'Blurred times' in a quantum world

When measuring time, we normally assume that clocks do not affect space and time, and that time can be measured with infinite accuracy at nearby points in space. Combining quantum mechanics and Einstein’s theory of general relativity theoretical physicists have demonstrated a fundamental limitation for our ability to measure time. The more precise a given clock is, the more it ‘blurs’ the flow of time measured by neighboring clocks.

(via WSJ)