In the beginning of the universe, there was only one force. All actions were done by a same force. Let's begin by explaining the present 4 forces that were once separated from one.

The four forces existing in the natural world are, gravity (universal gravitation), electromagnetic force, strong force and weak force. First, gravity (universal gravitation) is well known for working on all matter that has mass(energy). The story of Isaac Newton, and how the idea of gravity flashed in his mind when he saw a falling apple, is the most famous example. Another example is when a ball thrown into the air comes down to the ground. This is due to the earth pulling the ball, and if there was no gravity, the ball would keep on flying upwards forever. The reason why the humans can stay on this spherical earth is due to gravity between the earth and humans.
To the simulation of Universal Gravitation made with Java

Secondly, the electromagnetic force is the force of a magnet and electricity. The magnet and metal attracting toward each other, and pictures visible on the TV screen, are examples of electromagnetic force. The motion between matter with electromagnetic force, is controlled by photons. That is, photons are working as a medium between matter.

The strong force and the weak force are not commonly known. But they are very important in the microscopic world like the elements of matters, such as atomic nucleus and elemental particles. The strong force, as the name suggests, is the largest force among the four forces. It works only in a tiny space of 10^-13 cm, and it joins the protons within the atomic nucleus.

The weak force also works in a narrow space of 10^-12 cm. This force causes the neutrons to change into protons, a phenomenon called as the beta decay of the atomic nucleus.
To the animation of The Four Forces made with Shockwave Flash

The Grand Unified Theory

The four forces work at different places and they have different strengths. In microscopic world, gravity hardly works, thus it can be neglected compared to other three forces. Of the 3 remaining forces, the strong force is the strongest, then the electromagnetic force, and then the weak force.

The grand unified theory tried to explain the three forces, strong force, weak force, and electromagnetic force, by one theory. Only gravity is explained by a different theory named the theory of relativity.

Furthermore, physicists are building a theory connecting three forces (unified by GUT) and gravity.

There was Only One Force

How the forces separated

Why does it help us to understand planck time if the four forces are put into one? Because the four separate forces used to be a single force at the beginning of the universe. Saying that four forces can be explained by one theory, actually means that we can think about the force that used to be the only one.

We can imagine that, as time went on and the temperature of the universe fell, the single force separated into 4 natures, as explained earlier. At first, when planck time finished, the force of gravity separated first. Then after the inflation (which we will explain later) finished, the strong force separated. In the end, the weak force and the electromagnetic force separated, and there were then four forces.

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• Test - Ikuya Yamada (Administrator) 08/19/99 02:55:10 - [Others] (0)