Forces of Physics Change

Types of Matter

Before discussing forces, a brief fairy tale about the types of matter.

Once upon a time, in a land far, far away (Greece) and long, long ago (600 BC), the wise men determined that everything is made of four ingredients–earth, water, air, and fire. Over the subsequent centuries, other wiser men discovered that everything is actally composed of atoms–there are 94 different natural elements found in the familiar Periodic Table.

About 100 years ago, even more wiser men perceived that atoms, in turn, consisted of electrons, protons, and neutrons. Today, the list of sub-atomic particles is fast approaching 300. But wait–protons and neutrons are actually combinations of quarks. At first there were only three types of quarks; but presently there are believed to be at least 12; and who knows what the future will bring.

Almost simultaneously with the discovery of quarks, String Theory was developed by the wisest of the wise. Like atoms, strings are defined to be the ultimate element. Originally strings were two-ended linear things (strings). But strings yielded to loops, then multiple loops. And single dimensional strings lead to multi-dimensional strings. Will the unraveling ever stop? [READ MORE: String Theory Unraveled.]

Types of Forces

Unlike chaotic elementary matter, the situation with forces is simple and straight forward. There are four forces–no more, no less. Case closed–according to the scientific establishment.

However, only 200 years ago there were six forces known to mankind. Only one of them–gravity–has survived until today.

• Maxwell demonstrated in 1864 that electricity and magnetism were different aspects of the same force–the electro-magnetic force, or light, as we commonly call it.
• The other three forces–centrifugal, Coriolis, and Euler–have been classified as pseudo-forces produced as a consequence of rotation. (Actually they are different manifestations of gravity. You might call them secondary forces).

In the mid 1930s, two new forces were theorized: the weak nuclear force and strong nuclear force. Today, the four canonized forces (gravity, electro-magnetic, weak, and strong) are not as absolute as they might first seem.

• In 1979, the Nobel Prize was awarded to three rarely-named physicists for unifying the electro-magnetic and weak nuclear forces into the electro-weak force. (They were: Sheldon Lee Glashow, Abdus Salam, Steven Weinberg.)
• And other physicists are busy trying to unify the electro-weak and strong forces in a Grand Unified Theory. No doubt they will succeed some day. How many forces will we have then?

The strong force, or forces, is, or are, very unusual. This was originally called the strong nuclear force because it is much stronger than the other three forces and because its attractive strength held the protons and neutrons together in the atomic nucleus (using mesons).

• Further investigation has revealed the unique property that it (or another force) is even more repulsive to protons and neutrons at very short distances.
• The strong force was renamed the residual strong force when it was learned that the strong color force [Color is Quantum Theory terminology.] uses gluons to bind quarks into protons and neutrons with a strength 100 times more powerful than the original (residual) strong force.
• The strong color force is also unique in that it grows stronger with distance, as the quarks are joined together with flux tubes, which act like stretched springs.

How many forces are actually at work here depends on how you define them. Is a repulsive core and an attractive well one or two forces? Is acting directly through gluons on quarks and acting indirectly through mesons on protons and neutrons the work of one or two forces?

There are more cracks in the solid wall of exactly four forces.

• The van der Waals forces are three attractive and repulsive chemical interactions that relate to molecular polarity. These could be classified as a subset of the electro-magnetic force.
• And don't count out the Euler, Coriolis, and centrifugal forces just because they are labeled as pseudo forces. It turns out that in general relativity, gravity can be formulated as a pseudo force relative to curved space-time and that in string theory the fundamental forces are attributed to the curvature of differently scaled dimensions, which implies that all forces are pseudo forces.
• Then there is vacuum energy or anti-gravity. This new force is gradually gaining adherents. [I am one, so it must be real.] For the last decade many astronomers have searched in vain for missing dark matter (hot dark matter, cold dark matter, any dark matter) that would provide the mass needed to hold together galaxies and clusters of galaxies. They haven't found any but they know it is precisely 26% of the Universe. Anti-gravity does a much better job of explaining why individual galaxies and clusters of them do not fly apart.
• Not to be out done by the dark matter crowd, other theorists have discovered dark energy. They don't know what it is, but the are sure it comprizes exactly 69% of the Universe.

