Unruh Effect: Accelerated Observer's Thermal Bath

The Fulling–Davies–Unruh effect is one of quantum field theory's strangest and most rigorous results: whether the vacuum looks empty or warm depends on how you move through it. An inertial observer sees no particles at all — that is the definition of the vacuum state. A uniformly accelerating observer, riding the same vacuum, instead sees a genuine thermal bath of particles at a real, computable temperature T = ħa/(2πck_B), set purely by its proper acceleration a. This simulator computes that temperature live from the acceleration you set, feeds it into the exact Bose–Einstein occupation-number formula n̄(ω) = 1/(e^(ħω/k_BT) − 1) for a chosen field mode, and drives two side-by-side detector panels — one inertial, pinned at zero, one accelerated, clicking at the rate that occupation number implies — so the contrast is visible directly rather than just asserted.