Johanna Spyri: Heidi

Tourism— people visiting mountains provide local people with jobs and create reasons to protect natural areas. However, tourists can badly damage mountain environments unless they respect the places they visit, and unless good laws are in place to prevent unscrupulous people from building hotels, restaurants and car parks wherever they like.

Climate change— the world is getting warmer. Temperatures rose on average by 0.6°C (1°F) between 1900 and 2000, and today most scientists agree this warming is due to the greenhouse effect. In the mountains, glaciers are melting, snow is falling less often and less heavily, and animals and plants adapted to cold mountain conditions are struggling to survive.

1. Save energy. Turn off anything (such as lights, TV or computer) if you’re not actually using it.

2. Don’t be lazy! If it’s safe to do so, walk, cycle or take a bus, rather than asking your parents to take you in the car.

3. If you visit a mountain area (or any natural place), stay on the path so you don’t damage plants and erode the soil, and don’t disturb or feed wild animals.

4. Don’t drop litter — in a mountain area or anywhere else.

5. When you’re shopping, use your own bag instead of a plastic one from the shop.

6. Companies care what people say about them. If you hear about a company damaging a mountain environment, write to its president and tell them what you think.

Where is Switzerland exactly?

Switzerland is a small country situated in the middle of Europe, with many mountains but no coastline. Switzerland has remained a mostly independent, neutral republic for hundreds of years.

Because French, German and Italian are all spoken in Switzerland, its official name is actually in Latin — Confoederatio Helvetica — to avoid offending anyone. That’s why Swiss internet addresses end ‘.ch’.

What does it mean to be a ‘neutral’ country?

It means that Switzerland won’t attack other countries, but also that it won’t intervene to help another country or people, even if, for example, that country is a small, innocent one being attacked unfairly. Switzerland was neutral in the Second World War, and many people think it was wrong of Swiss banks to allow Nazis to open bank accounts and deposit millions of dollars — some of it stolen from Jewish Holocaust victims.

Is Switzerland as beautiful as it sounds in Heidi?

Yes! The Swiss Alps are famous all over the world (not least for their association with Heidi !). The Swiss people are very proud of their country, and look after it carefully — they have many laws designed to protect the environment.

Uncle Alp makes his own cheese from goats’ milk. But how exactly does liquid milk become solid cheese? Here are the basics of the science of cheese:

If you looked at fresh milk under a powerful microscope, you’d see large drops of fat and smaller pieces of protein, floating in a sea of sugary water.

Although the protein pieces are naturally attracted to each other, a substance coating the outside of each piece prevents them from joining up. The secret of making cheese is to destroy this substance, allowing the pieces of protein to join up.

Cheese‐makers kick‐start the necessary chemical reaction by adding an enzyme. Traditionally, this enzyme comes from a dried piece of calf’s stomach (called rennet), which is added to the milk. Today, there’s also vegetarian rennet.

Cheese‐makers also add a weak acid, usually produced by special bacteria added to the milk, as this helps the enzyme to work.

It takes several hours for the proteins to join up and set the milk into a gel.

This gel has lots of sugary water in it, but if the gel is squeezed, pressed or just allowed to drain, the water comes out, leaving a solid (the curds, containing most of the protein and fat), which looks a lot like cheese.

The type of cheese you get is determined by what happens next. There are many options, all producing different flavours and textures. Curds can be stretched, washed, heated, pressed and deliberately allowed to go mouldy. ‘Fresh’ cheeses (such as cottage cheese or mozzarella) are eaten soon after they’re made, while ‘aged’ cheeses (such as brie, cheddar or Monterey Jack) have to mature for days, weeks or even years.