{"knowledge_schema": {"broad_category": "Astronomy \u2192 Cosmology \u2192 Redshift and Spectroscopy", "refinement": "This problem involves understanding the concept of redshift in relation to the absorption of light by neutral hydrogen in deep space, specifically at the Lyman alpha wavelength.", "specific_scope": "The focus is on estimating the minimum redshift at which neutral hydrogen clouds can absorb light from quasars, making them detectable with optical telescopes.", "goal": "Determine the minimum redshift value that allows for the detection of neutral hydrogen clouds absorbing Lyman alpha light from quasars."}, "summary": "This problem pertains to the field of astronomy, specifically the study of redshift and its implications for detecting cosmic objects. It requires an understanding of how the Lyman alpha wavelength (1216 Angstrom) shifts due to the expansion of the universe. The task is to estimate the lower limit of redshift for neutral hydrogen clouds that can absorb light from background quasars, allowing for their detection with optical telescopes. The goal is to identify the correct redshift value from the given options."}