Archive for January, 2011

What does the sun actually do to your skin? Part 1.

January 28, 2011

This is part 1 of thatscienceguy’s articles about the effects that the sun has on your skin. This week we look at skin itself, the damage the sun does to the structure of your skin and the health benefits of sun exposure.

In Australia we’re encountering another typically sunny summer, and it’s extremely important to properly protect ourselves from the harmful effects of the sun. This makes it the perfect time to examine just what the sun does to your skin and why it’s important to protect ourselves.

Before we can talk about the effects that the sun has on skin, let’s first look at skin itself. Skin is the largest organ of the human body and its main job is to provide protection for the bones, tissues and internal organs and prevent too much water being lost from the body. It is made up of two main areas, the surface epidermis and the deeper dermis layer.

Cross section of human skin (Adapted from Stulberg et al)

The epidermis is the topmost layer, and is made up mainly of cells called keratinocytes. Keratinocytes begin in the deepest layer of the epidermis and are pushed upwards by the production of more cells beneath them. By the time they reach the surface they have died, and it is these layers of dead cells which provide protection and waterproofing to the layers underneath.

The dermis makes up most of the skin and acts as a base for the epidermis. As it acts as a base, the dermis is rich in a substance called collagen, which provides strength and resistance to damage. As well as collagen, the dermis is also rich in elastin fibres, which as the name suggests allows skin to stretch and recoil. Hair follicles and sweat glands are also found in the dermis.

Ultraviolet (UV) light from the sun has many effects on the skin. Australia receives some of the highest levels of UV of anywhere in the world – the UV levels during winter in Australia are equal to the UV levels during summer in The Netherlands. The map below shows the UV levels in Australia during a typical summer day, with every populated location on mainland Australia in the “extreme” level of UV radiation.

Map of summertime UV levels in Australia. Purple areas represent extreme UV levels. (Image courtesy of the Australian Bureau of Meteorology)

In between the epidermis and dermis are cells called melanocytes which, when exposed to ultraviolet radiation from the sun, produce a dark substance called melanin. Melanin is absorbed by the keratinocytes, which then use it to protect themselves from UV as a kind of sunshade. This melanin response to UV has evolved as a natural sunscreen, providing protection to the keratinocyte cells by absorbing incoming ultraviolet radiation and produces the visible tanning effect. People who tan darkly from sun exposure have a lesser risk of skin cancer because of the protection given by melanin.

In addition to the tanning effect, UV light also attacks the elastin and collagen of the skin, damaging collagen and causing tangling of elastin. This damage results in the loss of skin’s structure, which is what causes sagging, wrinkling and increased roughness of sun-damaged skin. UV also increases the production of free oxygen radicals, small molecules which attack and damage the skin cells. These effects are permanent and lead to noticeable premature aging.

Vitamin D

As well as protecting your body, skin also has a vital role in the production of a chemical in your body called vitamin D. Up to 90% of vitamin D is produced by the skin by a mechanism which actually requires UV radiation. Vitamin D is beneficial to health, and in fact the World Health Organisation recommends UV exposure to reduce diseases such as bone defects including osteoporosis and rickets, diabetes, some cancers and heart disease.

Because the production of vitamin D requires UV, theoretically there is the chance that using sunscreens or avoiding sun exposure may lead to vitamin D deficiency. However, this very rarely happens as the amount of  sun exposure needed to make enough Vitamin D is extremely small. Only a couple of minutes of exposure to the sun are enough to produce sufficient vitamin D, so just normal day-to-day exposure when people don’t normally wear sunscreen is satisfactory. Also, when applying sunscreen it is normal that people will accidentally miss a small area, or cover some areas lighter than others. The exposure to UV from these areas is also often sufficient for the production of vitamin D. While there may be rare cases of people not getting enough vitamin D, it is incredibly unlikely to happen due to using sunscreen or by being sunsmart and people should not be concerned, nor should they seek out sun specifically for the reasons of vitamin D production.

