TED2008
Garrett Lisi: An 8-dimensional model of the universe
Filmed:
Readability: 4.7
1,952,456 views
Physicist and surfer Garrett Lisi presents a controversial new model of the universe that -- just maybe -- answers all the big questions. If nothing else, it's the most beautiful 8-dimensional model of elementary particles and forces you've ever seen.
Garrett Lisi - Physicist
Physicist Garrett Lisi has proposed a new "theory of everything" -- a grand unified theory that explains all the elementary particles, as well as gravity. Full bio
Physicist Garrett Lisi has proposed a new "theory of everything" -- a grand unified theory that explains all the elementary particles, as well as gravity. Full bio
Double-click the English transcript below to play the video.
00:21
Whoa, dude. Check out those killer equations. Sweet. (Laughter)
0
3000
7000
00:30
Actually, for the next 18 minutes I'm going to do the best I can
1
12000
4000
00:34
to describe the beauty of particle physics without equations.
2
16000
2000
00:38
It turns out there's a lot we can learn from coral.
3
20000
2000
00:41
Coral is a very beautiful and unusual animal.
4
23000
3000
00:44
Each coral head consists of thousand of individual polyps.
5
26000
3000
00:48
These polyps are continually budding and branching
6
30000
2000
00:50
into genetically identical neighbors.
7
32000
2000
00:53
If we imagine this to be a hyper-intelligent coral,
8
35000
2000
00:55
we can single out an individual and ask him a reasonable question.
9
37000
4000
00:59
We can ask how exactly he got to be in this particular location
10
41000
3000
01:02
compared to his neighbors --
11
44000
2000
01:04
if it was just chance, or destiny, or what?
12
46000
3000
01:08
Now, after admonishing us for turning the temperature up too high,
13
50000
3000
01:11
he would tell us that our question was completely stupid.
14
53000
3000
01:15
These corals can be quite kind of mean, you see,
15
57000
2000
01:17
and I have surfing scars to prove that.
16
59000
2000
01:20
But this polyp would continue and tell us
17
62000
1000
01:21
that his neighbors were quite clearly identical copies of him.
18
63000
3000
01:25
That he was in all these other locations as well,
19
67000
1000
01:27
but experiencing them as separate individuals.
20
69000
2000
01:30
For a coral, branching into different copies
21
72000
3000
01:33
is the most natural thing in the world.
22
75000
1000
01:35
Unlike us, a hyper-intelligent coral would be uniquely prepared
23
77000
4000
01:39
to understand quantum mechanics.
24
81000
1000
01:42
The mathematics of quantum mechanics very accurately
25
84000
2000
01:44
describes how our universe works.
26
86000
1000
01:46
And it tells us our reality is continually branching
27
88000
3000
01:49
into different possibilities, just like a coral.
28
91000
2000
01:53
It's a weird thing for us humans to wrap our minds around,
29
95000
2000
01:55
since we only ever get to experience one possibility.
30
97000
2000
01:58
This quantum weirdness was first described
31
100000
2000
02:00
by Erwin Schrödinger and his cat.
32
102000
2000
02:02
The cat likes this version better.
33
104000
1000
02:04
(Laughter)
34
106000
4000
02:08
In this setup, Schrödinger is in a box with a radioactive sample
35
110000
3000
02:11
that, by the laws of quantum mechanics, branches into a state
36
113000
3000
02:14
in which it is radiated and a state in which it is not.
37
116000
2000
02:18
(Laughter)
38
120000
4000
02:22
In the branch in which the sample radiates,
39
124000
1000
02:23
it sets off a trigger that releases poison and Schrödinger is dead.
40
125000
4000
02:27
But in the other branch of reality, he remains alive.
41
129000
2000
02:30
These realities are experienced separately by each individual.
42
132000
3000
02:33
As far as either can tell, the other one doesn't exist.
43
135000
2000
02:36
This seems weird to us, because each of us
44
138000
2000
02:38
only experiences an individual existence,
45
140000
2000
02:40
and we don't get to see other branches.
