  By a simple physical consideration and uncertain principle, we derive that
temperature is proportional to the surface gravity and entropy is proportional
to the surface area of the black hole. We apply the same consideration to de
Sitter space and estimate the temperature and entropy of the space, then we
deduce that the entropy is proportional to the boundary surface area. By the
same consideration, we estimate the temperature and entropy in the uniformly
accelerated system (Rindler coordinate). The cases in higher dimensions are
considered.
