To measure the lifetime of a proton, scientists essentially build large, sensitive detectors that monitor a huge number of protons over long periods of time, looking for any signs of decay, as no proton decay has ever been directly observed; the current method is to set a lower limit on the proton lifetime by observing a large sample of protons and recording any potential decay events, with the absence of observed decays indicating an extremely long lifetime.No direct observation of decay:As per the Standard Model, protons are considered stable particles, meaning they don't decay on their own, so experiments focus on setting a lower limit on their potential lifetime by looking for decay events that might occur according to some theoretical models (like Grand Unified Theories - GUTs).

Large-scale detectors:Experiments typically involve massive tanks filled with a medium like water, with highly sensitive detectors placed around to capture any potential decay products (like photons) from a proton decay event.Underground location:To minimize interference from cosmic rays, these experiments are usually located deep underground.Statistical analysis:By monitoring a large number of protons over extended periods, scientists can calculate a lower limit on the proton lifetime based on the probability of observing even a single decay event if the decay rate was higher.

Challenges in measuring proton lifetime:Extremely long lifetime:The predicted proton lifetime based on current theories is extemely long, potentially in the range of 10^30 to 10^36 years, making it very difficult to bserve even a single decay event within a reasonable experimental timeframe.Background noise:Distinguishing a genuine proton decay signal from background noise created by other particles interacting within the detector is a significant challenge. If the proton's life time exceeds 10^34 years it must have existed before the current universe was formed. If so where was it located, in another Universe. That makes Multiverse closer the truth than the Bigband is!??