For other comparisons, see the table below. Absolute Zero Absolute zero, according to current scientific thought, is the lowest temperature that could ever be. In fact, it's so low that we can never quite reach it, although research teams have come within a fraction of a degree. The first clue to the existence of absolute zero came from the expansion and contraction of gasses. We know that hot air rises and cold air falls.
Air rises when it's heated because it expands, so it's less dense than the cooler air around it.
It has bouyancy, just like a piece of wood in a pond, which floats because it's less dense than the water. Suppose we took a certain amount of air and cooled it as much as we could. When scientists first began studying the behavior of of heated and cooled gasses, they didn't have our modern cooling methods. They measured as best they could over the temperature range that they could reach. Then they plotted their data on graphs.