The True Nature of Matter and Mass | Space Time | PBS Digital Studios

Einstein showed us that

matter

,

mass

and

time

are intrinsically linked, but he questioned whether they are real. Let's find out. In a previous episode we talked about the speed of light, the fastest speed that exists. And we discussed how this speed is actually the speed of causality. It is the maximum speed at which two neighboring parts of the universe can communicate with each other. Everything that has no

mass

must travel at the speed of light. But what is it about mass that prevents something from reaching the speed of light? The answer leads us to a much deeper question: what is the origin of

matter

and

time

?

However, it will take us several episodes to get there. So today we will take a closer look at the real

nature

of matter and mass. We have already discussed Einstein's famous equation E=MC^2, and we have shown that most of the mass of atoms comes from the kinetic and binding energy of the quarks that make up protons and neutrons. But saying that mass is the same as energy doesn't really get us very far. The question arises, what is energy? This is a broad topic that we will address. First, we analyze this energy according to what actually happens inside an object when it exhibits the property we call "mass." Let's ignore the gravitational effect of mass for a moment and consider mass only as the degree to which an object resists acceleration.

We call this inertial mass. It's a good place to start with a thought experiment we'll call the "photon box." Let's imagine a massless box with mirror walls; Impossible, I know, but there is an analogy with something in reality, as we will see. Now fill it with photons, also massless, colliding inside the box in all directions. All walls of the box feel the same pressure, so there is no resultant force on the box. But let's give the box a little push, let's increase the speed. Now the back of the box moves towards the incoming photons. You feel a little more pressure from its impact than before.

Meanwhile, the front of the box, which faces away from the incoming photons, feels less pressure. There is a net resultant rearward force that is felt as a resistance to the change in speed. The photons exert a force on the box, but the box also exerts a force on the photons. Newton's third law, which gives us the law of conservation of momentum. The momentum that the box has lost has been transferred to the photons. Now, when the box stops accelerating, everything around it will collide and the momentum will again be divided equally between the box and the photons.

But as long as the acceleration continues, the pressure difference will exist. The resistance to acceleration is such that it feels exactly like a mass. In reality, it is indistinguishable from dough, because it is dough. The photon box has mass, although none of the components, neither the photons nor the walls, have mass. Surprisingly, mass shows up in the whole, but does not exist in the parts. How much mass does the box have? It is the energy of the photons divided by the square of the speed of these photons. And the well-known 'E equals MC squared' can be derived by observing how momentum is exchanged between the photons in the box that is being accelerated.

But E equals MC squared describes the universal relationship between mass and trapped energy, not just trapped photons. So let's look at another example of trapped energy. A compressed spring contains more energy than a relaxed spring. It has potential energy. Does a compressed spring have more mass than a relaxed spring? Definitely. Once again we can describe this using a direct physical phenomenon. An already compressed spring is more difficult to compress than a relaxed spring. But that's exactly what you have to do when you try to move the spring. Push the spring and it won't move instantly. First, your back will sag a little.

And then a pressure wave communicates the force to the front until the entire spring moves. That initial push is harder on the compressed spring than on the relaxed spring. She feels like she has more mass, because she does. These apparently very different physical phenomena, the photon box and the pressed spring, both give the same conversion between mass and energy, E equals MC squared, because the underlying ratio is the same, since they contain interactions that in turn They move at the speed of light. Photons in the photon box, but even in spring, the density wave is ultimately communicated through electromagnetic interactions between atoms.

So that in itself is a light-speed interaction, even if the resulting density wave is not. Okay, so how do these things translate into something like a proton? 99% of the proton's mass is vibrational energy of the quarks plus the binding energy of the gluon field. The actual intrinsic mass of quarks is a tiny fraction. So a proton is very similar to the combination of our photon box and our pressed spring. The quarks bounce off the walls into the gluon field, which in turn behaves like a compressed spring and retains potential energy. And as we have seen recently, also these quarks and also the electrons obtain their tiny masses from a kind of storage through the Higgs field.

If you remove the Higgs field, they are massless particles moving at the speed of light. It seems that everything that has mass is made up of a combination of intrinsic massless particles moving at the speed of light, which are prevented from flowing freely through the universe, as well as the fields that support these particles. So mass really isn't a fundamental property? Is it simply the result of colliding fields and massless particles inside objects? Resist acceleration? Yes, that's really

true

. This mass that acts against acceleration, inert mass, seems to be an emergent property of the set. But we cannot talk about mass without talking about gravity.

Objects with mass exert and respond to gravity. They have the so-called gravitational mass. But how is the inertial mass of our photon box ultimately expressed as gravitational mass? Once we accept Einstein's description of

space

time according to general relativity, it is not surprising that the photon box feels the pull of gravity. The equivalence principle teaches us that the sensation of acceleration in free

space

is fundamentally the same as feeling weight in a gravitational field. Holding our box of photons in the Earth's gravitational field must be as difficult as accelerating the box 1g in empty space. The photon box feels heavy.

This also applies to the compressed spring. It is difficult to accelerate beyond a relaxed spring and feels heavier in a gravitational field. In effect, the equivalence principle tells us that the gravitational mass of an object and its inertial mass are the same. But mass does not simply respond to a gravitational field. It also generates one. The dough doubles the space. In fact, it turns out that not only mass curves space. The presence and exchange of energy and momentum, as well as pressure, have their own different effects on the curvature of spacetime. Individual photons influence space-time. And when you lock them in a box, the bending they cause looks exactly like gravity.

So the trapped massless particles actually generate a gravitational field. Okay, so mass is an emergent property of the interactions of massless particles. What to say about time? An individual photon does not experience time, no massless particle experiences time. Their clocks have stopped. But our photon box has mass, so it must experience time. Where and when does this time arise? Individual particles do not have it when they pass from one wall to another. Does the moment arise when you hit the wall? Does the array of photons somehow sense time that the individual photons do not? We explore these questions as we delve deeper into the mysteries of matter and time in the next episode of "Space Time." In the last episode of "Space Time" we discussed how the Higgs field gives mass to elementary particles.

As always, you had some interesting questions. Caled Limb asks: Does this mean that the Higgs field creates a little friction in space? Well, this is some nasty pop science misinformation. The Higgs field is not something viscous or like a multitude of physicists. It does not behave like friction, because friction slows down the particles. The Higgs field does not slow down particles. It gives them inertia, a resistance to acceleration. It makes it harder to speed them up or slow them down. And most importantly, it prevents them from moving at the speed of light. Felix Feist points out that since a right-handed electron does not have a weak hypercharge, shouldn't it be massless?

Well... yes and no. The right-handed electron can interact with the Higgs field by picking up a weak hypercharge. In reality, the change between left-handed and right-handed is probably best thought of as if an electron were left-handed and right-handed at the same time. Because the interaction occurs in a period shorter than the Planck time. There is a quantum confusion surrounding the current state of the electron. In reality, it is the composite particle that has mass. The left or right "bare" electron has no mass. 'Death by Powerpoint' asks if there is a point in space where the Higgs field has the value 'zero'.

And what consequences would this have? Well, actually yes... at least such a situation existed. At extremely high temperatures, the Higgs field takes the value "zero" throughout space. And it is believed that this was the case a fraction of a second after the Big Bang. So without an infinite source and sink of the weak hypercharge, the weak nuclear force and the electromagnetic force were all the same force. Only when the universe cooled could the Higgs field become nonzero in a phenomenon called "spontaneous symmetry breaking." Then, the weak nuclear force carriers acquired mass and were distinguished from the electromagnetic force carrier, the photon.

The consequences ? We would not have atoms without a non-zero Higgs field.