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Is there any experimental findings on behalf of the belief that all forces can be unified to a single force? Or the idea has it's inspiration from kind of thought experiment or philosophical belief.

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None! None at all! –  Cheeku Aug 25 '13 at 3:10
Actually a simple projection of the coupling constants fails to converge. That it fixes this "problem" is one of the usual desires of candidate next generation theories. On grounds of beauty, I believe. –  dmckee Aug 25 '13 at 3:12
You referred me to a closed question? @dmckee –  Arafat Aug 25 '13 at 3:21
What you describe seems more like a theory of everything than a GUT. –  Dimensio1n0 Aug 25 '13 at 4:03
@KaziarafatAhmed: So? So what? –  Dimensio1n0 Aug 25 '13 at 4:04

2 Answers 2

The experimental evidence comes from the running coupling constants.

One important clue that they (couplings) might all be the same comes from the fact that the coupling constants are not constants at all. Instead, they vary with the energy of the phenomenon in which they are measured. The value of as quoted above is only true for phenomena that occur at around 91 GeV of energy, the mass of the Z particle. Similarly, the coupling constant for the electromagnetic force has been measured to be about 1/137 in studies of atomic phenomena. When it is measured at the higher energies of LEP, however, its value has increased to about 1/128! The value of the coupling constant is said to 'run' with energy, and the constants themselves are usually referred to as running coupling constants.

running coupling constants

You might read the paragraph comparison to experiment on page 29 in this article.

In this talk the experimentally found running of the strong coupling is seen on a graph on page 3.

The running of the electromagnetic coupling is studied experimentally here.

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The reason to believe in a Unified Theory is more observational than experimental. Every subatomic particle has mass/momentum and magnetism, while most have charge as well. Obviously those force systems must be cohesive in order to exist. All unified theories seek to explain that cohesion.

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How did you differ observational and experimental? –  Arafat Aug 25 '13 at 3:25
Observations arise from surveying the data obtained in experiments, which is different than any one experiment since countless experiments went into compiling the data. –  JoeHobbit Aug 25 '13 at 3:27
I refrained from voting on this, but I feel that this is not an answer, but only a beat-around-the-bush0. –  Dimensio1n0 Aug 28 '13 at 17:33

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