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,



The science behind kissing: 10 things that happen when we kiss

Whether it’s a quick polite peck, or an awkwardly long PDA that spurs on a chorus of ‘Get a room’, there are several biological and chemical changes that happen inside us when we kiss- there is even a field of study dedicated to this – Philematology, which is the science of kissing.

People often say they can decide if there is ‘chemistry’ between you and a partner by one kiss – so here is the literal chemistry we all unknowingly refer to:

Can anyone else see the pheromones between them?
Can anyone else see the pheromones between them?

1. Kissing relieves stress:

Several studies have measured levels of the stress hormone, Cortisol, before and after a make out session, and in both men and women there is a consistent, significant drop in cortisol. So if you are stressed – have a little smooch (although if it is work related stress maybe don’t pucker up in the boardroom, that would be super awkward).

2. Kissing releases the love hormone – Oxytocin:

There is a reason Oxytocin is known as the love hormone – it is released from the pituitary gland when we engage in sexual activity. It has the effect of making us feel sexually aroused and can also makes us feel a closer bond and more trust with our partner. When we kiss our levels of Oxytocin sky rocket, so kissing does make us feel closer.

3. Men pass along their testosterone in saliva to activate women’s sex drives

An interesting theory by Helen Fisher from Rutger’s University found that there is testosterone present in men’s saliva. She also found that men preferred a more saliva filled, slobbery kiss. Her theory was that men were unconsciously passing their testosterone filled saliva on to women in an attempt to activate the part of the woman’s brain associated with sex drive. I think this idea is intriguing, it certainly makes evolutionary sense, though I’m not a fan of sloppy kisses myself!

4. All the happiness chemicals are released:

Kissing stimulates nerve endings on our lips, which sparks release of dopamine. Dopamine is a neurotransmitter that is active in circuits in the brain associated with pleasure, and it makes us feel happy. Dopamine is also associated with feeling rewarded, which can make us want to repeat a behaviour – so one kiss with someone really can lead you to wanting more of them. Endorphins are released when we kiss, these are neuropeptides that gives us a happy buzz, like after we exercise. Phenylethylamine levels also increase during a kiss, this chemical is actually similar to amphetamines, and it not only makes us happy, it has aphrodisiac effects too! Don’t worry if you don’t have a special someone to smooch, you can find phenyethylamines in chocolate!

5. Your adrenal system gets all excited

When we kiss the adrenal system releases adrenaline and noradrenaline. This puts our whole body into an excited, revved up state where our heart rate increases and sugars break down in the body to give us more energy so we are ready for action. Also, blood rushes away from the stomach to our muscles and our sexual organs, so we can be prepared for any impending…. further action….

6. You tone up your face muscles

You use about 30 muscles when you kiss (depending on the type of kiss) and repeatedly doing this can exercise these muscles in a way that tones up the muscles in your face, preventing them from drooping, so kissing can prolong your youthful looks.

7. Pheromones fly about between you

Pheromones are like hormones, but they are released outside of your body, and recognised by others of the same species. Nobody really understands them, but from what we know so far these chemicals are released when we kiss, and our partner can sense them with their nose and mouth and will be able to detect if you are aroused. This is much better documented in animals, but it is thought humans could act the same way.

8. You burn loads of calories:

Passionate kissing is said to burn 6.4 calories a minute. That means half an hour of kissing burns the same amount of calories as running for  around 25 minutes or swimming for about 30 minutes (depending on how fat or fit you are). Would you rather go to the gym or get some ‘alternative exercise’? Let me think about that one.

9. The way you tilt your head is learnt in the womb.

We have all had the awkward situation where you both lean your head one way, and then you bash heads and it’s super awkward and kills the moment. Head orientation preference in kissing is actually thought to be developed when we are a foetus, due to where our head and hands are positioned in the womb. Now there isn’t a huge amount of evidence on this, but I think the idea of it is cute. Research has found that most people do tend to tilt to the right anyway, and that when there is a clash of heads it is a real turn off! (I know you are tilting your head whilst reading this, and I know most of you are tilting to the right!)

10. Our pupils widen:

This is why we close our eyes when we kiss – it’s just creepy having big bug eyes staring at you!

So now we know that the little spark we feel in those tender moments is actually just a series of chemical reactions and our hormones flying about having a little party. It is thought however that these reactions don’t occur as strongly when the physical attraction isn’t there, so it is true that you can decide if there is real attraction and chemistry with just one kiss…

Till next time,



Mosquito bites – why some people always get bitten and a novel way to repel mossies

One thing that stands between us and a perfect summer is pesky mosquitoes buzzing around and leaving unsightly bites that you just can’t stop scratching. I seem to be one of those people who get eaten alive on holiday and have always wondered why. I had assumed that I was just really tasty, but I have now looked into the science behind why some of us are more prone to getting bitten. I also looked at how insect repellent works and a new way to repel those mossies.

Image from
Image from

Why do some people get bitten way more than others?

