question: How was the Planck constant calculated in the early 20th century ?
answer: the Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons
turker_answer: The Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons .
rule-based: The Planck constant was calculated in the early 20th century by the Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons .