Ben -   It’s a great effect and it’s a lovely, lovely question because I actually had – I had to look this up and as soon as I read the question, I thought, “That’s brilliant!  Why didn’t I look this up before?”  But it has all to do with the substance in toothpaste called sodium laureth sulfate.  There’s a few similar chemicals that do the same thing.  It’s a surfactant which means that it lowers the surface tension of a liquid.

Kat -   Those are classic cleaners, aren’t they?

Ben -   Yes.  You’ll find it in detergents, you’ll find it in all sorts of different things that rely on breaking surface tension, and it’s in the toothpaste, to make sure that you get a good foam from the toothpaste while you clean your teeth and look a bit rabid.

Kat -   Speak for yourself...

Ben -   But they also interact with that taste buds in two key ways:  They inhibit the taste buds that perceive sweetness, so whatever you eat afterwards will taste less sweet and then they break up fatty molecules called phospholipids and these phospholipids live on the surface of our tongue, and they inhibit the receptors for bitterness.  So, not only do we get the effect through the knocking down of the sweetness, but actually boosting the bitterness that you get as well.  So, that means anything you eat will taste less sweet and much more bitter which is why orange juice in particular, which we know is normally very sweet, is really quite foul.  There’s also menthol in there, and that has a temperature effect which fools your sensory nerves into being more sensitive to cold.  So, fresh orange juice, fresh from the fridge may sound great and refreshing, will be good with your breakfast, but it’ll taste bitter and it will be painfully cold.

Chris -   I met someone a little while back who’s at the Oxford University.  He’s a chemist and he showed me a wonderful trick with glucose because glucose comes in two 'handednesses'.  There’s right handed glucose and left handed.  What that means is, it’s a bit like if I had a glucose molecule and I put it in front of a mirror, you’ll have a molecule in one configuration in your hand, you’d have the molecule with its mirror image in the reflection.  And nature is just the same.  There are both forms of the sugar in nature.  It just so happens that the human body uses the D-form, the right handed form.  He brought with him some left handed glucose and I tasted it and guess what it tasted like?

Ben -   I have no idea.

Chris -   Do you think it’s sweet?

Kat -   Cherries.

Ben -   I’d assume it would be sweet because it’s the same atoms, isn’t it?  Built into their molecule, just kind of reflected.

Kat -   No, if it can’t be recognized.

Chris -   No.  It tastes like salt, which is salty.  It was disgusting.  It’s just a salty sort of (luhhrr) flavor.  It wasn’t very nice at all because it’s the wrong shape to fit into the taste receptors on your tongue, just like Kat says.

Ben -   Wow!

Kat -   This is a really lovely and interesting question.  But the answer is unfortunately, no, but they would be very similar.  So, what happens when you make babies?  What time is it?

Chris -   And how long do we have there?

Kat -   How much detail…

Chris -   Be careful.

Kat -   When mommy and daddy love each other very much in a special way, you make babies.  You make babies basically by using half of the chromosomes coming from mom and half of the chromosomes coming from dad and when you create egg and sperm cells in your ovaries and your testes, you kind of get a random assortment of whatever chromosomes you happen to have.  So, half from mom and half from dad, and they come together to make a baby.  And so, this process of random assortment of chromosomes will be going on in both sets of parents to make their children but because he’s starting from matching stocks as it were because if you got two identical sets of twins, they have identical sets of chromosomes.  So, it’s almost like you just have one set of mom and dad’s.  So, the children they produce would not be identical but they would be very similar, as similar as you are to your brothers and sisters because effectively, it’s just like having one set of chromosomes that are randomly sorting and going in to babies.  So yes, they wouldn’t look identical but they would look very similar.  In some families, brothers and sisters can look incredibly similar.  So, it would just really depend on the luck of the genetic draw.

Chris -   Because identical twins are effectively nature’s own natural clones.

Kat -   Nature’s clones, yes.

Chris -   And if you wanted to have clones on tap, you should become a nine-banded armadillo because they naturally make quads.  They naturally split their eggs into four identical derivatives which then turn into four genetically identical offspring.  I don’t know why, but they make quads, quite naturally that are genetically identical to each other, bizarre.

Ben -   Well, this basically depends on how stressed they are.

Chris -   Perfect timing for Wimbledon Week.

Ben -   Of course, yes.  Assuming that the rules of tennis stick out the rules that we’ve seen with this balloon experiment, then I assume, that yes, when stressed the men will take greater risks and women will perhaps take fewer risks.  But it’d be very interesting to see if there’s hormonal effect when you’re playing such a powerful sport that maybe their hormonal things override it.

