A Brief History of Time

by Stephen Hawking

the more accurately you try to measure the position of the particle, the less accurately you can measure its speed,

provided a stationary rotating black hole had an axis of symmetry, like a spinning top, its size and shape would depend only on its mass and rate of rotation.

nondecreasing property of the event horizon’s area

So in empty space the field cannot be fixed at exactly zero, because then it would have both a precise value (zero) and a precise rate of change (also zero). There must be a certain minimum amount of uncertainty, or quantum fluctuations,

In Euclidean space-time there is no difference between the time direction and directions in space.