Science – Page 9 – Dr. How's Science Wows

"Thought of the day"….Why do hens lay unfertilized eggs?

April 5, 2013August 28, 2016nao

Following on from this weeks blog about all things eggy – today’s thought is …”Why DO hens lay unfertilized eggs?”

It seems like quite a wasteful process, don’t you think? All that protein, fat, nutrients, calcium that go into the making of one hen’s egg – what is the point in going to all that trouble if there will be no offspring at the end of it?

Here are a few of my thoughts on the matter…

Firstly, we are looking at the fairly recent domestication of the species; in the wild it is likely that roosters would be naturally part of the flock and all eggs produced would be fertilized. In the domestic situation roosters are often not present but the evolution of the hen has not (as yet anyway) been modified!

If we look at egg production in any species we will notice that eggs are usually released and developed in a cyclic manner (we humans are no different). If you see this cyclic process as being wasteful at times then the label will fit for most animals, not just the humble hen!

photo credit: martinteschner via photopin cc

Finally, you could suggest that it is a downside to the evolution of the egg shell! Animals that produce soft shelled eggs usually have a requirement for water in the reproductive process. In fact, for many of these species the eggs are fertilized outside the female body. Although the addition of an egg shell removed the dependence on water for reproduction, it also removed the possibility of fertilisation once the egg is laid!

So there you have it, these are some of my thoughts on the subject. I am not suggesting that any of these points are backed up with scientific findings…. the are just the random thoughts of this simple scientist! Maybe you have your own theories to add?

…just a thought!

"Mammy I hatched an egg!"

April 3, 2013July 5, 2014nao

As a mother of three young children I have had many charming moments that I feel I will remember forever…. first steps, first words, how they pronounced a certain word, the list is endless. Memories to cherish for a lifetime…. and then I forget!! Startling but true! More moments forgotten than remembered. However, certain things will stay with me forever…. like when my daughter was five and we got chickens for the first time; she was beginning to learn the joy of finding and collecting the eggs each day. One day she came to the back door with her bounty only to trip at the step and drop an egg. The poor thing burst into tears with the dramatic exclamation…

……………………………….”MAMMY, I HATCHED AN EGG!

Image credit: Graham Ettridge

I will never forget that one! It was hard to keep a straight face as I tried to console my sobbing child. With all the egg activities and treats of the Easter it has certainly got us talking and thinking about eggs in this house, have you ever wondered about these marvels of nature?

WHAT IS AN EGG MADE OF?

Firstly, what exactly is an egg made of and what purpose does each component have?

Image source: http://www.exploratorium.edu

The shell: the egg shell is made of calcium carbonate (95%), just like the enamel of our teeth (see previous post). The other 5% of the egg shell is made up of calcium phosphate, magnesium carbonate and proteins. Although the shell gives the egg it’s strength you might be surprised to learn that it actually contains up to 7,000 tiny holes (pores); these pores allow air and moisture pass through the shell.

The bloom/cuticle: this is a protein coating outside the egg shell that acts as a natural barrier to bacteria and dust while reducing moisture loss.

The membrane: there are two layers of membrane just inside the shell called the outer and inner membrane. These membranes are like layers of skin and contain a protein called keratin, which is found in our own nails and hair!

The yoke: the yellow of the egg contained within a membrane called the vitelline membrane. The yolk is the part of the egg that feeds the developing embryo – it has a very high protein content and is also rich in vitamins and minerals. The yolk contains all of the egg’s fat and cholesterol. The yolk is the primary food store for the developing chick.

The Albumen: this is the white of the egg; it has a high protein and water content. The albumen cushions the developing chick and keeps it moist while still in the egg.

The air cell: this is a pocket of air at the wide end of the egg, created between the outer and inner membrane. The air cell gets bigger as the egg ages.

The chalazea: these are spiral ropes of egg white that keep the yolk in place.

WHAT ANIMALS LAY EGGS?

Animals that lay eggs are called oviparous and they include birds, fish, amphibians, many reptiles, many arachnids and insects, some molluscs and two mammals – the echidna and the platypus. Mammals that lay eggs are referred to as momtremes.

A BIT OF EGG EVOLUTION

The reptile is credited as inventing the egg shell, allowing their young to develop outside the mother’s body. All true dinosaurs are reptiles and they all laid eggs. The development of the egg shell has been a fundamental step in evolution as it allowed the embryo develop in self contained egg, without the requirement for water. This removed animals’ dependence on water for breeding.

HOW IS AN EGG MADE?

In the hen it takes about 24 to 26 hours to produce an egg. An egg is made from the inside out, starting with the yolk which is released from the hens ovary and moves through various parts of the body where another element of the egg is added until finally the finished egg reaches the vent and the egg is laid. Within 30 minutes of laying an egg, the process will start for the hen all over again.

SO WHAT GOES ON INSIDE THE EGG?

The embryo has started to develop in the egg while it is still being made within the body of the hen. Once the egg is laid the development of the embryo will only continue if conditions are correct. If the temperature and humidity levels are right (temp approx 22oC, relative humidity 50% ) the development of the embryo will continue after the egg is laid. This process continues for approximately 21 days. If the egg is being hatched under a broody hen then the hen must turn the eggs regularly.

THE HATCHING PROCESS

Image credit: http://www.waldeneffect.org

Finally, when the time is right, its time to crack out and see the world. The young of many egg-laying species are equipped with an egg tooth – a tooth like projection on the end of a beak (birds) or protruding from a jaw (reptiles) that helps the young animal tear through the membrane and break through the hard shell. The egg tooth will eventually be reabsorbed or fall off.

Chicks and many other animals will hatch from the larger, rounded side of the egg. That is because this is the end where the air cell is usually located. Once the chick becomes too larger to receive enough oxygen from inside the egg it will use it’s egg tooth to pierce through the inner membrane into the air cell space. This provides them with an extra supply of oxygen, just enough to sustain them as they continue the hatching process and crack and break though the egg shell.

We have been lucky enough to hatch a few broods of chicks over the years and it is always so exciting to meet the little ones for the first time.

This is chips – one of our brood!

So the only other question to be addressed is “which came first – the chicken or the egg?” but I think that’s a blog in itself, perhaps for another day!

AN EXPERIMENT TO TRY – HOW STRONG IS AN EGGSHELL?

