Not only God knows, I know. And by the
end of the semester, you will know.
This is how the physicist Sydney Coleman
would kick off his lectures on quantum
theory at Harvard. Coleman claimed that
he never really liked teaching, but his
enthusiasm was electric and his courses
were considered legendary. Though his
name is not as wellknown as Einstein or
Hawking, he was held in the highest
regard amongst his peers. Indeed,
groundbreaking physicist Sheldon Glashau
once said, "He's kind of a major god. He
is the physicist's physicist."
And yet, arguably, this jovial legend of
physics greatest achievement was
revealing something truly spine-
chilling. For in the late 1970s, Coleman
figured out how to destroy the entire
universe.
The possibility that we are living in a
false vacuum has never been a cheering
one to contemplate. However, one could
always draw stoic comfort from the
possibility that perhaps in the course
of time the new vacuum would sustain, if
not life as we know it, at least some
structures capable of knowing joy.
This possibility has now been
eliminated.
Coleman discovered that our universe is
under constant threat. That at any
moment, at any point in time and space,
reality could begin to change. Change in
a way so unforgiving that nothing could
survive it.
The story of the unraveling of this
mystery will introduce us to some of
science's great personalities. Men and
women who peeled back reality and
created a framework out of which our
universe could appear. But most
importantly of all, this story will pull
us deep into the bizarre world of the
standard model of particle physics and
the one particle that sits apart from
all the others. The one particle with
the power to eliminate everything in
existence. That godamn particle, or as
it's more commonly known, the God
particle.
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As the Trinity Test mushroom cloud
bloomed into the sky on July 16th, 1945,
physicist Kenneth Bainbridge turned to
Robert Oppenheimer and uttered the
immortal phrase, "Now we're all sons of
bitches."
Indeed, after the magnitude of the test
had set in, and the initial flurry of
excitement had dulled down, there was a
palpable sense of unease across many at
Los Alamos. In the initial rush of
adrenaline after the detonation, famed
New York physicist Richard Fineman had
played his iconic bongos on the hood of
a jeep. And in his words, "Everyone had
parties." But quickly the mood would
turn sour. I sat in a restaurant in New
York and I looked out at the buildings
and I began to think about how much the
radius of the Hiroshima bomb damage was
and so forth. And I would go along and
see people building a bridge or they'd
be making a new road and I thought,
"They're crazy. They just don't
understand why are they making new
things. It's so useless.
The Manhattan Project had employed over
130,000 people in its prime and 26 of
its scientists already had or would go
on to win a Nobel Prize. It had been the
focal point for much of the physics
community for half a decade. And so
after this long interruption, it was
decided that physicists should gather
together to return to science for
science's sake once again. And in 1947,
Oppenheimer himself helped organize a
conference on Shelter Island.
To quote later Nobel Prize winner Julian
Schwinger, "It was the first time that
people who had all this physics pent up
in them for 5 years could talk to each
other without somebody peering over
their shoulders and saying, "Is this
cleared?
And it would be at this conference that
Richard Fineman and Julian Schfinger
himself would propose some
groundbreaking quantum ideas.
But what does any of this have to do
with Sydney Coleman and the destruction
of the entire universe?
To answer this question, we must take a
journey downwards down into the deepest
layers of reality. down below the scales
of molecules and atoms beyond the pieces
of the atomic nucleus down to what we
think are the ultimate building blocks
of reality. And to a physicist, this
world is written in the language of the
standard model of particle physics.
The standard model is the result of more
than a century of deciphering the laws
of the universe. A world even more
fundamental than the atomic one explored
by the Manhattan Project.
First, there are the Firmians. The
fundamental particles that comprise the
stuff of matter, named after Italian
American physicist Enrico Fermy.
Firmians come in two types, the quarks
and the leptons that feel the
fundamental forces differently. The
quarks feel the strong force and are
bound together by it into composite
particles, collections of two or three.
Indeed, these include the protons and
neutrons that sit at the core of every
one of your atoms. Atoms though circled
by electrons, which as leptons
completely ignore the strong force
and the complement to the firmians are
the Bzons named after the Indian
physicist Chachendra Nath Bose. The
bzons are different as they carry the
fundamental forces between the firmians.
For the strong force we met a moment
ago, the carrier of force is the gluon.
For electromagnetism, the bzon is the
photon, the particle of light. For the
weak force, there are the W and Z bzons.
And for the final fundamental force,
gravity, physicists still aren't sure.
Now the idea of Bzons as force carriers
may seem strange but you have to
remember that particles are not really
particles
and this is key.