How many other forces are out there waiting to be discovered? Are we walking in Thales footsteps 2600 years later? Are we on the verge of discovering a vast array of forces heretofore unimagined? Here are some potential candidates:

• A force that explains the existence of matter in much larger amounts than anti-matter. (The ratio of mater to anti-mater is estimated at 9 to 1).
• A force that generates turbulence or clumpiness in a uniform, homogeneous body of gas and causes the formation of galaxies, stars, planets.
• A force to control the random, spontaneous creation and immediate annihilation of virtual matter-anti-matter pairs at the Quantum level.
• A force for each elementary particle that maintains it mass, charge, spin, color, etc. Or maybe a force for each of these properties.

Variable Forces

And this brings us to our last topic–variable forces. There is a nearly-universal assumption that the strength of forces is constant and unchanging. I am not so sure.

Everything in nature vibrates–unless it is at absolute zero temperature: light waves, sound waves, electrons in an atom, neutrons and protons in a nucleus, quarks in neutrons and protons, gas molecules in the air, water molecules in the ocean, iron molecules in steel. Even Earth and Sun vibrate. Probability distributions are equally ubiquitous.

So my thought is that perhaps the strength of forces is not absolutely the same and identical all the time. The strength of some forces could slowly oscillate over eons of time–periods too long for the human race to have noticed during its short history. The strength of other forces could vibrate with such a rapid staccato that we will never be able to measure the changes. Some forces may have so little variation that it cannot be detected. Other forces may have only occasional spikes or dips. In many situations, matter and energy are controlled by opposing forces–certain events may only happen when the strength of one force jumps while the strength of the opposing force drops.

If forces are variable, it would explain several puzzling phenomena:

• Quantum tunneling–The Coulomb barrier is an electrostatic field that repels objects with the same electric charge (both negative or both positive). Coulomb's barrier can be overcome by heating the objects, which increases their velocity so that their energy exceeds the Coulomb barrier and the objects go over the top of Coulomb's barrier. However, temperatures needed to overcome the Coulomb barrier turn out to be smaller than expected due to quantum-mechanical tunneling, in which objects that do not have enough energy to go over the top still manage to get to the other side.
• Radioactive decay–This is a process in which some atoms and sub-atomic particles release energy to achieve a lower entropy state by emitting or radiating away some of their matter. The decay is random and leads to the concept of half-life. There are three types of decay:
  • Alpha decay–Results in the emission of 2 protons and 2 neutrons (a helium nucleus) from the nucleus. It is controlled by the interplay between the strong nuclear force and the electro-magnetic force. Alpha decay is another quantum tunneling process.
  • Beta decay–Comes in two flavors, both governed by the weak nuclear force. Beta minus results in the emission of an electron and an anti-neutrino when the change of a down quark to an up quark causes a neutron to become a proton. Beta plus results in the emission of a positron and a neutrino when the change of an up quark to a down quark causes a proton to become a neutron.
  • Gamma decay–After alpha or beta decay, the nucleus may be in an more-excited (higher) state. It can then drop to a less-excited (lower) level by emitting a gamma ray, in much the same way that an atomic electron can drop to a lower energy level by emitting a photon. Gamma decay is controlled by the electro-magnetic force.
• De-excitation of atoms (spontaneous emission)–Each type of atom has its own unique set of discrete (quantized) electron energy levels. An electron can jump to a higher energy level when its atom collides with another atom or when an electro-magnetic photon with the proper energy level strikes the electron and gets absorbed by it. When an electron is in an excited state it can spontaneously drop to a lower level by emitting a photon having energy equal to the difference between the two levels. Einstein developed equations which gives the probability per unit time that an electron will behave this way.

The important point in these examples is that they are all random processes that function according to probability distributions. This implies that the forces that control these processes are not constant in strength, but rather fluctuate according to probability distributions.

Conclusions

• The number of forces known to mankind has varied over history.
• Forces are not discrete–they can be defined as differing aspects of each other.
• Some forces can manifest themselves in secondary or subsidiary forces.
• It is quite possible that there are many forces remaining to be discovered.
• In some circumstances forces behave according to probability distributions.
• This implies that forces are variable–if only slightly or infrequently.

[You may have noticed that I did not discuss gravity here at all, because gravity has its own page.] [READ MORE: Gravity is Attractive]