Unruh Effect

The Unruh Effect is a phenomenon in physics that suggests an observer who is accelerating through empty space will experience what seems like a warm bath of particles, or light, that a stationary observer would not perceive. Essentially, while an unmoving observer sees nothing, the accelerating observer detects a thermal radiation, or "heat," due to their acceleration. This effect highlights the deep connection between motion, thermal energy, and quantum fields, revealing that what one observes can depend significantly on their state of motion in the universe.