The standard model is written in the
language of quantum mechanics where
everything is a wave in a field. An
electron is a ripple in the electron
quantum field. A quark is a ripple in a
quark quantum field. And each Bzon is a
ripple in a Bzon field.
Everything is fields.
In the simplest form, a field is
something that is spread throughout
space. And that something attaches a
number to each point in that space. For
example, think about the temperature in
the air around you. Some spots may be
warmer, some cooler, and at each point,
the temperature is represented by a
single number. This is a simple scalar
field.
Other types of fields are more complex
but still familiar. For example,
electric and magnetic fields. At each
point in space, the electric and
magnetic fields have a number and
importantly a direction. And so with a
vector at each point in space, it is no
surprise that these are known as vector
fields.
And these and many more complex fields
are what many aspects of physics are
built from. in particular, a type of
field called a quantum field.
And to explore how these work, let's
talk about the electron.
The electron quantum field fills all of
space, encoding the properties of what
makes up an electron at every point. A
single ripple in the field corresponds
to a single electron traveling through a
region. Multiple ripples would represent
multiple electrons all encoded in the
field. And of course, when the field is
zero, there are no electrons in that
region. The electron field is joined by
fields for the other leptons, the muon
and the ton, and their associated
neutrinos.
There are also fields for each of the
quarks and for each of the force
carrying bzons. There was a quantum
field for each type of fundamental
particle. All around us at every point
sit all of these quantum fields.
But there's more to quantum fields than
simply existing. The real power in
quantum fields is how they interact.
Understanding just how this interaction
takes place was one of the most
important insights in all of physics.
And it is here we can return to Shelter
Island and Richard Fineman.
As part of his PhD, Fineman had realized
he could bring a mathematical shortcut
to quantum calculations.
Let's look at what happens when two
electrons with their negative charge
approach each other. To begin with, it's
important to remember that the two
electrons are ripples in the electron
quantum field. So they are not feeling
each other's presence through their
individual electric and magnetic fields.
Instead the presence of the two
electrons in the electron field
generates a new ripple and this ripple
is in the photon quantum field and the
photon is the bzon of the
electromagnetic force.
This photon ripple travels from one
electron to the other and in doing so it
transfers energy and momentum from one
electron to the other. This transfer of
energy and momentum is precisely why the
photon is known as a force particle. And
when you look at a lonely star on a dark
dark night, the absorption of a photon
on the retina in your eye receives
energy and momentum from that star.
Energy and momentum that was released by
an electron in its distant atmosphere.
[Music]
And so at the Shelter Island conference,
physicists were coming to grips with
this quantum picture of electrons and
photons.
Julian Schfinger, with his crisp and
refined New York accent, lectured first.
He was followed by Fineman and his
Queen's Draw who made his way to the
blackboard. Feman's talk was shorter and
shallower than Schfinger with lots of
concepts and ideas. But with his tricks
and famous Fineman diagrams, he showed
he could shortcut Schwinger's
mathematics. Other physicists were
initially confused, but in the long run,
his ideas won out and he shared the
Nobel Prize with Schwinger in 1965 for
their insights into how quantum fields
interact with Japanese physicist Shiniro
Dominaga also grabbing one-third of the
prize. He had delved into the nature of
quantum fields whilst isolated in his
war torn country in the 1940s on the
other side of the conflict to Fineman
and the Manhattan Project. And so by the
time of Fineman's Nobel Prize win, the
standard model was growing in success.
There were still theoretical holes that
needed to be patched, but things seemed
to be fitting together nicely. All
forces should be written in the same
quantum language with Bzons transmitting
forces between firmians. All of these
requiring the presence of quantum fields
to carry the particles with particular
numbers, the charges of the force
dictating how strong the interaction is.
Except a major mystery remained. A
mystery that had the potential to tear
it all down. For within the standard
model, all of the fundamental particles
seemed to have absolutely no mass. The
particle of light, the photon, appeared
to be massless. That was true. But not
the other particles. Clearly, not even
the electron.
And so to understand this mystery, we
have to talk about one more fundamental
force, the weak force.
The existence of quantum fields demanded
that there was the equivalent of
electric charge for the other
fundamental forces as well. The strong
force, for example, had three types of
color charge known as red, green, and
blue. Charges that determined how gluons
are exchanged and how the strength of
the strong force operates. But for our
story, it would be the charge of the
weak force that would play a pivotal
role. The weak force, unsurprisingly, is
weaker than the strong force and
electromagnetism, but it is still
stronger than the pull of gravity. But
unlike the other forces, the weak force
can flip the identities of quarks and
lepttons through the exchange of Bzons.