46
142000
1000
02:42
It's as if each of us, like Schrödinger here, are a kind of coral
47
144000
3000
02:45
branching into different possibilities.
48
147000
2000
02:49
The mathematics of quantum mechanics tells us
49
151000
2000
02:51
this is how the world works at tiny scales.
50
153000
2000
02:53
It can be summed up in a single sentence:
51
155000
2000
02:56
Everything that can happen, does.
52
158000
2000
02:58
That's quantum mechanics.
53
160000
2000
03:00
But this does not mean everything happens.
54
162000
2000
03:02
The rest of physics is about describing what can happen
55
164000
3000
03:05
and what can't.
56
167000
1000
03:07
What physics tells us is that everything comes down to geometry
57
169000
3000
03:10
and the interactions of elementary particles.
58
172000
2000
03:12
And things can happen only if these interactions
59
174000
3000
03:15
are perfectly balanced.
60
177000
1000
03:19
Now I'll go ahead and describe how we know about these particles,
61
181000
2000
03:21
what they are and how this balance works.
62
183000
3000
03:25
In this machine, a beam of protons and anti-protons
63
187000
3000
03:28
are accelerated to near the speed of light
64
190000
2000
03:30
and brought together in a collision, producing a burst of pure energy.
65
192000
3000
03:34
This energy is immediately converted into a spray
66
196000
2000
03:36
of subatomic particles,
67
198000
1000
03:38
with detectors and computers used to figure out their properties.
68
200000
2000
03:41
This enormous machine -- the large Hadron Collider
69
203000
2000
03:43
at CERN in Geneva --
70
205000
2000
03:45
has a circumference of 17 miles
71
207000
1000
03:46
and, when it's operating, draws five times as much power
72
208000
2000
03:48
as the city of Monterey.
73
210000
2000
03:51
We can't predict specifically what particles will be produced
74
213000
3000
03:54
in any individual collision.
75
216000
1000
03:56
Quantum mechanics tells us all possibilities are realized.
76
218000
2000
03:59
But physics does tell us what particles can be produced.
77
221000
3000
04:03
These particles must have just as much mass and energy
78
225000
2000
04:05
as is carried in by the proton and anti-proton.
79
227000
2000
04:09
Any particles more massive than this energy limit
80
231000
2000
04:11
aren't produced, and remain invisible to us.
81
233000
2000
04:15
This is why this new particle accelerator is so exciting.
82
237000
3000
04:18
It's going to push this energy limit seven times
83
240000
2000
04:20
beyond what's ever been done before,
84
242000
1000
04:22
so we're going to get to see some new particles very soon.
85
244000
2000
04:26
But before talking about what we might see,
86
248000
1000
04:27
let me describe the particles we already know of.
87
249000
2000
04:31
There's a whole zoo of subatomic particles.
88
253000
2000
04:33
Most of us are familiar with electrons.
89
255000
2000
04:35
A lot of people in this room make a good living
90
257000
1000
04:36
pushing them around.
91
258000
1000
04:37
(Laughter)
92
259000
3000
04:40
But the electron also has a neutral partner called the neutrino,
93
262000
2000
04:42
with no electric charge and a very tiny mass.
94
264000
3000
04:46
In contrast, the up-and-down quarks have very large masses,
95
268000
3000
04:49
and combine in threes to make the protons and neutrons
96
271000
2000
04:51
inside atoms.
97
273000
1000
04:53
All of these matter particles come in left- and right-handed varieties,
98
275000
2000
04:55
and have anti-particle partners that carry opposite charges.
99
277000
3000
05:01
These familiar particles also have less familiar
100
283000
1000
05:02
second and third generations, which have the same charges as the first
101
284000
4000
05:06
but have much higher masses.
102
288000
2000
05:10
These matter particles all interact with the various force particles.
103
292000
3000
05:13
The electromagnetic force interacts with electrically charged matter
104
295000
3000
05:16
via particles called photons.
