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. However, combining quantum mechanics and Einstein’s theory of general relativity theoretical physicists from the University of Vienna and the Austrian Academy of Sciences 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 neighbouring clocks. As a consequence, the time shown by the clocks is no longer well defined. The findings have been published in the journal “PNAS”.