This week at Collected Wisdom, where variety is our watchword, we tackle questions on the effects of radiation, the ultimate fate of Canada Customs forms, and we address a shipbuilding issue of Titanic proportions.
How is it that radiation is known to be a prime cause of cancer and yet it is also a prime therapy for cancer treatment? Debra Saxe of Markham, Ont., wants to know.
"Exposure to certain types of radiation, including ionizing radiation, has been shown to cause cancer," writes Gillian Bromfield, senior manager of cancer-control policy at the Canadian Cancer Society in Toronto. "Cancer risk is related to the type and dose of radiation a person is exposed to, but the greatest risks come from larger doses, longer exposures and high-strength forms of radiation."
Put simply, she writes, radiation therapy works by damaging a cancer cell's DNA. Cancer cells are generally more sensitive to radiation damage than normal cells because of their rapid growth and division and limited ability to repair DNA damage. "This makes them more vulnerable to the effects of radiation than most normal cells. Precise planning and targeting of radiation therapy helps deliver the greatest therapeutic dose to the cancer, and as little as possible to healthy surrounding tissue."
What happens to the millions of customs forms Canadians fill in when returning to Canada? asks Scott James of Toronto.
"The declaration card, also known as the E311 card, tells Canada Border Services Agency officers at airports of entry everything they need to know about you, your travels, and what you're bringing into the country," writes Luc Labelle, acting media spokesman for CBSA in Ottawa.
"Before you depart a CBSA- controlled area of the airport, a border services officer will collect your declaration card. The E311 cards are then sent to Statistics Canada for data-collection purposes."
But what exactly does Statistics Canada do with them?
Lotfi Chahdi of Statscan in Ottawa says the CBSA sends the agency the cards "for processing, analysis and publication. All the E311 cards are scanned and microfilmed for CBSA."
Meanwhile, Statscan uses data from representative samples of the cards to estimate the number of people who have been travelling abroad during given periods. After about three months, Mr. Chahdi says, all E311 cards are destroyed.
Charlie McKenzie of Montreal asks: "If the Titanic were to be rebuilt today, following the original blueprints, what would it cost?"
When the Titanic was built, the cost was $7.5-million (U.S.), says Norm Lewis of Simcoe, Ont., who is president of the Canadian Titanic Society. "Today, the same ship would be approximately $400-million."
Gary Pluim of Ottawa notes that you don't see lightning rods installed on buildings any more. Why?
Why, generally, do small birds sing, but large birds don't? Peter A. Murphy of Brampton, Ont., wants to know.
"Every alarm clock I have ever owned has had a nine-minute snooze function," writes Brenda Lawrence of Manilla, Ont. Why nine minutes?
Do people with photographic memories also have perfect recall of their dreams? Eric Morris of Montreal asks.
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