BBC Science Focus - 10.2019

Q&A

GETTY IMAGES X3, FLPA ILLUSTRATIONS: DAN BRIGHT

ABBEY-LEIGH THOMPSON, LEEDS

HOW DID THE

BOUNCING

BOMB WORK?

There’s some ni￿y physics behind the dam-busting

bombs that were used by the British in WWII. Just

like skipping stones, to make a bomb bounce o￿

water you need to have enough speed and a perfect

angle (about 7° in the case of the bomb). If you get

these just right, conservation of momentum means

that the water pushes back on the bomb and kicks it

up in the air. For multiple bounces, the magic

ingredient is spin. Spin the bomb and you stabilise

its motion, like a frisbee or a gyroscope. The

designers of the bouncing bomb made use of these

principles, with the aim of saving the British

bombers the tricky task of hi￿ing a German dam

bang on target. The cylindrical bombs were

spun on launch, making them bounce several times,

and as the bombs completed their final bounce, the

spin even made them sink in a curved trajectory

towards the dam. PB

QESTION OF THE MONTH

WINNER

Abbey-Leigh wins a Chronomics

epigenetics test kit, worth £179. Aer

taking a saliva sample, Chronomics

can reveal epigenetic insights, like

biological age (how old the body truly

is at DNA level), metabolic state (the

most accurate indication of metabolic

health), and exposures, such as the

eects of passive smoke exposure on

the body. chronomics.com

It’s unlikely, but not impossible. Most

commercial egg farms have strictly

all-female ocks because male chickens

aren’t needed for egg production and

aren’t suitable for meat either (chickens

raised for meat are a dierent breed).

Without a rooster in the ock, the eggs

will never be fertilised and can’t develop

into a chicken embryo. With other poultry

species though, such as quail or duck, the

males and females aren’t segregated so

strictly, and ducks can also come into

contact with wild males and mate with

them. There have been a few reported

cases of supermarket duck and quail eggs

being successfully incubated. LV

A horizontal bole keeps the cork moist, so it doesn’t dry

out and shrink. At least that’s the theory, but the science

says otherwise. The air gap in a wine bole has almost 100

per cent humidity, so the cork will never dry out as long as

there is wine in the bole. In 2005, the Australian Wine

Research Institute tested this and found that the

orientation of the bole makes lile dierence to the

wine’s keeping qualities. LV

TERESA HENDERSON, BLACKPOOL

IS IT POSSIBLE TO HATCH A CHICK FROM

A SUPERMARKET EGG?

EVERETT LOWENSTEIN, PORTLAND, USA

WHY IS IT BETTER TO STORE

WINE HORIZONTALLY?

EMAIL YOUR QUESTIONS TO [email protected] OR TWEET US @SCIENCEFOCUSQA

Bomb release

Bomb spins

Bomb bounces

Spinning bomb hugs dam

Point of explosion

Dam

Diagram not to scale

Q&A

GETTY IMAGES X3, FLPA ILLUSTRATIONS: DAN BRIGHT

ABBEY-LEIGH THOMPSON, LEEDS

HOW DID THE

BOUNCING

BOMB WORK?

There’s some ni￿y physics behind the dam-busting

bombs that were used by the British in WWII. Just

like skipping stones, to make a bomb bounce o￿

water you need to have enough speed and a perfect

angle (about 7° in the case of the bomb). If you get

these just right, conservation of momentum means

that the water pushes back on the bomb and kicks it

up in the air. For multiple bounces, the magic

ingredient is spin. Spin the bomb and you stabilise

its motion, like a frisbee or a gyroscope. The

designers of the bouncing bomb made use of these

principles, with the aim of saving the British

bombers the tricky task of hi￿ing a German dam

bang on target. The cylindrical bombs were

spun on launch, making them bounce several times,

and as the bombs completed their final bounce, the

spin even made them sink in a curved trajectory

towards the dam. PB

QESTION OF THE MONTH

WINNER

Abbey-Leigh wins a Chronomics

epigenetics test kit, worth £179. Aer

taking a saliva sample, Chronomics

can reveal epigenetic insights, like

biological age (how old the body truly

is at DNA level), metabolic state (the

most accurate indication of metabolic

health), and exposures, such as the

eects of passive smoke exposure on

the body.chronomics.com

It’s unlikely, but not impossible. Most

commercial egg farms have strictly

all-femaleocks because male chickens

aren’t needed for egg production and

aren’t suitable for meat either (chickens

raised for meat are a dierent breed).

Without a rooster in theock, the eggs

will never be fertilised and can’t develop

into a chicken embryo. With other poultry

species though, such as quail or duck, the

males and females aren’t segregated so

strictly, and ducks can also come into

contact with wild males and mate with

them. There have been a few reported

cases of supermarket duck and quail eggs

being successfully incubated.LV

A horizontal bole keeps the cork moist, so it doesn’t dry

out and shrink. At least that’s the theory, but the science

says otherwise. The air gap in a wine bole has almost 100

per cent humidity, so the cork will never dry out as long as

there is wine in the bole. In 2005, the Australian Wine

Research Institute tested this and found that the

orientation of the bole makes lile dierence to the

wine’s keeping qualities.LV

TERESA HENDERSON, BLACKPOOL

IS IT POSSIBLE TO HATCH A CHICK FROM

A SUPERMARKET EGG?

EVERETT LOWENSTEIN, PORTLAND, USA

WHY IS IT BETTER TO STORE

WINE HORIZONTALLY?

EMAIL YOUR QUESTIONS [email protected] TWEET US@SCIENCEFOCUSQA

Bomb release

Bomb spins

Bomb bounces

Spinning bomb hugs dam

Point of explosion

Dam

Diagram not to scale