Understanding the Four Forces

Harpreet Thandi

We want to understand the world around us. There are four theorized forces in our universe. These are the nuclear force (weak force), the strong force, gravity, and the electromagnetic force. These all act very differently around us.

The weak force is responsible for processes such as fission (radioactive decay), particles like muons, leptons, and others with short lifetimes. This is the 3rd strongest force and only stronger than gravity. It counteracts the strong force. With a range of just,10-18m smaller than an atom (10-15m). It exchanges energy with the bosons, the particles that carry charge. The Weak force has a very short lifetime. This seems like a problem. However, due to Heisenberg’s Uncertainty principle it is possible to have a large amount of energy for a short time.

One way to put this is if you multiply numbers to make 9 or another fixed value like ℏ/2 or higher. We can of course do 3×3; but if one of numbers is bigger let’s say, 3000000 then the other must be 0.000003 to compensate, now we have achieved 3000000×0.000003=9 as before.

The strong force binds (joins) the nucleus together. This has the 2nd   shortest range of 10-15m. This acts on quarks inside protons and neutrons equally to “glue it together”. The neutrons help control the atom and when they get too close this force keeps them apart. Like a sad romance. An analogy often given involves sellotape. First you feel nothing until, you get close and then it acts sticks “the strong force repels actually”. These two forces act inside of the atom. The outcome of these forces can be seen on the periodic table as the range is the size of a nucleus-this stops atoms from getting too big. In addition to this the larger atoms decay via the weak force.

Gravitation binds the universe together, keeps the planets in orbit, people grounded (well some of us!!), and acts on anything that has considerable mass, like Newton’s apple. In Einstein’s theory of general relativity, gravity causes a distortion of space and time. This is the weakest of the force, but has an infinite range and acts by using gravitons. These have never been observed yet, sadly.

Magnetism and Electricity were once thought of as separate concepts. However, after observations and mathematical reasoning were shown to be linked as a single force. Famously, in 1820 Hans Christian Ørsted saw a needle being deflected by a battery cable and James Clerk Maxwell proved the two waves were perpendicular to each other.

Electromagnetism binds atoms and anything else in the universe that has charge e.g. protons, electrons, muons. This is the 2nd strongest force and has an infinite range using photons. Another way of looking at this would be a fridge magnet. This is many magnitudes stronger than gravity-something to think about. These two forces act outside of the atom.

For the last 30 years of his life, Einstein tried to unify gravitation and electromagnetism without success. This seems possible, given the similarities with infinite range and both being the most visible to mankind. This pursuit was driven by a need to have things joined together which exist together. In a 1923 lecture stating “The intellect seeking after an integrated theory cannot rest content with the assumption that there exist two distinct fields totally independent of each other by their nature”. Back in the 1900s only protons, electrons and these two forces were known about. Einstein rejected the new quantum mechanics stating “god does not play dice”.  Over time Einstein became an outsider towards mainstream physics. Rather than using physical intuition “thought experiments” that birthed most of those great works, he now became obsessed with only mathematical understanding. Michio Kaku; professor of theoretical physics at the City College of New York, would consider Einstein to be thinking way ahead of his time. Most of the physics that Einstein would have needed as a base had not been discovered yet.

Physicists today take on this unification challenge. An idea called string theory is required. This requires 10 dimensions to explain the physics, and is a mathematical quest. It is an extension of Einstein’s 5 dimensions. This is hard to prove experimentally. However, researchers are constantly working on translating this into something observable. This is a very different and hard to imagine view of our universe. We must hope there is a way to translate these mathematical predictions into the real world.

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