What is the universe really made of? What is truly fundamental in the reality that
we perceive? In 400 BC, Greek philosopher Democritus came up with the idea of
atoms as being fundamental. He believed that these were solid pieces of matter
which could not be divided any further. 2,300 years later, in 1897 JJ Thompson
discovered something smaller than an atom called the electron. And in 1912,
Ernest Rutherford discovered that Atoms had nuclei. Then we found that nuclei
were composed of protons and neutrons. These were thought to be the fundamental
components that all things are made of, until the 1960s, when we found that
neutrons and protons were composed of even smaller things called quarks - two
kinds - up quarks and down quarks. Today, everything that you can see around you
is thought to be made up of just these three particles - electrons, up quarks, and
down quarks. That's what all atoms are made of - your phone, your desk, your skin
your grass, everything. At least, this is what most people are taught in science
class. The only problem is - it's not true. And physicists have known this for
decades. These particles are really not fundamental. The best theory in physics
tells us that there really are no particles at all.
Nature is made of fields. Reality is fundamentally many different fields.
These things we call particles are merely waves in the field - not that kind
of field though. So what in the heck are these fields? And what do they tell us
about the nature of reality?
The idea of particles, even the particles that I've talked about numerous times
composing the standard model, is not what the universe is actually made of. The
particles are fiction. They're convenient representations that are not really the
best understanding of the universe today. The fundamental nature of the universe
are not particles but fields. These are fluid-like substances that can be
perturbed. They can vibrate and experience excitations. What exactly are
fields? Mathematically, a field is something that takes a value at every
point in space. They're not really made of anything other than that from a
strictly physicist's point of view. Think of it this way,
If you have a fireplace in a room, the temperature at every point in that room
would have a value. This
would be a field of temperature. This is analogous to the universe's fundamental
fields. And these fields in nature are everywhere. You can't escape it. If you
take a strong metal box, and remove everything from it - all the gases, all the
atoms, all the photons, what will be left in that box? This is what we think of as
a vacuum - like the vacuum of empty space. But in fact, this vacuum is alive with
fields. And they're constantly moving and changing. The Heisenberg uncertainty
principle means that a quantum field cannot sit still. Instead, they're moving
and vibrating and changing their value over time. This is a computer simulation
of empty space. All the bubbles that you see popping and bursting are
perturbations of empty space. Particles are constantly being created
and destroyed in this emptiness. But these particles are really excitations
of fields that pervade all of space. What you can see in the world around you are
excitations of these fields. In fact, all you can see is really only the
excitations of four of the fields. You can see photons, or light, which are
vibrations in the electromagnetic field. Electrons are vibrations in the electron
field. Up quarks and down quarks make up the protons and neutrons in the nucleus
of all atoms. They are vibrations in the up quark field, and down quark field,
respectively. Amazingly, everything that you can see around you - your phone, your
desk, flowers, and trees - the earth below your feet, everything is composed of just
these four fields. But there are more than just these four fields. In fact,
everything that we designated as particles in the standard model, the best
theory of physics we have, are really excitations or vibrations of their own
fields. The total number of fields would be 17, including the Higgs field. Note
that space-time itself is thought to be a field, but so far has not been able to
be incorporated in quantum field theory. It would be the 18th field. All the
so-called particles are really waves. And when I say wave, I don't mean a wave like
an ocean wave. The 2d models are just a visual aid. But the waves would actually
be three-dimensional. Can you see any of these fields? Not really. But you can kind
of get an idea by putting a magnet together with some metal filings. The
lines that you see are really the magnetic field lines changing due to the
magnet. Another way to visualize fields is to imagine the volume of the universe
being filled with water, as if we were living in an ocean. Now, imagine that
instead of water, the ocean is filled with multiple fluids - about 17 different
kinds of fluids, and these fluids are of different colors. This may look really
spectacular and weird. But this is somewhat analogous to what our universe
actually looks like, except that you cannot see these fields. Why is this
theory better than the idea of particles? The key thing that this field eliminates
is the idea of action at a distance. So for example, in Newtonian gravity,
you have to concede that the gravity of the Sun somehow affects the earth, which
is a 120 millionkilometers away. How can something affect
something else so far away without touching it? This is action at a distance.
Even Newton thought that action at a distance was absurd. He said, "it is
inconceivable that inanimate brute matter should, without the mediation of
something else, which is not material, operate upon and
effect other matter, without mutual contact. Einstein's theory of general
relativity eliminated the idea of action at a distance, by replacing space with
something called space-time, which is a field that pervades all of reality. And
he showed mathematically, that gravity is really due to a bending of this field of
space. Whatever happens anywhere to a particle in space is governed by what is
happening in the field near the particle. In order for something to propagate over
distances, it has to affect its field locally, then propagate from the local
point to another distant point, then affect the field locally at that distant
point. This is similar to the way a wave will propagate in water if you throw a
rock in it, from the rock to the shore, and effect sand on the shore. Fields can
also explain how particles can be created and destroyed. So for example,
when a neutron decays to a proton and electron, and an anti-neutrino, how does
this happen? Was the electron hiding in there? Where did it come from? Fields have
the property that they can give their vibrations or energy away if you strike
the field hard enough. They will affect other fields. So in this decay, the energy
of the quark field of the neutron can be transferred to the quark fields of the
proton, plus electron field, and antineutrino fields. In addition, particles
and antiparticles are excitations in the same field.
