The science behind the ‘5 second rule’

5 second rule

We must have all had that devastating moment, when you are holding the most tantalising piece of food in your hand, then in slow motion the precious morsel slips out of your grip and tumbles on to the floor. Absolutely heartbreaking stuff, until of course somebody comforts you with three magical words – 5 second rule – and you realise this food is still fit for consumption. It is still OK to eat right?? Right??

Believe it or not people have researched whether there is truth in this rule, and the results may actually surprise you.

The research:

The logic behind this rule is that germs from the floor wouldn’t have enough time get all up in your food in just 5 seconds, so the food should be fine if you pick it up quickly. The research tested the rule based on this idea, and placed items of food on floors covered in bacteria for varying amounts of time and then measured how much bacteria had got into the food.

The results:

The less time food was on the floor, the less bacteria was able to transfer in to the food – which shows living by the 5 second rule isn’t a bad idea.

However, what did matter even more was the amount of bacteria on the floor to begin with, if your floor is infested with crap, the bacteria will likely get into your food, even if you do pick it up fairly quickly – but you would have to drop the food in that exact spot where the bacteria is for this to be a problem.

They also found that you can add more time on to the 5 second rule if the food is dropped on carpet. Bacteria transferred to food much slower on carpet compared to wood or tiles. This means if you drop food on the carpet it is likely to be safe – it just might be a bit furry.

Why does toast always drop butter side down?

Whilst on the topic of dropping food, I thought I would try and find an answer to why toast pretty much always falls butter side down. In most situations when we drop toast we knock it off a kitchen counter or a dining table, and the ‘knocking off’ motion as well as the difference in drag between the side with butter on (no air holes) and the plain side (loads of air holes) tends to give the toast some rotation in it’s flight to the floor. But, because our kitchen units, dining tables and sofas aren’t that tall, the toast can only manage about half of its rotation before it hits the floor, and a half rotation usually results in the toast flipping just enough so the butter side is facing the floor, absolutely gutting stuff. Apparently if you drop toast from a bigger height it will have less chance of falling butter side down as it will be able to complete the rotation before meeting the floor.

So there you have it, 5 second rule is a-ok, particularly with carpet. I have once again answered one of life’s big questions using science – you can thank me with a cheeky retweet or follow.

Till next time,




The science behind why getting kicked in the balls hurts so much

Hit in groin

The high pitch groan, the grabbing of the crotch and a staggered drop to the floor. All tell tale signs of a man having been kicked in his special place. A pain apparently so bad that it justifies a grown man squealing like a prepubescent chorister. Now I don’t have testicles myself, being a woman and all that, so I have to take your word for it men, that this really does hurt that badly. Because I’m all about answering life’s important questions, I have looked into the science behind why being hit below the belt really is so painful.

Testicles are really exposed:

Most parts of our body are protected by some muscle, bone or cartilage, but your balls aren’t quite so lucky. This leaves them in a really vulnerable position so any physical impact on them will really hurt with no muscles etc to soften the blow – unlucky lads.

Testicles are covered in nociceptors:

A nociceptor is a type of nerve that reacts specifically to pain, and they only send signals once a certain pain threshold is reached. Because the testicles are absolutely covered in these, it makes them super sensitive to pain.

Here’s how it works: your balls get hit, the many nociceptors are activated and send loads of pain signals to the brain, the brain then responds by causing the release of a substance which makes us feel a physical pain, which you very quickly react to.

Men can often get headaches when hit in the special place too, this is because the brain also releases endorphins in response to the pain, which depletes some of the oxygen available in the brain – as if you didn’t have enough to deal with?  

Testicles are connected to nerves in internal organs:

Men will know all too well that when kicked downstairs the pain spreads all across the abdomen. This is because testicles are linked to lots of nerves in the stomach. Balls also link up with the vagus nerve, which connects to the part of the brain that controls vomiting. This not only explains the pain but the other symptoms that make men a total mess in this situation, like nausea.

What hurts more – being kicked in the balls or giving birth?

This really is one of the biggest debates in life. Until recent years nobody thought anyone could ever experience both, so this debate has been left unanswered. However, fabulous work in pain simulation is allowing us to have a bit more of an insight.

