ANIMALS

Why do we never see birds urinating?

Nature designed birds to be as light as possible to enable them to fly. For this reason, they don’t have a bladder and any fluids they consume make their way, via the kidneys, to a device in the lower intestine called the cloaca. This combines liquids waste with solid waste to make the watery droppings so beloved of pavements, clotheslines and statues of previously dignified political and military leaders.

How high can a butterfly fly?

Some butterflies migrate and when doing so will quite happily fly a hundred or so metres up. It's been reported, for instance, that workers near the top of New York City's 443-metre-tall Empire State Building have seen Monarch butterflies flutter by their windows.

But that's not all. If caught in an updraught, butterflies can reach 3000 metres or more and survive.

BEAUTY

Why doesn’t the applicator brush reach the bottom of the nail-polish bottle?

“It’s all because of manufacturing variations,” explains Myléne Ménard of cosmetics manufacturer Maybeline in New York. “A typical nail-polish bottle can have four manufacturing variations.”

Once could be the length of the plastic applicator brush, or wand. Another could be the hair on the wand. A third variation cold lie in the thickness of the bottle and the fourth could be a very small variation in the amount of polish in the bottle.

“Since the first three parts are moulded separately, the outcomes are not always identical. For instance, the glass could be thicker or thinner, or the variation might lie in the length of the hair placed on the wand”

Often, “the only way to get to the last it,” says Ménard, “is to tilt the bottle,” and that unfortunately can often result in spilling and a sticky mess.

FRUITS

Is it true the kiwi is a human-engineered fruit and doesn't exist in nature?

Yes and no. Brian Husband, professor at the Department of Organismal Biology at the University of Guelph in Canada says, "The kiwi, which is known for its abundance of vitamin C and is commonly found in fruit or grocery stores around the world, is a modified version of the Chinese gooseberry or Actinidia chinensis, native to southeastern China." The fruit was altered for size, taste and hardiness in the 20th century by New Zealand fruit growers. Seeing that the kiwi's brown, furry skin resembled the body of the flightless kiwi bird, a new name was adopted for the "new" fruit.

HEALTH

Are soft drinks really bad for your teeth?

Yes, though some types are worse than others. Acids dissolve tooth enamel, and that can lead to cavities. To test which beverages are worst, scientists at the University of Maryland exposed enamel to 15 drinks.

Canned or bottled iced tea and lemon-lime drinks dissolve enamel fastest; colas were less damaging. Diet drinks were no better than full-kilojoule ones.

No need to give up on soft drinks. Drink them with meals (food helps absorb acid) or in one sitting (sipping all day bathes teeth in acid). Swishing with water after every drink helps too.

PEOPLE

Why, when you look at old photos, is there never anyone smiling?

Subjects in many old photos are not smiling at the camera for two reasons. Ann Thomas, curator of photographs at the National Gallery of Canada, says, “In the early days of photography, there existed a tradition of formality – handed down from portrait painting – in which posing for a photograph was considered a solemn occasion.”

The second reason, according to Thomas, is that “prior to the 1880s, photographs required long exposures – so depending on the process, it could involve 20 minutes or more. This necessitated the subject remaining still, and since maintaining a smile for such an extended period was difficult, it was discouraged.” The arrival of smiling faces in photos came after the invention of the snapshot in the 1880s with the introduction of the Kodak dry-plate camera.

TECHNOLOGY

Do mobiles fry your brain?

The debate continues as to whether mobile phones cause brain tumors: the results of a Swedish study suggest that ten years of mobile use does raise the risk of acoustic neuroma (a benign tumor of the auditory nerve). If you’re worried, here are steps to take:

• Use a hands-free earpiece or headset
• A shield that covers the whole phone can work, though some will impair the phone’s effectiveness
• Absorbing buttons that attach to the outside of your phone can absorb radiation, but only by 20 per cent or so
• Different phone models can vary in radiation output by up to 80 per cent – look for a low “SAR” level.