SUMMER SCIENCE SNIPPETS 6 - A SHADY KIND of DAY

THE SCIENCE BEHIND SUNGLASSES

Whatever your choice of style protecting your eyes from the sun is important. 
Your eyes are very sensitive to the damaging UV rays because the tissue is thin and transparent. Long term damage can lead to cataracts, tumours and scarring.

 We are fortunate to be subject to European regulations for sunglasses sold in this country 




 What really counts is the degree to which the lenses filter out harmful UV rays. Look for the CE mark, which proves they conform to the European Community Standard. They should also satisfy British Standard BSEN1836, meaning they will provide high levels of protection against damaging ultraviolet light.

The total amount of UV light we are exposed to and absorb is affected by how high we are relative to sea level, how much time we spend outdoors, how high the sun is in the sky, the amount of pollution in the atmosphere and whether you are taking any medicine that makes you more sensitive to UV rays. Also worth remembering is that UV rays bounce around and get reflected into the eye so wrap around glasses can be useful.

Children's eyes are especially sensitive to UV exposure. The lens inside their eye is very clear and the pupil is wider . So it is important to ake sure they wear protection too and you can buy teeny shades for your cool dudes! 

While you may think that the more expensive a pair of shades is, the better the UV protection will be that is not true. The European standard demands even cheap glasses must block and protect but they may not be optically great and if you are going to be wearing them often you might want to make sure you can actually see clearly.


Thankfully we can now get cheaper sunglasses as readers too and many opticians offer a second pair of lenses that can be coated to create prescription sunglasses - certainly worth considering.

The colour of the lenses, including how dark they are, has no bearing on the UV protection. It boils down to preference - brighter warmer colours from a brown or pink tint or grey for a faded darker look without altering colours. 

Really dark lenses block out more of the visible spectrum so if your eyes are more sensitive to light you might want to avoid lighter tints.

This image from Compound Interest shows how transition lenses - photochromic lenses - work. Interestingly many work much better in the cold - giving a much darker colour when skiing. If you want to wear transition glasses for driving you will need to remember that windscreens are designed to block some UV so your lenses won't darken as much plus of course if you enter a tunnel your lenses might not be reactive quickly enough. There are more sophisticated  (and  more expensive) transition lenses on the market now.

Summer is almost over - school uniforms are in all the shops. 

SEE YOU IN THE AUTUMN TERM

SUMMER SCIENCE SNIPPETS 5 - a day at the beach

A DAY AT THE BEACH
I love summer especially once the schools have broken up.
I really enjoy being outside, wearing lighter clothes and being by the sea. 
Do you love the smell of the sea?

The smell of the sea is so evocative wherever you are on holiday and for many of us is that childhood memory.....

One of the first things you notice when you arrive is that amazing smell. There is nothing quite like the smell of the sea...... salty, clean, fresh, sandy.........We often think the sea air is healthier for us and of course so bracing!

Did you know that distinctive smell has quite a bit to do with seaweed and decay......It is a sulphurous smell produced seaweed begins to break down and die.........

It is actually hydrogen sulphide produced anaerobically, which is toxic but not in the small quantities you find at the edge of the sea.
However you can also smell that amazing mix of salty water and sulphur tang when you are on a boat so it can't all be seaweed.
The oceans are full of minute phytoplankton and algae which contain and produce Dimethylsulphoniopropionate (!) DMSP used to regulate osmotic pressure in cells.
This compound can be broken down by the cells and also by bacteria giving DMS and this has a very distinct smell - that we associate with oceans.

So a day on the beach maybe wandering along the shoreline smelling the sea is a real science lesson!

While on that wander you might find a washed up jellyfish.

There are more and more jellyfish on our beaches and of course abroad. So there you are splashing around and suddenly you feel a stinging hot pain....yes you've brushed up against a jellyfish or tentacle portion in the water.

The harpoon like cells penetrate your skin easily and inject venom which is designed to paralyse and kill fish and depending on the species will raise a painful welt, blister or make you very ill indeed and could kill you.

However before we all race off the beaches - the sting of most jellyfish found around British water is painful but not lethal.

