ABOUT THE SPEAKER
Gian Giudice - Theoretical physicist
Gian Giudice is a theoretical physicist who has contributed greatly to our present understanding of particle physics and cosmology.

Why you should listen

Gian Giudice is a permanent member of CERN's group for theoretical physics. He has researched topics like supersymmetry, extra dimensions and dark matter, and has formulated theories that describe the earliest stages of the universe and that apply our knowledge of the particle world to smaller distances.

As author of the popular book, A Zeptospace Odyssey, Giudice is active in communicating the complex work of the Large Hadron Collider to the public. Meant for the lay reader, the book shares both the innovations needed to build the LHC and the theories it was created to prove. After the Higgs boson discovery, Giudice found the surprising result that, if the Standard Model continues to hold up at very small distances, the universe must be in a critical state, near to a phase transition that could lead to the collapse of all atomic matter. Luckily, in his TED Talk, he shares that this would happen very, very, very far in the future.

More profile about the speaker
Gian Giudice | Speaker | TED.com
TEDxCERN

Gian Giudice: Why our universe might exist on a knife-edge

Filmed:
2,152,454 views

The biggest surprise of discovering the Higgs boson? That there were no surprises. Gian Giudice talks us through a problem in theoretical physics: what if the Higgs field exists in an ultra-dense state that could mean the collapse of all atomic matter? With wit and charm, Giudice outlines a grim fate -- and why we shouldn't start worrying just yet.
- Theoretical physicist
Gian Giudice is a theoretical physicist who has contributed greatly to our present understanding of particle physics and cosmology. Full bio

Double-click the English transcript below to play the video.