And this means it is responsible for
certain types of radioactivity.
Of course, with Fineman's view of
quantum interactions and the need for
Bzons to transmit fundamental forces,
there was a need for a Bzon to transmit
the influence of the weak force. But one
of the complicating features of the weak
force is that there are three force
bzons that can be exchanged.
These are the Z0, the W plus and the W
minus. The plus and minuses signifying
that the W bzon carries its own electric
charge.
And as well as this, unlike the other
force bzons, the photons and gluons, the
W and Z bzons have mass, lots and lots
of mass. Indeed, each W and Z Bzon is
about 80 times as massive as a proton or
neutron. And it is this immense mass
that severely impacts the influence of
the weak force. While massless particles
and gluons mean that electromagnetism
and the strong force have infinite
range, the W and Z mass ensures that the
weak force can only operate over less
than a millionth of a billionth of a
meter. This is a result of Heisenberg's
uncertainty principle. one of the
central pieces of quantum theories. The
energy for such a high mass must be
conjured out of nothing. But because of
that high mass, the amount of energy can
only be borrowed for an extremely small
amount of time. The amount of energy
borrowed from the vacuum inversely
related to the amount of time it can be
borrowed for. And in this short time,
the Bzon can only move an extremely
small distance before it decays into
other particles.
[Music]
And so we have said that the weak force
is important and we have found that its
force bzons are massive. But still the
question of where this mass comes from
has yet to be answered or indeed what
this has to do with the possible end of
the universe.
It is time therefore to dive even deeper
into the physics of the fundamental. And
to do that we will need to find a man
who does not want to be found.
Dr. Higgs, the JD Salinger of physics,
has already let it be known that he will
not be available in any form on Tuesday.
[Music]
On the morning of October the 8th, 2013,
the world awaited the announcement of
the Nobel Prize in Physics.
Peter Higgs, however, wanted no part of
the expected media frenzy. Indeed,
instead of staying at home to receive
the expected calls and interviews, he
quietly slipped away to a local pub.
But as the hours ticked by and Higs
dined on soup and trout, the media
frenzy in the outside world was
building, and Higs could not hide
forever and headed out of the pub. Later
in the afternoon, he bumped into an old
neighbor on the street who immediately
congratulated him on the good news.
"What news?" Higs asked. If there could
be no doubting what the news could be,
he would be going to Stockholm.
But why had he been selected for this
coveted prize, one received by fineman
all those years before? To understand
that, we will have to return to another
Nobel ceremony, one perched between Higs
in 2013 and Fineman in 1965.
Nobel Awards ceremonies have always been
flashy affairs with pomp and regimented
protocol. And indeed, the 1979 award was
no different with the royal family of
Sweden leading the processions and
celebrations. All the men were dressed
in formal dinner wear, stiff black suits
and white ties.
Well, almost all. One man in distinctly
different clothing and a turban stood
out. The man was Abda Salam, only the
second Nobel Prize winner from a Muslim
country. And unlike Egypt's Anois Sedat,
who had collected the prize for peace
the previous year, Salam was in
Stockholm to receive the Nobel Prize in
physics. and his choice of dress
reflected his pride in his religion and
cultural origin.
Let us strive to provide equal
opportunities to all so that they can
engage in the creation of physics and
science for the benefit of all mankind.
[Music]
Although he was not alone as Sheldon
Glashau and Steven Weinberg would be
sharing onethird of the prize each and
they were all there for the same reason.
These three physicists had delved into
the similarities between
electromagnetism and the weak force
today known as electroeak theory. And
this unification of the two laid the
groundwork for understanding the origin
of mass.
But before we explore the electro week
and its consequences, we have to
remember that electromagnetism itself
used to be two separate things.
Electricity and magnetism used to be two
very different and distinct phenomena.
It was in the latter half of the 19th
century that the Scotsman James Clark
Maxwell wrote the equations that unified
the two. Maxwell, following work by
Michael Faraday, noticed a symmetry, the
echo of one field birthing another in
elegant reciprocity.
He also added a single term to make the
equations whole and in doing so
unleashed light. light, he realized,
wasn't separate either, simply a wave of
the unified electromagnetic field
rippling through space.
This was the first great unification,
not born of speculation, but of
mathematics, compelled by beauty and
truth. It was hugely important, as it
sparked an idea that still drives
physics forward today. For if things as
different as electricity and magnetism
could be shown as different aspects of
one underlying theory, then maybe other
seemingly disperate aspects of physics
could be unified together. And so
scientists did what scientists do. They
kept questioning,
what if all of physics could be
encompassed in a single set of unified
mathematics? What if all of physics
could be bound together into a single
theory of everything? The race was on.
