We CAN Understand Some Modern Physics, and Compare It to the Old !

(The new view of gravity: space and time have become melded together into a single field with massive objects bending its contours. Gravity is a force but it is now delivered by particles called “gravitons” that are wave lines. Gravitons are a particle with no mass–it seems–and can travel at the speed of light. See physics.aps.org)

I should not feel slighted by my inability to ‘get’ modern physics. Hell, Newtonian physics (“classical mechanics”) was not a strength of mine. I believe we should feel compelled to give quantum mechanics a shot. We should try to have some handle on it, just to feel vaguely up to date and competent. Below is an initial attempt to do that, and should not be taken as ‘the Gospel Truth’ on these important issues.

The newest physics is “particle ” or “quantum physics” and it is quite exotic. A physicist recently wrote, “we understand the equations for quantum physics but we don’t understand what quantum physics is.” He explains that maybe we should be happy with that, just the equations, and not be concerned with a ‘picture’ of what they are about in terms of objects, causes, and sequences of events.

To be satisfied with only the equations is to be what is called “an instrumentalist” philosophically. The equations—and all the ideas, measurements, and experiments—are tools we use to manipulate reality. In that sense. our physicist refers to this view with some disapproval: it’s “antirealism.” He thinks it has given up on the belief in finding what is really there.

The scientist above is Sean Carroll from Cal Tech. He is an award-winner and writer of many books including The Big Picture (2016) an effort to popularly explain modern physics and its philosophical implications. It is very good, so let me summarize some parts of it as engagingly as possible.

A Strange and Quarky Universe

(All Protons and Neutrons form the nucleus of atoms and are composed of two Up Quarks and a Down Quark held together by the Strong Nuclear Force transmitted by Gluon particles. A Proton and Neutron are held to each other in a nucleus by a kind of “spillover” of the Strong Nuclear Force. Forces of attraction and repulsion are still the opposite or same electrical charge, but now the charges are referred to, curiously, as Color Charge. Diagram from ck12.org)

This modern quantum physics has broken down the old picture of the atom into tinier parts and additional forces. One of its most interesting aspects, to me, is that forces are now also thought of in terms of particles. It seemed that traditionally forces were just ‘powers’ and ‘abilities’ between things—acting on things—and not composed of little things themselves. One of the dissatisfying aspect of Newton’s gravity was its character as “an action that took place over distance,” but what did the work through that distance of space between between attracted objects? The new theory answers that question; it is force particles and the fields that do the work. More on fields, soon.

Two Lists of Strange Beasts

Carroll provides us with two lists of the particles that populate this new physics. Just their names are worth the fun of knowing. Note that these particles are also the field around them; they are one and the same. So, there are two basic kinds of quantum fields and two basic kinds of particles: they are Fermions and Bosons.

Fermions are particles of matter: “they take up space and help explain the solidity” of all solid things, “including the ground beneath our feet,” writes Carroll. Fermion kinds are the —

  • Electron, muon, tau (-I)
  • Electron neutrino, muon neutrino, tau neutrino (neutral)
  • Up quark, charm quark, top quark (+2/3)
  • Down quark, strange quark, bottom quark (-1/3)

Bosons are not particles of matter; they are “force-carrying particles” that “pile up” to create forces (force fields) like gravity and electromagnetism. Boson particles are the—

  • Graviton (for gravity, spacetime curvature)
  • Photon (for electromagnetism)
  • Eight gluons (for the strong nuclear force)
  • W and Z bosons (for the weak nuclear force)
  • Higgs boson

It’s a far more complicated cast of characters than the former drama of the proton, neutron, and electron and their actions under the influence of gravity, electrical charge, velocity and inertia.

(The old picture of an atom, in this case Lithium–3 protons, 3 electrons. Importantly, Carroll argues that this theory is not wrong; it is now supplemented by a “deeper understanding.” In its own parameters, this picture is an “effective theory” that still forms the basis of chemistry.)


