Questions that have always intrigued you about the world will appear in this, your section,
and be answered by other readers. Please address your answers and questions to ‘Curiosities’.

Where does the Eastern hemisphere begin and the Western hemisphere end?
Is it just a variation of the First-Third World division? Where do Mexico and Turkey fit in?

Stirring skies keep the heavy high

There is no vertical equivalent of the equator but 0 degrees longitude runs through the London suburb of Greenwich and the international dateline which is both 180 degrees west and 180 degrees east on the opposite side of our planet form the nearest equivalent. This means that the Americas are in the Western hemisphere and Asia, Australasia, and most of Europe and Africa are in the Eastern hemisphere. None of which makes much sense if you live in Hawaii, and go east to reach California and west to reach Japan. But then British and Dutch cartographers dominated mapmaking for many centuries.

JP Lethbridge
Birmingham, England

How come gases which are normally considered heavier than air – such as chlorine,
carbon monoxide and carbon dioxide – are reaching the upper layers of our atmosphere?

Even gases that are heavier than air – which doesn’t include carbon monoxide, by the way – settle very slowly in the atmosphere. This is because they are constantly being bombarded by other gas molecules which move in a random way and help to force them upwards. This phenomenon also prevents fine dust from settling quickly. Just watch the dust in a shaft of sunlight – and dust is very much heavier than gas molecules.

Because the gases settle so slowly they can be transported through the troposphere – the first 12 kilometres of the atmosphere – on air currents caused by variations in temperature and pressure. Gases which only react slowly and which remain in the atmosphere for months or longer are generally well mixed in the troposphere. These gases include carbon dioxide, methane and CFCs.

Very long-lived gases such as CFCs, which can survive in the atmosphere for a few hundred years, are slowly transported into the next layer of the atmosphere.

As well as being transported to the higher layers of the atmosphere, gas may be formed there in reactions driven by sunlight. For example, ozone is formed naturally in the stratosphere by the action of sunlight on oxygen, and about half of the carbon monoxide in the troposphere is formed from methane and other hydrocarbons and oxygen in the sunlight.

Janet Moxley
Edinburgh, Scotland

Brownian movement – the random micro-movement of all molecules not locked in solids – adds to the stirring of the atmosphere. Also, some compounds have an affinity for each other. Alcohol and water, for example, have a loose molecular bonding which is why the lighter alcohol in your beer does not sit on top of the water.

Len Clarke
Uxbridge, England

awaiting your answers

What are revolutionaries such as Leila Khaled, Daniel Cohn Bendit, Bernadette Devlin,
Vo Nguyen Giap, Bobby Seale, Breyten Breytenbach, Abu Nidal and Wadi Haddad doing now?

J Cotton
Loughton, England.

Has anyone calculated the extent to which Britain’s former colonies helped make it a ‘developed’ nation?
What has been their economic impact over the centuries?

David Salter
Cardiff, Wales

If you have any questions or answers please send them to Curiosities, New Internationalist, 55 Rectory Road, Oxford OX4 1BW, UK, or to your local NI office (see inside front cover for addresses).


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