BBC_Knowledge_Asia_Edition_-_May_2016_

Why is your reflection

p ide-down in a spoon?

How much closer to the Sun could Earth’s orbit get and still be habitable?

is the approximate age of a

human foetus when the

brain’s characteristic folds

start to appear

22

weeks

catalogued piece of space

debris has fallen to Earth

every day, on average, over

the last 50 years

IN NUMBERS

This is called the occlusion e
Normally, the sounds of your own
breathing, chewing and swallowing are
mostly transmitted through the bones of
your jaw and skull. These vibrations,
especially the lower frequency ones, are
dissipated outwards by the shape of your
ear. But if you block your ears with your
fingers or earplugs, you create a
resonating chamber between your
eardrum and the blockage. It’s not just
that inside noises sound louder by
comparison with the muffled sounds from
outside, there is a real, measurable
amplification of up to 20 decibels. LV

Wh

uupsid

lusioneffect.

Why do earplugs

amplify internal noises?

Unlike a flat mirror, the curved surface of the spoon’s

bowl bounces incoming rays back towards a central

focus point lying between your face and the centre of

the spoon’s. In passing through this point, rays from

the upper part of your face are reflected downward,

while those from the lower part are reflected upward.

The result is an upside-down image of your face. RM

per cent a year is the rate at

which seagrass is declining

7

Sun

Earth

Distance from Sun (AU)

Habitable zone

0.1 1.0 10

1

It is difficult to be precise about the size of
the Sun’s ‘habitable zone’ because it
depends on many complicated factors,
including solar irradiance, atmospheric
composition, cloud and weather patterns,

the reflectivity (or ‘albedo’) of the Earth’s

surface, and so on. But the latest research

actually suggests that the inner edge of the

Solar System’s habitable zone is between

0.95 and 0.99 astronomical units. That

means the Earth would become

uninhabitable if its average distance from

the Sun was reduced by as little as 1.5

million km – which is only about four times

the Moon’s distance from Earth! AG