These wives managed to persuade their husbands to experience the pain of muscular contractions in labour:

It would be interesting to hear what these men thought was more painful, and I think I might be able to hazard a guess watching their reactions here. Maybe if somebody developed a simulator for the pain of being kicked in the balls for women to try then we could really settle this debate once and for all, (can’t say I will be volunteering for that one though).

Till next time,



Why does alcohol make us pee so much? – The science behind ‘breaking the seal’

Why is it that on every night out, I spend half the night queueing for the loo? And before that I face the inner turmoil of ‘do I go or hold it in?’ to avoid ‘breaking the seal’, because apparently when you let yourself pee once the floodgates are open and you just can’t stop needing to go. I just had to find out why alcohol has this effect on us, and if the ‘breaking the seal’ is a real thing.

breaking the seal
Alcohol making you pee so much is particularly an issue at a festival with horrible porta-loos that you queue 20 mins for the privilege of using…

Why does alcohol make us need to pee so much?

Drinking makes us need to go so often because it is a diuretic (that’s a fancy word for ‘substance that makes you need to wee a lot’). It has this effect by acting on the pituitary gland, reducing the amount of anti-diuretic hormone (aka Vasopressin) the pituitary gland releases. Normally anti-diuretic hormone would act on the kidneys and make them reabsorb water, so there is less volume of water in your urine – making you produce less pee. But when alcohol reduces the amount of anti-diuretic hormone, the excess water is not reabsorbed by the kidneys, and all that extra liquid ends up increasing the amount of urine we produce when we drink. 

By the way – when we are drunk, so much water gets flushed out of our body that our liver has to grab water from other organs to be able to deal with all the toxins we give it on a night out. This includes water being drawn from the brain, which gives us that all too familiar headache the next day.

Does switching to shots help?

Some friends think that switching from pints or other long drinks to shots will make the need to pee less because the volume of liquid is less. These friends are wrong – the diuretic effect is still just as bad with shots because it’s the alcohol that makes you go more, not the increased volume of liquid you are taking in. 

Does ‘breaking the seal’ make it worse?

As I said before, we all tend to hold it in until we are about to burst because of a common conception that the diuretic effect of alcohol works in a ‘once you pop you just can’t stop’ kind of way, in that once we have that first wee, we then won’t be able to stop. There is actually no evidence for this. It is a lie. What actually happens is that by the time you let yourself pee, enough time would have passed for the diuretic effect of alcohol to kick in. Its has nothing to do with when you decide to go / how long you wait – so just do everyone a favour and next time you drink stop squirming and just go and pee! 

So I have once again cleared up one of life’s great mysteries using science, you may thank me Friday night with a glass of champagne (you will probably find me in the line for the loo…)

Till next time,



Why does champagne pop? – The science of poppin’ bottles

Science of champagne pop

I love a glass of champers, but it’s always a tense moment when I try to open a bottle without causing an inevitable volcanic eruption of bubbles, resulting in an expensive puddle on the floor. Why does champagne have to be such an awkward drink, with it’s big explosion and obnoxious popping sound? It even demands a different shape glass! I just had to find scientific reason why something so good has to be so fussy…

Science of champagne
One simply can not graduate without a full champagne glass

Why does champagne pop?

To understand this you need to know that carbon dioxide is dissolved in the wine, and there is also some carbon dioxide in the air space between the wine and the cork. Before you open the bottle the amount of carbon dioxide gas in the wine and in the air space is balanced out. When you open the bottle, the carbon dioxide is released, this is what makes it pop!

But not all of the energy stored in the bottle is released as sound! You may be one of the unlucky people to have been hit with a flying champagne cork (first word problem). The reason the cork flies is because some of the energy stored in the closed champagne bottle is released as kinetic energy, which gives the cork some air time. If opening a bottle fills you with fear of breaking windows/ someone’s nose, you can change how much the cork flies by changing the temperature of the wine. Research has shown that the warmer the champagne, the bigger the CO2 cloud is released, so the cork flies further. This is because a change in temperature changes how soluble CO2 will be in the champers. A colder wine is a safer wine apparently.

Why so fizzy?

