This simulation shows four pressure sensors. One stays in air, the second can go into a container of water, the third can go into a container of mercury, and the fourth can go into a container of unknown fluid. The slider controls the vertical position of the pressure gauges. The horizontal white line shows the position of standard atmospheric pressure, which is at the top of each fluid. Note what happens to the pressure readings as you move the pressure gauges up and down. You can choose between displaying absolute pressure or gauge pressure - gauge pressure is simply the absolute pressure minus atmospheric pressure (101325 Pa). With this simulation, what can you determine about the unknown fluid?