00:13
So last year, on the Fourth of July,
0
1179
2344
00:15
experiments at the Large Hadron Collider
1
3523
2499
00:18
discovered the Higgs boson.
2
6022
2290
00:20
It was a historical day.
3
8312
1968
00:22
There's no doubt that from now on,
4
10280
2295
00:24
the Fourth of July will be remembered
5
12575
1834
00:26
not as the day of the Declaration of Independence,
6
14409
2442
00:28
but as the day of the discovery of the Higgs boson.
7
16851
3834
00:32
Well, at least, here at CERN.
8
20685
2432
00:35
But for me, the biggest surprise of that day
9
23117
4155
00:39
was that there was no big surprise.
10
27272
2499
00:41
In the eye of a theoretical physicist,
11
29771
2599
00:44
the Higgs boson is a clever explanation
12
32370
1893
00:46
of how some elementary particles gain mass,
13
34263
3523
00:49
but it seems a fairly unsatisfactory
14
37786
2836
00:52
and incomplete solution.
15
40622
2206
00:54
Too many questions are left unanswered.
16
42828
3024
00:57
The Higgs boson does not share the beauty,
17
45852
2835
01:00
the symmetry, the elegance,
18
48687
1885
01:02
of the rest of the elementary particle world.
19
50572
2728
01:05
For this reason, the majority of theoretical physicists
20
53300
3622
01:08
believe that the Higgs boson could not
21
56922
2942
01:11
be the full story.
22
59864
2482
01:14
We were expecting new particles and new phenomena
23
62346
2854
01:17
accompanying the Higgs boson.
24
65200
2450
01:19
Instead, so far, the measurements
25
67650
2318
01:21
coming from the LHC show no signs of new particles
26
69968
3758
01:25
or unexpected phenomena.
27
73726
2149
01:27
Of course, the verdict is not definitive.
28
75875
3653
01:31
In 2015, the LHC will almost double
29
79528
3994
01:35
the energy of the colliding protons,
30
83522
2691
01:38
and these more powerful collisions
31
86213
2071
01:40
will allow us to explore further the particle world,
32
88284
4584
01:44
and we will certainly learn much more.
33
92868
3132
01:48
But for the moment, since we have found
34
96000
3146
01:51
no evidence for new phenomena, let us suppose
35
99146
3149
01:54
that the particles that we know today,
36
102295
3164
01:57
including the Higgs boson,
37
105459
1856
01:59
are the only elementary particles in nature,
38
107315
3285
02:02
even at energies much larger
39
110600
2744
02:05
than what we have explored so far.
40
113344
2766
02:08
Let's see where this hypothesis is going to lead us.
41
116110
4632
02:12
We will find a surprising and intriguing result
42
120742
3432
02:16
about our universe, and to explain my point,
43
124174
3799
02:19
let me first tell you what the Higgs is about,
44
127973
3876
02:23
and to do so, we have to go back
45
131849
3134
02:26
to one tenth of a billionth of a second
46
134983
4357
02:31
after the Big Bang.
47
139340
1531
02:32
And according to the Higgs theory,
48
140871
2041
02:34
at that instant, a dramatic event took place
49
142912
3366
02:38
in the universe.
50
146278
1591
02:39
Space-time underwent a phase transition.
51
147869
4791
02:44
It was something very similar to the phase transition
52
152660
3077
02:47
that occurs when water turns into ice
53
155737
3545
02:51
below zero degrees.
54
159282
1961
02:53
But in our case, the phase transition
55
161243
2940
02:56
is not a change in the way the molecules
56
164183
2531
02:58
are arranged inside the material,
57
166714
2286
03:01
but is about a change
58
169000
1888
03:02
of the very fabric of space-time.
59
170888
3626
03:06
During this phase transition, empty space
60
174514
2626
03:09
became filled with a substance
61
177140
2672
03:11
that we now call Higgs field.
62
179812
3032
03:14
And this substance may seem invisible to us,
63
182844
2329
03:17
but it has a physical reality.
64
185173
2678
03:19
It surrounds us all the time,
65
187851
2058
03:21
just like the air we breathe in this room.
66
189909
3701
03:25
And some elementary particles interact
67
193610
2318
03:27
with this substance, gaining energy in the process.
68
195928
3828
03:31
And this intrinsic energy is what we call
69
199756
3075
03:34
the mass of a particle,
70
202831
2133
03:36
and by discovering the Higgs boson, the LHC
71
204964
3253
03:40
has conclusively proved that this substance is real,
72
208217
4532
03:44
because it is the stuff the Higgs bosons are made of.
73
212749
3919
03:48
And this, in a nutshell, is the essence of the Higgs story.