A rush of CO2 is released when we pop a cork, which is why it can erupt into a bubbly mess, but it gets fizzy in the first place from a process called fermentation. Yeast molecules digest sugars found in the grape juice into CO2 and ethanol, and its the CO2 that gives the bubbles and the ethanol that gives the happiness. What is special about champagne compared to other alcoholic beverages is that it ferments twice, the second time inside the bottle. Loads of chemicals help this process along and a different composition of chemicals will alter the taste of the champagne, which is partly why some are delightful and some are not so great.

Why does champagne need a special glass?

As if we didn’t have to be careful enough with this stuff it requires it’s own style of glass, but why? Research has found that the shape of a champagne flute really does affect the taste, with a taller, more narrow glass providing a better flavour. Much more CO2 was present at the top of a narrow champagne flute then at the top of a wider glass. This is important because CO2 bubbles in champagne carry aroma molecules on them up through the liquid and release them when they pop, so more CO2 bubbles reaching the top of the glass will stimulate your sense of smell, and in turn improve the taste.

This effect works even better when the bubbles form from the bottom, centre of the glass so that the gas can carry more aromas and stimulate your nose more. Bubbles will tend to form from where there is an imperfection in the glass, this is why really posh champagne flutes are often purposefully scratched in this place.

Here’s a top tip: pour your champagne at an angle – research has found that this preserves double the amount of CO2 bubbles, which gives us a better smell and therefore taste!


Till next time,



Is an invisibility cloak really possible?

This is a really cool guest blog by the awesome Jonny Brooks!

Have you had a moment so embarrassing that you just wanted the ground to swallow you up? Or you’ve ever wanted to sneak into a room where you know your boss or teacher is talking about you, just so you know what they really say about you? At times like these it would be so handy to have an invisibility cloak just like Harry Potter so no one would ever know you were there.

Well this is what scientists around the world are trying to do right now.

Figure 1: Harry Potter and his awesome invisibility cloak........... that you can't see
Figure 1: Harry Potter and his awesome invisibility cloak……….. that you can’t see

How does it work?

To be invisible you have to make sure that no one can see you. Obvious right? But that’s not the only thing (otherwise hiding behind the door would make you “invisible”). In addition to not being able to see you, the tricky part is also making sure that the person can see what’s behind you. This creates the illusion that people can see straight through the invisible object.

This can be done in several ways, although two of the most common methods are by transformation-optics cloaking and optical camouflage:

transformation-optics cloaking – This method makes use of materials known as metamaterials. These metamaterials are engineered so they exhibit properties that have not yet been found in nature. Built correctly, these materials allow us to bend light around an object making the object invisible and also making sure people can see what’s behind you.

Figure 2: Bending light around an object
Figure 2: Bending light around an object

optical camouflage – This is one of the simpler methods of making an object invisible. Take an object that you want to make invisible (like a human for example) and put a camera on the back of the object. This camera records the images behind the object. If that camera is connected to a video feed in front of the object, then you can project the images of the camera onto the object, creating the illusion that you can see right through it.

Are we close?

Good question. I guess the answer is “kind of”.  Transformation-optics cloaking was one of the first successful demonstration of the method in 2006, but it only worked with microwaves. This means that if our eyes were able to see microwaves, then we would have an invisibility cloak. Unfortunately this isn’t the case. Our eyes see visible light.

Not only that, but many of the methods used to make objects invisible scatter more light, at a different part of the light spectrum, than the object that they were trying to hide. For example, if you had a cloak that made an object invisible to red light, it may actually be scattering lots of blue light. Therefore it may be invisible to red light but if you shine blue light at it, then the object was probably more obvious than it was before.

Despite this, new methods of cloaking are being developed that use electricity to make an object appear invisible. These have the benefit that the device will not scatter light over a broad range of the light spectrum. However, much more research is needed before we have something that truly works for visible light.

So in short, it’ll be a very long while before we have a true Harry Potter style invisibility cloak, but we are making progress. For now, we’ll just have to keep dreaming.

Thanks for writing for Sparkly Science Jonny!

Give him a follow on twitter @Jonny_CBB and check out the work he does at the University of Oxford


The science behind why hair turns grey

Some of us embrace the idea of becoming a ‘silver fox’, while others will do literally anything to hide the 50 shades of grey sneaking into our hair. However we feel about it, the reality is we will all go grey as we age, so I was wondering – why does this happen? And could we use science to prevent us from going grey?

