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Crazy Shapes

What do a donut and a coffee cup have in common? Can you really turn a ring into a picture frame with a single cut? Find out yourself, in this week of Pop-up Science on topology, the science of crazy shapes!

Send us photos of your experiments to or share them using #ISTAustria or #PopUpScience on Facebook, Twitter or Instagram!

Activities for this week

DIY Experiment – Tricks with strips

Can you cut a paper ring with a single cut such that it forms a bigger ring? Find out about this and other tricks with the help of our young scientists Eva and Elisabeth. Can you discover all of the hidden shapes?

Watch the corresponding video on YouTube

Science leaflet

In this week’s science leaflet you’ll find a puzzling handcuff riddle to try with a friend. Learn more about topology and read the story of a young lady who escaped from an evil king thanks to topology!

Interview with a topology researcher

Our expert Kristóf Huszár talks about how he became a fan of mathematics. He also reveals whether it is true that topologists cannot distinguish between a donut and a coffee cup.

Watch the corresponding video on YouTube

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