The standard state of a substance does not have to exist in nature: for example, it is possible to calculate values for steam at 298.15 K and 10 5 Pa, although steam does not exist (as a gas) under these conditions.
A Mesopotamian wheel. Photo source. One of the reasons why the wheel was invented only at this point in history is due to the fact that metal tools were needed to chisel fine-fitted holes and axles. This leads to the next reason â the wheel was not just a cylinder rolling on its edge. It was a cylinder that was connected to a stable, stationary platform.
Another invention, closely kin to the wheel, was the compass for making circles. The first hinged compasses also trace to that same region, 5500 years ago. Early wheels show a progression of understanding. The first wheels were cut from huge wooden slabs, built up of boards.