So having seen that episode of Friends you run off to find someone to pee on you? Well no - because pouring fresh water - including urine - onto a jellyfish sting releases even more venom so experts suggest remove all trace of the tentacle and then  rinse in plenty of salty water and very recent research suggest that hot salty water is best. ( not too sure where you would find hot salty water on a beach!)

 Have I put you off going in the water? Why not stay on the beach and build a sandcastle instead!

My girls loved building sandcastles and digging very large holes with their dad - we even bought a shaped bucket to help us!

Amazingly there are people who spend their time making sand structures and there is quite an art (and some science) to it. A quick search online gives a huge amount of information about how to build the perfect sandcastle.

Here is an extract from a book Sandcastles Made Simple by Lucinda Wierenga, published by Stewart, Tabori & Chang

The list of ingredients for creating a simple sandcastle is short: sand, water and a few digging and carving tools. But that is only the start.......Sand - The first and most important thing you need to know about sand is that you can't do a thing with it unless it's wet. When you add water to grains of sand, the liquid forms "bridges" that connect the granules to one another. This is why damp sand sticks together, so you can shape and carve it.

Apparently the ideal method of building involves Mix Scoop Plop Jiggle and almost as important as understanding how to jiggle is knowing when to stop. 

When the sand has stopped flowing, further jiggling will form cracks in your structure. Don't jiggle sand that has already settled into place.

Have I whetted your appetite for more about sandcastles? There is a whole blog posting about it from 2015 - you can find it here:https://sueskimo.blogspot.com/2015/06/summer-science-snippets-3.html

SUMMER SCIENCE SNIPPETS 4 - in the garden

My family love being all together and in the garden - we treat our outdoor space as another room so you can imagine how annoying it is that we sit down to eat and every wasp in the neighbourhood crashes the party! August is certainly the month for wasps




Also we live near a marsh which is great for the waders but we have mosquitoes that think they are vampires - their bites leave a huge welt and are very itchy.
I do encourage bees and we have had lots this year and so far even with little ones racing about no stings.

So what should you do if you are unfortunate enough to be stung and do all those old wives tales work?
Vinegar for a wasp and blue bag ( as if we have those handy!) for a bee sting.
            


There are so many websites giving advice for "natural" cures for stings and repellents. It is worth a look but in the panic of a painful sting will you remember what to do??
A little bit of science can help you out.



Common knowledge says that bee venom is acidic so using a bicarbonate of soda paste will neutralise it and help with the pain. The calming effect of bicarbonate is true - it really does reduce itching and is useful for mosquito bites.

It is also true that some bees but not all,  have a sting that is barbed and will lodge in the skin of a mammal or bird pulling the sting from the abdomen of the bee and killing it. So most bees rarely sting unless on purpose and some bees don't have a sting at all. Their sting is used for inter bee battles when the hive is threatened.
Bee stings are amazingly complex with peptides to break down cells which releases histamines and this is where people with allergic reactions have trouble .  For most of us doctors usually recommend ice to reduce inflammation and give a mild anaesthetic effect with an antihistamine cream .



The alkaline nature of a wasp sting has led to old wives tales of vinegar or lemon juice to neutralise the sting. As with a bee sting it is unlikely that this will really work and will probably hurt because one of the things in wasp venom is acetylcholine which stimulates pain receptors - there is even more of this in a hornet sting.

The female mosquito causes the problem and she doesn't actually bite you - she uses her proboscis, which is razor sharp, to pierce your skin and drinks some blood which she can use in the production of eggs. As she finishes and flies away she leaves some of her saliva in the wound ( this is how  diseases  like malaria and zika virusare spread.)Your body reacts to the saliva producing histamine - so tissue swelling, itching and redness. People reacts differently some quite violently and an infected bite can need antibiotics but usually antihistamine will work.
If you are into natural remedies lavender oil works too - and scientists have researched that one.

