Day 7 - Shambles Advent

Blog in a Teacup by Dr Helen Czerski

Day 7 – @lucy_maddox

Every day until Christmas Dr Helen Czerski will be finding some cool, hidden science in pics of people’s every day lives. To get involved, tweet your pic to @helenczerski and @cosmicshambles with the hashtag #ShamblesAdvent

@lucy_maddox sent this in, and it’s a familiar sight on lots of trains, especially just after the tea trolley has been round.  I love that tea trollies still exist, even if it only seems to be on planes and trains these days.  Here, we can see wood and paper and plastic, and it’s a good reminder of much we take all these materials for granted – even a cup of tea can make use of a tree (as both paper and wood), plus plastic and also probably a bit of metal on the inside of the milk sachet. 

What this picture made me think of is the importance of flaws.  We tend to assume that the best possible object is blemish-free and strong in every possible way.  But living in a world full of perfectly strong materials would be a nuisance.   For example, how would you get at the milk in that sachet if it was perfectly strong?  You’d never force your way in.  And if you did, it would probably break somewhere unexpected, and then you’d have milk down your shirt instead of in your tea.  The solution is that we make beautifully strong materials, and then we shape them so they have weaknesses that we can exploit.  That milk sachet has a zigzag top, and a notch at the side.  If you just pulled on smooth plastic, it would gradually stretch and then burst in an uncontrolled way.  But that notch, the weakness, concentrates all that stress in one small area.  Instead of the force you exert being spread evenly across the sachet, it’s concentrated at the notch.  That high stress can easily break the plastic, and it also has the advantage of breaking it exactly where you want.  It’s the same with loo roll with perforations separating the squares, and the notches in chocolate bars.  The imperfections let us control how the material breaks.  We can share the chocolate out fairly, and drink milky tea on trains without drenching our seat mate.

So this is my mini hooray for an imperfect world, one where we accept the imperfections and make use of them rather than trying to eliminate them.  Because the world would be a lot worse off without them.  

Read all Helen’s advent entries here 

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Dr Helen Czerski is a physicist, first and foremost, but she’s acquired a few other labels along the way: oceanographer, presenter, author and bubble enthusiast. A regular on The Cosmic Shambles Network, she has also presented a number of acclaimed documentaries for the BBC and her first book, Storm in a Teacup, which looked at the physics of every day things, was a bestseller. Recently she was awarded the prestigious William Thomson, Lord Kelvin Medal and Prize from the Institute of Physics.

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