Modern Physics: The Story of Everything Jesse King

The Earth consists of four fundamental forces: gravity, electromagnetism, strong nuclear, and weak nuclear. These four forces are responsible for everything we know--and don't know--on Earth, in space, on other plants, and throughout all the galaxies in the universe.


Gravity is the force that keeps us, and other objects, on Earth and from floating away into space. The force pulls us toward the Earth's core at -9.8m/s/s. Newton thought gravity was a force between any two objects in the universe, but Einstein partly refuted this.

Strong Nuclear Force

Strong nuclear force is the force that keeps protons and neutrons together in an atom. Since protons are positively charged and should repel each other, the force to keep them together is very strong.


Electromagnetism is a unification of electricity and magnetism. This force is billions of times stronger than gravity and it keeps us from falling through the Earth by negatively charged atoms repelling each other.

Weak Nuclear Force

Weak nuclear force is the force responsible for radioactive decay.

General Relativity

General relativity is the "big scale" of physics. It is the study of gravity of "massive stuff" like planets and stars and how they affect space-time. Although it is the hope gravity can work on a quantum level, it can only be analyzed by general relativity and not quantum mechanics.

Quantum Mechanics

Quantum mechanics is the "small stuff" of physics. It is the study of "tiny stuff" like subatomic particles and atoms. Quantum mechanics includes weak nuclear force, strong nuclear force, and electromagnetism. These three forces in quantum mechanics cannot be analyzed in terms of general relativity.

Unification and String Theory

When Newton was first studying gravity, he was able to unify the heavens and the Earth into one equation. He discovered that the reason an apple fell off a tree and the moon rotated around the Earth were due to the same source--gravity. This is an example of unification.

Because quantum mechanics and general relativity cannot be combined, the string theory is thought to be the key to unifying them. Just like Newton unified gravity to explain it on all levels, using the string theory is hoped to allow quantum mechanics and general relativity to combine in one equation that can explain everything in the universe.


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