[Music]
The first clue was that some of the
Bzons of the weak force carried
electromagnetic charge, meaning that
those bzons could intrude on the
electromagnetic world, interacting with
the photon quantum field. And this gave
Glacia, Weineberg, and Salam the key to
a second unification, that of
electromagnetism and the weak force. But
to understand how electroeak theory
unites the two, we must take a deeper
look into a complex idea within physics.
We need to look at gauge theories.
A gauge theory takes its name from the
word gauge, a kind of measuring tool or
standard. It's about setting a local
reference, like choosing a map's grid at
every point on the land. Shifting those
local references only changes the
description, not the underlying
landscape itself. So, gauge theories
reveal laws of nature that stay constant
no matter how you adjust your view.
Physicists treasure these symmetries,
the scientific term for something that
stays the same even when you transform
it. They hint at hidden structures in
the universe.
And so let's consider a simple kind of
gauge field. A field represented by a
single value at every point. This value
is an angle between 0 and 360°.
So it tells you locally what direction a
small arrow, a vector is pointing.
But, and this is key, every single one
of these vectors has exactly the same
length. If your laws of physics care
only about the length of the vector, not
its direction, you have a gauge
symmetry. You could change the direction
of every single vector throughout the
space. But as long as the length remains
the same, your physics would too.
And from this quiet circular idea, we
can build the foundations of forces.
For from symmetry, deep laws of nature
begin to emerge.
This might sound abstract and have
little to do with the real world, but in
their simplest forms, quantum fields are
similar.
Quantum fields are built of complex
numbers. So the two numbers are encoded
at each point with the modulus of the
complex number the sum of the squares
the important element. Because it is
this quantity that corresponds to the
probability of finding a particle at a
particular location. This means that we
can rotate our complex numbers in the
same way as the example we explored
earlier. Meaning that quantum fields
also possess a gauge symmetry. We can
change the field and leave the physics
intact.
[Music]
And the person who kicked off this focus
on symmetry was Emmy Nerta.
Born in Heirlangan in 1882, Nera faced
the heavy doors of academia. A woman in
a man's world, her mathematical
brilliance was often left unspoken,
although not by her esteemed colleague
Albert Einstein. In the judgment of the
most competent living mathematicians,
Frine Nera was the most significant
mathematical genius thus far produced
since the higher education of women
began. And quietly and rigorously, she
laid the path to a universe built on
elegant symmetry. For what Nera
discovered was not mere mathematical
curiosity.
She saw that hidden symmetries whisper
deep truth about physical law. That if a
system stays the same when it is
changed,
something has to be conserved.
And suddenly the conservation of energy,
the idea that energy cannot be created
or destroyed, just transferred was no
longer just an assumption. It was a
theorem.
Things quickly got a lot deeper than
this. For Nerta's insight was profound.
A shift in time. Energy must remain. A
step to the side. Momentum preserved.
With this symmetry moved from mere
elegance to the engine room of the
cosmos.
The symmetry we mentioned before to do
with vectors and rotation goes by the
name of U1. And as it turned out, this
is the symmetry that is the mathematical
foundation of the electromagnetic force.
Technically, it's related to the phase
of the complex numbers of the electron
quantum field. And the conserved
quantity in the case of electromagnetism
is electric charge.
However, the U1 symmetry that defines
electromagnetism was too simple to
account for the weak force.
So the question became just what gauge
field and symmetry would work. And it
was wondering about this that brought
Glacia Weineberg and Salam to Stockholm
and their Nobel Prize. They realized
that two additional quantum numbers
known as weak isospin and weak
hypercharge were needed. And just like
the electric charge defined the
electromagnetic interaction, these
defined the weak interaction and that a
more complex symmetry group known as SU2
was needed.
Like U1, the SU2 symmetry group is a way
of describing certain kinds of
rotations, but instead of dealing with
regular space, it applies to a more
abstract kind of space used for quantum
fields.
Instead of the simple circle- like
rotations of U1, we have to imagine a
sphere where every point represents a
possible state of a quantum particle.
SU2 describes how these states can
smoothly rotate into each other while
keeping the overall structure intact,
the sphere.
It is difficult to visualize, but no one
said the quantum field theory was easy.
And so by combining the U1 symmetry of
electromagnetism with S U2 of the weak
force, the Nobel Prize winners had shown
that these disperate phenomena were two
sides of the same coin. And the
mathematics predicted the presence of
four force carrying Bzons called B, W1,
W2, and W3.
Problem solved.
