The Four Fundamental Forces

Posted by on 02/10/2013
The 4 Fundamental Forces

The 4 Fundamental Forces

The four fundamental forces of the universe are:  Electromagnetism, Gravity, Nuclear Strong force and Nuclear Weak force.  Modern physics attempts to explain the observed physical phenomenon between these fundamental interactions.   Reducing the interaction types between the forces is the objective.

Below is a brief overview of the 4 fundamental forces of our universe.  In addition, here’s an interactive, animation by Cary Huang, that details the vast scales of our observable existence–from 1026 at the Universe scale, to 10-35 at the Plank scale.


Electromagnetism icon

Electricity and magnetism are the same force

Electromagnetism – This is the force that acts between electrically charged particles.  This includes the effects of electricity and magnetic forces.   This means that the electricity that powers a house, or a city; and the magnetic forces of a compass, or the earth, are part of the same force.  Electromagnetism is infinite-ranged, like gravity, but much more powerful.  This force describes all human made devices using electric current (phones, TVs, lasers), as well as rainbows, lightning, and even friction.  It also determines the properties of chemical bonding down to the atomic level.


The weakest of the 4 interactions

Gravity –  By far the weakest of the four interactions.  The best example of the “weakness” of Gravity is to use a magnet to pick-up a paper-clip.  The magnet can hold the pin against the entire gravitational pull of the earth.  And yet, Gravity exerts itself through the very fabric of our universe. Gravity acts on all particles that have mass, and has an infinite rage.  Unlike the other forces, Gravity cannot be shielded against, absorbed, nor transformed; and it always attracts–never repels. Because Gravity acts on everything, is infinite, and only attracts, it has a huge significance in the formation of galaxies, black holes, and the expansion of space-time.  Where the other forces deal with close interactions, gravity matters on the large scale structure of the Universe itself. Gravity was tested famously by Galileo Galilei, as he dropped a cannonball and a feather.

Nuclear Weak Force

Initiates hydrogen fusion

The Nuclear Weak force is responsible for radioactive decay.  Thus it initiates the process of hydrogen fusion that occurs in stars, which in turn, powers the creation of galaxies, solar systems, planets, and at least one time on our humble Earth, conscious life.  It’s called the ‘weak’ force because it has a very short range of interaction, several orders of magnitude less than the other forces.  Where Gravity acts on the entire Universe (1022), the Nuclear weak force acts in the space between quarks (10-22).  The radioactive decay caused by the Nuclear Weak force makes radiocarbon dating possible, which allows us to determine the ages of rocks and fossils.

Nuclear Strong Force

Keeps protons together

The Nuclear Strong force is the most complicated interaction because of the way it varies with distance.   At an atomic scale, it’s about 100 times stronger than electromagnetism, which in turn, is orders of magnitude stronger than the Nuclear Weak force and Gravity.  At the 10-10 scale, the Strong force binds protons and neutrons together to form the nucleus of an atoms.  But at the much, much smaller scale of 10-18, the strong force controls the interactions between the special quarks that make up protons and neutrons.   This binding power of the Nuclear Strong force at both of these scales, is used in nuclear power and nuclear weapons.

All graphics by dano. Use with permission and attribution.

For more great info about the 4 Fundamental Forces, here’s a YouTube playlist by Scishow that details this concept in a fun and clever manner. Good stuff!

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