{"knowledge_schema": {"broad_category": "Physics \u2192 Astrophysics \u2192 High-Energy Processes", "refinement": "This problem involves understanding particle interactions in the context of cosmic radiation, specifically the annihilation of high-energy gamma rays with photons from the Cosmic Microwave Background (CMB).", "specific_scope": "The focus is on determining the threshold energy of gamma rays that would lead to significant interactions with CMB photons, resulting in the production of electron-positron pairs.", "goal": "Calculate the minimum energy of gamma rays that would have their lifetimes limited by the annihilation process with CMB photons."}, "summary": "This problem pertains to high-energy astrophysics, specifically the interaction between gamma rays and the Cosmic Microwave Background (CMB) radiation. It requires calculating the energy threshold for gamma rays that can annihilate with CMB photons to produce electron-positron pairs. The average energy of CMB photons is given as 10^-3 eV, and the task is to find the energy at which gamma rays would experience significant interactions, limiting their lifetimes in the universe. The correct answer is 2.6*10^5 GeV."}