QI: The Book of General Ignorance - the Noticeably Stouter Edition (40 page)

That depends.

A day is a single rotation of the earth about its axis. It is never exactly twenty-four hours long.

Astonishingly, it can be as much as fifty whole seconds longer or shorter. This is because the speed of the Earth’s rotation is continually changing as result of friction caused by tides, weather patterns and geological events.

Over a year, an average day is a fraction of a second shorter than twenty-four hours.

Once atomic clocks had recorded these discrepancies, the decision was made to redefine the second, hitherto a set fraction of the ‘solar’ day – i.e. an eighty-six-thousand-and-four-hundredth of a day.

The new second was launched in 1967 and defined as: ‘the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.’ Accurate, but not easy to say when tired at the end of a long day.

This new definition of a second means that the solar day is gradually drifting away from the atomic day. As a result, scientists have introduced a ‘leap second’ into the atomic year, to bring it into line with the solar year.

The last ‘leap second’ added (the seventh since Coordinated Universal Time (UTC) was established in 1972) was on 31 December 2005, on the instruction of the
International Earth Rotation Service based at the Paris Observatory.

That’s good news for astronomers and those of us who want our watches to correspond to the movement of the Earth around the Sun, but bad news for computer software and all technology based on satellites.

The idea was vigorously opposed by the International Telecommunication Union who made a formal proposal to abandon the leap second by December 2007.

One compromise might be to wait until the discrepancy between UTC and GMT reaches an hour (in about 400 years time) and adjust it then. In the meantime, the debate about what constitutes the ‘real’ time continues.

Not the blue whale. Sorry.

Or the lion’s mane jellyfish.

The bootlace worm,
Lineus longissimus
, reaches lengths of sixty metres (that’s just under 200 feet), almost twice as long as a blue whale and a third longer than the longest lion’s mane jellyfish, the previous record holder.

You could drape a bootlace worm from one end of an Olympic swimming pool to the other and still have some spare.

Bootlace worms, also known as ribbon worms, belong to the Nemertea worm family (Nemertea comes from the Greek
Nemertes
, a sea-nymph). There are more than a thousand species, most of them aquatic. They are long and thin: even the longest may be only a few millimetres in diameter.

Many sources claim the bootlace worm only reaches 30 metres (nearly 100 feet) in length, which is not quite as long
as the lion’s mane jellyfish. But the latest information reveals that their capacity to stretch is extraordinary. Several have been found that are over 50 metres (165 feet) when fully extended.

Fossil evidence shows they have been around for at least 500 million years.

Bootlace worms have no hearts – their blood is pumped by their muscles – and they are the simplest organisms to have a separate mouth and anus.

They are voracious carnivores, shooting out a long thin tube which is sticky or armed with poisonous hooks, to skewer and stun small crustaceans. This can be three times as long as the worm’s own body.

Most ribbon worms lurk in the murk of the ocean bottom but some are incredibly brightly coloured.

Nemerteans can regenerate if damaged. But some bootlace species actually reproduce by fragmenting into small pieces, each of which becomes a new worm.

You get two halves of a dead worm, usually. Sometimes the head end survives, but you can’t get two worms from one.

Some species of worm can regenerate amputated tails, depending on how many body segments they’ve lost, and some species jettison tails to escape predators, but the headless part will always die, as will the head if it hasn’t retained sufficient body. The death throes of the severed sections can go on for hours, and could easily be mistaken for lively wriggling.

The ‘both ends become a worm’ idea seems to have started as a way of shutting up small children. Sadly, nobody ever gets
round to telling you that it isn’t true once you’ve grown up.

The smooth band a third of the way along an earthworm isn’t the ‘join’ from which the ‘new worm’ grows. It is called the clitellum and is responsible for secreting the sticky clear mucus that covers the worm.

There is a freshwater flatworm called a planaria or ‘cross-eyed worm’ which also has an extraordinary ability to regenerate itself when damaged. The American geneticist and Nobel laureate T. H. Morgan (1866–1945) found that a piece of planaria 1/279th of its original size could regenerate into a full-sized planaria, and a planaria split lengthwise or crosswise will regenerate into two separate individuals.

Shrimps.

Though the blue whale produces the loudest noise of any individual animal in the sea or on land, the loudest natural noise of all is made by shrimps.

The sound of the ‘shrimp layer’ is the only natural noise that can ‘white out’ a submarine’s sonar, deafening the operators through their headphones.