For some people turning grey is not a problem at all....
For some people turning grey is not a problem at all….

To explain how our hair loses colour, we have to think of hair growing in cycles. There is a ‘growth phase’, where hair grows in length, and a ‘rest phase’ where hair stops growing and eventually falls out of the follicle. In this cycle the hair pigment is produced in the growth phase, and turns off in the rest phase, then production resumes again as we go back in to the growth phase. When the pigment production stays switched off after the rest phase and fails to turn back on in growth, we grow a grey hair (with no pigment).

With every hair cycle we have, some of the melanocytes (cells that produce pigment) in our hair become damaged.This isn’t a problem as we can replace the damaged/dead pigment producing cells with others from a little stash of them that we have, but when this store of melanocytes becomes depleted as we age and have used all of them up, we no longer have any cells to produce pigment – so our hair grows grey.

How would we stop hair going grey?

We would have to make the melanocytes live longer and be less susceptible to damage, or increase the amount of them we have in our stash. Sounds difficult but some scientists in France have identified a chemical that can protect the melanocytes from damage – so our hair can stay coloured for longer. If you’re already grey this won’t help you, but for those of us yet to turn grey there is hope!

Can we re-pigment hair?

Those of us who are bored of the chore that is hair dyeing, there may be a more permanent solution on the horizon to permanently turn grey hair back into pigmented hair! A study found particular antioxidants can reverse the greying of hair – although this was intended to help those with the genetic condition ‘vitilligo’, this could also work on those who no longer want the salt and pepper look.

So, ladies and gents, do not stress about turning grey (by the way, stress won’t make you turn grey, so even if you are stressed about it, doesn’t matter!), there is hope on the horizon that we can prevent and reverse all 50 shades of grey, white and silver (if you insist on calling it that).

Till next time,



6 Scientific reasons why chocolate is good for you

In keeping with the spirit of Easter and the imminent chocolate binge I thought I would find some research that will make us all feel slightly less guilty when we overindulge in chocolate in the next few days. 

Master chocolatier- or pretty much a life saver?
Master chocolatier- or pretty much a life saver?

 1. Chocolate can boost memory – A study at Columbia University has found that chocolate improved scores in memory tests in a cohort aged 50-69, to the extent that they had the memory of someone 10 or 20 years younger. However, this only worked if you ate INSANE amounts of chocolate…. I think I could definitely manage that though. 

2. Dark chocolate is a source of antioxidants – Research has found that the antioxidant activity of dark chocolate is actually really high, with some studies finding it a better antioxidant than fruits such as blueberries, cranberry and pomegranate.

3. Chocolate can sort out your PMS – Chocolate (particularly dark chocolate) can allegedly increase the release of the hormone serotonin, which improves your mood at your ‘time of the month’. I’m not totally convinced on the evidence for this one, but I know I am definitely a nicer person after some chocolate, so maybe there is some truth here, even if it is just a psychological effect. While we are on the subject – dark chocolate has high levels of iron and magnesium, which can be lacking during menstruation, which helps to explain why women crave chocolate on their period and why it can make us feel better. 

4. Chocolate can sort out your cholesterol – Trials have found cocoa powder to reduce LDL cholesterol (the bad one) activity and overall levels of LDL, while increasing HDL levels (the good one). This is partly due to the antioxidant activity of cocoa. Reducing LDL and increasing HDL leads to a reduced risk of cardiovascular disease, therefore chocolate is super important for a healthy lifestyle.

5. Chocolate can lower blood pressure – Chocolate contains compounds called flavanols, which can act directly on the walls of your arteries to stimulate the production of nitric oxide.The nitric oxide relaxes the artery walls, so blood flow is stimulated and blood pressure is lower. Studies found this effect to be small but significant.

6. Chocolate can reduce stroke risk – A large study in Canada has found that chocolate eaters were 22% less likely to suffer from a stroke than non-chocolate eaters. Chocolate eaters who had suffered a stroke already also had a better outcome being 46% less likely to die from a stroke.

Of course chocolate is full of fat and sugar etc that we know is really bad for us, but I choose to ignore that evidence for the next few days and focus on research that says chocolate is basically essential to our health.

Happy Easter!

Till next time,