BBC_Earth_UK_-_January_2017

142 / / JANUARY 2017

Curious

world

Doctor Who fans rejoice! Time travel is

possible and has already happened. But it

does not involve flying in a blue police box

and will certainly not send you to another

era. Albert Einstein was the first to suggest

that time is relative – it speeds up and slows

down according to how fast you move in

relation to something else. Time also moves

slower as gravity increases. So astronauts

orbiting round the Earth at 7.66 km/s on the

International Space Station experience time

a tiny amount faster – just a fraction of a

millisecond – than us down on the ground.

Is time travel possible?

Contrary to what you might think, the animal with

the most teeth is not a shark. Neither is it a lion or

a crocodile. In fact, it’s an animal that you wouldn’t

think of having any teeth at all. It lives in your back

garden and, compared with some of the creatures

that might spring to mind in answer to the question,

is not the least bit threatening.

The answer is the snail. Despite having a mouth

no bigger than a pinprick, snails have thousands

of teeth lurking within.

But they’re not the

same kind of teeth

that humans and other

animals have. They are

microscopic ‘toothlets’

lining a tongue-like

structure forming a

‘radula.’ Snails extend

this through their food, using it like a file to patiently

grate bits off and move them into the back of their

mouths and down into their stomachs. The action

wears down the teeth at the front of the radula and

new ones are constantly being formed at the back,

which gradually move forward to replace them.

Which is the

animal with the

most teeth?

World uncovered
January

Words: Yashi Banymadhub. Photographs: iStock, Shutterstock, FLPA

What is the

smallest mammal?

Depending on how you define size, there

are two contenders for the title of smallest

terrestrial mammal: the Kitti’s hog-nosed

bat from Thailand and Burma and the

Etruscan shrew, which is found around the

Mediterranean and in parts of Asia.

The Kitti’s hog-nosed bat is the smallest in

terms of length at 29-33mm. It is sometimes

referred to as the bumblebee bat as it is a

similar size to one of those insects (see p104).

With reddish-brown or grey fur and a pig-like

snout, it has tiny wings that allow it to hover.

The species lives in caves in colonies of about

100 bats (though sometimes congregates with

up to 500 batty friends) and feeds on insects.

The Etruscan shrew is the smallest in terms

of mass, despite eating 80-90 per cent of

its body weight in food each day. Weighing

around two grams, it has a hyper-fast

metabolism: its heart beats an average 800

times a minute and it cannot survive even half

a day without food. It mostly lives off animals

such as slugs and insects.

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