Modern Physics BY Alli Grinde

The Four Fundamental Forces

Strong Interaction

Strong Interaction or Strong Nuclear Force is one of the four fundamental forces, and it is responsible for the binding of nuclei. In order to do this, the strong fire must overcome the great repulsion forces of the protons. It is the dominant force in most reactions and decays. However strong, it still has a very short range. No such force will be felt beyond the order of 1 femtometer.

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Weak Interaction

The weak interaction changes one flavor of quark into another. The weak interaction is the only process in which a quark can change to another quark, or a lepton to another lepton, AKA "flavor changes". The existence of the weak interaction was first revealed in radioactive decay, which it is responsible for, as well as other similar decay processes. The weak force is necessary for the burning of the sun and the buildup of heavy nuclei. The range of this force is smaller than 1 fm, making it weaker than the strong force.

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Gravitational Force

Though gravity, the force that holds us onto the Earth, is important in our daily life, it has little to no effect in the atomic world. There is gravitational pull between any two objects, whether they are a centimeter away or as far away as stars and galaxies. The effect is so small, however, that it is often difficult if not impossible to detect. It is possible to sense Earth's gravitational pull due to the cumulative effect of the billions and billions of atoms that make up earth with the billions and billions of atoms that make up Earth. This means that the larger the body, the stronger the force. But on the scale of individual particles, the force is extremely small, only in the order of 10^38 times that of the strong force.

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Electromagnetic Force

Electromagnetism exists between all particles that have an electric charge. Many everyday experiences such as friction and air resistance are due to this force. This force is also responsible for the resistance we feel when we press our palm to a wall, because no two atoms can occupy the same space. However, the strength of electromagnetic force is about 100 times weaker within the range of 1 fm, where the strong force dominates. But because there is no shielding within the nucleus, the force can be cumulative and can compete with the strong force. This competition determines the stability structure of nuclei.

Einstein's Theory of General Relativity

The Theory

"Albert Einstein's general theory of relativity is one of the towering achievements of 20th-century physics. Published in 1916, it explains that what we perceive as the force of gravity in fact arises from the curvature of space and time. Einstein proposed that objects such as the sun and the Earth change this geometry." ( from www.newscientist.com, see below)

The General Theory of Relativity is Einstein's explanation of gravity in space-time. Einstein stated that the universe is like a giant sheet or trampoline that is stretched out. Objects create a dent in the sheet, and those with greater mass create a larger dent. Gravity comes from the steepness of the dent, and it influences space-time.

https://www.newscientist.com/round-up/instant-expert-general-relativity/

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Barriers to Relativity

Einstein is widely known as one of the most intelligent beings to ever grace the earth, but some still question his theory. What creates the indentation in space-time around the masses? Why doesn't it line up mathematically with quantum physics? These are questions that, even now, 102 years after Einstein came up with this theory, scientists are still trying to solve.

Quantum Mechanics

The Quantum Level

By definition, Quantum Mechanics is the fundamental theory of nature at small scales and low energy levels of atoms and subatomic particles. On the quantum level, anything is possible. Things can happen there that seem impossible in the world that we see, and there are infinite possibilities on the quantum level in parallel universes. Quantum Mechanics describes strong and weak nuclear forces and electromagnetism.

Unification & String Theory

The Struggle to Unify

As said before, people still have questions about Einstein's General Theory of Relativity. It doesn't seem to match up perfectly with all other theories, such as the quantum theory. This has created a division in the world of physics. Some believe that the theories should line up, and that there is a source of human error somewhere. Others might believe that one or both of the theories are wrong. A new theory, however, called the String Theory, has provided yet another explanation for the differences in Relativity and Quantum Mechanics.

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The String Theory

The String theory was developed in the 1970s and is still a source of controversy in the world of physics. Some embrace the idea, while others scorn it. Regardless, the String Theory could be key to the unification of physics. "Hand-in-hand with the question of quantum gravity, string theory attempts to unify the four forces in the universe — electromagnetic force, the strong nuclear force, the weak nuclear force, and gravity — together into one unified theory. In our universe, these fundamental forces appear as four different phenomena, but string theorists believe that in the early universe (when there were incredibly high energy levels) these forces are all described by strings interacting with each other." (from www.dummies.com, see below)

Credits:

Created with images by FelixMittermeier - "night photograph starry sky night sky"

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