You would be amazed how strong an egg shell is, although you might want to try this one over a sink!
Hold a raw egg between your thumb and first finger, holding at the two ends and then apply pressure – as hard as you can! You might be surprised to notice that the egg doesn’t break!

If you repeat this but apply the pressure to the sides of the egg, things might not go so well and you might find yourself covered in egg!

So why is this? Although an egg shell can be very fragile, it’s shape can provide it with great strength. This is because the egg is dome shaped at the top and the bottom, just like a bridge structure; this structure means that when you apply pressure the force is distributed evenly over the shell, not just on one point, hence the egg does not crack!

Further reading:
Anatomy of an egg
Eggshell
Poultry reproduction and incubation

"What’s for dinner?"

March 21, 2013July 4, 2014nao

I had planned a different blog for today but something funny happened yesterday evening and it has lead me down a different path! My children commented on the nice smells from the kitchen and asked me what was for dinner…. “Carbonara” I replied. The two oldest started to chat and whisper to themselves and I was bracing myself for some kind of “I don’t eat that” protest, but instead they just asked the question again…..”What did you say we are having Mum?”. This time they heard my answer more clearly and the two of them cracked up laughing. I couldn’t understand what was so funny until the laughter subsided and they told me…..

……………………………”WE THOUGHT YOU SAID CARBON DIOXIDE!”

This lead to a super nerdy science discussion over dinner about all things carbon dioxide like. The little three year old was very proud of himself telling the others how he made carbon dioxide is his science video with mammy. I have posted this one before but here is a link if you want to see the little Einstein in action!

I was surprised at how much the children knew and how interested they were about carbon dioxide. It is a simple but essential molecule that is an integral part of life on earth.

WHAT IS CARBON DIOXIDE?

Carbon Dioxide is a colourless gas. It is made up of one carbon molecule bound to two oxygen atoms and is written as CO2.

Image source: explainscience.tumblr.com

WHERE DO WE FIND IT?

Although CO2 makes up less than .04 % of the gases in air it is crucial for the existance of life on earth as we know it. Most of us know that we need oxygen to breath but plants need CO2 for their survival. Green plants take CO2 in from the air and, using energy from the sun, break the molecule down into carbon (C) and two oxygen molecules (O2). The carbon is kept by the plant and converted into starch and sugar. This process is called Photosynthesis. The O2 is then released into the air by the plant.

Image source: nskamericas.com

So how does CO2 get replenished back into the air again? This happens through a process called respiration! Animals (including us humans) breath in O2 into our lungs and pass it to every cell in our bodies, through our bloodstream. Our cells need this O2 to grow and to make the energy that powers the body. During the body’s energy making process some of the carbon (from our food) is combined with the O2 forming CO2. This is a waste product in our bodies so it is carried back to the lungs to be released into the air in our breath.

THE CARBON CYCLE

You can start to see a cycle emerging in all this; plants take in CO2 and convert it to food (sugar and starch) and O2. The O2 gets released into the atmosphere. Animals eat the plants and break down the sugar and starch, combining the C part released with O2 forming CO2 again! This is called the carbon cycle.

Other things contribute to the carbon cycle: Carbon is present in our bodies, in fact it is present in all animals, and plants, even rocks and dirt. When bodies and plants die and rot this carbon ends up in the earth. Over time some of this carbon get converted into fossil fuel such as coal, peat or oil.

When we burn these fossil fuels the carbon gets combines with oxygen releasing CO2 back into the atmosphere.

Image source: eschooltoday.com

Another step in this cycle is what the plants do at night! In the absence of sunlight plants switch to respiration, which means that, just like us, plants take in O2 and release CO2.

SUBLIMATION

CO2 exists as a gas at standard atmospheric temperature and pressure. It will freeze into a solid state at temperatures below -78oC. Solid CO2 is often called “dry ice”. Dry ice can be used to create a fog or smoke effect and is a great ingredient in many fun science experiments. One of my favourites is making a big bubble using dry ice – I found this demo showing how (click the image below to link to the experiment). If you ever do get some dry ice make sure you work with an adult supervising as it is VERY COLD!

An interesting fact about CO2 is that it does not exist in a liquid state at standard atmospheric pressure. This means that under normal conditions dry ice will turn straight into a gas as it thaws (i.e. it does not go from solid to liquid to gas as most substances do). This process (solid straight to gas) is called sublimation.

GLOBAL WARMING

Some of the gases within our atmosphere are known as greenhouse gases as they absorb some of the sun’s heat that is reflected off the earth and stop it escaping into space. CO2 is one of the greenhouse gases naturally present in our atmosphere.

These greenhouse gases maintain the earth’s temperature and this process is called the greenhouse effect. If the level of a greenhouse gas changes significantly then we experience global climate change. Global warming is the term used to describe an overall increase in global temperature due to an increase in greenhouse gases in our atmosphere. Increased levels of CO2 are thought to be the main contribution to current global warming; These increases are primarily due to the large number of fossil fuels burned by humans and a vast and steady decline of trees globally. Recent reports show a 30 percent increase in atmospheric CO2 levels since the dawn of the industrial revolution. While there is still much debate about the extend of global warming it would appear that consequences such as melting ice caps, rising water levels, global temperature increases, droughts and floods must, at least in part, be attributed to human actions!

Science has turned it’s attention to natural and renewable energies that provide some solutions to preventing and potentially reversing many of the current issues observed with global warming.

“We need to support the companies that support the earth.“

Woody Harrelson

AN EXPERIMENT TO TRY

Did you know that some types of fire extinguishers contain CO2? You can make a “mini” fire extinguisher using just vinegar and breadsoda….. but I thought I would let the experts show you!

Further reference:

The carbon cycle
Living in the greenhouse

What’s your favourite colour?

March 5, 2013July 4, 2014nao

With three children in my house I get asked a lot of questions. “Whys?” “What ifs?” “How comes?” are all part of the household daily dialogue. Apparently, the average three year old asks at least 50 questions a day, although I reckon our resident three year old easily doubles this number! I have noticed, of all the many questions my youngest asks, the most frequent one is….

……………………”MAMMY, WHAT’S YOUR FAVOURITE COLOUR?”

Your favourite colour seems to be one of the most defining aspect of your character when you are three years old! Apart from your food preferences, I think it is the first main expression of personal preference. The answer to this question can change at any given moment, but my three year old has been consistent with his favourite colour of yellow and I have to admit it really fits with his personality – but why do different things appear different colours? I thought this week I could share a bit about the science of colour!

