Question - Why are barometers so important to science. What is the purpose of the barometers. Any input would help. Barometers are instruments to measure the pressure of the atmosphere. The barametric pressure tell us the weight of air pushing down.
Cold air is denser and pushes down harder.
If the readings from several locations are marked on a map, there is often one part of the map where all the readings are higher than on others. There are a number of ways to measure the pressure of the atmosphere. So you have a hollow chamber. Now you will have pumped out the hollow chamber with a vacuum pump so that there is no air in the chamber. How that is done doesn't concern us here, just accept that it can be done easily.