105
298000
2000
05:18
There is also a very weak force called, rather unimaginatively,
106
300000
3000
05:21
the weak force, that interacts
107
303000
3000
05:24
only with left-handed matter.
108
306000
2000
05:27
The strong force acts between quarks which carry
109
309000
2000
05:29
a different kind of charge, called color charge,
110
311000
2000
05:31
and come in three different varieties: red, green and blue.
111
313000
3000
05:34
You can blame Murray Gell-Mann for these names --
112
316000
2000
05:36
they're his fault.
113
318000
1000
05:38
Finally, there's the force of gravity, which interacts with matter
114
320000
3000
05:41
via its mass and spin.
115
323000
2000
05:44
The most important thing to understand here
116
326000
2000
05:46
is that there's a different kind of charge associated
117
328000
2000
05:48
with each of these forces.
118
330000
1000
05:50
These four different forces interact with matter
119
332000
2000
05:52
according to the corresponding charges that each particle has.
120
334000
3000
05:57
A particle that hasn't been seen yet, but we're pretty sure exists,
121
339000
2000
05:59
is the Higgs particle, which gives masses to all these other particles.
122
341000
4000
06:04
The main purpose of the Large Hadron Collider
123
346000
1000
06:05
is to see this Higgs particle, and we're almost certain it will.
124
347000
3000
06:09
But the greatest mystery is what else we might see.
125
351000
3000
06:13
And I'm going to show you one beautiful possibility
126
355000
2000
06:15
towards the end of this talk.
127
357000
1000
06:19
Now, if we count up all these different particles
128
361000
1000
06:20
using their various spins and charges, there are 226.
129
362000
4000
06:25
That's a lot of particles to keep track of.
130
367000
1000
06:27
And it seems strange that nature would have
131
369000
2000
06:29
so many elementary particles.
132
371000
2000
06:32
But if we plot them out according to their charges,
133
374000
2000
06:34
some beautiful patterns emerge.
134
376000
2000
06:38
The most familiar charge is electric charge.
135
380000
2000
06:41
Electrons have an electric charge, a negative one,
136
383000
2000
06:43
and quarks have electric charges in thirds.
137
385000
2000
06:45
So when two up quarks and a down quark are combined
138
387000
2000
06:47
to make a proton, it has a total electric charge of plus one.
139
389000
3000
06:51
These particles also have anti-particles, which have opposite charges.
140
393000
3000
06:55
Now, it turns out the electric charge is actually
141
397000
1000
06:56
a combination of two other charges:
142
398000
3000
06:59
hypercharge and weak charge.
143
401000
2000
07:02
If we spread out the hypercharge and weak charge
144
404000
1000
07:03
and plot the charges of particles in this two-dimensional charge space,
145
405000
5000
07:08
the electric charge is where these particles sit
146
410000
2000
07:10
along the vertical direction.
147
412000
2000
07:13
The electromagnetic and weak forces interact with matter
148
415000
2000
07:15
according to their hypercharge and weak charge,
149
417000
2000
07:17
which make this pattern.
150
419000
1000
07:19
This is called the Unified Electroweak Model,
151
421000
1000
07:20
and it was put together back in 1967.
152
422000
3000
07:24
The reason most of us are only familiar with electric charge
153
426000
2000
07:26
and not both of these is because of the Higgs particle.
154
428000
3000
07:30
The Higgs, over here on the left, has a large mass
155
432000
3000
07:33
and breaks the symmetry of this electroweak pattern.
156
435000
2000
07:36
It makes the weak force very weak
157
438000
1000
07:37
by giving the weak particles a large mass.
158
439000
2000
07:39
Since this massive Higgs sits along the horizontal direction
159
441000
3000
07:42
in this diagram, the photons of electromagnetism remain massless
160
444000
4000
07:46
and interact with electric charge along the vertical direction
161
448000
2000
07:48
in this charge space.