To understand the science behind colour we need to consider a bit about the science of light. Light, either from the sun or a light bulb, may appear white to us, but it is actually made up of seven different coloursmixed together; these colours are red, orange, yellow, green, blue, indigo and violet.

Light is a type of energy called electromagnetic (EM) energy. EM energy actually travels in waves, even though we see light as straight lines. Light is the only type of EM energy that humans can see. The wavelength of light determines it’s colour. Light with the longest wavelength is red. Light with the shortest wavelength is violet.

SO HOW DOES LIGHT RELATE TO COLOUR?

When we look at a red flower, what are we really seeing? When light shines on an object, some of that light gets bounced back (reflected) off the object. The rest of the light gets absorbed by the object. We see the object as the colour that it reflects. So, when we are looking at a red flower we are looking at a flower that has absorbed all the light that is shining on it EXCEPT red light. It is reflecting red light so that is the colour it appears to the human eye. When an object appears white it is reflecting all the light shining on it and when an object appears black it is absorbing all the light and not reflecting any of it.

Scientist and artists sometimes look at colour in two very different ways; a scientist, observing light, will say that when you combine all the colours you end up with white (as discussed above). An artist may see it all very differently, when we mix paints, for example, if we mix all the colours together we will end up with black!MIXING COLOURS

Image credit: www.gelighting.com

AN EXPERIMENT TO TRY:

You can try this yourself at home: use torches to create the coloured light…fix two different coloured pieces of cellophane (say red and green) over the end of two torches (one colour on each torch). Shine the torches on a white wall or piece of paper. When you overlap the red and green colours you should get yellow! Now repeat with paint – mix red and green paint and what do you get? Not yellow this time but brown!

HOW ARE RAINBOWS MADE?

When light travels through water it slows down and the light bends. Different wavelengths of light bend to different degrees so the light gets split up into its component colours. This is how rainbows are made…
when sunlight travels through drops of rain each colour of light bends to a different angle and the white light is separated out into it’s seven colours.

Photo credit: Eric Rolph

Did you ever notice that usually when you see a rainbow there is a second, more faint rainbow around the first one? This second rainbow forms because some of the light is reflected off the back of the raindrop and bent a second time! These secondary rainbows appear more dark as the light has been bent twice and the colours appear in reverse. Check it out next time you see a rainbow!

HOW DO ANIMALS SEE COLOUR?

Some animals, such as cats and dogs, rely more on what they can hear or smell, than on the colours they see. Their colour vision would not be as good as humans. Like Humans, many primates and marsupials have good colour vision that they may use to allow them to recognise prey or food. Good colour vision is common among fruit eating animals as it allows them determine ripe from un-ripe fruit.

Many species of birds and fish have better colour vision than humans. If you consider how elaborately colourful these animals often are then it is not too surprising to accept that they must be able to see these lovely displays of colour among their own species. Pigeons, for example are thought to be among the best animals at detecting colour and can see millions of different hues.

Reptiles and amphibians are thought to have colour vision equal to, or better than, that of humans.

Many insects can see light (colour) that is not visible to humans. Bees, for example, can see Ultra Violet (UV) light. This allows them to see UV patterns on flowers, leading them to the source of nectar.

Finally, a myth buster…do bulls really “seeing red”? Infact, no they don’t – they are colour blind. The only reason that they charge the red cape is because it is fluttering in front of them!

Image credit www.valencia-property.com

A good night’s sleep!

February 26, 2013July 11, 2014nao

I awoke this morning to find NO CHILDREN at all in my bed. A very rare event indeed. I can’t remember the last time that happened but I am certainly not complaining. It was lovely to have a full night’s sleep with no interruptions for a change. I was perfectly happy to have little Rohan crawl into bed beside me at the reasonable hour of 7 am for a cuddle. Turns out it wasn’t Rohan but a “baby Dolphin” and I was the “Mammy Dolphin” and the bed was actually the sea. It did not take long for Rohan’s clever little mind to start to wonder….

……………………. “HOW DO DOLPHINS SLEEP IN THE SEA, MAMMY?”

SO, HOW DO DOLPHINS SLEEP?

Dolphins (and whales) are mammals just like us, they need to breathe in air. Unlike us, dolphins have adapted their bodies breathing system (respiratory system) to be able to go long periods between breaths. This allows them to stay under water for up to 30 minutes at a time before they need to surface and take the next breath. The other difference between dolphins and other land mammals is that we breathe involuntarily (without thinking about it) while they make a conscious decision to take a breath.

HOW CAN DOLPHINS SLEEP IF THEY NEED TO STAY CONSCIOUS TO BREATHE?

Dolphins have overcome the problem of having to stay conscious to breath by only shutting down one half of their brains at a time while sleeping. This process is called unihemispheric sleep and basically means that one half of the brain sleeps while the other half stays awake and alert. Interestingly, one eye stays open while the dolphin sleeps, it is the eye on the opposite side to the sleeping brain. This allows the dolphin to stay alert to its environment at all times, a requirement necessary for its survival.

Scientist determined unihemispheric sleep in dolphins by monitoring brain activity in captive dolphins using a process called electroencephalography. This process involves attaching electrodes to the dolphins head and tracking brain wave activity as electrical pulses. Such research suggests that dolphins are in this sleep state for approximately eight hours a day.

Studies into the unihemispheric sleep patterns of some mammals suggest hopeful correlations and potential solutions to human sleep disorders such as narcolepsy.

WHERE DO DOLPHINS SLEEP?

There is no real reason why dolphins can’t sleep anywhere within the ocean, but, given that they need to surface fairly frequently to breathe, it is most likely that they sleep just below the surface.

DO ANY OTHER ANIMALS SLEEP LIKE THIS?

Mammals, other than dolphins, that use unihemispheric sleep include whales, porpoises, manatees, sea lions and seals.

This types of sleeping has been observed in some birds and is suggested as a probable form of “sleeping on the wing” for migrating birds.

"Tooth & Nail"

February 19, 2013July 22, 2014nao

We waited a long time for my sons front tooth to finally come out – it spent the last week sticking horizontally out of his mouth – in a “Nanny Mc Phee” kind of fashion! Finally, last week, it did come out and there was great salutation and rejoicing – from me anyway. With suitable formality and ceremony the said tooth was placed in the very special “tooth bag” that we have for such occasions and carefully placed under his pillow. As I lay with him that night we chatted about all things “toothy” and just before I kissed him goodnight he threw me one of his wonderful questions…..

