# data[].attributes.attachment_link.readable_text
By Amy Cowen on March 26, 2013 3:29 PM
When it comes to structural engineering, there is a lot to be learned from the shape of the mighty egg. At the same time, sitting on an egg doesn't always work out so well. From eggs to domes to bridges, there is family science at hand perfect for spring break exploration for young builders and engineers! Be prepared to be slimed by some breakages and dazzled by some shows of surprising strength!

Egg and Engineering: Over-easy Science

Eggs break easily when force is applied from a certain direction, but held or positioned differently, an egg can withstand a surprising amount of pressure! Put eggs-and structural engineering and design-to the test with your kids in fun hands-on engineering activities that will challenge them to think creatively, to innovative, and to experiment!

There are chickens at my son's elementary school, and it is great to see kids running to the coop in the afternoons to interact with the chickens, to help with coop duties, and, to check for eggs. With only a few chickens and a few eggs relative to the number of interested chicken watchers, there are some basic school coop rules about gathering the eggs. But when you are the only student around in the afternoon, and you find an egg, you may find that you just got lucky. My student stopped by the coop one afternoon last week and was excited to find an egg that had not yet been collected. It was, indeed, fresh from the chicken, and he insisted I feel how warm it was to the touch-warm and smooth and perfectly ovoid in shape.

Unfortunately, in addition to being warm and smooth, eggs are also fragile. Elementary school students know this. Most of them have had plenty of experience cracking eggs in school and home kitchen science and baking projects. But despite what they "know"-that eggs crack-sometimes maybe there is an irrepressible need to goof around with an egg. Maybe that need is especially strong when you've just gathered it, warm and smooth. But when you joke around and pretend to sit on the egg as the chicken must have, chances are good you will end up with a pile of gelatinous goo, even if you are not really trying to sit with all of your weight, even if, really, you are just being silly.

That is what happened to us, and egghead excitement quickly turned to nine-year-old despair. A broken egg isn't nearly as much fun, and the chickens didn't care that his egg had cracked. The chicken was done for the day. There wasn't another egg ready and waiting to be found. These are sometimes hard lessons that go along with chicken care, egg gathering, and any kind of hands-on science.

Unexpected Connections

The incident with the egg was a reminder to us that eggs are fragile. We crack them to break them open when we want to cook or eat them. While looking at science project ideas in preparation for this week's focus on Easter and family and class egg boiling and dyeing activities, I ran across the "Fallen Arches: The Surprising Strength of Eggshells" materials science Project Idea.

As the title suggests, the project is all about the strength of the egg shape or, more specifically, of half an egg-an arch. This is a fun hands-on engineering experiment for even the youngest of student scientists. With three half eggs, sitting point-side up and arranged in an evenly-distributed triangle, how much weight will they hold before caving? You and your young scientists might be surprised!

If you keep a few eggs aside when you boil others for dyeing, you can engage your students with a great hands-on science activity that easily feeds into other questions and experiments about structures and building designs. As you and your students talk about arches as a structural element, you may find that there are examples in your neighborhood that can add even more relevance to your exploration and your student's understanding of arches in the real world. A small stone bridge walkway that crosses a favorite duck pond of ours is built using arch shapes. An arch bridge is a classic bridge design, in fact. (To extend your discussion, look up keystones!)

From Eggs to Engineering

The following hands-on engineering projects can easily be turned into fun family science activities, great for spring break, summer vacation, or a rainy day. Many of these projects involve some combination of physics, structural engineering, materials science, and math, which gives them great range and versatility. A lot depends on what questions you and your kids want to ask and explore. Why, after all, are the half eggshells arranged in a triangle in the "Fallen Arches" project?

That you can spend an afternoon assembling straws or rolls of newspaper and wind up with an awesome three-dimensional object worthy of display gives these projects added pizzazz for families that love DIY projects and the art that evolves from hands-on exploration. On the flip side, there are structural engineering projects where the goal is to build them so that you can break them. For some kids and families, that is exactly the ticket for thrilling science!

Check the following Project Ideas for more suggestions for families that love to build:

"Dome Sweet Dome": build a geodesic dome using struts made from rolled-up newspaper. (You can do a similar activity with straws.)

"Building the Tallest Tower": great for the younger crowd as long as no one gets upset when the tower tumbles!

"The Effect of Bridge Design on Weight Bearing Capacity": test two different bridge designs, a Warren truss bridge from Popsicle sticks and a Howe truss bridge made from straws. This is a build and break project, so be prepared!

"Can a Toilet Paper Tube Support Your Weight? *": how big would a tube need to be for you to stand on it without it caving in? How does the answer change if you fill the tube with various materials?

