All Access. All in one subscription. From $2 per week
Subscribe now

All Access Weekly

From $2 per week
Pay just
$15.75
$2
per week ongoing
Subscribe now
BEST VALUE

All Access Annual

Pay just
$449
$49
per year ongoing
Subscribe now
Learn more
30
NZ Herald
  • Home
  • Latest news
  • Herald NOW
  • Video
  • New Zealand
  • Sport
  • World
  • Business
  • Entertainment
  • Podcasts
  • Quizzes
  • Opinion
  • Lifestyle
  • Travel
  • Viva
  • Weather

Subscriptions

  • Herald Premium
  • Viva Premium
  • The Listener
  • BusinessDesk

Sections

  • Latest news
  • New Zealand
    • All New Zealand
    • Crime
    • Politics
    • Education
    • Open Justice
    • Scam Update
  • Herald NOW
  • On The Up
  • World
    • All World
    • Australia
    • Asia
    • UK
    • United States
    • Middle East
    • Europe
    • Pacific
  • Business
    • All Business
    • MarketsSharesCurrencyCommoditiesStock TakesCrypto
    • Markets with Madison
    • Media Insider
    • Business analysis
    • Personal financeKiwiSaverInterest ratesTaxInvestment
    • EconomyInflationGDPOfficial cash rateEmployment
    • Small business
    • Business reportsMood of the BoardroomProject AucklandSustainable business and financeCapital markets reportAgribusiness reportInfrastructure reportDynamic business
    • Deloitte Top 200 Awards
    • CompaniesAged CareAgribusinessAirlinesBanking and financeConstructionEnergyFreight and logisticsHealthcareManufacturingMedia and MarketingRetailTelecommunicationsTourism
  • Opinion
    • All Opinion
    • Analysis
    • Editorials
    • Business analysis
    • Premium opinion
    • Letters to the editor
  • Politics
  • Sport
    • All Sport
    • OlympicsParalympics
    • RugbySuper RugbyNPCAll BlacksBlack FernsRugby sevensSchool rugby
    • CricketBlack CapsWhite Ferns
    • Racing
    • NetballSilver Ferns
    • LeagueWarriorsNRL
    • FootballWellington PhoenixAuckland FCAll WhitesFootball FernsEnglish Premier League
    • GolfNZ Open
    • MotorsportFormula 1
    • Boxing
    • UFC
    • BasketballNBABreakersTall BlacksTall Ferns
    • Tennis
    • Cycling
    • Athletics
    • SailingAmerica's CupSailGP
    • Rowing
  • Lifestyle
    • All Lifestyle
    • Viva - Food, fashion & beauty
    • Society Insider
    • Royals
    • Sex & relationships
    • Food & drinkRecipesRecipe collectionsRestaurant reviewsRestaurant bookings
    • Health & wellbeing
    • Fashion & beauty
    • Pets & animals
    • The Selection - Shop the trendsShop fashionShop beautyShop entertainmentShop giftsShop home & living
    • Milford's Investing Place
  • Entertainment
    • All Entertainment
    • TV
    • MoviesMovie reviews
    • MusicMusic reviews
    • BooksBook reviews
    • Culture
    • ReviewsBook reviewsMovie reviewsMusic reviewsRestaurant reviews
  • Travel
    • All Travel
    • News
    • New ZealandNorthlandAucklandWellingtonCanterburyOtago / QueenstownNelson-TasmanBest NZ beaches
    • International travelAustraliaPacific IslandsEuropeUKUSAAfricaAsia
    • Rail holidays
    • Cruise holidays
    • Ski holidays
    • Luxury travel
    • Adventure travel
  • Kāhu Māori news
  • Environment
    • All Environment
    • Our Green Future
  • Talanoa Pacific news
  • Property
    • All Property
    • Property Insider
    • Interest rates tracker
    • Residential property listings
    • Commercial property listings
  • Health
  • Technology
    • All Technology
    • AI
    • Social media
  • Rural
    • All Rural
    • Dairy farming
    • Sheep & beef farming
    • Horticulture
    • Animal health
    • Rural business
    • Rural life
    • Rural technology
    • Opinion
    • Audio & podcasts
  • Weather forecasts
    • All Weather forecasts
    • Kaitaia
    • Whangārei
    • Dargaville
    • Auckland
    • Thames
    • Tauranga
    • Hamilton
    • Whakatāne
    • Rotorua
    • Tokoroa
    • Te Kuiti
    • Taumaranui
    • Taupō
    • Gisborne
    • New Plymouth
    • Napier
    • Hastings
    • Dannevirke
    • Whanganui
    • Palmerston North
    • Levin
    • Paraparaumu
    • Masterton
    • Wellington
    • Motueka
    • Nelson
    • Blenheim
    • Westport
    • Reefton
    • Kaikōura
    • Greymouth
    • Hokitika
    • Christchurch
    • Ashburton
    • Timaru
    • Wānaka
    • Oamaru
    • Queenstown
    • Dunedin
    • Gore
    • Invercargill
  • Meet the journalists
  • Promotions & competitions
  • OneRoof property listings
  • Driven car news

