24,046 --> 00:09:27,054
the Equivalence Principle, 
also discovered by Galileo:

210
00:09:27,054 --> 00:09:30,142
all objects fall at the same speed

211
00:09:30,142 --> 00:09:33,330
if two things were dropped at once,
they would fall at the same time,

212
00:09:33,330 --> 00:09:36,628
a bowling ball or a ping pong ball
would fall just the same,

213
00:09:36,628 --> 00:09:39,943
the heavier one does not fall faster,
in case you were wondering.

214
00:09:39,943 --> 00:09:42,056
That means, from another point of view,

215
00:09:42,353 --> 00:09:47,057
that the trajectory of an object 
when there is gravity,

216
00:09:47,057 --> 00:09:48,871
does not depend on the object.

217
00:09:48,871 --> 00:09:51,294
All objects follow the same trajectory

218
00:09:51,294 --> 00:09:53,500
curved trajectories, you've seen that,

219
00:09:53,500 --> 00:09:56,989
I throw objects and they move 
in parables and ellipses

220
00:09:56,989 --> 00:10:00,652
but if those trajectories are curve 
and nondependent of the object

221
00:10:00,652 --> 00:10:03,826
then trajectory is a property of space,
but they are curve,

222
00:10:03,826 --> 00:10:05,573
then space must be curve.

223
00:10:05,573 --> 00:10:07,219
Einstein concluded

224
00:10:07,219 --> 00:10:09,923
that gravity is a space deformation.

225
00:10:09,923 --> 00:10:11,938
An interesting and beautiful thing,

226
00:10:11,938 --> 00:10:14,606
and what is beautiful about it
is that I can cheat,

227
00:10:14,886 --> 00:10:17,620
I can use space deformation

228
00:10:17,620 --> 00:10:19,385
to cheat on Einstein himself,

229
00:10:19,385 --> 00:10:22,068
so I use Einstein to cheat on Einstein.

230
00:10:22,068 --> 00:10:25,271
I can imagine ways to distort space

231
00:10:25,711 --> 00:10:29,317
to work around the statement
"nothing can go faster than light"

232
00:10:29,317 --> 00:10:32,500
and, technically, I could 
reach a faraway star

233
00:10:32,500 --> 00:10:34,736
and then come back in time for dinner.

234
00:10:34,736 --> 00:10:38,452
I will share with you two possibilities,

235
00:10:38,452 --> 00:10:41,414
that are allowed on Einstein theory,

236
00:10:41,414 --> 00:10:42,636
one is beautiful

237
00:10:42,636 --> 00:10:46,328
and its technical name
is Einstein-Rosen bridge,

238
00:10:46,328 --> 00:10:48,726
sounds technical because Einstein

239
00:10:48,726 --> 00:10:50,795
and another scientist called Rosen

240
00:10:50,795 --> 00:10:53,887
had this idea in 1935.

241
00:10:53,887 --> 00:10:57,077
But in literature and on sci-fi movies

242
00:10:57,077 --> 00:10:58,793
it is called a Wormhole.

243
00:10:58,793 --> 00:11:02,104
If you like science fiction
then you might have seen it recently,

244
00:11:02,104 --> 00:11:04,371
in the movie Interstellar.

245
00:11:04,371 --> 00:11:07,952
On the movie, they travel 
through a wormhole.

246
00:11:07,952 --> 00:11:09,782
A wormhole is like a tunnel,

247
00:11:09,782 --> 00:11:13,677
I enter here and I end up
in Alpha Centauri,

248
00:11:13,677 --> 00:11:15,589
but traveling a shorter distance,

249
00:11:15,589 --> 00:11:17,885
like a shortcut in space.

250
00:11:17,885 --> 00:11:19,018
These structures --

251
00:11:19,018 --> 00:11:22,553
here is a beautiful diagram
of a wormhole in two dimensions --

252
00:11:22,933 --> 00:11:26,101
are allowed by the Einstein's theory,

253
00:11:26,101 --> 00:11:28,905
because this theory allows these tunnels,

254
00:11:28,905 --> 00:11:30,700
one thing is that the theory allows it

255
00:11:30,700 --> 00:11:33,119
and another is having
an idea of how to do that.

256
00:11:33,119 --> 00:11:36,115
Nobody knows how to make a wormhole,

257
00:11:36,115 --> 00:11:38,760
but at least theory allows it.

258
00:11:38,760 --> 00:11:42,017
Another idea,
and I'll let you think about it,

259
00:11:42,017 --> 00:11:45,370
another idea is that it is not necessary
to make holes in space,

260
00:11:45,370 --> 00:11:48,415
an idea that thought by some guy
not so long ago,

261
00:11:48,415 --> 00:11:51,221
in 1994, this guy on the picture,

262
00:11:52,286 --> 00:11:55,289
and the idea is different;
instead of making holes in space

263
00:11:55,289 --> 00:11:57,341
let's use another property of space.

264
00:11:57,341 --> 00:12:01,748
Space can bended, twisted and expanded,

265
00:12:01,748 --> 00:12:05,208
maybe you heard about 
how universe expands,

266
00:12:05,208 --> 00:12:07,406
galaxies move away from one another

267
00:12:07,406 --> 00:12:10,649
not because they are
drifting away from a center

268
00:12:10,649 --> 00:12:12,663
where an explosion occurred, no.

269
00:12:12,952 --> 00:12:16,100
The way we understand it in physics 
is that galaxies are still,

270
00:12:16,100 --> 00:12:20,105
and what is growing bigger is space;
space is expanding.

271
00:12:20,856 --> 00:12:23,484
So I can use this idea in a small scale.

272
00:12:24,254 --> 00:12:26,784
Imagine I'm standing here and somehow

273
00:12:26,784 --> 00:12:29,229
I can expand the space behind me.