“MAMMY, HOW COME THE TOOTH FAIRY COMES WHEN WE LOOSE A TOOTH BUT IF WE LOOSE A NAIL THERE IS NO NAIL FAIRY?”……

Look at that for a smile!

Well, where do you start with that one? I hummed and hawed and spluttered and muttered some kind of an answer (which of course was countered and refuted) and beat a hasty retreat. The next day we went to visit family only to be met by another toothless smile from my lovely nephew. So naturally teeth were a hot topic of conversation for the weekend, so much so that my brother suggested they become the topic of my next blog. Not terribly enamoured with the idea (or should I say “enameled”) I changed the subject. However, the seed had been sown and the idea rattled around in my head for a few days. Today I have been chatting with my brother again, he has his own tooth woes this week with a few trips to the dentist and a tooth that didn’t fall out naturally. So, I figure I owe it to him….this ones for you Bro!

In for a penny-in for a pound… I guess I may as well keep my own son happy too and consider his question, so teeth and nails and the science there-of…although I make no promises on the whole “nail fairy” thing!

WHY DO CHILDREN LOOSE THEIR “BABY” TEETH?

When teeth begin to grow in a baby’s mouth the gum and jaw are not developed enough to allow for extensive roots to form under the tooth and so smaller, weaker roots are formed on these early teeth. By the age of (usually) six or seven the jaw has matured to a point that allows it to hold adult teeth- and their larger roots- securely. The smaller baby teeth start to get loose at this stage and fall out. Cue the “Tooth Fairy”!

WHEN DO BABY TEETH START TO FORM?

Baby teeth start to form when the baby is still in the womb, in fact the first part of their production begins when the fetus is only four weeks old. Once the baby is born the teeth usually start to push through the gum any time from about six months on. However there are exceptions to this – some babies are born with visible teeth – these are called natal teeth. Teeth sometimes appear within the first month after the baby is born and these are referred to as neonatal teeth. The full compliment of 20 baby teeth are usually all grown by age three.

Baby teeth usually fall out in the order in which they first appeared! Babies who get their teeth later than most will usually start to loose their teeth at a later stage too. This is certainly true in our house… my daughter finally cut her first tooth at the age of 11 months and lost her first baby tooth at the age of eight!

HOW LONG DOES THE “LOOSING BABY TEETH” PHASE LAST?

Loosing baby teeth and growing new ones usually takes six or more years.

The new adult teeth tend to be less white than baby teeth, often appear very large in the child’s mouth (at first anyway) and usually have noticeable ridges on them (that is because they have not been worn down from chomping and chewing)!

Adult teeth do not actually push their predecessors out of the gum. Instead a group of cells called odontoclasts form between the root of the baby tooth and the tip of the adult tooth. These cells are responsible for absorbing the roots of the baby teeth, leaving them without their anchor in the gum.

HOW MANY ADULT TEETH DO WE END UP WITH IN TOTAL?

The 20 baby teeth are ultimately replaced by 28 adult teeth. Then the four wisdom teeth get added, usually in our 20’s, bringing the total number of adult teeth to 32! However it is common for some, or all of the wisdom teeth to be completely absent from an adult. This may happen if the jaw is not big enough to accommodate the extra teeth. I myself got my wisdom teeth very late (and slowly) and only got three of them- I like to think I am wise enough not to need them all – but there are plenty who will argue that one!

WHAT ARE THE DIFFERENT TYPES OF TEETH?

A full set of baby teeth is made up of …

8 X Incisors
4 X Canines
8 X Molars

A full set of adult teeth contains…

8 X Incisors
4 X Canines
8 X Premolars
8 X Molars
4 X Wisdom teeth

Adult human dentition: image credit – www.tutorvista.com

INCISORS are for cutting.
CANINES (also known as CUSPIDS) are used for tearing.
PREMOLARS (also known as bicuspids) are used for tearing and crushing.
MOLARS are ideal for crushing and grinding.

WHAT ARE TEETH MADE OF?

Teeth have two parts, the top part that we can see, called the crown and the part we cannot see, the root, which below the gum. The root is embedded in the jaw bone.

Image Credits: www.enchantedlearning.com

Teeth are made up of…

ENAMEL…this is the shiny white part of the tooth that we brush. It is the strongest material in our bodies which makes it ideal for all the cutting, chewing, chomping and grinding that the teeth have to do. This layer contains a lot of calcium.

DENTINE… this is the layer just under the enamel. It actually makes up most of the tooth. Although a hard substance it is not as hard as enamel.

CEMENTUM… this covers the dentine part of the root of the tooth (below the gum) and helps to anchor the tooth into the jawbone.

PULP… this is the inner most part of the tooth. It is the only living part of the tooth, made up of blood vessels and nerves and other soft tissues.

………………………AND NOW FOR A LITTLE BIT OF NAIL-SCIENCE…

WHY DO WE HAVE NAILS?

Why do we have nails and what purpose do they serve us? Nails are considered a protective layer at the sensitive ends of our fingers and toes. However their function goes well beyond protection, they are also great tools and implements for finer dexterity such as peeling, gripping and scratching.

WHAT ARE NAILS MADE OF?

Nails are made up of layers of protein called Keratin, this is the same protein that hair is made of and that we find in the outer layer of our skin. The different sections of the nail are described below:

Image credit: www.scholl.com

The nail plate- is the part of the nail that we see, made of layers of keratin.
Nail folds – this refers to the nail skin around the nail.
Cuticle – this is the tissue that covers the bottom of the nail to protect the newly formed nail cells.
Nail bed – this is the are of skin that is covered by the nail.
Lunula – this is the white “half moon” that we see at the base of the nail.

HOW DO NAILS GROW?

Nails do not actually grow from the top of the nail, they grow from the base of the nail, just under the skin. As new cells are made the older cells harden and get pushed out along the nail.

Fingernails grown about 3 milimetres per month. Usually fingernails grow faster than toenails. The fingernails on our dominant hand grow more quickly than the nails on the non-dominant hand (American Academy of Dermatology).

WHAT CAN OUR NAILS TELL US ABOUT OUR HEALTH?