As I said, I always get eaten alive on holiday and it drives me absolutely mad. There are a few potential reasons as to why this is:

Genetics: If you carry genes that make you release more uric acid than others, mosquitoes will be more attracted to you. (Thanks parents for my genes… not)

Type O blood type: A study has found that mosquitoes landed on those with Type O blood nearly twice as much as those with Type A. Some of us also release a chemical out of our skin that indicates to mosquitoes what type of blood we have, which would invite the mossies onto the Type O bodies even more so.

Exercising: If you tend to exercise a lot on holiday your skin temperature will be warmer and you will secrete more lactic acid. Both hot skin and lactic acid have been found to be attract mosquitoes. (So stop jogging, get a cocktail and holiday properly!)

Breathing out more carbon dioxide: Mosquitoes are experts at detecting carbon dioxide and they use this to locate their next victim. So if you breathe out more co2, then you are more likely to have a mossie land on you. As a general rule, larger people breathe out more co2 , which may explain why you probably got bitten less as a tiny kid then you do now as an adult.

Being pregnant: This one doesn’t relate to me (thank god) but pregnant women are twice as likely to get bitten. This is thought to occur because they are warmer and exhale more carbon dioxide.

Drinking beer: Nobody is quite sure why, but drinking beer makes you much more likely to get bitten.

How does insect repellent work?

There are a vast range of products claiming to repel mosquitoes, many of these contain a chemical known as DEET. There are two ideas about how DEET works, and scientists just can’t agree on which is the most likely reason. One idea is that DEET confuses the insects by interfering with their odour receptors in their antennae. This makes it difficult for the bugs to smell and detect us. The other idea is that the insects just do not like the smell of DEET and will therefore avoid us if we are wearing repellent.

The vitamin B trick: 

A friend of mine swears by ‘the vitamin B trick’ to repel mosquitoes. It involves taking a vitamin B1 supplement every day in the week leading up to your holiday and throughout your trip. The idea is that the excess vitamin B leaks into your sweat, producing a odour that the mosquitoes dislike, so they are repelled. This may seem like an easy solution to the mosquito problem, however research on this is a bit hit and miss. I’m not sure I completely buy it, but I guess it couldn’t hurt to try it?

So there we have it, some of us are destined to be bitten, but we have a few options to help reduce the amount of bites we endure.

Fun fact: only female mosquitoes bite!

Till next time,



The science of sunbathing

Looking out my window right now I can see some blue peeking through the clouds, the temperature is above 10ºC and my calendar tells me it is the end of May. Therefore it is officially the great British summer. Instagram is already filling up with images of barbeques, tents and people pretending to like salad, which means it must nearly be time for some sunbathing! From sun cream to mossie bites (next post) to prolonging your tan – I have used science to get your summer sorted.

Look how good at sunbathing I am...
I am clearly a sunbathing expert…

The science behind how sun cream works:

Sun cream contains a whole cocktail of chemicals that prevent the suns UV radiation from sinking into our skin and causing damage. These include inorganic chemicals like titanium dioxide and zinc oxide, which literally create a barrier layer on the skin and reflect off the UV waves, scattering them away from the skin. The organic chemicals work differently; their chemical bonds absorb the UV radiation, and then release the energy as heat. The list of chemicals on the back of the bottle is pretty long, this is because using a wide range of organic chemicals means there is a variety of bond lengths, so the full range of UVA and UVB wavelengths can be absorbed – this maximises the protection. These organic chemicals do eventually break down after absorbing lots of UV radiation, that’s why you have to reapply sun cream regularly to avoid burning, (and you really don’t want to burn – particularly on your thighs/bum the day before zip lining – new levels of pain).

How to prolong your tan:

When our skin tans, particular pigments in the top layer are activated. Skin cells are in a constant cycle of renewal, so when the pigmented cells on the top layer turnover (old ones die, new ones made) the tan will fade. The cycle of skin cell renewal lasts around 10 days so in theory your tan could be gone just over a week after returning from holiday. A fading tan makes me so sad, so I looked at ways of clinging on to the colour.

One way to ensure a longer lasting tan is to prevent yourself from burning. This is because the burnt skin is damaged so it will regenerate really quickly, causing you to peel – not a good look. Another idea is that if you exfoliate your skin before a holiday, the cells will be at the beginning of the cell cycle when you start to tan, so in theory the tan should last longer. I have personally found this quite effective. Another idea is to moisturise like your life depends on it, this hydrates the skin cells which extends their life. As your skin is hydrated from the inside too it is a good idea to drink loads of water to help fight the fade.

Sunbathing can be as addictive as heroin:

A study from Harvard has looked at how addictive sunbathing can be and the results are a tad scary. Sunbathing was found to release endorphins, which are the same happy hormones released when we exercise to give us that feel-good buzz. This natural high feels so good that our body begins to crave it, the same way that an addict would crave a high from drugs. This is an issue because as you probably know, too much sun can dramatically increase your risk of skin cancer. This is why we need to tan with care, tanorexia is a recognised addiction and it is becoming increasingly common.

By the time you’ve read this, the British summer is probably nearly over, so you better quickly share this and get outside before the rain comes back.

Till next time,