QandA

Q&A Tabs

Lobsters and other shellfish have harmful bacteria naturally present in their flesh. Once the lobster is dead, these bacteria can rapidly multiply and release toxins that may not be destroyed by...

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...

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...

Scars form at any injury site that takes more than three or four weeks to heal. The body produces collagen fibres in a criss-cross pattern. The normal shedding process of skin doesn’t affect scars...

The powder is actually tiny scales made from modified hairs. Moths, like butterflies, belong to the order Lepidoptera, which means 'scale wing'. The scales are pigmented but they also contribute...

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...

This is because our estimates of time depend on how much we remember, and more memories are laid down in an emergency. Experiments have investigated this. In one case volunteers fell back into a...

The main ozone-depleting gases are chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). The Montreal Protocol, which came into force in 1989, lists 56 CFCs and 34 HCFCs, and production...

A potentially hazardous asteroid (PHA) is an asteroid whose orbit comes nearer than 0.05AU (about 7.5 million km) to the Earth and whose brightness implies a size of the order of about 100m across...

Physicists have determined that there is a lower limit to the temperature scale called ‘absolute zero’. It occurs at –273.15°C (or –459.67°F). No matter how much...

People have been inventing knots for millennia; the oldest known – used in a fishing net found in Finland in 1913 – dates from around 8000BC. Thousands are now known, but they’re...

No. Even from low Earth orbit the Great Wall of China is extremely hard to spot with the naked eye. It’s a very thin line, almost the same colour as the landscape. Lots of other things are...

They are incredibly well insulated with a layer of blubber that can be up to 10cm thick covered with another 15cm of fur.

Polar bears lose so little heat to their environment that they are...

Sometimes, but it can also do the opposite. Photography can spoil our memories if we rely on having pictures to take home instead of enjoying life as it happens.

Tourists who hold their...

Our nervous system has evolved to become progressively less sensitive to a stimulus, the longer it persists. This enables us to concentrate on the newest sensations that are more likely to be an...

Nothing physical can exist with literally zero thickness, as its atoms have a finite size. But there are many examples of so-called ‘monolayers’ just one molecule – or a few tens...