162
450000
1000
07:52
So the electromagnetic and weak forces are described
163
454000
2000
07:54
by this pattern of particle charges in two-dimensional space.
164
456000
3000
07:58
We can include the strong force by spreading out
165
460000
2000
08:00
its two charge directions and plotting the charges
166
462000
3000
08:03
of the force particles in quarks along these directions.
167
465000
3000
08:07
The charges of all known particles can be plotted
168
469000
2000
08:09
in a four-dimensional charge space, and projected down
169
471000
3000
08:12
to two dimensions like this so we can see them.
170
474000
2000
08:15
Whenever particles interact, nature keeps things in a perfect balance
171
477000
3000
08:18
along all four of these charge directions.
172
480000
2000
08:21
If a particle and an anti-particle collide, it creates a burst of energy
173
483000
3000
08:24
and a total charge of zero in all four charge directions.
174
486000
3000
08:28
At this point, anything can be created as long as it has
175
490000
3000
08:31
the same energy and maintains a total charge of zero.
176
493000
2000
08:34
For example, this weak force particle and its anti-particle
177
496000
3000
08:37
can be created in a collision.
178
499000
2000
08:39
In further interactions, the charges must always balance.
179
501000
3000
08:42
One of the weak particles could decay into an electron
180
504000
3000
08:45
and an anti-neutrino,
181
507000
2000
08:47
and these three still add to zero total charge.
182
509000
3000
08:50
Nature always keeps a perfect balance.
183
512000
2000
08:53
So these patterns of charges are not just pretty.
184
515000
2000
08:55
They tell us what interactions are allowed to happen.
185
517000
3000
08:58
And we can rotate this charge space in four dimensions
186
520000
3000
09:01
to get a better look at the strong interaction,
187
523000
2000
09:03
which has this nice hexagonal symmetry.
188
525000
2000
09:06
In a strong interaction, a strong force particle, such as this one,
189
528000
4000
09:10
interacts with a colored quark, such as this green one,
190
532000
3000
09:13
to give a quark with a different color charge -- this red one.
191
535000
4000
09:18
And strong interactions are happening millions of times
192
540000
2000
09:20
each second in every atom of our bodies,
193
542000
3000
09:23
holding the atomic nuclei together.
194
545000
2000
09:27
But these four charges corresponding to three forces
195
549000
3000
09:30
are not the end of the story.
196
552000
1000
09:32
We can also include two more charges
197
554000
1000
09:33
corresponding to the gravitational force.
198
555000
2000
09:35
When we include these, each matter particle
199
557000
3000
09:38
has two different spin charges, spin-up and spin-down.
200
560000
3000
09:42
So they all split, and give a nice pattern
201
564000
2000
09:44
in six-dimensional charge space.
202
566000
2000
09:46
We can rotate this pattern in six dimensions,
203
568000
2000
09:48
and see that it's quite pretty.
204
570000
2000
09:53
Right now, this pattern matches our best current knowledge
205
575000
4000
09:57
of how nature is built at the tiny scales
206
579000
2000
09:59
of these elementary particles.
207
581000
1000
10:01
This is what we know for certain.
208
583000
2000
10:03
Some of these particles are at the very limit
209
585000
1000
10:04
of what we've been able to reach with experiments.
210
586000
2000
10:07
From this pattern, we already know the particle physics
211
589000
3000
10:10
of these tiny scales. The way the universe works
212
592000
3000
10:13
with these tiny scales is very beautiful.
213
595000
3000
10:17
But now I'm going to discuss some new and old ideas
214
599000
2000
10:19
about things we don't know yet.
215
601000
1000
10:22
We want to expand this pattern using mathematics alone,
216
604000
2000
10:24
and see if we can get our hands on the whole enchilada.
217
606000
3000
10:27
We want to find all the particles and forces
218
609000
2000
10:29
that make a complete picture of our universe.
219
611000
2000
10:32
And we want to use this picture to predict new particles
220
614000
2000
10:34
that we'll see when experiments reach higher energies.
