Dave -   To understand this, you've got to understand first of all, what is frost and how is it happening?  Basically what happens is, at night especially, there’s a clear sky at night, anything which is warm radiates heat.  You're radiating heat all the time, that’s the thing which the heat cameras you sometimes see on these films on the TV are seeing when people glow really brightly. That’s because they're warmer.  They're radiating more infrared heat.  So basically, the warmer something is, the more heat it loses.  If you're inside the house, you're losing heat all the time, but so are the walls.  You're heated up by the heat coming off the walls and it’s heated by you, so you don't feel that cold, because actually quite a lot of energy is beamed into you from the walls of the house.

But if you go outside on a cold clear night, you're basically just seeing the sky and the temperature of deep space is about 2.9 degrees above absolute zero - about minus 270 degrees centigrade.  That's really, really cold.  So there’s no heat coming down onto you and so you're just radiating heat and you lose heat very quickly.  The same thing happens to the ground.  The ground loses heat very quickly.  It cools down and then once it gets below the frost point of the air, water starts condensing out of the air onto it and starts forming frost.  Eventually all the water is condensed out of the air and it becomes very dry. There’s nothing more left to condense out.

Whereas under a carport, the top of the roof will cool down quite a lot, probably down to slightly below zero, but that’s still a lot, lot warmer than the sky.  So the roof is still radiating some heat down onto the ground, inside the carport, so that keeps it slightly warmer than everything else.  Because of this, all of the moisture tends to condense everywhere else rather than inside the carport.  So, even if, by the end of the night, it did get down to below zero, all the water vapour is already condensed everywhere else.  So, there's no frost inside the carport.

Chris -   And I will add that perhaps the water which is going to condense is going to come down out of the sky and if there is a physical barrier there, then it’s likely to settle on that roof, more than on the car underneath the roof, and therefore, there isn’t anything to freeze on the glass even though the glass is very, very cold anyway.  You're going to end up with a clear windscreen rather than a frosty one.

If you look at things from a long way away like the Sun, like the Earth, like Mars – yes, they do look like big circles in the sky, that’s true.  If you zoomed in a bit closely, you'd see that actually, the surfaces are quite lumpy and bumpy.  The Earth has mountains and volcanoes, and so does Mars.

So the surface isn’t completely smooth, but yes, they have been pulled into a circular shape.  Whereas, smaller objects like things in the asteroid belt can be an irregular shape.

What's different between the things in the asteroid belt and big planets like the Earth and even big blobs of gas like the Sun is that the Earth, Mars and the Sun are very big, therefore they have enormous amounts of mass, and therefore, they have an enormous amount of gravity.  And what that gravity is doing is pulling all of the particles together, and the way in which the particles can arrange themselves so they are as close as they can be to each other is into a spherical shape.  It gives you the best surface area to volume ratio.  So in other words, everything is surrounded by everything else and pulling towards everything else as tightly as it can.

A smaller object like an asteroid doesn’t have the same mass.  It’s much smaller and they're much therefore more loosely bound together and there isn’t the gravity to pull the material together into a spherical shape.  If you kept adding material then it would accrete slowly to make a planet.

In fact, the asteroid belt is a failed planet.  It’s rubble left over from planet building, probably because there wasn’t sufficient gravity there to pull a planet together and hold it together, up against the gravitational tugs of all of the other planets forming in the solar system.  So that's really the reason.

We put this to Dr Suzy Lishman:

Suzy -   To be a pathologist, you need to do a medical degree first.  So, after getting good  GCSEs and A levels, hopefully get into medical school which is getting harder to do year by year.  Then you'll spend 3 or 6 years as a medical student, followed by 2 years of foundation training that all doctors do before they start to specialise.  Then you can apply to a specialist training program which is a minimum of 5 years.  So we’re looking at probably 12 years or so from deciding to go medical school, to actually getting to the end of your pathology training.  Many people actually take time out along that time to do some extra research, perhaps a PhD or specialise in something.  So it can take even longer.

Chris -   When I tell people I'm still taking exams at the age of 35 - I think I finally finished them, I think I've taken my last exam now - they're normally quite gobsmacked!