Puzzles & Quizzes

  • Puzzles
    • All Puzzles
    • Sudoku
    • Code Cracker
    • Crosswords
    • Cryptic crossword
    • Wordsearch
  • Quizzes
    • All Quizzes
    • Morning quiz
    • Afternoon quiz
    • Sports quiz

Regions

  • Northland
    • All Northland
    • Far North
    • Kaitaia
    • Kerikeri
    • Kaikohe
    • Bay of Islands
    • Whangarei
    • Dargaville
    • Kaipara
    • Mangawhai
  • Auckland
  • Waikato
    • All Waikato
    • Hamilton
    • Coromandel & Hauraki
    • Matamata & Piako
    • Cambridge
    • Te Awamutu
    • Tokoroa & South Waikato
    • Taupō & Tūrangi
  • Bay of Plenty
    • All Bay of Plenty
    • Katikati
    • Tauranga
    • Mount Maunganui
    • Pāpāmoa
    • Te Puke
    • Whakatāne
  • Rotorua
  • Hawke's Bay
    • All Hawke's Bay
    • Napier
    • Hastings
    • Havelock North
    • Central Hawke's Bay
    • Wairoa
  • Taranaki
    • All Taranaki
    • Stratford
    • New Plymouth
    • Hāwera
  • Manawatū - Whanganui
    • All Manawatū - Whanganui
    • Whanganui
    • Palmerston North
    • Manawatū
    • Tararua
    • Horowhenua
  • Wellington
    • All Wellington
    • Kapiti
    • Wairarapa
    • Upper Hutt
    • Lower Hutt
  • Nelson & Tasman
    • All Nelson & Tasman
    • Motueka
    • Nelson
    • Tasman
  • Marlborough
  • West Coast
  • Canterbury
    • All Canterbury
    • Kaikōura
    • Christchurch
    • Ashburton
    • Timaru
  • Otago
    • All Otago
    • Oamaru
    • Dunedin
    • Balclutha
    • Alexandra
    • Queenstown
    • Wanaka
  • Southland
    • All Southland
    • Invercargill
    • Gore
    • Stewart Island
  • Gisborne

Media

  • Video
    • All Video
    • NZ news video
    • Herald NOW
    • Business news video
    • Politics news video
    • Sport video
    • World news video
    • Lifestyle video
    • Entertainment video
    • Travel video
    • Markets with Madison
    • Kea Kids news
  • Podcasts
    • All Podcasts
    • The Front Page
    • On the Tiles
    • Ask me Anything
    • The Little Things
  • Cartoons
  • Photo galleries
  • Today's Paper - E-editions
  • Photo sales
  • Classifieds

NZME Network

  • Advertise with NZME
  • OneRoof
  • Driven Car Guide
  • BusinessDesk
  • Newstalk ZB
  • Sunlive
  • ZM
  • The Hits
  • Coast
  • Radio Hauraki
  • The Alternative Commentary Collective
  • Gold
  • Flava
  • iHeart Radio
  • Hokonui
  • Radio Wanaka
  • iHeartCountry New Zealand
  • Restaurant Hub
  • NZME Events

SubscribeSign In
Advertisement
Advertise with NZME.
Home / New Zealand

Why are eggs egg-shaped?

By Dr Marcus Wilson
Herald online·
14 Sep, 2010 11:17 PM3 mins to read

Subscribe to listen

Access to Herald Premium articles require a Premium subscription. Subscribe now to listen.
Already a subscriber?  Sign in here

Listening to articles is free for open-access content—explore other articles or learn more about text-to-speech.
‌
Save

    Share this article

Eggs are surprisingly strong for their weight. Photo / Nicola Topping
Eggs are surprisingly strong for their weight. Photo / Nicola Topping

Eggs are surprisingly strong for their weight. Photo / Nicola Topping

Opinion

This post originally appeared on Sciblogs.co.nz.

Here's a nice bit of news that's come out of Christchurch in the last few days. The kiwi eggs being incubated at Willowbank wildlife reserve survived the earthquake, and one of them has now hatched into an adorable baby bird,
who now carries the name 'Richter'. (NB: Kiwi aren't adorable - from what I've heard they are vicious things - but very very endangered, so anything that warms people to them has to be good)

At first thought it might be surprising that an egg could survive an earthquake, but eggs are actually well shaped for that purpose. The round shape means there are no sharp edges, which can act as stress concentrators. It is at these points that structures are most likely to fail. It's why you can usually rip a piece of paper in half fairly cleanly. Once you have a small tear in it, the stress will be concentrated at the tip of the tear, and the tear will propagate forward. It's the same reason why a small crack in your car windscreen can easily turn into a larger crack - the stress is concentrated at the ends of the cracks.

Round things such as eggs obviously don't have sharp points to them and therefore it is much harder for a crack to form in the first place. Also, the shape ensures the shell is strong in compression (squashing) but weaker in tension (stretching). External forces are likely to squash it, whereas internal forces (the chick trying to get out) will stretch it, and it breaks more easily.