221
616000
2000
10:39
So there's an old idea in particle physics
222
621000
2000
10:41
that this known pattern of charges, which is not very symmetric,
223
623000
4000
10:45
could emerge from a more perfect pattern that gets broken --
224
627000
3000
10:49
similar to how the Higgs particle breaks the electroweak pattern
225
631000
2000
10:51
to give electromagnetism.
226
633000
1000
10:53
In order to do this, we need to introduce new forces
227
635000
3000
10:56
with new charge directions.
228
638000
2000
11:00
When we introduce a new direction, we get to guess
229
642000
2000
11:02
what charges the particles have along this direction,
230
644000
3000
11:05
and then we can rotate it in with the others.
231
647000
1000
11:08
If we guess wisely, we can construct the standard charges
232
650000
3000
11:11
in six charge dimensions as a broken symmetry
233
653000
3000
11:14
of this more perfect pattern in seven charge dimensions.
234
656000
3000
11:18
This particular choice corresponds to a grand unified theory
235
660000
3000
11:21
introduced by Pati and Salam in 1973.
236
663000
3000
11:24
When we look at this new unified pattern,
237
666000
3000
11:27
we can see a couple of gaps where particles seem to be missing.
238
669000
3000
11:31
This is the way theories of unification work.
239
673000
2000
11:34
A physicist looks for larger, more symmetric patterns
240
676000
2000
11:36
that include the established pattern as a subset.
241
678000
3000
11:40
The larger pattern allows us to predict the existence
242
682000
2000
11:42
of particles that have never been seen.
243
684000
2000
11:45
This unification model predicts the existence of these two
244
687000
3000
11:48
new force particles, which should act a lot like the weak force,
245
690000
4000
11:52
only weaker.
246
694000
1000
11:54
Now we can rotate this set of charges in seven dimensions
247
696000
2000
11:56
and consider an odd fact about the matter particles:
248
698000
3000
11:59
the second and third generations of matter
249
701000
3000
12:02
have exactly the same charges in six-dimensional charge space
250
704000
3000
12:05
as the first generation.
251
707000
2000
12:08
These particles are not uniquely identified by their six charges.
252
710000
2000
12:12
They sit on top of one another in the standard charge space.
253
714000
2000
12:16
However, if we work in eight-dimensional charge space,
254
718000
3000
12:19
then we can assign unique new charges to each particle.
255
721000
4000
12:23
Then we can spin these in eight dimensions,
256
725000
3000
12:26
and see what the whole pattern looks like.
257
728000
2000
12:30
Here we can see the second and third generations of matter now
258
732000
2000
12:32
related to the first generation by a symmetry called "triality."
259
734000
4000
12:38
This particular pattern of charges in eight dimensions is actually
260
740000
3000
12:41
part of the most beautiful geometric structure in mathematics.
261
743000
3000
12:46
It's a pattern of the largest exceptional Lie group, E8.
262
748000
3000
12:50
This Lie group is a smooth, curved shape with 248 dimensions.
263
752000
3000
12:54
Each point in this pattern corresponds to a symmetry
264
756000
3000
12:57
of this very complex and beautiful shape.
265
759000
2000
13:00
One small part of this E8 shape can be used
266
762000
2000
13:02
to describe the curved space-time of Einstein's general relativity,
267
764000
3000
13:05
explaining gravity.
268
767000
1000
13:07
Together with quantum mechanics, the geometry of this shape
269
769000
3000
13:10
could describe everything about how the universe works
270
772000
2000
13:12
at the tiniest scales.
271
774000
2000
13:14
The pattern of this shape living in eight-dimensional charge space
272
776000
3000
13:17
is exquisitely beautiful,
273
779000
3000
13:21
and it summarizes thousands of possible interactions
274
783000
2000
13:23
between these elementary particles, each of which
275
785000
2000
13:25
is just a facet of this complicated shape.
276
787000
2000
13:30
As we spin it, we can see many of the other intricate patterns
277
792000
2000
13:32
contained in this one.