74
216668
3444
03:52
But this story is far more interesting than that.
75
220112
4743
03:56
By studying the Higgs theory,
76
224855
2311
03:59
theoretical physicists discovered,
77
227166
2360
04:01
not through an experiment
78
229526
1904
04:03
but with the power of mathematics,
79
231430
2476
04:05
that the Higgs field does not necessarily exist
80
233906
3712
04:09
only in the form that we observe today.
81
237618
3337
04:12
Just like matter can exist as liquid or solid,
82
240955
5045
04:18
so the Higgs field, the substance that fills all space-time,
83
246000
4572
04:22
could exist in two states.
84
250572
3354
04:25
Besides the known Higgs state,
85
253926
2310
04:28
there could be a second state in which the Higgs field
86
256236
3147
04:31
is billions and billions times denser
87
259383
3536
04:34
than what we observe today,
88
262919
2045
04:36
and the mere existence of another state
89
264964
3487
04:40
of the Higgs field poses a potential problem.
90
268451
4245
04:44
This is because, according to the laws
91
272696
3238
04:47
of quantum mechanics, it is possible
92
275934
2693
04:50
to have transitions between two states,
93
278627
2832
04:53
even in the presence of an energy barrier
94
281459
2949
04:56
separating the two states,
95
284408
2628
04:59
and the phenomenon is called,
96
287036
2209
05:01
quite appropriately, quantum tunneling.
97
289245
4142
05:05
Because of quantum tunneling,
98
293387
1891
05:07
I could disappear from this room
99
295278
2533
05:09
and reappear in the next room,
100
297811
3322
05:13
practically penetrating the wall.
101
301133
3395
05:16
But don't expect me to actually perform the trick
102
304528
2815
05:19
in front of your eyes, because the probability
103
307343
2578
05:21
for me to penetrate the wall is ridiculously small.
104
309921
4388
05:26
You would have to wait a really long time
105
314309
2598
05:28
before it happens, but believe me,
106
316907
2132
05:31
quantum tunneling is a real phenomenon,
107
319039
3177
05:34
and it has been observed in many systems.
108
322216
3195
05:37
For instance, the tunnel diode,
109
325411
2562
05:39
a component used in electronics,
110
327973
2197
05:42
works thanks to the wonders
111
330170
2422
05:44
of quantum tunneling.
112
332592
2320
05:46
But let's go back to the Higgs field.
113
334912
2292
05:49
If the ultra-dense Higgs state existed,
114
337204
4563
05:53
then, because of quantum tunneling,
115
341767
2354
05:56
a bubble of this state could suddenly appear
116
344121
3713
05:59
in a certain place of the universe at a certain time,
117
347834
3242
06:03
and it is analogous to what happens when you boil water.
118
351076
3765
06:06
Bubbles of vapor form inside the water,
119
354841
3089
06:09
then they expand, turning liquid into gas.
120
357930
3856
06:13
In the same way, a bubble of the ultra-dense Higgs state
121
361786
4804
06:18
could come into existence because of quantum tunneling.
122
366590
3427
06:22
The bubble would then expand at the speed of light,
123
370017
2837
06:24
invading all space, and turning the Higgs field
124
372854
3486
06:28
from the familiar state into a new state.
125
376340
3649
06:31
Is this a problem? Yes, it's a big a problem.
126
379989
4161
06:36
We may not realize it in ordinary life,
127
384150
2745
06:38
but the intensity of the Higgs field is critical
128
386895
3205
06:42
for the structure of matter.
129
390100
2645
06:44
If the Higgs field were only a few times more intense,
130
392745
4073
06:48
we would see atoms shrinking, neutrons decaying
131
396818
2944
06:51
inside atomic nuclei, nuclei disintegrating,
132
399762
3686
06:55
and hydrogen would be
133
403448
2340
06:57
the only possible chemical element in the universe.
134
405788
4352
07:02
And the Higgs field, in the ultra-dense Higgs state,
135
410140
3011
07:05
is not just a few times more intense than today,
136
413151
3814
07:08
but billions of times,
137
416965
2195
07:11
and if space-time were filled by this Higgs state,
138
419160
3202
07:14
all atomic matter would collapse.
139
422362
3153
07:17
No molecular structures would be possible, no life.
140
425515
4490
07:22
So, I wonder, is it possible
141
430005
3338
07:25
that in the future, the Higgs field
142
433343
2586
07:27
will undergo a phase transition and,
143
435929
2565
07:30
through quantum tunneling, will be transformed
144
438494
3129
07:33
