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(Stock photo/Thinkstock)
(Stock photo/Thinkstock)

COLLECTED WISDOM

Billions of people don’t add a thing (to the planet’s weight) Add to ...

This week, Collected Wisdom tackles a topic that is massively weighty. So weighty and massive, in fact, that it’s positively cosmic.

THE QUESTION

Adam Dougall of Windsor, Ont., wonders how much mass the Earth has gained over the past 100 years through increased human population.

THE ANSWER

“We can do a back-of-the-envelope calculation to get an idea of the mass of people on Earth,” writes Scott M. Ramsay, chair of the biology department at Wilfrid Laurier University in Waterloo, Ont.

The current population of the world is just over seven billion, he notes. “Assuming the average mass per person is 65 kilograms, the total mass of the human population is about 455 million tonnes.” In 1912, the population was about 1.65 billion, with a total mass of about 107 million tonnes. “So the total mass of people on the planet has gone up by about 348 million tonnes.”

So, how much has the mass of the planet increased because of this?

“The answer to that is zero,” Dr. Ramsay says. “The 348 million tonnes of new people came from an equivalent mass of food, water, oxygen and minerals that were already present on the planet.”

The only thing that has entered the Earth to fuel the growth in all that time, he says, is sunlight, “captured by plants to convert water and carbon dioxide into carbohydrate for usable energy and other functions, which together with minerals (mostly nitrogen and phosphorus) combine to build proteins and other necessary components of life. Everything else was already here; it has just been relocated into the bodies of people.”

Steven Kolodziejczyk of Ottawa adds: “Upon death, our bodies will eventually decompose into simpler elements that will be recycled into the biosphere. Our organic components are essentially dismantled and reused, in the form of nutrients, to form new life, be it human, plant or other.”

And Alain Gingras of Notre-Dame-de-la-Salette, Que., quotes French chemist Antoine de Lavoisier (1743-94), who said: “Nothing is lost, nothing is created, everything is transformed.”

THE QUESTION

David Patterson of Aurora, Ont., noticed while watching diving at the Olympics that divers often entered a whirlpool. Why?

THE ANSWER

“In competition, each diver performs one dive and then has to wait up to half an hour for his or her next turn,” says Igor Kopecky, former head coach of Dive Calgary and a former competitive diver. “The water and air are cool, and evaporation leaves the athletes cooling off as soon as they get out of the pool. So the whirlpool or hot tub helps the diver stay warm between dives.”

Also, he says, competition is stressful, and the hot water in the tub helps to calm divers’ nerves.

HELP WANTED

Why does the sound of our voices change as they age? asks Gail Benjafield of St. Catharines, Ont. When talking to someone on the phone, you can easily tell whether they’re young or old. How come?

In books, TV and films, police detectives often pay people for information, writes Peggy

Dillman Taschereauof Stratford, Que. Does this happen in real life? If so, where does the money come from?

David McCray of Walkerton, Ont., was watching a documentary about the Second World War and noticed that German U-boat skippers wore their peaked caps backward while peering through the periscope to stop the peaks getting in the way. Why wear a cap in a U-boat at all?

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