Healthy nails are smooth and uniform in colour. Sometimes our nails get little white spots due to knocks and damage and these usually grow out of the nail with time. Nails may often develop ridges running from base to top, often becoming more dominent with age but these ridges are usually harmless. However notable changes to the overall colour or shape of the nail or surrounding skin can be more serious and such things should always be brought to the attention of a doctor (Mayo Clinic).

SO BACK TO THE ORIGINAL QUESTION…. WHY TOOTH FAIRIES BUT NO NAIL FAIRIES?

To address the original question of why we have tooth fairies but not nail fairies…. I am still not much the wiser. We could argue the value in a beautiful baby tooth, sparkling and white, full of calcium and minerals … all which might be of interest to the fairies. I really like the suggestion in Rise of the Guardians, that fairies take children’s teeth to guard the memories contained within. When you consider that they are made before we are even born then there is a strong argument to this proposal.

Image credit: greenpoint dental

But as for nails? I’m not so sure of this one. Most of what we call a nail is actually a clump of long dead cells. You could argue that the fairies might like to collect the Keratin that is found in our nails but this is already freely available from our hair, which we shed a lot of and is easily collected, if the fairies were so inclined! Some say that our toenails are of value as they are the part of our bodies that accumulates any gold, but I can’t find any strong evidence to back this one up. I have to conclude that fairies just do not have any interest in our nails, to be honest I would not greatly blame them, would you?

AND FINALLY AN EXPERIMENT TO TRY AT HOME:

Here is an experiment that can demonstrate to children what fizzy drinks can do to our teeth.

What you need:

3 hard-boiled egg (shell still on)
3 jars or glasses
A bottle of vinegar
A bottle of fizzy drink
A bottle of water (or tap water will do)

What to do:

Place a hard boiled egg into each of the three glasses. Cover one egg with vinegar, one egg with fizzy drink and one egg with water. Cover all three glasses and leave them like this overnight. Next day remove each egg and record what you find.

What happens:

If you examine the egg in the vinegar you should see that the shell has disappeared. If this is not the case, place the egg back in the glass and leave it for another day.

The vinegar is an acid (acetic acid); it reacts with the calcium in the egg shell (calcium carbonate) and breaks it down, producing a gas as it does so. You may have observed the gas as bubbles being formed, during the experiment. Effectively the vinegar (acid) eats away at the egg shell until it is all gone.

Now look at the egg that was left in the fizzy drink. You should see that the shell has been dissolved away (or at least partially) just like the vinegar. The enamel of our teeth contains a lot of calcium just like the egg. The fizzy drink is acidic, just like the vinegar. You begin to get an idea of what fizzy drinks can do to our teeth if we don’t look after them!

Now check the egg that was left in water, it should still contain a strong shell, the water should not have changed it!

Pancakes- everything you didn’t realise you needed to know

February 12, 2013July 4, 2014nao

Ok, this week’s blog inspiration is slightly different to the norm. Usually the idea comes from a question that a child has posed – this time there is a slight deviation, but only slight…. this weeks question came from an adult, but only in the chronological sense – as in fact he is classified as the biggest kid in our house- it was posed by my husband. I was making pancakes the other morning (as I do every weekend on the request of my son) when my husband pondered aloud…”I wonder what the reason behind each ingredient is… and who made the first pancakes”. As I was wondering what next to blog about the two ideas seemed to merge into one, and so was born the question…..

…..”WHAT IS THE SCIENCE BEHIND A GOOD PANCAKE, AND WHO’S IDEA WAS IT?”…..

Made in the name of science

A BIT OF HISTORY…

So, before I delve into the science behind the PERFECT PANCAKE, I thought I’d look at a little bit of history first. The pancake as we know it seems to be accredited to the ancient Greeks, who in the 6th century started combining ground wheat with olive oil, honey and milk – and so the first pancake was born. If we expand on our concept of what a pancake really is we could look back further still to the process of making flat bread from ground grains and nuts mixed with milk or water, dating back to the neolithic period.

WHAT DO WE FIND IN A MODERN PANCAKE?

If we start within Europe a modern pancake can be classified as the round flat variety similar to the french crepe which contains some form of flour, and a liquid such as milk or water. These flat pancakes usually also contain eggs and butter, and sugar in the sweetened variety. Then we also have the thicker, fluffier pancakes that contain a raising agent, the name and variation of these include drop scones, Scottish pancakes and of course the well know buttermilk pancakes that are most common in America.

In our house the three most common pancakes made are the buttermilk pancakes, drop scones and the sweet flat crepe like ones.

WHAT GOES INTO A PANCAKE…

If we take a closer look at the primary ingredients we begin to see the complexity and science that really goes into making these delights:

FLOUR… this ingredient can be considered the backbone of the pancake as it provides structure
SUGAR….as well as adding the nice sweet taste and contributing to the colour of the pancake, sugar also keeps the pancake from getting to thick and stodgy
EGGS…. the proteins in the eggs add to the structure of the pancake and to the overall flavour
BUTTER/FAT… as with the sugar, the fats keep the pancake tender and prevent them becoming overly stodgy
MILK/WATER… the liquid portion of the pancake adds to the structure and is necessary for certain chemical reactions to occur
RAISING AGENT… as the name suggests, these agents help raise the pancake, making them light and fluffy

You can of course find many varieties with their own local changes and substitutes, potatoes are commonly used as the starch ingredient instead of flour.

First lets take a look at the thin flat pancake or crepe… in this case we will assume they contain flour, milk and sugar. From the above list we can now predict that the flour is the body of the pancake, it provides the structure, but how does it do this? There are two proteins found in flour called glutenin and gliadin. When moisture is added to flour (in this case the milk) these two proteins link together to form gluten. Gluten is a “sticky” protein, this stickiness allows it to form a network and it is this that adds structure to the batter. Finally we come to the sugar which caramelizes with the heat adding sweetness to the mix and contributing to the colour of the pancake as it cooks. The sugar also prevents the pancakes becoming too thick and stodgy by reducing the amount of gluten produced.

Image credit: jbeancuisine.com

So now we move on to the thicker pancakes; the main difference with these is that they contain a raising agent! Yeast is a biological raising agent used in some baking, it produces carbon dioxide gas while digesting sugar and this gas forms tiny bubbles within the yeast. When heat is added during baking these bubbles expand making the bread/cake “rise”.

The main drawback with baking with yeast is that it requires time and who really wants to wait too long for their breakfast? That is why, when using raising agents in pancake mixtures, we substitute the yeast for bread soda and/or yeast; but who can really tell what the difference is between these two?