Not quite. To quote Steven Weinberg,
"One of the consequences of the
electroeak symmetry is that if nothing
new was added to the theory, all
elementary particles, including
electrons and quarks, would be massless,
which of course they're not." And so the
quest continued with the answer
lingering in the fizzing chaos of the
Big Bang.
[Music]
Just after the universe was born, it was
extremely hot. And this meant that all
particles were zipping around at almost
the speed of light. That amount of
energy in the mass of any particle would
be negligible compared to its energy of
motion, effectively like a particle of
light with no mass at all. And what this
meant is that in the earliest instance
of the cosmos, there were not two
distinct forces, no separate
electromagnetic and weak. There was only
the single electroeak force operating.
And so something must have happened as
the universe expanded and cooled and
split this into two. Something must have
happened to tear apart this perfect
picture and split electromagnetism from
weak. Something must have happened to
give mass to the bzons of the weak
force.
Something called symmetry breaking.
[Music]
And this is where in 1964
Peter Higgs and his fellow physicists
took the stage.
Although Higs himself, ever keen to shun
the spotlight, wasn't sure of his
suggestion. This summer I have
discovered something useless, he wrote
to a colleague that year about his Nobel
Prize winning idea. The answer, he and
others realized, was in the addition of
another quantum field. A simple quantum
field that just had a single number at
every point, a scalar field.
This quantum field, however, had to have
quite different properties to other
quantum fields. And it all came down to
what it means for a quantum field to
empty.
To understand this, let's go back 13.8
billion years to roughly one picoscond
after the big bang.
In this hot energetic state, all of the
quantum fields of the universe buzzed
with energy. with all of this energy
washing back and forth between the
various fields. But this super hot
universe was only temporary as it
expanded and cooled. And so the flow of
energy began to dwindle, meaning the
buzz in the quantum fields also started
to die away. Eventually the cooling
resulted in the fields losing all of
their buzz, becoming zero except for the
odd ripple here or there representing a
particle passing through. But for the
Higsfield, as it is now known, things
were very different.
In the early universe, the Higsfield
buzzed and fizzed interacting with the
other quantum fields. And as with the
other fields, as the cosmos cooled, the
buzz in the Higs field also died away.
But unlike the other quantum fields, the
buzz in the Higsfield never completely
vanished. At some point in the cosmic
cooling, the Higsfield got hung up such
that the Higs field possessed a value
which was non zero at every point in
space.
But why? What made the Higs field
different? Why didn't the Higs field
eventually fade to zero?
We can think about a typical quantum
field as being like a pendulum. In the
early universe with lots of energy, the
pendulum swings wildly from side to
side. For the quantum field, this
amplitude represents the values over the
field. But as the universe expands and
cools, the amplitude of the swings gets
smaller and smaller. Eventually, all the
energy dissipates and the pendulum comes
to rest, hanging straight down with
swings of zero amplitude.
Effectively, the quantum field vanishes
all over space. However, for the Higs
field, as the universe cooled, it didn't
settle down like a pendulum. Instead,
due to its particular properties, it
became like a pencil, balancing on its
very tip, with the rest of the universe
cooling around it. its balance becoming
ever more precarious.
And yet, despite its precarious
position, in this balanced state, the
Higsfield was zero everywhere.
But it couldn't last. Whilst the
Higsfield was balanced like a pencil,
the electroeak bzons remained completely
massless. But just as a pencil falls and
drops to a lower potential energy, the
Higs field dropped as the energy fell,
finally taking on a nonzero value
everywhere.
And so, just as a balanced pencil is
symmetric, looking the same as you walk
around it, with a fallen pencil, that
symmetry is lost.
[Music]
The result of this symmetry break for
the electroeak force was profound. The
bzons predicted in the theory B, W1, W2
and W3 quantumly mixed together and
formed four new Bzons. One of them
remained massless and is the photon of
the electromagnetic force and the other
three gained mass from the breaking
becoming the weak force Z0, W plus and W
minus.
We can now take a deep breath. We have
found the origin of mass of the
fundamental bzon of the weak force.
But what about the masses of the other
fundamental particles? Where do they
come from?
The answer lies in the fact that after
symmetry breaking the Higs field is non
zero everywhere.
And it is this fact that could also hold
the key to the end of the universe.
The Higs field is a relatively simple
quantum field characterized by a single
number. This number is known as the
vacuum expectation value or VEV for
short. And basically every particle's
mass depends on how strongly it
interacts with the Higsfield. But just
how does the Higsfield confirm mass on
these fundamental particles? To
understand this, it is important to
understand what mass is. You might think
mass is simply the amount of stuff that
comprises something. Or maybe mass is
the thing that produces the force of
gravity. But the important definition is
the one that was given to us by Newton's
second law of motion more than 400 years
ago.