We put this question to Dr Suzy Lishman:

Suzy -   Thanks, Daniel.  It’s a good question.  I think the first thing to say is the petroleum jelly itself has no medicinal effect and it doesn’t actually effect whether a blister forms, and it’s not absorbed.  So, it doesn’t get absorbed into the wound.  But its effectiveness in wound healing is related to its sealing effect on cuts and burns.  So what it does, it stops germs getting into the wound so it doesn’t get infected so it can heal more quickly.  It also keeps the area supple.  It prevents the skin’s moisture from evaporating, so it stays nice and moist, and supple, and it enables that area to heal without cracking.

The really important thing about putting petroleum jelly on burns for example is, you must not put it on a fresh burn because burns continue to damage the surrounding skin for some time because the heat continues after the initial burn occurs.  If you put Vaseline over the top of that, then it will actually trap the heat in and more damage will be done to the underlying skin.  So it’s essential that you wait until the burn is completely cooled down before sealing it.

Chris -   The other interesting about the way wounds heal, that has been discovered fairly recently, is they actually create an electrical current into the wound.  Researchers in Aberdeen started measuring this, they put a wire in the root of the wound and the wire on the edge of the wound, and they could measure an electrical voltage difference between the two, and the cells flowed down the potential difference.  So they can sense the voltage and they move into the base of the wound from the margin of the wound where it’s healing up.  And because they're blebbing off from the side, if you do put a layer of petroleum jelly over the top, they're just going to go underneath it.  Aren’t they, Suzy?

Suzy -   Yes, they are.  They're not bothered whether it’s there.  It just gets in the way.  They go around the edge of it.  So, it doesn’t actually have much effect on the wound healing itself.  It just enables it to happen.

Dave -   Well, the simple answer is yes.  It’s done all the time.  Virtually any laser which you've seen cutting anything would’ve been focused with a lens.  In fact, the beautiful thing about laser light is it’s far more focusable that ordinary light.  It essentially behaves as if it was coming from a very, very small point source so you can focus it very, very, very tight and it works beautifully.  Focusing multiple lasers into the same beam is much more difficult.   You can focus lots and lots of different lasers in to the same place so you can get lots of crossing focused laser beams onto a single point which is what certainly the American government is trying to do for nuclear fusion things.  They put little tiny pellets of frozen hydrogen, deuterium, into the focus of these hugely powerful lasers.  That then compresses it so much that it can actually get so hot – far hotter than the centre of the Sun - that the hydrogen atoms start fusing and form helium, and you can produce an immense amount of energy that way and they're trying to get energy out of it.  But actually, focusing two laser beams exactly on top of each other is always impossible.

Chris -   When a baby comes out the normal way, I said, quite appealingly, the baby’s first taste of life is a mouthful of much which is its mum’s muck.  Those are bacteria which have colonised mum and have become optimised both to her genetically and also to the food she eats, and environment she inhabits.  And therefore it’s perfect for the baby because that's the same environment in which the baby is going to grow up.

Babies born by caesarean, as you suspect, when they're inside their mum, they're completely sterile.  A baby inside the mother has no bacteria at all in it and on it, and it acquires its bacteria only on the way out of the body.  So babies which are whipped out via the caesarean route  - where you make an incision in the abdomen and then make a cut through the wall of the uterus, the womb, and you get the baby out that way, those babies are not going to get colonised by flora in the same way as a baby delivered the normal way.

So what do they get?  Well people have studied this quite carefully now actually and what they have found is that in fact, the baby picks up bacteria from its immediate surroundings.   When it’s born by caesarean, that means it picks up bugs from the hospital surroundings and babies born that way tend to get a different spectrum of bacteria, at least initially, compared with babies that are born the normal way.  They tend to get more – for instance, Clostridia, for instance, Clostridium difficile which causes C. diff diarrhoea in elderly people for instance.  They pick that up.  They pick up Staphylococci and they pick up Streptococci, so they get a very different spectrum of bugs which then does eventually change and become more normal and resemble what their family carry.  But it’s still maybe slightly and subtly different.

There may also be a longer term legacy because doctors have shown that babies born via that route may actually have an increased risk of asthma, allergies and diarrhoea, at least for the initial part of their life and maybe there may be a lifelong risk of those allergy situations.  

So the bugs you acquire in the early part of your life have an important role to play in educating your immune system, and they also protect you from diarrheal illnesses because they keep the bad guys at bay.