Chris -   Well the reason that a window or a cold surface mirror goes misty and foggy is because when you have a hot shower, you have got lots of water molecules in the form of steam or water vapor drifting around in the room.  These then lose some energy to the cold surface and this enables them to condense.  So in other words, instead of being free molecules floating around, they begin to stick together and they form little tiny droplets on the surface because water has attraction between one molecule and another.  So, it pulls in other molecules and it likes to form little droplets and those droplets tend to be little spheres because that’s the best arrangement, so you maximize your surface area to volume relationship, so you have the least amount of water in contact with the air for the most volume.  Now, what that means is that you’ve covered your cold surface in a tiny series of little lenses because the water droplets are of course behaving like lenses and this is why it distorts or deforms the light which is coming back off of their reflective surface and you can’t see through it.  If you put a blob of soap or a smear of soap up and down on a shiny surface like a mirror, you won’t get that mist forming.  You will get a clear reflective surface remaining, for the simple reason that the way soap works is that it gets between the water molecules and it stops those interactions of the water molecules being so sticky.  It has what’s called a ‘surfactant effect’ and what that means is that the water molecules, instead of forming lots of little droplets, will instead spread out to form a thin film which is continuous across the surface and although a film of water will refract or bends the light going through it very slightly, they will nonetheless be a straight path to the light in and out and therefore, you will see clearly.  So, this is effectively how anti-misting surfaces work.  They have a surface coating which is very attractive to water molecules and instead of forming little droplets, they’re pulled into a flat sheet which doesn’t bend the light in the same way as the little droplets would.

Ben -   So, does grease from your skin do the same thing if you write a message on a window?

Kat -   I was going to say, yes because the grease is obviously repellant to water.  Oil and water don’t mix.  But it’s a nice thing to do if you have a clean bathroom mirror and you write something on it with your finger then when your housemate or partner goes into the shower and it says, “Don’t forget to put the lid back on the toothpaste you get” or something like that.  You know, a lovely message like that.

Chris -   It’s a good question.  Water has energy.  So, in other words, at any given temperature, the water molecules are vibrating or moving around, proportional to the temperature of the water and when we give energy to water sufficient to raise the temperature to 100 degrees, what that means is that the molecules of water are vibrating or moving around sufficiently fast, that they can readily break the attraction that’s holding them onto other water molecules because water is sticky and this enables them to escape and get out into the atmosphere as vapor.

Kat -   But you don’t dry your clothes at 100 degrees so what’s going on here?

Chris -   Absolutely, not.  What you are doing though if you, say put them in a tumble dryer or hang them on the line is that you are putting some heat into the clothes or just because they’re at ambient temperature.  They’re not absolute zero.  The atoms and molecules therefore have some energy.  Now, because the energy is not shared equally amongst all the atoms or molecules and anything, in other words, if I come up to you and I shake your hand, I can give you some energy.  When the molecules are bashing into each other, sometimes some of them will end up transiently with a load of energy from lots of other molecules bashing into them and others will have much less.  This means that occasionally, you’ve got the odd molecule there that has sufficient levels of energy that it can break the bonds holding onto other molecules and it can escape.  The reason its slower to dry at less than 100 degrees or however hot you want to make is because obviously, it takes longer for those interactions to occur so that the odd molecule gets enough energy to escape and that’s why the sea for instance, can evaporate water when sunlight falls on it and warms up the ocean without having to boil itself.  It’s just much slower.  If you put a pot on the stove, you give lots more energy to lots more atoms and molecules all at once and as a result, more of them have more energy more of the time and therefore, they’re able to evaporate, and that’s the reason.

Ben -   Do you reach any equilibrium between water in the clothes and humidity in the air?  I assume that when there’s more wind blowing then you’ve got lower humidity in the air because it’s more of its moving parts.

Chris -   Yes.  I mean around the item that you’re drying, the air that’s in contact with the clothing will become slightly higher saturation of water.  So, in order to maintain the gradient, in other words, water wants to move from an area where there is lots of water to an area where there is much less water.  If you have full winds blowing, this is moving away any molecules of water that get off of the clothing and into the surrounding air very quickly and therefore, you maintain that gradient.  So, the molecules want to move more readily away from the clothing.

Kat -   So, this explains why tumble dryers are great because they’re hot and they’re sort of blowing air around and tumbling things about?

Chris -   Absolutely! 

Kat -   They do.

Chris -   Maybe you do.  I don’t know.

Kat -   It’s called Friday night.

Chris -   Very regular mating.  It’s three times a week.

Kat -   Many animals do have a mating season.  Dogs coming to season will.  If you have foxes in your back garden, you’ll very much know that foxes do have a mating season and are really annoying and very prominent about it.  But humans don’t really and there’s been quite a lot of discussion on The Naked Scientists forum as to why this might be, but it’s mainly, I think because humans have evolved not to need one and many animals do have a mating season because their food resources or the temperature where they live changes throughout the year.  So, you want your babies to be born at the optimum conditions where they’re going to survive, where there’s lots of food to nourish the mother during her pregnancy, when there’s a nice warm temperature for the babies to be born in and they’re not going to freeze, and you know, when it’s not obviously really wet or really horrible.  But with humans because for a long time, we’ve lived in habitats like caves, we’ve been able to stabilize our temperatures through clothing.  We’ve been able to sort of, farm, and all that kind of stuff.  Probably, we’ve just evolved not to need a mating season and we have very regular ovulation that’s hidden most of the time.  It depends on the papers you read whether you believe that or not.  So there’s no real need for us to have a mating season and I did read an interesting paper.  I think that the weights of babies generally born, change throughout the year depending on whether your mother was pregnant during the harvest season or not whether your mother had more food during the pregnancies so there may be a hangover from that, but certainly in the modern world, there’s no real need for a mating season for humans.