Force is equal to mass times
acceleration.
Mass is the way an object responds to a
push. Because of this, this form of mass
is known as inertial mass. And it is the
reason why moving an elephant is much
harder than moving a mouse. It is the
Higs field that gives particles their
inertial mass, making them harder to
push. And it does this by effectively
making space sticky for particles that
can interact with it. For the massless
photon, for example, the Higs field is
effectively transparent, and so it moves
at the speed of light. But the electron
and other massive particles feel its
sticky presence. And it really is that
simple.
And so there it is. It may seem that we
have come to the end of the journey in
understanding the origin of mass.
But there's still a couple of questions
that remain to be answered. Because the
mass of the fundamental particles
especially the electron and the up and
down quarks the particles that make up
matter are very very small.
If we consider a proton which is
comprised of two up quarks and a down
quark the masses of these three
fundamental quarks make up only 1% of
the mass of the sun total. And so where
does the rest of the mass come from?
What is the origin of all the rest of
the mass that makes up you?
We have to remember that inside each
proton and neutron, there's a lot more
than just the three quarks.
Inside each and every one of these
particles, there is a swirling mass
driven by the strong force. A hail of
gluons is constantly being exchanged
between the quarks. And these gluons are
popping in and out of existence as quark
anti-quark pairs. Whilst the gluons
themselves are intrinsically massless,
they still carry a swirl of energy and
momentum. And through Einstein's E= MC²,
this swirl of energy corresponds to
mass.
It is this that gives the particles of
matter at the center of your atoms most
of their mass. Just think about that the
next time you find it difficult to heave
yourself off the sofa.
And so there was a time when the
universe was a thousandth of a billionth
of a second old, when the temperature of
the cosmos was a million billion Kelvin,
that a defining symmetry was irrevocably
broken and the cosmos was imbued with
mass.
But again, what does this have to do
with the destruction of the universe?
To answer this, we will have to do
something that seems counterintuitive
after all we have learned so far. We
will have to weigh the source of mass,
the Higs itself.
[Music]
Sydney was both an incomparable teacher
and the sharpest critic in the world of
theoretical physics. He was Powi's
tongue in Einstein's image. We have been
deprived all too soon of one of our
generation's most profound and
imaginative minds.
Sydney Coleman died in 2007 after a long
illness to an outpouring of affection
from many in the physics community. His
obituary in the Harvard Gazette
proclaimed that almost everyone had a
Sydney story, his costic wit and
legendary lectures almost universally
loved. But it would be 5 years after his
death in 2012 that other physicists
would finally start to answer a mystery
he had uncovered years before with the
help of the most energetic experiment
ever performed.
[Music]
In the late 1970s, Coleman had looked
again at the symmetry breaking that led
to the Higs field fizzing with constant
energy, in turn giving mass to
fundamental particles. and he asked why
why did the Higsfield fizz with the
particular energy it has? Why didn't the
Higsfield settle on a different energy
as the universe cooled after its birth?
In the initial work of Peter Higs and
others, they had simply assumed the
energy of the Higsfield. They didn't
know what this energy must be. In their
mathematics, the Higsfield just settled
at this energy. But Coleman realized
that with only a little mathematical
manipulation, things could change. There
might be more than one energy that the
Higsfield could settle into. Indeed, due
to the intrinsic randomness of symmetry
breaking, it seemed to be nothing but a
game of chance. Just like the pencil
balancing on its tip could topple to the
left or right, front or back, the path
the Higsfield toppled from its symmetric
state seemed equally random as it fell
into an energy minimum.
And it was here that Coleman realized
something disturbing.
This meant that after the birth of the
universe, the energy in the Higsfield
may not have fallen to a true minimum.
Instead, it could be hung up in a local
minimum, not a global minimum of the
Higs energy. But why should this be a
problem? Surely, even if we are in a
local minimum, it's clear that our
universe happily exists and functions in
this local minimum. Well, the issue is
that quantum fields are quantum.
Remember our picture of a quantum field
like a ball rolling about a landscape.
In the simplest picture, the ball ends
sitting at the very bottom of the
valley. In the simplest Higsfield, this
picture of the valley remains, the ball
still making its way down to the lowest
point. However, in the more complex
landscape envisioned by Coleman, the
ball can be trapped, stuck in a dip in
the peaks, but still a very long way
above the valley floor. Of course, in
the classical picture of the universe
provided by Isaac Newton, this is no
problem. The ball would be forever stuck
in this divot. But quantum mechanics
offers the ball an escape. For within
the mathematics of quantum mechanics,
there is something called tunneling.
