QandA

Q&A Tabs

Phlegm is the mucous secretion of the respiratory passages. The cilia cells that line these passages are continually driving the phlegm upward to the throat, where it triggers the swallow reflex...

Men grow beards because the hair follicles on their jaw are stimulated by the hormone dihydrotestosterone (DHT), which is produced from testosterone. Women have the same number of follicle cells...

Trees release oxygen when they use energy from sunlight to make glucose from carbon dioxide and water. Like all plants, trees also use oxygen when they split glucose back down to release energy to...

Astronomer Fred Hoyle was the first to point out that if you could drive a car upwards at 95km/h (60mph), it would only take about an hour to get into space. To get to the Moon would take a little...

Mammals remove excess nitrogen from their bodies by converting it to a dilute solution of urea, stored in the bladder. Birds convert nitrogen to uric acid instead: this is metabolically more...

All female mammals have a clitoris, the sole purpose of which is to react to sexual stimulation, and presumably this stimulation has evolved to be pleasurable for most species. But establishing...

To create a sound, we have to set matter - whether it's a gas like air, a liquid or even a solid material - in regular motion, creating a wave of specific frequencies, which we hear as a sound of...

Mirrors don’t reverse left and right either – that’s just our interpretation of what happens. Your reflection in the mirror is actually reversed front to back – if you have...

Discovered by an American student named Gary Flandro in the mid-1960s, the slingshot manoeuvre usually involves spacecraft briefly 'coat-tailing' a planet orbiting the Sun, extracting some of the...

The ice disappears because the wind blows away water molecules that have evaporated or 'sublimed' from the ice, so the ice slowly shrinks in size. The molecules that escape are those with the...

Recent Q&A...

Men grow beards because the hair follicles on their jaw are stimulated by the hormone dihydrotestosterone (DHT), which is produced from testosterone. Women have the same number of follicle cells...

Studies using functional magnetic resonance imaging (fMRI) have shown that scratching causes patterns of brain activity that are associated with pleasure and reward. This effect is strongest when...

Diet definitely affects the flavour of the milk of all mammals. A 2008 study at Copenhagen University gave flavour capsules to nursing mothers and found that the taste made its way into their...

Yes. When you wash your hands, you transfer a thin film of bacteria, skin flakes and oils to the bar of soap. A 2006 study of 32 dental clinics found bacteria growing on the soap in all of them...

Nickel-based batteries were blighted by the ‘memory effect’, and would lose capacity unless regularly discharged completely. Most phones nowadays have lithium batteries, and these do...

The ingredients required to make a rainbow are sunlight and raindrops. Currently, there is no other planet known to have liquid water on its surface or in sufficient quantities in the atmosphere...

A study at Newcastle University in 2014 found that organic fruit and vegetables had higher levels of antioxidants than non-organic varieties. This isn’t too surprising – since plants...

Although it seems very likely that most spiral galaxies (and possibly all types of galaxies) contain a black hole, these are not the only places where these gravitational beasts reside.

By...

Rainbows are formed when light emerges from water droplets that are in just the right place for the rays to enter our eyes. Such droplets always lie on a circle facing the Sun. Unless we’re...

Putting conkers around the house to deter spiders is an old wives’ tale and there’s no evidence to suggest it really works. Spiders don’t eat conkers or lay eggs in them, so...

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