The best remedy is not to get bitten at all so how do you repel them?
Insect repellents usually produce an odour that insects don't like and so they stay away.
There are plenty of insect repellents that you can buy over the counter which work in similar ways DEET being one well known brand. It does have a greasy feel and unpleasant odour so many people turn to "natural" products and at the moment the trend is for lemon eucalyptus oil. Citronella candles and spray can work too


I love the posters produced by Compound Interest and usually check to see if they have anything on whatever I am writing about. I found plenty of info on bites and stings


click here to go to their page with lots more information
https://www.compoundchem.com/2014/08/28/insectvenoms/

SUMMER SCIENCE SNIPPETS 3 - ICE CREAM

ICE CREAM

Where we live there is an ice cream man who comes around with his van and sells the most amazing cones covered in popping candy, nuts, sprinkles, sauce and if you are lucky a flake.

But what about trying to make it at home?
Everyone loves ice cream and home made can be simple or complex - it all depends on what you want and how much effort you put in.

There are custard based ice creams that have you cooking before you freeze
   
and there are simple mix together and freeze recipes. There are slushies and granitas and so many recipes on the web it is hard to decide.

I invested in an ice cream maker a few years ago - you freeze the bowl overnight and then add your ingredients as the paddle churns.
We have had some amazing successes and plenty of dismal failures - often because we want to use it on a hot day so it never really freezes.
The machine works by churning using paddles - the cold sides of the bowl freeze the mix and the paddles scrape it off . The real trick is to freeze but not to make large ice crystals - little crystals make a smooth ice cream.
Adding a flavour is important because when frozen things taste very different to when warm - so you have to get a good balance between strong enough but not overpowering


Now I have discovered frozen yoghurt  - just regular yoghurt churned until soft frozen and eaten straight away - it is delicious.

Surprisingly I still love ice cream even though I have spent many summers when I was at Catalyst making liquid nitrogen ice cream

this is me many years ago at Catalyst Science Discovery Centre Widnes

 I did a spot of teaching in Tennessee and a favourite of teachers there is to make "baggie" ice cream using a plastic bag, ice cubes and salt.
Amazingly it does actually work!



      

Here is a link to a website with more information
http://www.instructables.com/id/How-to-Make-Homemade-Ice-Cream-in-a-Bag/

One tip from someone who has had ice cream all  over the place and mixed in with the salt....use a double bag! All that manipulation of a very cold plastic bag can cause it to split.
Don't forget to keep everything clean and follow good food hygiene rules - enjoy!

The actual science of ice cream is quite complex because you would think that mixing cream, milk and sugar together would be easy but that doesn't make good ice cream. Think about the smooth texture, whether it is full of air or very solid, how fast does it melt and of course what does it feel like in the mouth.
Here is a poster from those amazing folk at Compound Interest. Follow the link to their page to find lots more about our favourite treat.

https://www.compoundchem.com/2015/07/14/ice-cream/

SUMMER SCIENCE SNIPPETS 2 - SUNSCREEN and the OCEANS

As I am writing this it is pouring with rain and has been for 48 hours - some of the country has had a heatwave and in some places people are asking what heatwave???

On the supposed hottest day I was engulfed in a torrential hailstorm!

hailstones on July 25th

However whatever the summer weather most of us are totally converted to wearing sun protection and if you read the last posting you will have got a good understanding of why.
Now, of course, there are so many things the conscientious person has to think about including the latest - sunscreen and the ocean. There are findings that seem to suggest that certain chemicals in sunscreen can cause coral bleaching and in the light of this research some places are banning many sunscreens.

Some sunscreens contain inorganic pigments and minerals like titanium oxide and many contain organic compounds such as oxybenzone and octinoxate that absorb UV radiation. It is the latter that are causing concern. 
Apparently sunscreen formulation has not really changed over the last 25 years and many ecologists are demanding that the industry gets up to date and creates new products. 

Last year, the Pacific nation of Palau announced that, from 2020, it will ban sunscreens containing certain chemicals linked with coral degradation. Tourists will have offending suncreams confiscated and anyone importing them will face a $1,000 fine. 

 Jellyfish Lake is one of Palau’s key tourist attractions. Photograph: Ullstein Bild/Getty Images

Hawaii’s ban on sunscreens that contain oxybenzone or octinoxate – the two most controversial chemical compounds – comes into force in 2021, and tourists swimming at certain beauty spots in Mexico are already forbidden from wearing not just chemically active but non-biodegradable sunscreens - so the local advice is to buy there because this ban is strictly enforced.

