Storm in a Teacup: The Physics of Everyday Life

Critical thinking is essential to make sense of our world, especially with advertisers and politicians all telling us loudly that they know best. We need to be able to look at the evidence and work out whether we agree with them.

This process of discovery is science: the continual refinement and testing of our understanding, alongside the digging that reveals even more to be understood.

Nothing that is in equilibrium can be alive.

Destruction doesn't always have to be a bad thing.

humans; we’re not aware of the ultraviolet light in the first place, so we don’t lose anything when it gets turned into something we can use.

Tuberculosis is an airborne disease. Carried out of the lungs with each cough are thousands of fluid droplets, plumes of minuscule crusaders. Some of them will contain the tiny rod-shaped TB bacteria, each only three-thousandths of a millimetre long. The fluid droplets themselves start off fairly big, perhaps a few tenths of a millimetre. These droplets are being pulled downwards by gravity and once they hit the floor, at least they’re not going anywhere else. But it doesn’t happen quickly, because it’s not just liquids that are viscous. Air is too – it has to be pushed out of the way as things move through it. As the droplets drift downwards, they are bumped and jostled by air molecules that slow their descent. Just as the cream rises slowly through viscous milk to the top of the bottle, these droplets are on course to slide through the viscous air to reach the floor. Except they don’t. Most of that droplet is water, and in the first few seconds in the outside air, that water evaporates. What was a droplet big enough for gravity to pull it through the viscous air now becomes a mere speck, a shadow of its former self. If it was originally a droplet of spit with a tuberculosis bacterium floating about in it, it’s now a tuberculosis bacterium neatly packaged up in some leftover organic crud. The gravitational pull on this new parcel is no match for the buffeting of the air. Wherever the air goes, the bacterium goes. Like the miniaturized fat droplets in today’s homogenized milk, it’s just a passenger. And if it lands in a person with a weak immune system, it might start a new colony, growing slowly until new bacteria are ready to be coughed out all over again.

As the droplets drift downwards, they are bumped and jostled by air molecules that slow their descent. Just as the cream rises slowly through viscous milk to the top of the bottle, these droplets are on course to slide through the viscous air to reach the floor.

Learning the science of the everyday is a direct route to the background knowledge about the world that every citizen needs in order to participate fully in society.