A 1500-year-old calculation by Dionysius Exiguus, a 5th-century monk, is still shrouded in mystery, with his method for determining Easter remaining unsolved.[810638] The advent of space exploration has brought attention to the complexities of representing four-dimensional space-time in a simple diagram, such as the Minkowski diagram.[810638][749317] The space industry's growing presence in our atmosphere has led to a rise in atmospheric pollution, with discarded satellites and rockets leaving behind toxic clouds.[810638][733032]