# Back (page) to front

In this edition we have explored the science behind backwards and upside down faces, but it’s not just faces that go funny when we look at them in different ways.

## You can da Vinci code

For years, the Renaissance scientist and artist Leonardo da Vinci kept his journals secret using a simple code: he wrote all his letters and numbers backward. You can train your brain to learn his secret code too. All it needs is paper, a mirror and practice. Start by writing out all the letters of the alphabet and the numbers in your best handwriting. Then take a mirror and use it to reflect what you have written. Copy all the letters as seen in the reflection on to another sheet of paper, and when that’s done put the mirror away. Now take the sheet with your mirror copies and start to duplicate these on another sheet of paper. You will probably find that the capital Q, lower-case b, d, j, k and q, and the numbers 2, 3, 6 and 9 seem to be the most difficult, but keep at it. After a bit of practice in duplicating the shapes, get the mirror out again. This time you’re going to try and draw those letters and numbers so that they look right in the mirror. Get a bit of paper and stick it to the wall so you can see it in the mirror. Now swing your arms and body and write the letters and numbers on the paper so that they look the right way round in the mirror. Keep practising. After a while your brain will learn the body and hand movements (called motor memory) for mirror writing in the same way you learned to write the first time round. You can then code like da Vinci.

## Sounds backwards?

It’s been shown that when people listen to recordings of piano music played backwards they believe the sounds are played on an organ. This is because when played backwards, piano tones start quietly and grow in volume. This type of sound, we have learned, is the way an organ sounds. Our brains’ preconceptions are fooled and so we make a mistake. Playing music backwards was something of a fashion in days gone by. In the fifteenth century it was fashionable to create palindromic canons – pieces of music containing two melodies. One melody was the notes of a tune played forward and the other, called the counterpoint, was the same notes but in the reverse order. Beethoven, Bach and Haydn all got into this mixing of musical symmetry. Mozart once helpfully composed a canon in which the second melody was the same as the first, but backward and upside down. That meant it could be read by the player from the opposite sides of the music sheet. What a thoughtful guy, that Mozart.

## Upside down weather

The sun heats the land and the land heats the air above it, so as you go up things get cooler. However from time to time things get a little upside down. This is called a temperature inversion: a layer of dense cold air traps the lighter, warmer air underneath it. When it does, smog from car fumes can be trapped near the ground, leading to an increase in health problems. If the trapped warm air contains a lot of moisture, an inversion can lead to violent thunderstorms as the cold layer prevents the humid warm air from rising. Understanding how our weather works in order to make the daily weather forecast needs complex computer programs to calculate future events. Being able to look at the weather from lots of different angles in a computer helps us plan for a rainy day.