278
794000
1000
13:36
And with a particular rotation, we can look down through this pattern
279
798000
2000
13:38
in eight dimensions along a symmetry axis
280
800000
3000
13:41
and see all the particles at once.
281
803000
2000
13:44
It's a very beautiful object, and as with any unification,
282
806000
3000
13:47
we can see some holes where new particles are required
283
809000
2000
13:49
by this pattern.
284
811000
2000
13:52
There are 20 gaps where new particles should be,
285
814000
2000
13:55
two of which have been filled by the Pati-Salam particles.
286
817000
2000
13:58
From their location in this pattern, we know that these new particles
287
820000
2000
14:00
should be scalar fields like the Higgs particle,
288
822000
3000
14:03
but have color charge and interact with the strong force.
289
825000
2000
14:06
Filling in these new particles completes this pattern,
290
828000
2000
14:08
giving us the full E8.
291
830000
2000
14:10
This E8 pattern has very deep mathematical roots.
292
832000
3000
14:13
It's considered by many to be the most beautiful structure
293
835000
3000
14:16
in mathematics.
294
838000
1000
14:17
It's a fantastic prospect that this object of great
295
839000
3000
14:20
mathematical beauty could describe the truth of particle interactions
296
842000
3000
14:23
at the smallest scales imaginable.
297
845000
2000
14:25
And this idea that nature is described by mathematics
298
847000
5000
14:30
is not at all new.
299
852000
2000
14:32
In 1623, Galileo wrote this:
300
854000
2000
14:36
"Nature's grand book, which stands continually open to our gaze,
301
858000
3000
14:39
is written in the language of mathematics.
302
861000
2000
14:42
Its characters are triangles, circles and other geometrical figures,
303
864000
3000
14:45
without which it is humanly impossible to understand
304
867000
2000
14:47
a single word of it;
305
869000
1000
14:49
without these, one is wandering around in a dark labyrinth."
306
871000
3000
14:54
I believe this to be true, and I've tried
307
876000
2000
14:56
to follow Galileo's guidance in describing the mathematics
308
878000
2000
14:58
of particle physics using only triangles, circles
309
880000
3000
15:01
and other geometrical figures.
310
883000
1000
15:03
Of course, when other physicists and I actually work on this stuff,
311
885000
3000
15:06
the mathematics can resemble a dark labyrinth.
312
888000
3000
15:11
But it's reassuring that at the heart of this mathematics
313
893000
3000
15:14
is pure, beautiful geometry.
314
896000
2000
15:18
Joined with quantum mechanics, this mathematics
315
900000
2000
15:20
describes our universe as a growing E8 coral,
316
902000
2000
15:22
with particles interacting at every location in all possible ways
317
904000
4000
15:26
according to a beautiful pattern.
318
908000
2000
15:30
And as more of the pattern comes into view using new machines
319
912000
2000
15:32
like the Large Hadron Collider, we may be able to see
320
914000
3000
15:35
whether nature uses this E8 pattern or a different one.
321
917000
4000
15:40
This process of discovery is a wonderful adventure to be involved in.
322
922000
3000
15:44
If the LHC finds particles that fit this E8 pattern,
323
926000
3000
15:47
that will be very, very cool.
324
929000
2000
15:50
If the LHC finds new particles, but they don't fit this pattern --
325
932000
3000
15:53
well, that will be very interesting, but bad for this E8 theory.
326
935000
4000
15:58
And, of course, bad for me personally.
327
940000
2000
16:00
(Laughter)
328
942000
3000
16:03
Now how bad would that be?
329
945000
1000
16:04
Well, pretty bad.
330
946000
2000
16:06
(Laughter)
331
948000
4000
16:10
But predicting how nature works is a very risky game.
332
952000
2000
16:13
This theory and others like it are long shots.
333
955000
3000
16:17
One does a lot of hard work knowing that most of these ideas
334
959000
3000
16:20
probably won't end up being true about nature.