"Newspaper Tower *": how tall of a tower can you build with two sheets of paper-and nothing else? What shape will it take to reach the greatest height and to maximize the paper and to make it stand?

"Paper Bridge for Pennies *": a bridge made out of one sheet of paper, a few paper clips, and the challenge to have it support 100 pennies? Let your engineers loose and see what creative solutions they devise!

Cracking Family Science

In the end, eggs do break easily when force is applied from a certain direction. But held or positioned differently, an egg can withstand more pressure than you might expect. Put eggs-and other building designs-to the test with your kids, and let us know what you discover and what fun you have doing science together!

You Might Also Enjoy these Previous Entries:

# data[].attributes.attachment_link.title
Egghead Science: The Strong and the Weak of It | Science Buddies Blog

# data[].attributes.attachment_link.description
By Amy Cowen on March 26, 2013 3:29 PM When it comes to structural engineering, there is a lot to be learned from the shape of the mighty egg. At the same time, sitting on an egg doesn't always work out so well.

# data[].attributes.attachment_link.description
Use your existing Discovery Education username and password.

# data[].attributes.attachment_link.readable_text
Anyone who has a tried to squeeze a chicken egg from end to end knows how strong eggshells are. Not much in nature mineralizes as quickly as a bird egg. How is it that fertilized chicken eggs manage to resist fracture from the outside while, at the same time, can be broken open from the inside by a tiny chick? It's all in the eggshell nanostructure, according to a new study led by McGill University scientists and published in the journal Science Advances .

For millions of years, birds have been evolving to make the perfect eggshell. The result is a thin, protective, biomineralized growth chamber that contains all the nutrients required for the development of a baby bird. The shell is not too strong, not too weak, and resists breaking until it's time for hatching.

How are bird eggshells so perfect?

To find out, a team of researchers from several different fields, including engineering and dentistry, took a very close look at the molecular nanostructure and mechanical properties of eggshells.

"Eggshells are notoriously difficult to study by traditional means, because they easily break when we try to make a thin slice for imaging by electron microscopy," says Marc McKee of McGill University.

"Thanks to a new focused-ion beam sectioning system recently obtained by McGill's Facility for Electron Microscopy Research, we were able to accurately and thinly cut the sample and image the interior of the shell."

It turns out eggshells are made of both inorganic and organic matter. They contain calcium-containing minerals and abundant proteins. The amazing strength of eggshells comes from a nanostructured mineral associated with osteopontin, an eggshell protein also found in composite biological materials such as our bones.

Inside incredible eggshells

When first laid and during brooding, eggshells are hard enough to protect them from breakage. As the chick grows inside the eggshell, it needs calcium to form its bones. The growing chick gets that calcium from its eggshell. During egg incubation, the inner portion of the shell dissolves to provide this mineral ion supply while at the same time weakening the shell enough to be broken by the hatching baby bird.

In other experiments, the researchers were able to re-create a nanostructure similar to that which they discovered in eggshells by adding osteopontin to mineral crystals grown in the lab.

This research was funded by grants from the Natural Sciences and Engineering Research Council and the Canadian Institutes of Health Research.

Reference

Athanasiadou, D., et al. (2018). Nanostructure, osteopontin, and mechanical properties of calcitic avian eggshell. Science Advances , (4), 3. DOI: 10.1126/sciadv.aar3219.
GotScience Magazine, published by the nonprofit Science Connected, is made possible by donations from readers like you. For as little as $1, you can support open-access science news - and it only takes a minute. Thank you. Donate now.
Featured image

Eggshells in the lab. Photo courtesy of Laurie Devine, McGill University

# data[].attributes.attachment_link.title
Why Are Eggshells So Strong? - GotScience.org

# data[].attributes.attachment_link.description
How can fertilized chicken eggs manage to resist fracture from the outside while, at the same time, can be broken open from the inside by a tiny chick? It's all in the eggshell nanostructure, according to a new study led by McGill University scientists and published in the journal Science Advances.

# data[].attributes.attachment_link.description
Use your existing Discovery Education username and password.

# data[].attributes.attachment_link.readable_text
Scientists build a better understanding of the strength of the shape.

Mike Lucibella, Contributor

(ISNS) -- Breaking an egg is a lot easier along its side than at its tip, and scientists can now say exactly why -- and by how much.

This new information could help bioengineers better understand the biological structure of egg-shaped cells -- and how those cells might respond to medications.

Two different research teams independently developed a way to derive how strong an egg-like object is based on its shape and what it's made of.