The ozone layer

Just a final note about the importance of the ozone layer. UV light is separated into 3 types, UVA, UVB and UVC, although effectively all UVC and most UVB is absorbed by the ozone layer. This means that around 90-99% of UV radiation reaching the surface of the earth is UVA, with the remaining 1-10% being UVB. Although the ozone layer does filter out a lot of UV radiation, it has been calculated that a 1% decrease in ozone actually results in a 2% increase of UV dose, so the integrity of the ozone layer is vital for human health.

The hole in the ozone layer over Antarctica. Purple and blue areas are regions of very low levels of ozone (Image courtesy of NOAA)

Over the last decade the breakdown of the ozone layer has been slowing due to the ban of CFC-containing aerosols. CFC’s contain chlorine which is very reactive in breaking down ozone, and human activities are responsible for around 75-85% of the chlorine in the atmosphere. Estimates suggest however that chlorine levels in the atmosphere may be peaking at the moment, and as levels begin to drop the ozone hole may begin to close. However, this is a slow process and it will be at least a decade before any measurable changes to the size of the ozone layer can be seen.

Part 2 will be published next week looking at skin cancer and the importance of sunscreens.


Weird Science – The top ten weird science stories from 2010

January 15, 2011

This is a list which I recently compiled for the Australian Science Media Centre. It could potentially also be called “What happens when scientists get bored”, as some of the stories seem the product of simply having too much time on their hands.

Chocolate, gunfights and dancing – just another year in science.

10. The science of chocolate. Scientists love chocolate, so imagine how happy they are when they can study it! This year’s chocolate breakthroughs included that small to moderate chocolate intake leads to a lower risk of heart failure. But for those who are watching their weight, scientists also found that just imagining chocolate is enough to satisfy cravings. Unfortunately it probably doesn’t mean you can daydream your way to a healthy heart.

I’ll be blogging about some of the science of chocolate in the future.

9. The maths of skipping stones. English mathematicians have developed a mathematical model to study how stones skip across water surfaces. Okay, this actually has more useful applications (like studying ice formation on planes), but now we know how to skip a stone like never before!

8. To quiet the mind after a tough choice, use soap. US researchers suggest washing your hands after making a difficult choice may help you live with your decision. Often after making a tough choice people will try to justify their choice, even to themselves. However, after washing or even just wiping their hands they no longer feel the need to justify the decision and feel less worry or concern about their choice. This effect is seen even when there was no moral dilemma in the choice.

7. Bad moods are infectious. American researchers have shown that positive and negative emotional states behave like infectious diseases between people in large social networks.

The scientists found that the likelihood of feeling happy is increased by 2% for every happy friend you are in contact with, while the likelihood of feeling unhappy is increased by 4% for every unhappy friend you are in contact with. In other words you can catch someone else’s mood, so best avoid that grumpy friend of yours.

6. How cats have perfect drinking manners. For three and a half years a team of researchers from US universities studied just how a cat drinks milk. Rather than unrefined slurping or just using their tongue like a scoop like a dog, they use gravity and inertia – they skim the surface of the milk with their tongue before pulling it back, creating a little column of milk which the cat closes its mouth around (see picture below). To do this a cat’s tongue moves at around one metre per second. Let’s see dogs beat that!

P M Reis et al. Science 2010;330:1231-1234

5. The physics of the “wet dog shake”. Physicists have defended the pride of dogs by examining how animals shake themselves dry. Using a range of video techniques, including looking at the animal’s skeleton using x-rays, they found that larger dogs don’t have to shake as much to dry themselves as smaller animals. To remove water from fur, it needs to have force applied to it. Because bigger animals are bigger, the speed they need to move to apply this force is less than the speed small animals need to move.

Yes there’s a video.

We wait with bated breath for the next round of dog vs. cat studies.