Bread soda verse baking powder

Bread soda (also known as baking soda) is pure sodium bicarbonate. Baking powder contains bread soda but it also contains a powdered acid (usually cream of tartar – potassium bitartrate). Bread soda is an alkali/base and will therefore react with an acid (such as the buttermilk used in pancake batter) producing salt, water and carbon dioxide gas…

BREAD SODA + ACID —–> SALT + H20 + CO2

This carbon dioxide gas gets trapped in thousands of tiny bubbles within the gluten making the pancake batter rise on cooking into light and fluffy wonders! (The same process as with the yeast but a lot quicker).

The baking powder has the added advantage of having the acid already present, so once a liquid is added the dry acid and alkali can react in the same manner as above.

So now that we are starting to understand the science of it all how do we use this knowledge to make the best pancakes. before we jump into this one we first have to consider the science of flavour and odour!

THE SCIENCE OF FLAVOUR

The Maillard reaction describes a chemical reaction requiring certain amino acids and sugars and the addition of heat to produce the molecules responsible for the odours and flavour of food. Now there is a science worth studying!

MAILLARD REACTION: Amino Acids + sugar + heat —-> flavour and odour

So what does this have to do with our pancakes? Well Maillard reactions work best in alkali conditions so bread soda is a definite plus is making golden tasty treats. HOWEVER, add too much bread soda and the pancake will brown too quickly and will have an acrid burnt flavour, not to mention the unpleasant taste produced from the left over breadsoda. It is trickier than we think and yes, of course, someone has already done the science bit for us to work out the ideal amount of bread soda required.

WE ARE HUNGRY – SPEED IT UP

You will be glad to hear that speed is recommended when preping pancakes; Although it is good to allow the batter sit for a few minutes to allow the gluten to “relax” (build up a sufficient network) it has been shown that if left too long the bubbles will have burst and the pancakes will be flat and dense once cooked.

SCIENCE IN MY KITCHEN

I decided I had to try some of this pancake science out for myself so turned to my original buttermilk pancake mix from the wonderful NIGELLA LAWSON. This recipe actually uses both baking soda and baking powder (I omitted the banana). I decided to test out two theories…

1. Does the amount of bread soda determine the colour and flavour of the pancake?
2. Does the length of time the batter is left standing really make that much of a difference?

To keep it simple, I decided to keep everything else (including the amount of baking powder) constant.
So I donned my apron in favour of my labcoat and I set to work. I prepared the basic batter mix excluding the addition of bread soda. To digress for a moment, I also followed another golden pancake rule – not to over-mix the batter (a few small lumps of flour allows it better absorb the liquid and produce gluten).

My “slighlty lumpy” pancake batter

I dived my basic batter mix between four bowls and then added different amounts of bread soda to each (the first bowl had no bread soda, the second had half the recommended amount, the third had the recommended amount and the fourth had double what was recommended!). Then I let the batter sit for five minutes before cooking the pancakes.

Here are my results… the pancake on the top left had no bread soda, top right had 1/2 the recommended amount, bottom left had the ideal amount and bottom right had twice the recommended amount. You can see how the pancake gets darker with the addition of more bread soda, with the last one being just a bit too dark. The taste test revealed that the one on the bottom left had the best taste (and texture) and that the one with the most bread soda had that unpleasant taste of bread soda!

To investigate my second question I left the same pancake batters sit for two hours before cooking them. As you can see the pancakes cooked after two hours were indeed a lot less light and fluffy and were a bit soggy inside!

The batter for these was left sit for five minutes

The batter for these was left two hours

WHY ARE PANCAKES ROUND?

Pancakes are round for two main reasons: gravity and surface tension. Assuming that the pancake pan is flat then once the batter is added gravity will pull on all parts of the batter uniformly in all directions, pulling it out into a round shape. Surface tension pulls evenly on the edges keeping them restrained into the round shape.

THE SCIENCE OF FLIPPING A PANCAKE…

Would you believe that someone has actually looked into the exact science of pancake flipping? How cool is that ….

According to University Professor of Mathematics Frank Smith, the simple mathematical formula for the perfect flip is: L = 4 H /P- D / 2
(L = hand distance from inner edge of the pancake / H = height of flip / D = diameter of pancake)

If that sounds a bit too complicated check this out …

Dr. Tungate, a senior physics lecturer at Birmingham University, found that “a pancake should be flipped into the air at a speed of 10 miles-an-hour, which means that it takes less than .5 of a second to reach the top of its trajectory.”

AND THEN THERE IS THE SCIENCE OF WHAT YOU ACTUALLY PUT ON YOUR PANCAKES…

… but I think that is a whole other blog! So whatever toppings you choose I hope you enjoy your pancakes today!!

All that science made me hungry!

And if you still want more….HERE IS AN EXPERIMENT YOU CAN TRY….

Inflating balloons… This experiment shows two fun ways of inflating balloons, kids will love it, it’s easy to do and it teaches some kitchen science… like the difference between using yeast and bread soda as raising agents in baking!

Further reading:
Pancakes served with a side of science.
Celebrate your pancakes with a side of science.
Baking powder verses baking soda.
The history of pancakes.

There’s "snow" place like home

February 5, 2013July 4, 2014nao

We were lucky enough to go on a family skiing holiday this January…. sunlight, snow, fresh air, exercise, skiing and just an all round great experience. I have asked my three children the best things about the holiday and here are their responses….

Caer (age nine)….”relaxing, drinking hot chocolate every day… oh and THE SNOW”

Culann (age seven)….”the snow, eating meat all the time, everything really – except for ski-school!”

…and “Curly” Rohan (age three)….”the hotel, the ski slopes and the snow!”

So a mixed bag of responses there but with the one common denominator… THE SNOW!!!! And who could blame them, I loved it too! Especially on our last day, the weather got colder and we had a wonderful day of snow. At lunch time our entire group (15 of us in total) took the cable cars to the top of the mountain for lunch. The snow up there was thick and deep and as it fell on us we all remarked on the beautiful snow flakes… each one a perfect crystal, large enough to see the tiny branches coming off each arm of the structure. So the inevitable question came from the children….

……………………..”WHY DOES THE SNOW AT HOME NOT LOOK LIKE THIS?”