Egg-shaped objects, or ovoids, are common throughout nature, and can be seen in chicken eggs, the organelles of cells and the outer shells of some viruses. Up to now, finding the rigidity of any size of egg-shaped shell had to either be approximated with estimates based on the properties of spheres and cylinders, or measured directly using specialized lab equipment.

It's well known that the strongest part of an ovoid is at its narrow tip. The sharper the curve of an ovoid, the stronger and more rigid it is at its tip.

"What's new is that we kind of tried to study a class of shapes," said Dominic Vella, a mathematician at the University of Oxford, in the U.K., and lead author of one of the papers.

In the past, researchers studying the structural properties of ovoids had to approximate their calculations using equations for other shapes for simplicity's sake.

Massachusetts Institute of Technology engineer Arnaud Lazarus, and lead author of the second paper, said that the two teams' work could be used to infer the properties of an ovoid without breaking it open.

"Our formula is that if you apply a force on that shell, and it deforms, you can predict how thick the shell is," said Lazarus.

Conversely, a researcher can deduce the cell's internal pressure by knowing the thickness and material properties of a cell's outer casing. This is important when developing new treatments because if a cell is under a lot of internal pressure, it might be harder for a new medicine to seep inside, but could be more prone to bursting.

"The field of cellular mechanics is always searching for theoretical models through which to extract material parameters from experiments," said K.C. Huang, a bioengineer at Stanford University who did not work on the research. "Beyond important fundamental questions of biological material properties, these studies may also find applications in the design of thin shell geometries with specific mechanical behaviors such as differential rigidity and buckling."

Reis said that their work could also be extended to a variety of applications in addition to biomechanics.

"If you know the material properties and the geometry of your shell quite well, and if you are sure that there are not too many imperfections such as micro-cracks in it, the results predicted by our formula ... are indeed very accurate," said Pedro Reis a mechanical engineer at MIT, who worked with Lazarus.

Ironically these micro-cracks limit the formula's usefulness for chicken eggs. Though the perfect shape and seemingly smooth, eggs have a lot of tiny imperfections along the surface of their shells, and are prone to break at the weakest spots. A hard-boiled egg would be more in line with what their formula can easily predict.

"We didn't set out to understand the shape of an egg, it was just an inspiration," said Reis.

Though the two teams arrived at nearly identical conclusions, they took complementary approaches to reach them. Lazarus's team used a 3-D printer to make molds for silicone casts of four different ovoid egg shapes. Using a precision laboratory scale, the team pressed down on the tip of the mold, and measured how much each "egg" pushed back. The team ran the experiment several times using different molds with different densities and shapes to get a general understanding of how the shape of an egg affects its strength.

"You can tune that stiffness, you can tune that rigidity by playing with the shape," said Reis.

Vella's team started from the ground up, using computer models of egg shapes. They built an idealized eggshell inside a computer-modeling program, and ran simulations based on different possible shapes, shell materials and internal pressures.

"We tried to base that more mathematically on equations that we know govern elastic shells," said Vella.

"Thin shells are everywhere," said Yves Pomeau, a mathematics professor emeritus at Arizona University. "I expect applications in biology to measure small scale elasticity, and perhaps in other fields as well."

The two papers are both set to be published in an upcoming issue of Physical Review Letters.
Mike Lucibella is a contributing writer to Inside Science News Service.

# data[].attributes.attachment_link.description
Scientists build a better understanding of the strength of the shape. Mike Lucibella, Contributor (ISNS) -- Breaking an egg is a lot easier along its side than at its tip, and scientists can now say exactly why -- and by how much.

# data[].attributes.attachment_link.description
Why does holding an egg between two hands and pressing along its long axis make it almost impossible to break? Professor Marc Andre Meyers was first puzzled by this as a child growing up in Brazil. He subsequently proposed ...

# data[].attributes.body
How Strong are Eggshells

# data[].attributes.attachment_link.readable_text
Advertisement

Key concepts
Architecture
Engineering
Materials science
Structures

Introduction
Have you ever noticed that some big doorways-especially in old buildings-have arches over them? Arches have been used in engineering since ancient times. In this activity you'll test the strength of a naturally occurring arch shape: the shell of an egg. So grab some leftover Easter eggs and put them to good use in trying to answer the following question: Just how much mass can an eggshell support?

Background
Arches have been used as important elements in structural engineering for thousands of years. For example, more 2,000 years ago Romans used the arch to give support for aqueducts and other large stone structures. The shape of the arch distributes the forces to the weight-bearing piers that support the arch.