4. Going up stairs makes you older. Einstein came up with many theories, one of which said that gravity has an effect on time. This theory says that objects which are above the surface of a body with a gravitational field (such as earth) experience a relative increase in the speed of time compared to those on the surface. US scientists used incredibly accurate clocks to show this can happen at very small differences in height, less than one metre in fact. This does actually mean that you age faster when you stand a couple of steps higher on a staircase, relative to someone at the bottom of the stairs.

So why is this important (except for the building industry)? Well it shows that Einstein’s theory of relativity was correct and can be measured at distances far shorter than previously found. It also has importance for scientists who study hydrology or geophysics, or indeed any research which measures the Earth.

3. “Go ahead, make my day”. A study directly inspired by Hollywood movies has investigated why the cowboy who draws his gun second wins the showdown.  UK researchers found that people move faster when reacting to something than when initiating the same movement. In fact, people move around 10% when reacting to a situation than when they initiate the same situation. This can be linked to survival instincts, where an animal which can react faster is more likely to survive. So there you go, there was a scientific reason Clint Eastwood would provoke his foe into moving first.

2. The world’s oldest shoe discovered. Everyone hates losing their shoes. The world’s oldest leather shoe was found this year in Armenia, dating back around 5,500 years. This makes it 1000 years older than the Pyramids of Giza and 400 years older than Stonehenge. And like when you are looking for your own shoes, they only found one of the pair…….

Shoe design seems to have improved somewhat as this shoe was merely leather wrapped around the foot, however it was shaped to the foot to provide some support and protection (pictured below). While this is the oldest shoe found, there have been shoes found in other regions from similar times which showed the style of shoe varied depending on where in the world you were.

Pinhasi R, Gasparian B, Areshian G, Zardaryan D, Smith A, et al. (2010) First Direct Evidence of Chalcolithic Footwear from the Near Eastern Highlands. PLoS ONE 5(6): e10984.

And my weirdest science study of the year:

1. Bust a Move – The science of male dancing. Every weekend guys are in bars and clubs hoping to attract ladies with their dance moves. Now scientists have found the sure-fire styles! Using computer-generated models they showed which body movements are associated with female perceptions of quality male dancing.

So why is this important? Well in nature the quality of the courtship display reflects the quality of the animal as a potential mate – animals with better genes or who are stronger will normally have a better courtship display. And in this case, humans may very well be the same. The scientists filmed male dance moves and found that there were 11 moves in particular which were thought of by women as a good dance move. Even better, they found that the speed of movement of the right knee, and the amount of movement of the body and neck were the key parts which split good dancers from bad.

What does that all mean? Watch these videos to find out!

“Good” dancing

“Bad” dancing

You can definitely list me under “Bad”.

Courtesy of the Australian Science Media Centre

Links to the studies:











Welcome to thatscienceguy

January 13, 2011

For whatever reason you may have stumbled across this blog, welcome!

thatscienceguy will be posting around twice a month about science, whether it be science which you come across every day, the weird world of science, or science you may never have known existed.

But firstly a bit about myself. My name is Ben and I recently finished my PhD at the University of South Australia. My project there was to investigate how a new treatment for skin cancer actually works – what does it do inside a cancer cell to make it die. The problem with many drugs is that they do more than one thing inside a cell, and each change inside the cell may cause a different effect. If we can find out what the drug does to kill the cancer cell we would be able to design new drugs which only cause that effect, or cause that effect but much more potently, which may increase the effectiveness of treatment and reduce side effects.

Despite my background in pharmacology and cancer biology, I’m hoping to keep this blog pretty broad, so there may be posts about medicine, health and biology, but also about astronomy, chemistry, physics, who knows what!

Hopefully you enjoy this blog and find it interesting. An admission though – this is my first time keeping a blog so bear with me, it might take a little while to get into the groove of writing one!

Also, if you have any sciencey questions or feedback, email them to thatscienceguy(at), even if it’s that question you thought too basic to ask before.

So again, welcome!

Ben, that science guy.