into this nasty, ultra-dense state?
145
441623
4687
07:38
In other words, I ask myself, what is the fate
146
446310
3525
07:41
of the Higgs field in our universe?
147
449835
3083
07:44
And the crucial ingredient necessary
148
452918
2251
07:47
to answer this question is the Higgs boson mass.
149
455169
4386
07:51
And experiments at the LHC found that the mass
150
459555
4111
07:55
of the Higgs boson is about 126 GeV.
151
463666
4274
07:59
This is tiny when expressed in familiar units,
152
467940
3036
08:02
because it's equal to something like
153
470976
1320
08:04
10 to the minus 22 grams,
154
472296
2207
08:06
but it is large in particle physics units,
155
474503
3970
08:10
because it is equal to the weight
156
478473
2104
08:12
of an entire molecule
157
480577
2246
08:14
of a DNA constituent.
158
482823
2420
08:17
So armed with this information from the LHC,
159
485243
3387
08:20
together with some colleagues here at CERN,
160
488630
1944
08:22
we computed the probability
161
490574
1909
08:24
that our universe could quantum tunnel
162
492483
3015
08:27
into the ultra-dense Higgs state,
163
495498
3118
08:30
and we found a very intriguing result.
164
498616
3677
08:34
Our calculations showed
165
502293
2149
08:36
that the measured value of the Higgs boson mass
166
504442
3172
08:39
is very special.
167
507614
1845
08:41
It has just the right value
168
509459
2919
08:44
to keep the universe hanging
169
512378
2693
08:47
in an unstable situation.
170
515071
2570
08:49
The Higgs field is in a wobbly configuration
171
517641
3256
08:52
that has lasted so far
172
520897
2049
08:54
but that will eventually collapse.
173
522946
3045
08:57
So according to these calculations,
174
525991
3179
09:01
we are like campers
175
529170
2030
09:03
who accidentally set their tent
176
531200
2452
09:05
at the edge of a cliff.
177
533652
1794
09:07
And eventually, the Higgs field
178
535446
1790
09:09
will undergo a phase transition
179
537236
1936
09:11
and matter will collapse into itself.
180
539172
3044
09:14
So is this how humanity is going to disappear?
181
542216
3444
09:17
I don't think so.
182
545660
1755
09:19
Our calculation shows that quantum tunneling
183
547415
3353
09:22
of the Higgs field is not likely to occur
184
550768
3656
09:26
in the next 10 to the 100 years,
185
554424
3504
09:29
and this is a very long time.
186
557928
3042
09:32
It's even longer than
187
560970
1768
09:34
the time it takes for Italy to form a stable government.
188
562738
3669
09:38
(Laughter)
189
566407
2407
09:40
Even so, we will be long gone by then.
190
568814
3791
09:44
In about five billion years,
191
572605
2608
09:47
our sun will become a red giant,
192
575213
2457
09:49
as large as the Earth's orbit,
193
577670
2513
09:52
and our Earth will be kaput,
194
580183
3277
09:55
and in a thousand billion years,
195
583460
2357
09:57
if dark energy keeps on fueling
196
585817
2286
10:00
space expansion at the present rate,
197
588103
2835
10:02
you will not even be able to see as far as your toes,
198
590938
4177
10:07
because everything around you
199
595115
1697
10:08
expands at a rate faster than the speed of light.
200
596812
3701
10:12
So it is really unlikely
201
600513
1985
10:14
that we will be around to see the Higgs field collapse.
202
602498
3870
10:18
But the reason why I am interested
203
606368
3579
10:21
in the transition of the Higgs field
204
609947
2012
10:23
is because I want to address the question,
205
611959
3285
10:27
why is the Higgs boson mass so special?
206
615244
4965
10:32
Why is it just right to keep the universe
207
620209
2974
10:35
at the edge of a phase transition?
208
623183
3490
10:38
Theoretical physicists always ask "why" questions.
209
626673
3862
10:42
More than how a phenomenon works,
210
630535
2675
10:45
theoretical physicists are always interested in
211
633210
2472
10:47
why a phenomenon works in the way it works.
212
635682
3232
10:50
We think that this these "why" questions
213
638914
3362
10:54
can give us clues
214
642276
1723
10:55
about the fundamental principles of nature.
215
643999
3538
10:59
And indeed, a possible answer to my question
216
647537
3905
11:03
opens up new universes, literally.
217
651442
4364
11:07
It has been speculated that our universe
218
655806
3441
11:11
is only a bubble in a soapy multiverse
219
659247
4133
11:15
made out of a multitude of bubbles,
220
663380
2563