Below the layer they can hear nothing above it and vice versa. Hearing from below can only be accomplished by raising a mast up through it.

The noise of the collected shrimps amounts to an ear-splitting 246 decibels, which even adjusting for the fact that sound travels five times faster in water, equates to about 160 decibels in air: considerably louder than a jet taking off
(140 dB) or the human threshold of pain. Some observers have compared it to everyone in the world frying bacon at the same time.

The noise is caused by trillions of shrimps snapping their single oversized claw all at once. Snapping shrimps, members of the various
Alpheus
and
Synalpheus
species, are found in shallow tropical and subtropical waters.

But it’s even more interesting than it sounds. Video shot at 40,000 frames per second shows clearly that the noise occurs 700 microseconds after the claw has snapped shut. The noise comes from burst bubbles – not the shutting of the claw itself – an effect known as ‘cavitation’.

It works like this. A small bump on one side of the claw fits neatly into a groove on the other side. The claw is shut so rapidly that a jet of water travelling at 100 kilometres (62 miles) per hour squirts out, fast enough to create expanding bubbles of water vapour. When the water slows down and normal pressure is restored the bubbles collapse creating intense heat (as high as 20,000 °C), a loud pop and light – this last being a very rare phenomenon called sonoluminescence, where sound generates light.

Shrimps use this noise to stun prey, communicate and find mates. As well as ruining sonar, the sharp, hot intense noise makes dents in ships’ propellers.

Because they eat a lot of blue-green algae.

Flamingos do eat shrimps, but the colour of the birds comes from the algae. Despite their name, blue-green algae can be red, violet, brown, yellow or even orange.

Flamingos are named for their bright colour. Like
flamenco
, the word comes from the Latin for ‘flame’. The red and white flag of Peru was inspired by them.

There are four species of flamingo. They are at least ten million years old and once ranged over Europe, America and Australia. Now they live in isolated pockets of Africa, India, South America and southern Europe.

All species are monogamous. They lay only one egg a year which is balanced on a mound of soil. Both parents take turns to incubate it and both produce bright red, highly nutritious ‘milk’ from their throats, which the chicks feed on for their first two months. Flamingos are one of only two kinds of bird to produce milk: the other is pigeons. In captivity, flamingos that are not parents will spontaneously produce milk if they hear the cries of chicks.

After leaving the nest, flamingos live in vast crèches. Though these may contain more than 30,000 birds, the young flamingo is fed only by its parents, who recognise it by its cry. A family of flamingos is called a ‘pat’.

Flamingos eat with their heads upside down. Unlike other birds, they filter their food in the same way as whales and oysters. Their beaks are lined with rows of plates that sift items from the water. The lesser flamingo (
Phoeniconaias minor
) has such a dense filter it can strain single-celled plants less than 0.05 mm (
inch) in diameter. The flamingo’s tongue acts as a pump, pushing water through its beak four times a second.

Pliny the Elder recommended eating flamingo tongue as a tasty delicacy.

Flamingos sleep on one leg, with one half of their body at a time – like dolphins – while the other remains alert for predators. Flamingos can live for fifty years. They inhabit inhospitable lakes that have high levels of salt and soda, where the water is undrinkable by other animals and nothing grows. Their main predators are zookeepers.

There is no such thing as ‘a’ panther.

The word probably comes from the Sanskrit for whitish-yellow,
pandarah
, which was originally applied to the tiger.

The Greeks borrowed the word and adapted it as
panthera
, meaning ‘all beasts’. They used it to describe mythological as well as real animals

In medieval heraldry, the panther was portrayed as a gentle, multicoloured beast that had a very sweet smell.

Scientifically speaking, all four of the largest species of big cat are panthers.

The lion is
Panthera
leo; the tiger,
Panthera
tigris, the leopard,
Panthera pardus
and the jaguar
Panthera onca
. They are the only cats that can roar.

The animals that most people think of as panthers are, in fact, either black leopards (in Africa or Asia), or black jaguars (in South America).

Neither animal is completely black. Close examination shows that their spots are still faintly visible on their skin. They carry a genetic mutation that means the black pigment in their fur dominates the orange.

Rare ‘white panthers’ are in fact albino leopards or jaguars.

In the USA, when people say ‘panther’ they mean a black puma. Despite many unproven reports and supposed sightings, no one has ever found one.