Chris -   They've got leaves, they can photosynthesise, which means they can use energy in sunlight to drive a reaction between carbon dioxide and water which they get from the air and from the ground to make glucose – sugar (that’s food).  So, why on earth do they need to catch flies to supplement that diet?  What’s wrong with that?

Well, the point is that plants don't just rely on glucose alone.  It’s a bit like that poster, “Men can't live on bread alone.”  It’s that picture of a beer bottle, isn’t there?  Plants also need other micronutrients and minerals, and things which they normally obtain through their roots.  So in other words, they would put down roots into the soil, those minerals will be drawn up with the water they take in, and they would then be used.  Other things like proteins and amino acids will be brought in that way and other macromolecules produced by fungi that plants make associations with in the soil.  Those are called their hartig nets, their mycorrhizal relationship.

Carnivorous plants often live in awful places.  In other words, very nutrient poor environments where they're very boggy, so most of the nutrients have probably been leached away by water.  As a result, the soil is so poor that many of those trace elements that keep plants growing normally, just aren’t available in appreciable amounts.  So the plants need to look to the air to obtain that nutrition and they do it by catching insects because if they catch an insect, insects have got lots of iron, they've got lots of proteins, they've got lots of other micronutrients in them that the plants have adapted and evolved to make use of, and to supplement the poor source of things that are coming in through the soil.

What that means is that the plant can now exploit a niche in the environment that other plants can't.  They can grow in places where the competition from other plants for light is really quite weak because other plants can't grow very well.  So despite being able to photosynthesise, they've made up for the short fall in the general, other nutritional requirements of the plant by looking to the air in the form of insects that they grab and eat to supplement their diet.

Dave -   So eating not for energy, but for fertiliser essentially.

Chris -   Yes.  They're finding their fertiliser from the sky.

We put this question to Dr Suzy Lishman:

Suzy -   Thanks for that question, Fred.  I'm sorry to hear about your wife, my condolences.  Well, an aneurysm, as you know, is a bulge in the blood vessel wall.  It’s a bit like a balloon that blows up and it becomes weak, and so it can burst.  When that happens, blood leaves the blood vessel and goes out into the brain.  The effect it has on the brain depends a little bit on exactly where the vessel is, in relation to the layers of the brain.  If it bursts into the main matter of the brain itself, then it will destroy that brain tissue and that would present with somebody having a stroke for example.  It could burst into the surroundings of the brain, the subdural space, and then it can cause an extremely bad headache because blood is very irritant and it can cause pain over the surface of the brain.  But when somebody suffers a fatal aneurysm, as it sounds like your wife did, the blood destroys the brain so that it can no longer make the body function and breath, and somebody would stop breathing instantly because of the damage to the brain.  So it’s like a large stroke that kills bits of the brain that were essential for life.

Dave -   Quite a lot of this effect is down to the fact that if the air is very humid, it’s likely to also be drizzling - there’s actually droplets of water in there that will drop on your skin and then it’ll evaporate, and that make you feel very, very cold.  Also, I think water vapour will have a slightly higher specific heat capacity, it will be able to absorb slightly more energy per unit volume than normal air, because it’s a more complicated molecule so it can vibrate in more exciting different ways so it can absorb more energy as it warms up.  Whereas when it’s warm, if it’s very, very high humidity, sweating doesn’t work anymore because water doesn’t evaporate very well and you feel very warm.

Chris -   So on a cold day, if you've got air which has got a bit of water in it and it’s cold, you got to supply a lot of energy to that wet air to make it get any hotter.  Therefore, it’s always going to feel a bit colder, isn’t it...

Dave -   Yes.

Chris -   ...Then in summer when the water is already saturating the air because of high humidity, and you're trying to sweat to lose the energy, and you can't lose the heat quick enough.  So it’s two slightly different things going on which is why you've actually got the difference.

Dave -   Of course in this country as well, it tends to be windier when it’s wet, just because of the way the weather works.  So, you get wind chill added on top of that.  I think windchill is probably bigger when it’s low humidity than the high humidity but I think it’s windier when it’s damp.

Chris -   You shouldn’t have a baby that’s allergic to breast milk because breast milk has proteins in it that we make in our own body and therefore, it’s very difficult to be allergic to things like that.  Breast milk is a pretty special mixture.