(“One can model a gravitational field by a vector field where a vector indicates the acceleration a mass would experience at each point in space.” Quote and diagram from Wikipedia)

“Modern physics says that the particles and the forces that make up atoms all arise out of fields…[and] that is called quantum field theory,” writes Carroll. Particles are fields. Forces are fields. It was Einstein who first started moving in this direction when in the early 1900s he unified space and time into a single field—spacetime. The force of gravity was now the curvature or warping of this field, and soon the very objects in the field were not independent of the field.

Traditionally, Newton thought of space as if a flat and uniform grid stretching in all direction. It could be full of objects or empty of them, that did not basically matter to space itself. Time, too, was like an arrow moving forward; it also did not depend on objects in time or objects moving through space and time. Time was still there in each case and just the same. None of this holds anymore for the new physics. Space, time, objects, forces are all mixed together and interdependent within field theories.

There are four kinds of fields and each has their associated particle.

  • The Gravitational Field is the weakest of the forces, but also the most universal. All the different kinds of particles exert gravitational attraction on each other. The graviton is the particular particle that conveys this force of attraction. Gravity is most significant over large distances and larger objects, at least relative to the other forces and their distances and objects. In this way it is a force very familiar to us and our ordinary life. This field is depicted in the image that leads this post.
  • The Electromagnetic Field is most significant in binding electrons to nuclei in and between atoms. In many ways it is also very familiar to us, as ordinary humans, as commonly known events (or ‘things’) like magnetism, electricity, and light. Each of these common things are basically about electrons and their relations to a nucleus or various nuclei. The photon is the particle that interacts in this field and carries the associated force—electromagnetism.
(The electromagnetic force and field: an electron has and is an electrical charge. It therefore interacts with its field. When “shaken” says Carroll, by heating up or just moving, it emits an electromagnetic wave through the field. This is the source of the light we see and other important waves. )
(An invisible thing, a magnetic field, becomes visible with the use of iron filings. Many kids enjoyed this activity when I taught 7th grade science.)
  • The Strong Nuclear Force or Field holds between Up and Down Quarks to compose a proton or a neutron. It is “carried” by gluon particles. A form of this force also holds protons to neutrons to form nuclei.
  • The Weak Nuclear Force or Field holds between a nucleus and a particle I (we) know little about, the neutrino. It is like an electron but with no electrical charge and little to no mass. It was discovered in 1955, but theoretically postulated prior to that in order to preserve conservation principles in several situations. A neutrino hardly ever interacts with matter. “A low-energy neutrino will travel through many light-years of normal matter before interacting with anything,” according to Scientific American magazine! 

Yet, Carroll tells us that “a field is kind of opposite of a particle; while a particle has a specific location in space, a field is something that stretches all throughout space” and it “takes on some particular value at every point.” Carroll illustrates this relation by describing the concept of “spin” as applied to electrons and gravitons. “We can think of the particle almost like little spinning tops, except…[they] don’t have size.” There is not a body (the top) that is “revolving around an axis.” “Their spin is an intrinsic property,” he explains. In other words, they are not like the planet Earth where we can think of it as a thing not spinning, and then also think of it as a thing but now spinning. Field theories blur the line between “a thing” and “the stuff around that thing.” An electron is only its spin of -1/2 and a graviton is spin -2 within their respective fields.

(We use this same thinking–somewhat– in identifying a hurricane. There is no absolute outer boundary to it, and there is no ‘thing’ [no body] at the middle of it that is doing the spinning. Curiously, for a hurricane, its middle is ’empty;’ it is calm with no spin.)

But in an Important Way, It Does Not Matter!

I will continue the above exposition in the next post because there are several more important areas to cover, but now it is important to get to Dr. Carroll’s general and philosophical implications of this new physics.