11:17
and each bubble is a different universe
221
665943
2216
11:20
with different fundamental constants
222
668159
1894
11:22
and different physical laws.
223
670053
1865
11:23
And in this context, you can only talk about
224
671918
2006
11:25
the probability of finding a certain value of the Higgs mass.
225
673924
4711
11:30
Then the key to the mystery
226
678635
2343
11:32
could lie in the statistical properties
227
680978
3263
11:36
of the multiverse.
228
684241
2228
11:38
It would be something like what happens
229
686469
2414
11:40
with sand dunes on a beach.
230
688883
2237
11:43
In principle, you could imagine to find sand dunes
231
691120
2872
11:45
of any slope angle in a beach,
232
693992
2430
11:48
and yet, the slope angles of sand dunes
233
696422
4161
11:52
are typically around 30, 35 degrees.
234
700583
3470
11:56
And the reason is simple:
235
704053
1668
11:57
because wind builds up the sand, gravity makes it fall.
236
705721
3678
12:01
As a result, the vast majority of sand dunes
237
709399
2884
12:04
have slope angles around the critical value,
238
712283
3919
12:08
near to collapse.
239
716202
1984
12:10
And something similar could happen
240
718186
2997
12:13
for the Higgs boson mass in the multiverse.
241
721183
4537
12:17
In the majority of bubble universes,
242
725720
2872
12:20
the Higgs mass could be around the critical value,
243
728592
3057
12:23
near to a cosmic collapse of the Higgs field,
244
731649
3596
12:27
because of two competing effects,
245
735245
1947
12:29
just as in the case of sand.
246
737192
3586
12:32
My story does not have an end,
247
740778
3145
12:35
because we still don't know the end of the story.
248
743923
3735
12:39
This is science in progress,
249
747658
3288
12:42
and to solve the mystery, we need more data,
250
750946
3834
12:46
and hopefully, the LHC will soon add new clues
251
754780
4616
12:51
to this story.
252
759396
2621
12:54
Just one number, the Higgs boson mass,
253
762017
3830
12:57
and yet, out of this number we learn so much.
254
765847
5329
13:03
I started from a hypothesis, that the known particles
255
771176
3047
13:06
are all there is in the universe,
256
774223
2036
13:08
even beyond the domain explored so far.
257
776259
2706
13:10
From this, we discovered that the Higgs field
258
778965
3768
13:14
that permeates space-time may be standing
259
782733
3443
13:18
on a knife edge, ready for cosmic collapse,
260
786176
4557
13:22
and we discovered that this may be a hint
261
790733
3550
13:26
that our universe is only a grain of sand
262
794283
4033
13:30
in a giant beach, the multiverse.
263
798316
3613
13:33
But I don't know if my hypothesis is right.
264
801929
3251
13:37
That's how physics works: A single measurement
265
805180
3683
13:40
can put us on the road to a new understanding
266
808863
2864
13:43
of the universe
267
811727
1663
13:45
or it can send us down a blind alley.
268
813390
3019
13:48
But whichever it turns out to be,
269
816409
2564
13:50
there is one thing I'm sure of:
270
818973
3192
13:54
The journey will be full of surprises.
271
822165
3349
13:57
Thank you.
272
825514
1373
13:58
(Applause)
273
826887
5248

▲Back to top

ABOUT THE SPEAKER
Gian Giudice - Theoretical physicist
Gian Giudice is a theoretical physicist who has contributed greatly to our present understanding of particle physics and cosmology.

Why you should listen

Gian Giudice is a permanent member of CERN's group for theoretical physics. He has researched topics like supersymmetry, extra dimensions and dark matter, and has formulated theories that describe the earliest stages of the universe and that apply our knowledge of the particle world to smaller distances.

As author of the popular book, A Zeptospace Odyssey, Giudice is active in communicating the complex work of the Large Hadron Collider to the public. Meant for the lay reader, the book shares both the innovations needed to build the LHC and the theories it was created to prove. After the Higgs boson discovery, Giudice found the surprising result that, if the Standard Model continues to hold up at very small distances, the universe must be in a critical state, near to a phase transition that could lead to the collapse of all atomic matter. Luckily, in his TED Talk, he shares that this would happen very, very, very far in the future.

More profile about the speaker
Gian Giudice | Speaker | TED.com