An eggshell is a natural example of an arch. One end of the shell has a larger, rounder arch and the other end is narrower and more pointed. It is pretty easy to crack an eggshell if you tap it against a hard surface. But if you interlock your fingers and try to squeeze an egg lengthwise to break it, you'll find that it can withstand more force than you might expect. (If you try this, be sure to wear work gloves because the eggshell pieces will be sharp if you do break the egg.)

Materials

At least three raw eggs

Pencil or marker

Ruler (optional):

One bowl

Small triangular file or a rotary motor tool with a cut-off disk (If you are using a rotary tool, you will also need adult help, safety goggles and may want to wear a dust mask.)

Dinner plate or other large, flat surface to place eggshells on for testing

Hardcover book

Several magazines or lightweight books

Preparation

Use a pencil or marker to make a line all the way around one of the eggs, dividing the egg halfway between its two pointed ends. This line should approximately be at the eggs' widest point (around the egg width-wise, not lengthwise). You may want to use a ruler to help you determine the halfway point as you make the line.

Carefully crack the eggshell at the pointy end. Make a small hole and drain the contents of the egg into a bowl. Rinse the empty eggshell out with some water. Be sure to thoroughly clean any surface the raw eggs touch (including the shells and your hands) with soap and water because they can carry salmonella.

Use a triangular file or rotary motor tool with a cut-off disk to score the eggshell on your marked line all the way around. If you are using a rotary tool with a cut-off disk, work with an adult and wear safety goggles. You may also want to wear a dust mask. Work slowly, using just the edge of the cut-off disk. Why do you think it's important to work slowly on this step?

Carefully break or cut the eggshell back to the scored line you created. Slowly break off small pieces of the shell, one at a time, working your way around. How hard does the eggshell feel as you handle it?

Repeat this process two more times so that you have prepared a total of three eggshells.

Note that it is okay if the edges of the eggshells are a little jagged, but if any prepared eggshell half develops big chips or hairline cracks, you will want to start over with a fresh egg. There should be no cracks or big chips weakening your prepared eggshells.

Procedure

Place the three prepared eggshells on a flat surface, such as a dinner plate, with the open end facing down. Equally space them apart on the surface so that they form an equilateral triangle. Why do you think it's important to equally space them apart?

Carefully lay a hardcover book on top of the three prepared eggshells. The book should be centered over the eggshells so that the mass will be distributed evenly among them. Do the eggshells support the weight of the book?

One at a time, carefully add magazines (centered on top of the book) to see how much mass the eggshells can support. How many magazines can you add before the eggshells crack and break?

Lift up the magazines and book that could be supported. Are they very heavy? Are you surprised by how much mass the empty eggshells could support?

Extra: Use a kitchen scale to measure the combined weight of the book and magazines that the eggshells supported without breaking. Just how much weight (mass) could the eggs support? Are you surprised by your results?

Extra: In this activity you broke the pointy end of the egg, and measured the strength of the arch made from the larger diameter curve. What do you think the results would be if you instead broke the larger end of the egg and tested the strength of the "pointy" arch?

Extra: Try this activity again but cut the eggs lengthwise instead of width-wise. How much load-bearing capacity do eggshells have when prepared this way?

Observations and results
Were the eggshells able to support the hardcover book and several magazines?

The eggshells likely supported a surprisingly heavy load. You may have seen them hold up a small hardcover book and a stack of more than a dozen magazines before all of the eggs cracked and were crushed under the mass. (If any eggshell had a hairline crack or a big chip, however, the eggshells may have only held the book and a couple of magazines before the weakened eggshell cracked and then the others were crushed as well.) In a building the shape of the arch distributes the forces to weight-bearing piers that support the arch, and this is similar for the arch of the eggshells as well. This in turn eliminates some tension stress in the structure. Overall, the arch's shape allows it to support a relatively large amount of mass being placed on top of it.

Cleanup
When you are done with your tests, thoroughly clean any surface the raw eggs (including the shells and your hands) touched with soap and water because they can carry salmonella.

More to explore
The Arch Bridge, from The Science Museum and Peter Symonds College
Egg and Embryo Development, from EnchantedLearning.com
Fun, Science Activities for You and Your Family, from Science Buddies
Fallen Arches: The Surprising Strength of Eggshells, from Science Buddies
This activity brought to you in partnership with Science Buddies

ABOUT THE AUTHOR(S)

# data[].attributes.attachment_link.title
Structural Science: How Strong are Eggshells?

# data[].attributes.attachment_link.description
Key concepts Architecture Engineering Materials science Structures Introduction Have you ever noticed that some big doorways-especially in old buildings-have arches over them? Arches have been used in engineering since ancient times. In this activity you'll test the strength of a naturally occurring arch shape: the shell of an egg.