Ben -   It stays in the hose pipe, surely.

Chris -   Absolutely!  I mean that’d be my thought, but there’s a couple of reasons why.  One is that fluids, liquids are incompressible and as a result, when it’s a bit like a Newton’s cradle, you put some water at one end of the hose and it pushes an equivalent volume of water out the other end of the hose.  You could argue that water running through the hose has a bit of momentum but the point is that if you’ve got a perfectly sealed hose and it’s at the same height as the tube at the other end, so the gravity is not helping and you don’t wait for an air bubble to go in and displace water out, the only way more water could come out is by creating a vacuum between the end of the tap in the tube.

Kat -   And that ain’t going to happen, in nature...

Chris -   And that’s not going to happen quickly and so for that reason, the water turns off because you’re pushing something which is effectively incompressible out the end of tubes.  There’s no effective stored elastic energy in there.

Kat -   So, if you got like a skewer or something and stuck it in the tap end of your hose, then the water will dribble out because you’re letting air in the hose.

Chris -   It would possibly come out quicker.  It’s a bit like shot gunning a can of drink, isn’t it?  When you turn a can of drink upside down, it goes glog, glog, glog, glog, glog because you have to replace the drink volume that’s coming out with an equivalent volume of air.  Otherwise, there’ll be a vacuum above the drink whereas if you get the can and make a hole in the bottom and then pop the top off, it will empty very, very fast because air can enter easily without having to form bubbles and pass through the liquid to let it go through.

Kat -   Shotgun your hose pipe.

Ben -   Well, this depends on exactly what type of venom they all are.  Most venoms are actually a collection of different chemicals.  They have different effects and there’s things like phosphodiesterases which lower blood pressure.  There’s something that inhibits cholinesterase which makes you loose muscle control.  There are things that affect your nerves, that stop your heart, that actually cause your muscles to necrose or actually break down.  So yes, really, if you are to combine them all, then you’d have something that attacks every single tissue in one go, could stop your heart, stop your brain, and breakdown your muscles, and it would be terrible.

Kat -   The answer to the magnet question is, no.  There’s absolutely no evidence that magnets have healing properties.  It’s all a scam.  In terms of copper bracelets, there’s a lot of old wives’ tales about copper bracelets and when they’ve been investigated for arthritis, again, the scientific studies don’t actually show any significant benefit.  There may be psychological benefit.  The placebo effect as we know is extremely powerful, but no.  There’s no real scientific evidence.

Chris - And we know what color she is referring to and the answer actually is that the food itself doesn’t necessarily contribute very much to the color of what comes out the back end.  The reason being that the dominant determinant of the color of what comes out the back end is bile and bile salts, what your liver squirts into your small intestine to help you to absorb fat.  And the reason for that is that there is a chemical which is called bilirubin which is a breakdown product of hemoglobin, the stuff that makes your red blood cells red, that goes into your intestines and it gets modified by a bacteria in the small bowel and as a result of that modification, it gets oxidized into a chemical first called urobilinogen which is what gets reabsorbed into your blood stream and makes your wee go yellow but then it also ends up back in your gut and gets turned into an even browner chemical called stercobilin and stercobilin is the brown stuff that it makes pooh a brown color.  And if you have a blockage in the supply of bile into your intestines from the liver, what that does is actually prevent you from getting any of this stercobilin being made and you actually do very pale colored poohs and so, you can use that as a way to diagnose people who have gall stones or liver problems.

Kat -   Or if you’re Gillian McKeith, just so you know, look at it for fun. 

Ben -   I think it’s just the conditions that created the sneeze don’t go away, so you sneeze again.  I’m not sure though.  If anyone else has any ideas, please get in touch.

Chris -   I’m just trying to think whether, I mean, there was someone I know who used to have some congenital problem that used to make him sneeze excessively.  I think that there can be a sort of miswiring effect in the nervous system and also certain brain diseases and maybe in brain tumors can cause compulsive unrepetitive sneezing.

Ben -   And we know that we have the photic sneeze response as well so perhaps there’s something going on there whereby if you’re exposed to bright light, you’ll sneeze but then you’re still exposed to bright light so there’s no reason why you wouldn’t sneeze again.

Chris -   Possibly.  That’s also genetic and we know that about one person in five has that.  This is when you’re in a dark room, you go into the bright lights of the streets and suddenly, wow you feel the sneezing fit come on.  No one actually knows exactly why it happens so if you have an answer, let us know.