This comes to mind often when I am crossing a railway bridge and a fast-moving train thunders past on the track directly below where I am on the bridge. When the train passes, I heave a sign of relief and say, “thank God for the 3rd dimension.” You see, if there were no 3rd dimension, I would have been run over by the train, but which I wasn’t as we (thankfully) share only 2 of the 3 physical dimensions available to us.
But then I once had to cross an unmanned railway crossing as there were no bridges around. After I had safely crossed the unmanned crossing a train trundled past behind me, and I heaved a sigh of relief and said, thank God for the 4th dimension. You see, the train and I shared the same 3-dimensional space; however, the time at which I passed the crossing, and the time at which the train passed were different; if they weren’t, I would have been run over and killed.
We humans are pretty adept at using the notion of the 4th dimension to our benefit without really thinking of it as such.