274
00:12:29,229 --> 00:12:31,292
I would start to drift away
from that wall,

275
00:12:31,292 --> 00:12:34,190
and if at the same time
I shrink the space in front of me

276
00:12:34,190 --> 00:12:36,494
I would become closer
to the wall in front of me.

277
00:12:36,494 --> 00:12:39,357
If I combine
the expansion and contraction,

278
00:12:39,357 --> 00:12:42,087
I could move from here
to that wall without moving,

279
00:12:42,087 --> 00:12:44,350
because the space made all the moving.

280
00:12:44,350 --> 00:12:47,973
This is called warp drive 
or drive through distortion

281
00:12:48,841 --> 00:12:51,570
and it's another way 
to travel faster than light,

282
00:12:51,570 --> 00:12:54,200
actually you could travel 
as fast as you wish.

283
00:12:54,200 --> 00:12:57,801
These are two ideas on how 
we could travel faster than light.

284
00:12:58,912 --> 00:13:01,333
But there is a price to pay.

285
00:13:01,333 --> 00:13:04,332
Such is life, whenever 
you find something cool

286
00:13:04,332 --> 00:13:05,721
it's too expensive.

287
00:13:05,721 --> 00:13:08,017
We have a similar case here:

288
00:13:08,615 --> 00:13:10,951
from those two ideas,

289
00:13:10,951 --> 00:13:13,554
both worm holes and warp propulsion

290
00:13:13,554 --> 00:13:16,095
require, whenever we do 
the math of something

291
00:13:16,095 --> 00:13:19,264
called negative energy, which might 
not be crystal clear for you,

292
00:13:19,264 --> 00:13:21,590
but remember what Einstein said:

293
00:13:21,590 --> 00:13:24,348
"mass and energy are equivalent",
the same thing.

294
00:13:24,348 --> 00:13:27,354
Remember nuclear reactors 
and atomic bombs,

295
00:13:27,354 --> 00:13:29,095
mass and energy are the same.

296
00:13:29,095 --> 00:13:32,574
So negative energy equals negative mass,

297
00:13:32,940 --> 00:13:36,798
and I'd never went to buy 
minus 9 pounds of tortilla.

298
00:13:38,211 --> 00:13:40,213
There are no negative masses,

299
00:13:40,213 --> 00:13:42,791
without negative masses 
there are no negative energies

300
00:13:42,791 --> 00:13:46,063
and without negative energies
none of this is possible,

301
00:13:46,063 --> 00:13:48,043
No holes in space-time,

302
00:13:48,043 --> 00:13:50,422
no warp propulsion,

303
00:13:50,422 --> 00:13:51,589
and that's a problem.

304
00:13:51,589 --> 00:13:53,846
Negative energy is not forbidden,

305
00:13:53,846 --> 00:13:56,043
physics laws don't forbid it,

306
00:13:56,043 --> 00:13:57,743
but we've never seen it.

307
00:13:57,743 --> 00:14:00,544
It's one of those things
that simply do not exist.

308
00:14:01,449 --> 00:14:04,763
So, with this initial question:

309
00:14:04,763 --> 00:14:06,705
Can we travel faster than light?

310
00:14:06,705 --> 00:14:09,830
will we someday travel the stars 
and get back in time for dinner?

311
00:14:09,830 --> 00:14:13,131
In 1905 Einstein told us 
it was not possible,

312
00:14:13,131 --> 00:14:15,497
that light speed was a limit,

313
00:14:15,497 --> 00:14:17,798
but sometimes, 
using Einstein's other theory,

314
00:14:17,798 --> 00:14:20,890
general relativity, we can cheat 
and bend the space,

315
00:14:20,890 --> 00:14:23,154
expand it, compress it, make holes on it,

316
00:14:23,154 --> 00:14:25,541
and travel faster than light,

317
00:14:25,541 --> 00:14:27,068
however, the price of it

318
00:14:27,068 --> 00:14:29,696
is finding energies or negative masses,

319
00:14:29,696 --> 00:14:31,774
though they might not exist.

320
00:14:31,774 --> 00:14:33,488
So we are a bit stuck,

321
00:14:33,488 --> 00:14:36,882
but such is science 
and that's part of my message,

322
00:14:36,882 --> 00:14:39,462
science moves forward by making questions,

323
00:14:39,462 --> 00:14:41,864
and sometimes we find answers,

324
00:14:41,864 --> 00:14:44,690
sometimes we find answers we don't like,

325
00:14:44,690 --> 00:14:48,083
that aren't what we wanted,
but universe is not how we want it.

326
00:14:48,089 --> 00:14:50,149
It is what it is and we 
sometimes find out

327
00:14:50,149 --> 00:14:53,092
that we don't have enough information,

328
00:14:53,092 --> 00:14:55,046
to answer the question,

329
00:14:55,046 --> 00:14:57,131
and that is our current situation.

330
00:14:57,131 --> 00:14:59,443
Currently, we do not have 
all the information.

331
00:14:59,443 --> 00:15:02,533
Luckily, in 20, 30 or 100 years 
someone will come

332
00:15:02,533 --> 00:15:05,570
and find the answer and tell us for once

333
00:15:05,570 --> 00:15:09,179
if we can reach the stars 
faster than light speed.

334
00:15:09,179 --> 00:15:12,016
Before I go I will ask you 
to do something,

335
00:15:12,016 --> 00:15:15,840
tonight, if clouds allow it, please go out

336
00:15:15,840 --> 00:15:17,889
and take a look of the stars

337
00:15:17,889 --> 00:15:19,831
and think, what is out there?

338
00:15:19,831 --> 00:15:20,934
Thank you so much.

339
00:15:20,934 --> 00:15:23,063
(Applause)