335
962000
1000
16:22
That's what doing theoretical physics is like:
336
964000
1000
16:24
there are a lot of wipeouts.
337
966000
1000
16:26
In this regard, new physics theories are a lot like start-up companies.
338
968000
3000
16:32
As with any large investment, it can be emotionally difficult
339
974000
2000
16:34
to abandon a line of research when it isn't working out.
340
976000
2000
16:37
But in science, if something isn't working, you have to
341
979000
2000
16:39
toss it out and try something else.
342
981000
1000
16:42
Now, the only way to maintain sanity and achieve happiness
343
984000
3000
16:45
in the midst of this uncertainty is to keep balance
344
987000
2000
16:47
and perspective in life.
345
989000
2000
16:51
I've tried the best I can to live a balanced life.
346
993000
2000
16:53
(Laughter)
347
995000
3000
16:56
I try to balance my life equally between physics, love and surfing --
348
998000
3000
16:59
my own three charge directions.
349
1001000
2000
17:01
(Laughter)
350
1003000
2000
17:03
This way, even if the physics I work on comes to nothing,
351
1005000
2000
17:05
I still know I've lived a good life.
352
1007000
2000
17:08
And I try to live in beautiful places.
353
1010000
2000
17:10
For most of the past ten years I've lived on the island of Maui,
354
1012000
3000
17:13
a very beautiful place.
355
1015000
2000
17:15
Now it's one of the greatest mysteries in the universe to my parents
356
1017000
3000
17:18
how I managed to survive all that time without engaging
357
1020000
3000
17:21
in anything resembling full-time employment.
358
1023000
2000
17:23
(Laughter)
359
1025000
4000
17:27
I'm going to let you in on that secret.
360
1029000
1000
17:31
This was a view from my home office on Maui.
361
1033000
1000
17:35
And this is another, and another.
362
1037000
4000
17:39
And you may have noticed that these beautiful views
363
1041000
2000
17:41
are similar, but in slightly different places.
364
1043000
2000
17:45
That's because this used to be my home and office on Maui.
365
1047000
3000
17:48
(Laughter)
366
1050000
2000
17:50
I've chosen a very unusual life.
367
1052000
2000
17:53
But not worrying about rent allowed me to spend my time
368
1055000
2000
17:55
doing what I love.
369
1057000
1000
17:57
Living a nomadic existence has been hard at times,
370
1059000
2000
17:59
but it's allowed me to live in beautiful places
371
1061000
2000
18:01
and keep a balance in my life that I've been happy with.
372
1063000
3000
18:05
It allows me to spend a lot of my time hanging out
373
1067000
2000
18:07
with hyper-intelligent coral.
374
1069000
2000
18:11
But I also greatly enjoy the company of hyper-intelligent people.
375
1073000
2000
18:14
So I'm very happy to have been invited here to TED.
376
1076000
2000
18:17
Thank you very much.
377
1079000
1000
18:18
(Applause)
378
1080000
13000
18:31
Chris Anderson: I probably understood two percent of that,
379
1093000
1000
18:32
but I still absolutely loved it. So I'm going to sound dumb.
380
1094000
6000
18:38
Your theory of everything --
381
1100000
3000
18:41
Garrett Lisi: I'm used to coral.
382
1103000
1000
18:42
CA: That's right. The reason it's got a few people
383
1104000
2000
18:44
at least excited is because, if you're right, it brings
384
1106000
3000
18:47
gravity and quantum theory together.
385
1109000
2000
18:50
So are you saying that we should think of the universe,
386
1112000
3000
18:53
at its heart -- that the smallest things that there are,
387
1115000
3000
18:56
are somehow an E8 object of possibility?
388
1118000
7000
19:03
I mean, is there a scale to it, at the smallest scale,
389
1125000
2000
19:05
or ...?