You do get babies that won't breastfeed properly and so, parents then in frustration would turn to bottled feeds - because the baby needs the energy, and the baby is not growing fast enough so you put the baby on bottled feeds to try and get the baby growing a bit quicker.  Then a baby can show an allergic reaction to what’s in the bottled feed.  That’s because bottled milk does contain cow’s milk proteins and as you know, the bulk of what we get in milk is things like calcium plus protein, and the body can recognise the cow’s milk proteins as being foreign, and that’s one reason.

Another thing that is in milk is lactose and humans have evolved, not necessarily to eat milk.  And so, some people, especially people who are white and from our part of the world, actually may have a thing called lactose intolerance, and this is where they can't make an enzyme which is normally expressed in the intestine and breaks down lactose which is a sugar.  It’s two glucose molecules stuffed together.  They lack an enzyme, lactase which will break those molecules apart.  And so, the lactose carries on down the intestine and it pulls water into the intestine, causing bloating and diarrhoea-like symptoms and that’s lactose intolerance.  People who eat a lot of milk or dairy products, if they overdo it and they have that particular deficiency will get those symptoms.  So that’s another reason why a baby might be intolerant.

Some babies are just very allergic to things and some of the other things we’re discussing earlier, with things like having lots of antibiotics or having a caesarean section can make some people more prone to develop more allergies as they go along.

Dave -   A normal bar code encodes information in black and white stripes, and there’s a very limited amount of data you can store because you can't get very many black and white stripes without making your product about the size of the planet.  So if you want to get more information on that, you can store the information, instead of in stripes, in spots.  You can't read it with a conventional bar code reader anymore because it can't scan across it.  It’s got to take a picture of it and then decode the picture, but this can store – instead of maybe 30 or 40 characters of data, it can store up to 3,000.  So you can actually store useful information about the product as well as just to identify it.

Dave -   A very good question.  It depends what you mean by break up the atom.  Actually, an atom is made up of a nucleus in the centre with all the electrons on the outside.  It’s relatively easy to break electrons off the outside of an atom and sometimes when you break a material, you can rip off some of the electrons on one side and not the other.  This is the reason why, if you crush things like sugar, sometimes you build up more charge on one side than the other, and you get sparks going back again and so you'll get little flashes inside the sugar.  But the actual nuclei of the atoms don't break at all when you do anything like that.  You need to do something far more violent to it, involving a nuclear reactor or radiation, something far bigger and more violent than that.

We posed this question to Dr Suzy Lishman...

Suzy -   There is a tube connecting the lungs to the mouth and that’s called the trachea.  It’s the one you can feel - if you just feel the front of your throat just under the Adam’s apple, that’s the trachea.  That’s lined by mucous membranes, the epithelial cells that produce mucous which is a thick liquid that forms a phlegm.  It has several functions; it’s partly a lubricant, so it stops the airways from drying out when you breath dry air in and out, and it also helps get rid of bacteria and things that you really don't want to have down in your lungs.  So they get stuck in this sticky mucous that lines the airways and then it can be coughed up, and it keep it away from the lungs.  What happens when you get a cold is in reaction to the extra irritation of your airways, these epithelial cells produce more and more mucous.  When you're fit and healthy, the mucous is normally clear and white, but if you get an infection, it can go yellow or even green, as you cough up all the bacteria and the dead cells that your lungs don't want.

The average adult makes 200 billion red blood cells every single day.  It’s about 2 ½ million every second which is absolutely incredible because you've got about 20 to 30 trillion in your circulation and you have to replace that – about 1% of them - every single day.  So you kill 1% of them and you make another 1% of them.  So, it should be fairly simple.  You just take the number that get made every single day, you times it by how many days in a year 365, you times that by 75 years in a lifetime, and then you times it by the weight of a red blood cell, and you get the answer. 

How much does a red blood cell weigh? Well I had to look for that and it turns out, the weight of a red blood cell can change across your lifetime.  In fact, I found a paper my Mischlinzski and Koshak who are from Gdanks Medical School and they tell me that the weight of a red blood cell is about 45 pikograms, 45 x 10^-12 grams in every cell.  So if you times all those numbers together, you get 246,375 grams of red blood cells made in a lifetime which is 246 kilos or a quarter of a ton, an absolutely staggering number, or weight, of red blood cells.  Just red blood cells who have made a lifetime. 

Reference: Andrzej Mysliwskia and Anna Korczak, Mechanisms of Ageing and Development, Volume 34, Issue 2, April 1986, Pages 111-115