Ben Sanders, Medical Observer
My exciting tale of seeing @DoctorKarl, a real, live science geek, in my home town’s writers festival was first published here in Medical Observer, Oct 2013.
This morning I took two of my sons to see Dr Karl Kruszelnicki at the Brisbane Writers Festival. He was even louder and more brilliant than his orange shirt, and my kids couldn’t get enough of him.
My younger one asked him whether, if you stand on accurate scales and breathe in, your weight changes. He asked me the same question last week, and Dr Karl’s answer exactly matched my own, although mine was done while yelling at him (my son, not Karl) to get ready for school, which doubles the degree of difficulty. Everyone clapped Karl’s answer, whereas mine just made me late for work.
You weigh the same unless you pressurise the air in your lungs. My 12-year-old preferred Dr Karl’s explanation over mine, even though I spent the first five minutes on the derivation of the word Valsalva.
Dr Karl’s talk was witty and erudite, and at the subsequent book signing my older lad, who is rarely effusive, told Karl, ‘You’re a legend among many’. Many what? Many dads whose clever answers don’t count, due to their slight inaccuracies? I want to count. I want my dad jokes to simply be ‘jokes’ and my dad answers to be taken seriously (except when they are actually dad jokes).
I want many things, but in short, I think I want to be Dr Karl.
By this, I don’t mean I want to genetically modify myself to literally become him, which is currently impossible in any case (I checked with Karl). But wouldn’t it be grand to sit up in front of the clapping crowds, confident that the quirky facts rapid-firing out of your mouth are both interesting and true. My facts are more like Ripley’s ‘Believe it or not’, making considerable use of the ‘not’ option.
At the writers festival, the talk turned to pubic hairs and someone asked Dr Karl a curly one. Turns out I was wrong telling my son the shape was for shock absorption. Dr Karl knew absolutely everything about pubic hairs, from their sulphur bonds and helical cross section, to their reduced point contact on the bath surface, which makes them float more than straight hairs. This bloke has a PhD in groin cilia.
I guess I just have to accept that Dr Karl’s brain is smarter than mine, his facts are more factual and his jokes aren’t dad-like. Although they will be by the time I’m finished with them. I still have one more son who hasn’t heard them yet.
drjustincoleman 
So – does breathing in on the scales change your weight? I would guess minimally?
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I am so glad you asked, Jill. A complex explanation didn’t seem to fit either the word count or the article genre! Now you’ll have to forgive my long-winded answer…using all the air in my lungs, so to speak. Other readers, feel free to switch off now.
Undoubtedly, whatever weight on the scales we are talking about is merely the weight of a few cubic centimetres of air, which is ridiculously tiny, and less than a bit of fluff settling on your clothing. But if we imagine an incredibly precise scale, then it all depends on air pressure in your lungs.
If your mouth (glottis) is open and the air pressure in your lungs is the same as atmospheric pressure, then breathing in makes no difference at all. It is like weighing a lump of clay, then reshaping the clay into a larger, hollow bottle shape and re-weighing it; no difference. We are all ‘floating’ in the atmosphere, so the weight of the increased volume of air inside us is exactly negated by the extra buoyancy due to the atmosphere around us.
However, if we pressurise the air in our lungs, our chest volume decreases without any loss of mass, so we are slightly less buoyant, and the scales will measure an increased weight.
The sad thing is, I love this stuff, but I guess I haven’t fostered a readership who necessarily shares my fascination!
For further reading, I recommend a great website called http://what-if.xkcd.com/
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Thanks for taking the time to respond, Doc. Your sons are lucky to have a dad who they can ask such questions and get great answers.
My darling late Dad used to answer my endless questions on the hows and whys of the world, and I treasure having had that. I hope that I can be half as useful to my future children!
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Not a sad thing at all – very cool! Or maybe I’m just sad too – another science nerd who likes to know the how and why.
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Intriguingly, Genevieve, our shared sadness makes me happy!
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My parents and friends think it’s sad the only things I look forward to in the mail are my uni textbooks sigh.Mum says that it’s very sad and I should get a life . Therefore I can appreciate where you’re both coming from in terms of enjoying science stuff etc
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