A Dendrite Snow Crystal

In order to answer this question we need to understand how snow is made and what can influence this process! We also need to understand the different shapes that snow can take!

So firstly HOW IS SNOW MADE?…

Snow is made much in the same way as rain, it is created from the moisture that makes up clouds. Moisture from the earth (seas, rivers, lakes, puddles etc) is constantly EVAPORATING (changing from a liquid to a gas form). This water vapour (gas) is picked up by warm air and carried to the sky where it forms clouds. When the temperatures get cold enough the water vapour turns into ice crystals that form around tiny particles of dust or dirt in the atmosphere. These ice crystals fall to the earth as snow.

So what is the difference between SNOW CRYSTALS and SNOW FLAKES?

A snow crystal is a single crystal of ice that can come in many different shapes. A snow flake is the term we are more familiar with – it can refer to one snow crystal or a group of snow crystals all grouped together. Some snow flakes can contain a clump of hundreds of tiny snow crystals.

WHAT ARE THE DIFFERENT SHAPES A SNOW CRYSTAL CAN BE?

When you think of the shape of a snow flake what do you think of? Do you think of the lovely star like ones with six branches just like the photo above? This shape of snow crystal is called an HEXAGONAL shape (having six sides) but finding these in such perfect condition is actually quite rare. With melting and refreezing, wind interference and snowflake collision most snowflakes we see are much more irregular structures. The snow crystal shown above is a STELLAR DENDRITE which means a star-shaped snow crystal with six branches that have lots of side-branches coming off them (dendrite means tree-like). More often than not snow crystals are small, NEEDLE, COLUMN or FLAT PLATE shaped and clumped together into one snow flake. This is certainly what we are more used to in Ireland when it snows. The array of shapes and sizes of snow flakes is really well described in this guide to Snowflakes.

This is what we saw in Austria!!

The lovely snowflakes that we saw on the top of the mountain in Austria were particularly intricate and beautiful. I would say they were FERNLIKE STELLAR DENTRITES and if you are thinking of skiing these are ideal. There is so much side branching that they look like ferns. Although these snow crystals are the largest that we see they are actually individual snow crystals which makes them all the more spectacular. They are often 5 mm or more in diameter and are clearly visible to the naked eye! So we were really lucky to see these lovely snow flakes. These crystals are very light and make the best powdery snow!

WHAT INFLUENCES THE SIZE, SHAPE AND SYMMETRY OF A SNOWFLAKE?

So what factors influence the distinctive shape of each snow crystal? Well for starters there is the temperature at which they form – snow crystals start to form when the cloud temperature reaches or drops below freezing (zero degrees Centigrade (C)); the amount of dust or dirt particles available also effects snow formation. Then there is the location of the clouds in which the snow crystals form… in general snow flakes are larger when formed in high clouds compared to snowflakes from lower clouds. This factor links with the length of time the snow flake takes to fall to the ground along with the air temperature as it falls and with how many collisions the snow flakes might encounter. Snowflakes will often heat and cool as they drop due to differences in air temperature, this often leads to large snowflakes as they become more “sticky” when they melt at the edges, allowing them to clump together as they collide and refreeze. Other weather factors such as humidity (how much water vapour is in the air) and the wind speed all contribute to the final size and shape of the snowflake formed.

Taking these factors into consideration the lovely fernlike stellar dendrite snowflakes we saw in Austria were probably formed under the following conditions: formed at very low temperatures, in low lying clouds and fell through dry cold air with little wind!

Now lets consider what we are used to here in Ireland!

So this is today’s snow in the west of Ireland!

As I write this I am looking out on a typical “Irish” snow scene… the ground is covered in patchy white snow that is made up of small ball shapes of snow flakes that are a bit wet and sticky. On the plus side these make great snow balls… I can vouch for this one myself as my back is still wet from the pelting I got from my husband as he left for work today (the biggest child in the house)!! So this snow was probably made at lower temperatures in high clouds and melted and froze as it fell to the earth through moist air; this would result in large snow flakes (like small snow balls) made up of a number of small snow crystals joined together. This snow does not tend to last too long, beginning to melt as it hits the ground, making for that wet sticky snow!

SO IS IT TRUE THAT NO TWO SNOW FLAKES ARE IDENTICAL?

The simple answer to this is YES and NO! Although we cannot vouch for every single snowflake that ever existed, science does suggest that the exact shape and structure of each natural snow crystal is unique – so that means YES – no two snow flakes are identical. Especially if you consider the different factors that are involved in creating each snowflake! HOWEVER, for more simple snow crystal structures it can at times be hard to tell the difference between two under a microscope!

WHY IS SNOW WHITE?

When we observe the colour of an object we are actually seeing the colour of light that the object REFLECTS (bounces back)- so green grass, for example, is ABSORBING (taking in) all light expect green light, which it is reflecting. When an object appears white that means it is actually absorbing very little light and reflecting most or all of the light falling on it. This is the case with snow, it’s crystalline structure creates many reflective surfaces making the light that falls on it “bounce back” or be reflected. You can read more about this here.

IS IT EVER TOO COLD TO SNOW?

The simple answer to this is NO, once there is enough water vapour around to make snow, and enough circulating air to transport it then snow can be made at very low temperatures! However, as warmer air can hold more water vapour we tend to get most snowfall at temperatures around freezing point or a bit below.

MAKE YOUR OWN SNOW FLAKE…

Now that you understand all about snow, how it is made and the different shapes and patterns it can take, I thought it would be fun to end with an experiment you can try yourself at home. These are worth the bit of time and effort (and waiting overnight) as the results are really great! Let me know if you try it and how you get on!

Images:
Dendrite snowflake photo National Geographic – Kenneth Libbrecht
Images of Fernlike Snowflakes by Kenneth Libbrecht

Further information:
Snow crystals photo gallery
Observe and photograph snow
Fun snow facts for kids
Met Eireann Primary School Resource
10 Science Facts About Snow

Sticky toes

January 28, 2013July 4, 2014nao

We are amassing quite a collection of geckos around our house these days. Not the organic variety of course, although that would really please the kids! No, our collection consists of ornaments, wall hangings, trinkets and even jewellery. It all started ten years ago when on honeymoon in Barcelona … the little guys were everywhere and we were drawn to them with fascination – especially their ability to scale any surfaces they encountered (even glass). So the collection started from there, anytime we come across a quirky gecko decoration or ornament we like, we purchase and add it to the collection!

