The Leaning Tower of Pisa has never really been straight

Soon after building started in 1173, the foundation of the Pisa tower settled unevenly. Construction was stopped, and was continued only a 100 years later. It then became visibly clear that the Tower of Pisa is leaning, tilting to the south.

Since regular measuring of the tower began in 1911, the top of the tower has moved 1,2 millimetres per year. Today the top of the Tower of Pisa is some 5,3m off-centre. Engineers are working on the footing of the Tower rather than the structure, hoping to ease the top back about 20cm. But it means that the 800-year-old tower will remain leaning.

More than 5 billion crayons are produced each year

More than 100 billion crayons have been produced so far. The first crayons consisted of a mixture of charcoal and oil. In the early 1900s, Edwin Binney and Harold Smith developed a nontoxic wax crayon. Binney’s wife, Alice, attached the French word for chalk, craie, with “ola” from oily, to form the Crayola name.

The first Crayola crayons came in a box of eight. By 1957, 40 new colours were introduced. Today there are more than 120 crayon colours. Over five billion crayons are produced each year.

Why do I feel hotter when I wear dark colours?

Dark colours tend to absorb light energy. Light colours and white reflect light energy. That’s why you might feel warmer wearing a dark-coloured jacket than a light-coloured one. When light shines on your dark jacket, the jacket fabric absorbs light energy. The absorbed light energy causes electrons in the atoms of the jacket to vibrate. This activity releases heat energy, which makes the jacket – and you – warmer. That’s why people tend to wear more dark colours in winter and more light colours in summer.

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