The structure of his book, The Big Picture, suggests to us the answer. All the above takes up very little of this 441 page book. The implications of the new physics are limited, he contends, and for a very important reason: Reality is in layers or has “levels,” and at each level there is a significant degree of autonomy. Changes in how we understand levels below any particular level do not need to necessarily change our understanding of the level of our interest. Most of Carroll’s book is about these other “useful” vocabularies and the conditions that allow for their legitimate use.

Chemistry works perfectly fine using a model of atoms in terms of protons, neutrons, and electrons and their bonds in terms of electrical charges. It does not now need to talk of quarks and boson particles. Only in very high energy situations does the old vocabulary break down.

Newtonian physics is also accurate for most uses. Quantum physics is not necessary, nor used, to understand the orbit of the moon or other planets nor plot a course to land astronauts on them. Classical Physics has its legitimate domain or “regime” says Carroll. Only in areas of extreme gravity, like a black hole or near the sun, do we need to use the new physics for many purposes.

(For a craft in flight through the air around it is best to think of air as a fluid. Atmospheric scientists and aeronautical engineers would use this kind of thinking and this equation to calculate “drag” or “air resistance” to a vehicle’s movement: Fd​=−21​ρv2ACdv^. Thanks to Khan Academy for diagram and equation)

Carroll’s “classic example of emergence,” or of the variety of “effective vocabularies,” is air. We can think of ‘air’ in two ways. We know air as a fluid when we think of it as having a “temperature,” a “pressure,” and providing “resistance.” This is a more macroscopic, “coarse-grained,” approach. Air, as a fluid, is continuous; it forms an unbroken field for which at every point there is a value for its temperature and pressure.

(Air as a fluid, again. The Venturi Effect: ‘The static pressure in the first measuring tube (1) is higher than at the second (2), and the fluid speed at “1” is lower than at “2”, because the cross-sectional area at “1” is greater than at “2”.’ Thanks to Wikipedia for diagram and quote.)

But to understand air “in a deeper way,” our physicist says we can think of it as a collection of molecules with energy. This is what Carroll calls “fine-graining,” and it allows us to “zoom in” and think of temperature and pressure as the movement of molecules and their collisions with each other and their container. I will add a third possibility, air as sub-atomic particles and fields. Of these last two possibilities—molecules and sub-atomic fields—each are “legitimate” but “incredibly cumbersome” ways to deal with air, says Carroll and therefore for practical purposes, “nobody ever talks that way.”

(Air as particles. Air Pressure is then  “the amount of force applied perpendicular to the surface of an object per unit area.” Thanks to Wikipedia for diagram and quote.)

Yet, air is all three things, and in a way, each is legitimate, useful, and functions independently of the other two vocabularies. Historically, our understanding of air as a fluid preceded our understanding of it as molecules, and the latter does not undermine the earlier. This is the case—in general—with our most modern quantum physics and its historically preceding vocabulary, Newtonian physics.

(“Fine-graining”: Yes we can see atoms. “This device, held together with hardware-store fiberboard and eyebolts and connected to a breadboard, is taking pictures of actual atomic structures.” “The device brings a needle atomically close to the object to be measured (by hand), applying a small voltage (+-15V), and stopping when it starts to conduct. Depending on the distance between the tip and the target, the voltage varies and does so precisely enough to identify whether an atom is underneath or not, and by how much.” Thanks to hackaday.com for picture and quote.)

So, hang on to your top quarks, strange quarks and muons, and may the gravitons continue to keep your feet firmly planted on the ground! In the following post, I will consider several more ‘charming’ aspects of the new Quantum Physics.

(Particles colliding in the Large Haldon Collider in Switzerland–i.e. equipment not available at your hardware store. Recent experiments have “found that so-called beauty quarks (or bottom quarks)  are not behaving the way that they should.” Quote and photo from Live science.)
Zooming in on pollen grains through the use of a Scanning Electron Microscope. Here at the naturereligionconnection.org)


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