Ten years on and our fascination has grown along with our collection. I was delighted to show my children a recent photo from National Geographic of a gecko. Of course that lead to the children asking questions, that lead to questions, that led to the ultimate… “How do they walk up walls?” After answering their questions I decided this might be a good topic to start my 2013 blog with. So…how do these amazing little creatures manage their “spiderman-like” feats? It truly is a marvel of nature but before I delve into that, I want to tell you a few other quirky facts about these lovely little creatures.

Geckos are a type of lizard. They are found on all continents except Antartica. They come in many shapes and sizes and are in fact the most species rich order among lizards. They are also among the most colourful lizards in the world.

Most species of geckos can actually sever part of their tail, usually to escape the hold of a predatory or threat. The released tail segment can keep wriggling as a distraction while the gecko escapes. PRETTY COOL DON’T YOU THINK? This process of severing the tail is called caudal autotomy!

photo credit: Tambako the Jaguar via photopin cc

Another very interesting fact about geckos is that nearly all species of geckos have no eye lids and can therefore not blink. Instead, they use their long tongues to clean any dust from their eyes.

Already you can begin to see how fascinating these creatures are, and that is before we have even looked at their ability to apparently defy gravity! DID YOU KNOW THAT A GECKO CAN SUPPORT ITS ENTIRE BODY WEIGHT ON ONE TOE?

So here is the science bit behind HOW THEY DO IT…the toes of a gecko are covered in hundreds of small ridges called lamellae. Each ridge is covered in millions of hairs called setae. Setae are much thinner that human hair (up to 30 times thinner). Each seta then splits at the top into tiny strands called spatulae – there can be up to 1000 spatulae on one seta (if you think you have problems with split ends, pity the poor gecko!). So you can begin to imagine how tiny these spatulae are, in fact, they are so tiny that they can bond with the molecules of the surface they are touching. This bonding is referred to as van der Waals interaction! The great thing about it is that it is what is called dry adhesion – it doesn’t require any sticky compounds or leave any messy residue.

photo credit: bernat... via photopin cc — photo credit: bernat… via photopin cc

This gives us an idea of how the gecko sticks to the surface, but HOW DOES IT UNSTICK? The adhesion (sticking) process is said to be one-directional…imagine sticking a piece of sticky tape to a surface and then taking hold of one edge and peeling it back to remove it… the gecko does something similar. Geckos toes bend in the opposite direction to humans so they can “peel” their toes off the surface from the tip backwards. Add to this the fact that geckos have rotating ankles and you start to understand how they can move in any direction.

As you can imagine this ability has captured the interest of Scientist for a long time. Imagine if we could copy this adhesion from the gecko… what could we do with the technology??? Robots that can scale any surface would be great in extreme or rescue situations, right? Or how about a suit we could wear to allow us to climb like a gecko? Did you know that geckos can climb in a vacuum? So now we can start thinking about using this technology in space! Or how about using the technology in bandages – inspired by the observation that geckos can climb in wet conditions… a bandage that stays on when wet.

Maybe YOU can think of another novel way to use gecko technology? If you have any ideas I’d love to hear them!

More on geckos…
Nat Geo Kids Creature Facts – Geckos
The dance of the disembodied gecko tail
Geckos evolved sticky feet many times

carrots, cabbages and cups of tea!

November 6, 2012August 17, 2016nao

It’s funny how Autumn comes around every year and I realise how much I love this time of year…. it’s as though I seem to forget I like it all throughout the other seasons. Of course we have had a particularly nice Autumn this year in the West of Ireland and maybe that has re-enforced my happy memories of the season. The days have been bright and crisp showing off all the beautiful colours in all their glory and splendour.

photo credit: Stellas mom via photopin cc

I grew up in Co. Wicklow surrounded by some beautiful deciduous woods and forests and this Autumn has really brought my childhood memories flooding back. My mother brought us often to the woods as children and we would hunt around for hidden treasures and delights to bring home and turn into some “masterful” collage in homage to the season. There was also the foraging, a distinctive primordial instinct in us all, there is nothing as pleasing as returning home with your bounty… be it blackberries or sweet horse chestnuts- to be turned into jams and tarts or painstakingly peeled of all nasty layers to reveal the divinely sweet, fruity, nutty delight beneath. In fact the joy that came with eating the nut always made it suddenly worth your while to start the arduous task of peeling all over again!

…and I hope that I will never outgrow the delight of running, kicking, shuffling through a crisp new crop of fallen leaves!

As many people know, the lovely green of most leaves is caused by the pigment chlorophyll… green in colour (obviously) and capable of using sunlight to convert water and carbon dioxide into energy (sugar) for the plant. However, when the sunlight hours fade coming into winter so too does the chlorophyll in the leaves of trees, or, to be more precise, the pigment begins to degrade and is not replaced. Once the green colour is gone other pigments that are often present in the leaf come into view… carotenoids are pigments responsible for the yellow/orange colour of leaves, anthocyanins are responsible for the redder colour of leaves and tannins are responsible for the brown colour of leaves. There is, within this pigmented system, a sense of hierarchy, at least in part. But did you ever wonder about the science behind those wonderful colours? I did… why the green suddenly disappears, where does it go and how do the other colours get there in its place? So, if like me, you ever wondered about these things… here is some insight into the why and what of Autumn!

Carotenoids are the pigments responsible for the orange colour of carrots. If carotenoids are present their colour tends to dominate leaving the leaves yellowy and orange.

In the absence of carotenoid, anthocyanin is the dominant pigment. Anthocyanin (the same pigment found in red onions, red grapes, red apples and red cabbage) is a natural pH indicator, meaning that it can change colour depending on the levels of acids or bases/alkali in its environment. In fact one of my favourite experiments that I often do with children is to demonstrate this colour changing using anthocyanin extracted from red cabbage (but that’s a whole other blog in itself). Anyway, at the beginning of Autumn the levels of sugar in the leaves tends to be quite high, increasing the acid levels in the leaves, this strengthens the red colour of Anthocyanin if it is present in the leaves.

At the end of Autumn the leaves die off and the levels of carotenoids and anthocynins die off too, leaving another pigment to dominate… and this is the brown pigment of tannin, the same pigment that give a cup of tea it’s colour!

So there you have it… next time you are crunching through those leaves you may wonder why you are suddenly thinking of carrots and cabbages and cups of tea!!!