Quantum tunneling is something not seen
in the mathematics of Newton as things
in quantum mechanics are represented as
waves and are never truly localized. As
we've seen before, quantum waves, like
waves on the ocean, spread out through
space and time. And so quantum waves can
leak between seemingly distinct and
separated regions of space.
Imagine
an electron locked in a highsecurity
prison cell. A Newtonian electron would
be stuck in the cell forever, bouncing
back and forth off the wall. But the
wave function of a quantum electron,
whilst initially confined to the cell,
will spread beyond its walls and bars.
The existence of the wave function
beyond the walls of the cell gives the
electron a chance to escape. a nonzero
probability that the electron will be
found outside the cell.
This ability to quantum tunnel is
extremely important for the workings of
the universe as it provides a vital
pathway for things as varied as the sun
shining and electricity flowing into
your phone.
But quantum fields can also make use of
this quantum tunneling, allowing them to
transition from one state to another.
And so this means if the Higs field is
stuck within a local minimum, there is a
probability that it can transition to a
lower energy.
But what would this mean? Surely it's
just the presence of the Higs field
that's important. So it's still there.
Fundamental particles would still have
mass and the universe would be more or
less the same.
But this is not the case.
for transitioning to a lower vacuum
energy has a drastic effect. It floods
the cosmos with energy, completely
destroying the universe as we know it.
To quote Sydney Coleman, "By
macrofysical standards, once the bubble
materializes, it begins to expand almost
instantly with almost the velocity of
light. As a consequence of this rapid
expansion, if a bubble were expanding
towards us at this moment, we would have
essentially no warning of its approach.
until its arrival.
This quantum tunneling of the Higs field
would occur at a particular point in
space, at a particular point in time,
and would roar away at the speed of
light, incinerating everything in its
path.
And within this expanding bubble, a
strange new universe would remain. A
universe very unlike the one we inhabit
today.
This is because the lower Hig state
within the bubble would change not only
the masses of the fundamental particles
but the action of the fundamental
forces.
This would change everything including
the ultimate stability of matter. There
could be the prospect of no atoms, no
stars and no planets.
Not only that, but the roaring turmoil
inside the expanding bubble could be
even more dramatic, and it might
influence the very structure of space
and time themselves.
Within the bubble, the expansion of
space might completely cease and instead
whatever is inside the bubble could
undergo complete gravitational collapse.
And so, how worried should we be? Is the
decay of the Higsfield a realistic
possibility for the cosmos? Or could our
universe be sitting at the true minimum
of the Higsfield, so there's nothing to
worry about? Physicists aren't
completely sure on the answer to this
question, but there is one incredibly
powerful recent experiment that has
given glimpses of an answer.
[Music]
Nestled in the coal mining valleys of
South Wales lies the small community of
Kumbach. It was here that Lynn Evans was
born in the mid 1940s. As a young boy,
he found his love for science.
Originally studying chemistry at the
University of Swansea before finally
being drawn into the mysteries and magic
of physics. This was a fortuitous move
as his studies led him to the subatomic
world and by the close of the 1960s he
found himself at CERN on the Swiss
French border. This small collection of
buildings around a particle accelerator
was still only a few decades old, but it
was already the premier place to study
the fundamental nature of reality on the
smallest scales.
[Music]
Energy is the name of the game in
particle smashing. Accelerating beams of
matter to almost the speed of light.
Colliding the beams concentrates these
immense energies into tiny volumes. And
through the wizardry of Einstein's E=
MC², this energy can be transmuted into
new massive particles. And so, of
course, physicists worked on getting
particles to go faster and faster. By
1989, the large electron posetron
collider was constructed in a circular
27 km tunnel, zipping electrons around
at nearly the speed of light before
smashing them into equally zippy
posetrons.
But the physicists at CERN were thinking
ahead to what would come next, a machine
even more powerful. And the job was
given to Lynn Evans to make it happen.
Evans the Atom, as he was known, took on
the role of project director at the
Large Hadron Collider, upgrading the
large electron posetron collider to
accelerate protons instead of electrons.
Being 2,000 times more massive than the
Electron, the Proton could bring a lot
more energy to the collisions.
This project would take the effort of
tens of thousands of scientists and
billions of dollars as well as a decade
of construction under Lin Evans guiding
hand. And despite hiccups and setbacks,
in 2008 they were ready to turn on the
proton beams and begin operations.
Usually the start of operations are
quiet affairs overseen by the scientists
responsible for the beams and detectors.