In Hawaii a report found that oxybenzone and octinoxate can cause coral bleaching and high levels had been found at popular tourist swimming resorts.


It is a minefield because we know our ocean ecosystems are in trouble from climate change and pollution so the last thing we want to be doing is contributing to that with our sun protection. 
The brilliant folk at Compound Interest have produced a poster explaining the issues.

you can find one of the research articles here

 https://www.icriforum.org/sites/default/files/ICRI_Sunscreen_0.pdf

I have done a little research too and it is quite hard to make sure we are doing the right thing! Plus as ever there are companies jumping on the bandwagon with amazing claims and high prices.
Big name companies have claimed their products do not affect the ecosystem and are safe because of the extensive testing needed for personal products but consumers are taking matters into their own hands a turning away from the big brands to smaller names such as Banana Boat and other "ocean friendly" sunscreens.

ocean friendly sunscreen

Australia is getting very involved in the issue

I read a very level headed article from the Guardian which ended with the advice - if you are holidaying in the banned areas buy your sunscreen there because they are not allowed to sell anything on the banned list. If you plan a trip to a delicate ecosystem  then try to buy ocean friendly sunscreen. If you are staying in the UK you'll be fine - at the moment!!
One great fact I did find is that the old faithful Boots Soltan is ocean & coral friendly and has always been - they don't use any of the culprit ingredients.

And to make matters worse it could be that the mineral oils  and some nanoparticles in sunscreens can cause problems too
Just when you thought it was safe to go in the water...........

SUMMER SCIENCE SNIPPETS 1 Sunscreen

I've been trawling the archive having a look at old SUMMER SCIENCE SNIPPETS to see what can be updated and what is just so good it is worth sharing again! So over the next few weeks while UK schools are closed I will be sharing some old and some new and some tweaked Science Snippets. Here is an updated one first shared in 2015!

SUNSCREEN

Depending where you live you may have had a decent amount of sun or very little at all this summer so you might be thinking that it is an umbrella you need not sunscreen but UV can damage our skin even on a cloudy day so the science of sunscreen is always worth another look.

When choosing sunscreen you need to look for one that includes UVA and UVB protection - UVA penetrates deeper into dermis giving the deeper damage - ageing, wrinkles and some skin cancers whereas UVB is the redness and sunburn and can also contribute to skin cancer.

There are creams, gels and sprays on the market that only need applying once a day even if you go swimming and you can get very high factors beyond 50 for fair skins, sensitive skins and the very young. Plus don't forget if you are taking medication or pregnant that can have an effect on your sensitivity. 

Apply liberally - and it really does means that - you need to make sure that you have covered your skin and all those easy to miss spots like the top of your feet!

special UVA filters on the camera show the effect of wearing sunscreen

There are some fun creams for youngsters that go on in neon colours so you can see where you have applied and the kids think it is cool. 

There are also some great gels around for sporty folk who will get sweaty and for the more hairy who hate putting heavy creams on.

You can now get clothes, flip flops, hair bobbles and wrist bands that change colour in UV and give you an idea about exposure.

Over the years we have used our UV beads many times and always everyone is so surprised at how reactive they are even in weak sunlight.

If you haven't seen them before they are little creamy coloured beads that turn brightly coloured when exposed to UV.
We often use them in investigations to test whether the different factors of sunscreen make a difference. I have seen them made into scrunchies for hair, tied on flip flops and even sewn onto baby clothing. I think many people are not aware how UV can bounce around even when you think you are in the shade.
The images here speak for themselves.

You can see the beads exposed to full sunlight at the top of each bag and then one bag is smeared with Factor 20 and the other Factor 30. The F20 beads are quite noticeably darker than the F30.

The very first time we did this I made the mistake of smearing the sunscreen onto the beads themselves and it took me forever to get it all off! So now we use a plastic bag smeared with sunscreen to show the effect .
You can also use the beads to show how sunglasses protect your eyes ( or not) from UV but that is for another post!