Egg shells also have a wonderful structure to them, that makes them very strong for their weight. It's not really surprising eggs have to be like that, when you consider that they have to be built inside the female bird and go through the stress of being laid and then sat on. So I was not completely surprised to hear that the eggs had survived the quake.

Here's a nice egg strength experiment to do at home, which I got from this Q+A site. It includes a great electron microscope picture of the lattice structure of an egg shell, which will give you some idea of its strength compared to its weight.

Dr Marcus Wilson is a lecturer in the Engineering Department at Waikato University. View his work and that of 30 other scientists and science writers at Sciblogs, New Zealand's largest science blogging network.

Discover more

Opinion

<i>Gareth Renowden</i>: IPCC verdict - done well, could do better

01 Sep 10:00 PM
World

Are you descended from Neanderthals?

02 Sep 03:05 AM
New Zealand

Rare kiwi hatches

12 Sep 07:05 PM
All Access. All in one subscription. From $2 per week
Subscribe now

All Access Weekly

From $2 per week
Pay just
$15.75
$2
per week ongoing
Subscribe now
BEST VALUE

All Access Annual

Pay just
$449
$49
per year ongoing
Subscribe now
Learn more
30
Advertisement
Advertise with NZME.
Advertisement
Advertise with NZME.
Save

    Share this article

Latest from New Zealand

New Zealand

Home detention for husband who helped public servant wife defraud Oranga Tamariki of $2m

19 Jun 12:44 AM
New Zealand

Man dies after hit-and-run; police release new images of suspect

19 Jun 12:37 AM
New Zealand

Coldest morning of the year hits Hawke's Bay, just in time for Matariki

19 Jun 12:19 AM

Jono and Ben brew up a tea-fuelled adventure in Sri Lanka

sponsored
Advertisement
Advertise with NZME.
Recommended for you
Coldest morning of the year hits Hawke's Bay, just in time for Matariki
Hawkes Bay Today

Coldest morning of the year hits Hawke's Bay, just in time for Matariki

19 Jun 12:19 AM
'Sobering' downturn: Bay of Islands cruise bookings nearly halve
Northern Advocate

'Sobering' downturn: Bay of Islands cruise bookings nearly halve

19 Jun 12:16 AM
'Crunch time': Urgent warnings from scientists on climate trajectory
World

'Crunch time': Urgent warnings from scientists on climate trajectory

19 Jun 12:10 AM
Film director killed, diamond Rolex feared motive in stabbing
Entertainment

Film director killed, diamond Rolex feared motive in stabbing

18 Jun 11:49 PM
New flight route to turn Auckland into China-South America gateway
Travel news

New flight route to turn Auckland into China-South America gateway

18 Jun 11:36 PM

Latest from New Zealand

Premium
Audrey Young: Cooks crisis complicates Luxon's big meeting with President Xi

Audrey Young: Cooks crisis complicates Luxon's big meeting with President Xi

19 Jun 12:49 AM

OPINION: The timing of Winston Peters' announcement is curious.

Home detention for husband who helped public servant wife defraud Oranga Tamariki of $2m

Home detention for husband who helped public servant wife defraud Oranga Tamariki of $2m

19 Jun 12:44 AM
Man dies after hit-and-run; police release new images of suspect

Man dies after hit-and-run; police release new images of suspect

19 Jun 12:37 AM
Coldest morning of the year hits Hawke's Bay, just in time for Matariki

Coldest morning of the year hits Hawke's Bay, just in time for Matariki

19 Jun 12:19 AM
Help for those helping hardest-hit
sponsored

Help for those helping hardest-hit

NZ Herald
  • About NZ Herald
  • Meet the journalists
  • Newsletters
  • Classifieds
  • Help & support
  • Contact us
  • House rules
  • Privacy Policy
  • Terms of use
  • Competition terms & conditions
  • Our use of AI
Subscriber Services
  • NZ Herald e-editions
  • Daily puzzles & quizzes
  • Manage your digital subscription
  • Manage your print subscription
  • Subscribe to the NZ Herald newspaper
  • Subscribe to Herald Premium
  • Gift a subscription
  • Subscriber FAQs
  • Subscription terms & conditions
  • Promotions and subscriber benefits
NZME Network
  • The New Zealand Herald
  • The Northland Age
  • The Northern Advocate
  • Waikato Herald
  • Bay of Plenty Times
  • Rotorua Daily Post
  • Hawke's Bay Today
  • Whanganui Chronicle
  • Viva
  • NZ Listener
  • Newstalk ZB
  • BusinessDesk
  • OneRoof
  • Driven Car Guide
  • iHeart Radio
  • Restaurant Hub
NZME
  • About NZME
  • NZME careers
  • Advertise with NZME
  • Digital self-service advertising
  • Book your classified ad
  • Photo sales
  • NZME Events
  • © Copyright 2025 NZME Publishing Limited
All Access. All in one subscription. From $2 per week
Subscribe now

All Access Weekly

From $2 per week
Pay just
$15.75
$2
per week ongoing
Subscribe now
BEST VALUE

All Access Annual

Pay just
$449
$49
per year ongoing
Subscribe now
Learn more
30
TOP
search by queryly Advanced Search