Very Interesting – July-August 2019

How does the phone network

know where to send the signal

when someone rings me?

Amy Rouse, St Francis Bay

W

hile smartphones are pretty smart,

their ability to make and receive calls

is due primarily to the clever network they’re

in touch with. Known as the cellular network,

it’s made up of thousands of masts across

the nation, each able to pick up

transmissions from phones in its vicinity. By

detecting whose phones are currently nearby

(using each phone’s unique, 15-digit ‘IMSI’

code), they can send calls from other parts

of the network. As we move, we enter the

coverage area (‘cell’) of a different mast,

which notes our presence in turn. The

cellular network also means that phones

don’t have to be powerful: they only have to

communicate with the mast in their local

cell. The network does the hard work of

transmitting the calls across the country

and beyond.

S

urprisingly, the total mass of material in the

asteroid belt is only about 4% of the mass of the

moon. About half of this mass is contained in the four

largest asteroids: Ceres, Vesta, Pallas and Hygiea. If

all this material were concentrated into a single

object with the same density as Ceres, it would be a

dwarf planet about 700km in radius (Pluto, another

dwarf planet, has a radius of 1,188km).

Such a small object would have little impact on the

solar system as a whole.

T

he ancient Chinese game of rock-paper-

scissors is governed by three simple

rules: rock beats scissors, scissors beats

paper, paper beats rock. On the face of it, the

chances of winning are just one in three, but

that presumes people pick rock, paper or

scissors at random. In fact, studies have

shown that our choice often depends on what

happened in the previous game. Losers tend

to switch to the choice that would have won

the game they just lost, while winners tend to

stick. And these habits can be exploited as

follows: if you won, then play what your

opponent just used, but if you lost, then play

what neither of you played. That can tilt the

odds in your favour.

What’s the best way to win at

rock-paper-scissors?

Nick Mkwanazi, Vereeniging

If all the asteroids in the asteroid

belt had coalesced to form a planet,

what size would it have been?

Adam Harrison, Pietermaritzburg

Q&A

Questions & Answers

Got questions you’ve been carrying

around for years? Very Interesting

answers them! Mail your questions

to [email protected]

A Samsung makes

more from the sale of

parts it makes for

Apple than it does

from sales of its own

smartphones.

A Android systems are

named after sweets,

with the most recent

version called

‘Nougat’.

Q

&

A

FLASH

IN NUMBERS

The percentage of the

world’s annual rainfall that

falls on the 12 wettest days

of the year.

50%

The number of adults in

England who have at least

one unhealthy trait:

smoking; drinking more

than 14 units of alcohol a

week; eating fewer than five

portions of fruit and veg a

day; being obese; or having

low levels of physical

activity. This is according to

data from Health Survey

for England.

9 in 10