The Standard Model gathers three forces into a single quantum framework, yet only electromagnetism and the weak force genuinely merge, at a scale of about 100 GeV, a merger confirmed when the W and Z bosons were found in 1983. Folding the strong force in as a grand unified theory has no supporting evidence, and gravity stands entirely apart because quantising it the usual way throws up infinities that will not cancel. Vibrating strings and loop quantum gravity are two candidates starting from completely different premises, and neither has been tested experimentally.
The Standard Model gathers three forces into a single quantum framework, yet only electromagnetism and the weak force genuinely merge, at a scale of about 100 GeV, a merger confirmed when the W and Z bosons were found in 1983. Folding the strong force in as a grand unified theory has no supporting evidence, and gravity stands entirely apart because quantising it the usual way throws up infinities that will not cancel. Vibrating strings and loop quantum gravity are two candidates starting from completely different premises, and neither has been tested experimentally.
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