390
1127000
1000
19:06
GL: Well, right now the pattern I showed you that corresponds
391
1128000
3000
19:09
to what we know about elementary particle physics --
392
1131000
4000
19:13
that already corresponds to a very beautiful shape.
393
1135000
3000
19:16
And that's the one that I said we knew for certain.
394
1138000
1000
19:18
And that shape has remarkable similarities -- and the way it fits
395
1140000
4000
19:22
into this E8 pattern could be the rest of the picture.
396
1144000
3000
19:26
And these patterns of points that I've shown for you
397
1148000
3000
19:29
actually represent symmetries of this high-dimensional object
398
1151000
4000
19:33
that would be warping and moving and dancing
399
1155000
3000
19:36
over the space time that we experience.
400
1158000
2000
19:39
And that would be what explains all these
401
1161000
2000
19:41
elementary particles that we see.
402
1163000
1000
19:42
CA: But a string theorist,
403
1164000
3000
19:45
as I understand it, explains electrons in terms of much smaller
404
1167000
2000
19:47
strings vibrating --
405
1169000
1000
19:48
I know you don't like string theory -- vibrating inside it.
406
1170000
2000
19:51
How should we think of an electron in relation to E8?
407
1173000
5000
19:57
GL: No, it would be one of the symmetries of this E8 shape.
408
1179000
3000
20:01
So what's happening is, as the shape is moving over space-time,
409
1183000
4000
20:05
it's twisting. And the direction it's twisting as it moves
410
1187000
4000
20:09
is what particle we see. So it would be --
411
1191000
2000
20:11
CA: The size of the E8 shape,
412
1193000
2000
20:13
how does that relate to the electron?
413
1195000
1000
20:14
I kind of feel like I need that for my picture.
414
1196000
2000
20:16
Is it bigger? Is it smaller?
415
1198000
1000
20:17
GL: Well, as far as we know electrons are point particles,
416
1199000
2000
20:20
so this would be going down to the smallest possible scales.
417
1202000
3000
20:24
So the way these things are explained in quantum field theory
418
1206000
2000
20:26
is, all possibilities are expanding and developing at once.
419
1208000
4000
20:30
And this is why I use the analogy to coral.
420
1212000
2000
20:33
And in this way, the way that E8 comes in is
421
1215000
7000
20:40
it will be as a shape that's attached at each point in space-time.
422
1222000
4000
20:45
And, as I said, the way the shape twists --
423
1227000
4000
20:49
the directional along which way the shape is twisting
424
1231000
2000
20:51
as it moves over this curved surface --
425
1233000
1000
20:52
is what the elementary particles are, themselves.
426
1234000
4000
20:56
So through quantum field theory, they manifest themselves
427
1238000
4000
21:00
as points and interact that way.
428
1242000
1000
21:02
I don't know if I'll be able to make this any clearer.
429
1244000
2000
21:04
(Laughter)
430
1246000
4000
21:08
CA: It doesn't really matter.
431
1250000
1000
21:09
It's evoking a kind of sense of wonder, and I certainly
432
1251000
4000
21:13
want to understand more of this.
433
1255000
3000
21:16
But thank you so much for coming. That was absolutely fascinating.
434
1258000
2000
21:18
(Applause)
435
1260000
3000
ABOUT THE SPEAKER
Garrett Lisi - PhysicistPhysicist Garrett Lisi has proposed a new "theory of everything" -- a grand unified theory that explains all the elementary particles, as well as gravity.
Why you should listen
Working from principles of differential geometry, physicist Garrett Lisi is developing a new unified theory that purports to explain all the elementary particles, and gravity, in one elegant model. His theory is based on a mathematical shape called E8. With 248 symmetries, E8 is large, complex and beautiful -- and Lisi believes the relationships of its symmetries correspond to known particles and forces, including gravity.
His work, explained in his paper "An Exceptionally Simple Theory of Everything," and in an ongoing discussion on FQXi, is still on science's speculative fringe. But some physicists believe he could be pointing the way toward a truly unified theory.
Garrett Lisi | Speaker | TED.com