Autumn quickly turns to winter in this part of the world, but that doesn’t necessarily just mean more grey days. The science of shifting weather is fascinating, and there is a fantastic activity for watching a part of that change that is normally invisible.

In this month’s Let’s Discover, we will teach you how to build a barometer from household materials so you can watch the changing air pressure.

All you need is a balloon, tape, an elastic band, scissors, a jar and something light and pointy (we use drinking straws, but a wooden skewer works) and a piece of cardboard.

To make your barometer, cut a piece of balloon to fit tightly over the mouth of your jar, stretch the elastic over the jar’s rim to hold the balloon on tightly. No air should be entering or leaving the jar. To monitor air pressure, tape a straw to your balloon’s surface, with its point in the balloon’s centre, and plenty of straw (or skewer, or any pointer) sticking out over the edge.

All the details for how to make it are found in this step-by-step video made just for us by the Discovery Centre team:

Your barometer contraption will indicate whether the air pressure outside of the jar is higher or lower than inside the jar by its pointer sticking up or down (up for higher, or down for lower). The way it works is that air always moves from areas of high pressure to lower pressure — your balloon will bulge up when pressure in the jar is higher than outside and it will suck downward when air pressure outside is higher. Standing a cardboard or paper scale behind to chart the movements of your straw will help to know when it’s changing! Changing air pressure is usually one indicator that there may be a change in the weather coming (a storm, or weather clearing for example), and barometers give the very best results when used outside (where the weather is!).

If the changing weather has got you and your family down, come inside to the Discovery Centre. On November 23, SMU Robotics will be at the Centre competing their robots in a Mars Mission!