Vacuum cleaners don’t suck

Anyone that’s known me for more than a few years will know that I am not exactly the biggest fan of cleaning. I like to hoodwink people into thinking I have things sorted and that I exude domestic goddess status but in reality, I honestly don’t care that much. This is slightly problematic for someone with a crazy dust allergy but at the risk of this becoming a personal confessional, let’s move on shall we?

Henry is secretly disgusted in all of us

This deficiency in ability-to-adult is possibly why, when handed a vacuum cleaner as a pivotal prop to use in one of my shows and told to explain how it worked, I laughed hysterically.

But then it occurred to me that it’s highly likely the vast majority of people who frequently use a vacuum cleaner, have no idea how it works either. It’s like any piece of commonplace machinery in modern life; we use it but if asked to pull it apart and put it back together we’d end up with a mess.

Vacuum cleaners, it turns out, don’t suck. In fact a “vacuum” is more than a misnomer – it’s entirely not how they don’t suck and to explain just exactly how they don’t suck, I’m going to need to explain pressure.

First things first we need to think about air pressure. Take a look at your thumbnail. It’s about one square centimeter in area right? Well now I want you to imagine there’s a 1L carton of milk balancing on it. Heavy? Awkward? A contrived gedanken experiment? All answers to these questions should be “yes”. If you ever get a chance, you can actually feel what this is like. All you need to do is get a plastic bag and a vacuum cleaner (stay with me). Wrap the plastic bag around your hand and remove the air from inside it with the vacuum cleaner. You should be able to feel the air outside the bag, pressing onto your skin. Atmospheric pressure is CRAZY.

Vacuum cleaners work on the principle that any areas of high (so higher than atmospheric) and low pressure, if given the opportunity, will want to equalise. This means we can have some fun like this (with added cute-factor) or this (skip to 2 minutes for awesomeness). Now inside a vacuum cleaner, there’s a chamber with a fan. This fan is constantly rotating and works to push the air out of the chamber creating an area of low pressure. This means that the high pressure outside of the vacuum cleaner, instead of getting sucked in, is pushed in so that the high and low pressure equalises.

So vacuum cleaners don’t suck. I’ll definitely be thinking about how I know that the next time I “clean my carpets”*.

*”leave the vacuum cleaner in the cupboard to languish for eternity”.


How to smash a wine glass with your voice

For reasons which will hopefully become clearer as the year goes on, my internet search history has been getting weird. Weirder than usual. Last year, I found myself searching things like “Linear Discriminant Analysis”, “Photosystem II”, “Electron transport chain” and “can you take ibuprofen and paracetamol at the same time?” (you can totally do that without dying by the way but I am by no means a medical professional).

This week, I’ve found myself looking for decidedly more fun things. Including the topic of today’s post: Can you break a wine glass with your voice?


The answer is yes, but there are some caveats.

First of all, you need to be able to sing. Sound is essentially a vibration of the air around the object making the noise. The faster the vibration, the higher the sound and when I say “fast” I mean it. If you think about how fast you can wave your hand back and forth, you’d need to multiply that by about 20000 times to be able to hear your hand…. and you probably wouldn’t have a hand anymore…

Sound waves are what’s called “longitudinal waves”, meaning they move back and forth horizontally rather than, say, waves in the ocean which move up and down. When a thing makes a sound, it’s pushing the air out in really fast compressions. These compressions hit your ear and, through a complex process involving teeny tiny bones and millions of neurons, your brain converts them to sound. This is part of the theory behind the glass smashing. Point your horrifically powerful voice towards a glass and it starts to get bombarded by compressed air. The higher the sound, the faster the vibration which increases the amount of air hitting the glass and boom! It should explode.

But there’s actually one other thing happening; resonant frequency. If an object is hit with just the exact right pitch of sound, it will start to vibrate. Crystal glasses are really really good at resonating depending on the pitch of the sound. The more the glass vibrates, the more the molecules making it up are disrupted. If you hit a glass with a mallet, it makes a ringing noise. Match the frequency of the ring with your voice and you’ve got a very good chance of breaking it. Especially if it’s got a few cracks in it already.

So essentially, you need to be good, you need to be loud and you need to be very, very lucky. Like this guy on Mythbusters that one time. Awesome right?