But the sheer power of the large hadron
collider had sparked conspiracy theories
in the media and online. Some even
claimed that many black holes would be
created instantly destroying the Earth.
And so, even though he initially hadn't
wanted to, Lynn Evans decided the launch
of the LHC would be a public event.
In front of the world's media, the LHC
was brought up to speed. People around
the world held their breaths. Some
willing everything to work properly,
others afraid that the LHC would spell
doom for the planet. Well, as Lynn
narrated what was happening to the
press, the room erupted into applause.
The LHC was alive. The protons were
circling at almost the speed of light,
and the planet Earth was seemingly safe.
At least so it seemed at first.
The energy of the LHC was steadily
ramped up and physicists started sifting
through the outcomes of the collisions.
All kinds of particles were created and
spat out into the massive detectors. But
some physicists were on the lookout for
a particular pattern. And in the flood
of collisions, they found it. A whisper
of the Higs written in light itself. A
decay path predicted decades before by
Peter Higs and many others. now etched
in lines of data.
And so to understand what happened,
we're going to have to look a little
more deeply into collisions between
protons and anti-rotons.
To begin with, we have to remember that
protons are not fundamental, but are
constructed from smaller particles.
Inside a proton is a broiling mess of
quarks and as well as quarks gluons
zipping back and forth carrying the
action of the strong force and binding
the proton together. It is the collision
between pairs of gluons that is the
source of Higs Bzon production combining
to create a buzzing mixture of top
quarks the heaviest of the quarks. It is
this mix of top quark that has enough
energy to condense into a Higs Bzon, a
brand new ripple in the Higs quantum
field. This Higs Bzon can decay through
various different ways through Z Bzones,
quarks, and photons. Decays that cascade
through other decays. And it is these
that were picked up in the immense
detectors that dot the LHC. the patterns
of these bursts leaving a signature
hidden in the mess of possible outcomes
in proton collisions.
And so eventually with enough time and
enough collisions and cascading energy
bursts, an unambiguous signal emerged
out of the noise. The physicists held
their breath as the significance climbed
above 5 sigma, the threshold for
scientific discovery. enough to whisper,
"Yes, this particle exists. Mass does
not arise by magic alone."
[Music]
In no time at all, the God particle, as
the Higs Bzon was known, was everywhere.
Even though this name is despised by the
majority of the physics community, its
origin, a book written by Nobel Prize
winner Leon Lederman, a title to drive
up sales rather than please the
sensibilities of physicists. Indeed,
Lady at one point even considered the
nickname the godamn particle instead.
The media whirlwind made the discovery
the biggest physics news of the year.
But the announcement was too late for
the 2012 Nobel Prize as that decision
had already been made. Although everyone
knew that the 2013 Nobel Prize was
surely in the bag and Peter Hicks would
be in Stockholm.
And so all's well it ended well.
[Music]
more or less.
For now, scientists knew the mass of the
Higs. They could therefore estimate the
stability of the Higs field by comparing
the mass of the Higs to the mass of the
heaviest of the firmians, the top quark.
And it turned out that the top quark is
about 38% more massive than the Higs
Bzon. And that places us in a very
tricky position.
If the ratio was less than about 36% the
minimum of the Higsfield would be stable
and we would be safe from its decay
tearing through the universe. If this
ratio was greater than about 42% the
minimum of the Higsfield would be
unstable. The Higsfield would have
collapsed instantaneously at the birth
of the cosmos.
However, at 38% the Higsfield is neither
stable or unstable. Instead, it is
metastable.
It is stuck in its local minimum with
the potential of transitioning to the
true minimum.
This means that in 2012, we discovered
that the decay of the Higsfield hangs
over the cosmos like the sword of
Damocles, waiting to drop and bring the
universe to an end.
However, to finish on a more positive
note, physicists have a few words of
reassurance. There is still a lot of
uncertainty in the theories and so we're
currently unsure of the true stability
of the Higsfield and also the
probability of the transition is very
low and so the decay would not occur
until the universe is much much older
than today. Although having said this,
the decay of the Higsfield is really
just a question of probability
and like all games of chance even rare
events can happen.
Perhaps at some point in the universe,
at some point in the past, the decay of
the Higsfield began and is roaring
towards us at the speed of light.
In the words of Sydney Coleman, "One
could always draw stoic comfort from the
possibility that perhaps in the course
of time, the new vacuum would sustain,
if not life as we know it, at least some
structures capable of knowing joy.
This possibility has now been
eliminated.
You've been watching the entire history
of the universe. Don't forget to like
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tell us what you think. Thanks for
watching and we'll see you next time.
[Music]