They're just described as equal and opposite excitations of the field. This
is represented by two opposing waves. When these waves come together, they
annihilate each other. You are affected by these fields every day. When you call
someone on your cell phone, you're putting excitations
the field, and affecting the electronics within the cell phone of the person
you're calling. This is action at a distance in practice, except it's not
action at a distance. Your cell phone is creating excitations in the
electromagnetic field, that is propagating from you, to the cell
tower, and eventually onto the receiver on the other end. But there appears to be
a dilemma here because you have learned in school and in my videos too, that
quantum mechanics is all about discrete things. That's why it's called "quantum."
But fields are continuous not discrete. So there appears to be a conflict here,
between the idea of the discreteness of particles as presented in quantum
mechanics, and the continuous nature of fields. So how are these two ideas reconciled?
The combining of field theory with quantum mechanics is called quantum
field theory, or QFT. So essentially, all the excitations of fields happen only in
chunks of energy. The energy of the wave is determined by the mass of the
particle. What is a mass? A mass of a particle is just the energy needed to
vibrate its field. Energy, if you recall, is equivalent to mass using Einstein's
famous equation, E = MC^2 . The field will simply not accept energies
below a certain threshold. Once you tap the field hard enough however, a particle
is created. This discrete unit of energy that the field can accept, is what we
call the rest mass energy of the particle. In a field, it is the
fundamental amount of energy that must be added to the field in order to create
a particle. So for example, one electron is created when an electron field is
excited by 0.511 mega electron volts, which is the mass of one electron. If you
add energy equivalent to 0.4 mega electron volts, no particle gets created.
If you put in 1.1 mega electron volts, then two electrons get created, and so on.
This works for all the particles. All the electrons in your body and my body are
waves in the same underlying field. The field is fundamental. The electrons are
not. Also present in this room, and in your room, are the up quark field, and the down
quark field. And all the atoms in your body are composed of particles which are
ripples in these three fields. It's the same feel that you, I, and
everyone on earth is in. In fact, it's the same field that all the other planets
and the Sun are in. We are basically composed of ripples in the same three
fields everywhere in the universe. Now, there's no indication that ripples in my
field can communicate with the ripples in your field, but it's one continuous
field. And everything is connected to it. Fields don't tell us everything though.
It does not tell us what dark matter is, what dark energy is, or how the Big Bang
occurred, or why there is more matter than antimatter in the universe. So,
there's still work to be done. Now, how are waves in the field related
to the probability waves of quantum mechanics, and the Schrodinger equation?
When we say that an electron is a particle with a position and velocity, this is
wrong. And it's not because we can't measure its position in velocity. It's
because there's no such thing as a position and velocity. All there is is a
wavefunction. It is spread all throughout space, and it only tells us what the
position and velocity will be if we choose to measure it. So for example, the
shape of the electromagnetic field is the wave function of photons. The shape
of the electric field is the wave function of electrons, and so forth.
The wave function is what really exists. And when you observe the electron, you
don't see the wave function, because the wave function has collapsed into a
discrete value. This can be predicted by Schrodinger's equation. The fields are
vibrating and modulating, but when you measure them, they resolve into
individual packets of energy called particles. So quantum mechanics says that
fundamentally, reality is different when you measure it versus when you don't.
Every particle in the universe is a tiny ripple in the underlying field, moulded
into a particle by the machinery of quantum mechanics. The quantum fields
vibrating at every location in space and throughout time are the fundamental
building blocks of nature. So the age-old question of whether light is a particle
or wave can be answered. They are waves. A particle is just what manifests when we
measure the wave. Who discovered fields? It should be noted that Michael Faraday
came up with the idea, and actually use the word "field" in his
notebook in 1845. Are fields a real thing, or are they just mathematical constructs?
Even though a field is made of no substance that physicists know of, fields
are considered real physical stuff. This is because they exist in space and have
energy. In addition, their properties can be calculated and accurately predicted
by experimental results. Now we get back to the question, "Are these fields
fundamental?" Well, I think it's fundamental in the sense that it is the
limit of our understanding. But it could very well be that these fields are just
an approximation of a deeper level of reality, because ultimately there should
be some fundamental reason why these fields have the properties that they do.
Why does the electron field have a minimum requirement of 0.511 mega
electron volts? Why does it obey mathematical rules? Will we ever know the
answer? Unlike many physicists, I think we will.
We may not even be asking the right questions. In the famous words of a
certain Secretary of Defense, there are known unknowns, and unknown unknowns.
And I think the answer will come when we humans know enough to ask
the right question.