What type of radiation was Planck studying in the late 19th century?
In the last years of the nineteenth century, Planck was investigating the problem of black-body radiation first posed by Kirchhoff some forty years earlier. It is well known that hot objects glow, and that hotter objects glow brighter than cooler ones. The electromagnetic field obeys laws of motion similarly to a mass on a spring, and can come to thermal equilibrium with hot atoms. The hot object in equilibrium with light absorbs just as much light as it emits. If the object is black, meaning it absorbs all the light that hits it, then its thermal light emission is maximized.
Among Ike's objectives in not directly confronting McCarthy was to prevent McCarthy from dragging the Atomic Energy Commission (AEC) into McCarthy's witch hunt for communists, which would interfere with, and perhaps delay, the AEC's important work on H-bombs. The administration had discovered through its own investigations that one of the leading scientists on the AEC, J. Robert Oppenheimer, had urged that the H-bomb work be delayed. Eisenhower removed him from the agency and revoked his security clearance, though he knew this would create fertile ground for McCarthy.