Diana -   Well, the short answer is no.  We had a really good answer from the forum about this actually from databit who said that hair grows actually in a cone shape.  So, when you let it grow naturally, the end looks thinner and therefore, the hair looks thinner.  But when you actually shave it, you cut it right at the base where it’s at it’s very thickest and that makes it look much thicker.  So, once you’ve start shaving your hair, the stubble will look much thicker and make it look like more like it’s actually growing, but there isn’t.  It’s the same.

Chris -   And the other point I think also to make is that when you’re cutting a hair that is growing already, it’s got a head start because it’s already an actively growing hair compared with a hair follicle that was not active because hair follicles go through various cycles of activity and inactivity.  So therefore, you’re cutting a growing hair already therefore, it’s already growing.  Therefore, it’s going to grow back quicker.

Diana -   That’s right.  You sort of bring all the hairs back down to the same level of growth and so, it appears as if they’re all sort of growing at once.

Dave -   On the moon, the gravity is about a sixth of the earth so you can jump much, much higher.  Whether this helps you with running, it depends on what kind of running you’re doing, I think.  If you’re trying to sprint, if the sixth amount of gravity then you’re going to have a sixth of the amount of friction between your feet and the floor because friction basically goes at how hard you’re pushing against the floor, and this means – but your mass is still the same, so you still need the same force to accelerate.  So, he’ll be able to accelerate about a sixth of the rate as he could do normally.  So, in a 100-meter sprint, he’s almost certainly going to be a lot slower.  But if you’re running a very long way, you could probably get an advantage because you can take huge strides.  So, you can sort of – you could take a huge stride and then not do anything for a three or four seconds while you fly through the air and then you can land and do a little bit of exercise and fly through the air for a bit.  So, you get some time to recover in between so I think you could probably run long distances faster, but short distance is not maybe as quickly.

Diana -   So, it’d be like the laziest race ever then, wouldn’t it basically?

Dave -   Oh, it depends how fast you’re going but, yeah.

Chris -   Brilliant.  Yeah, well limonene, it’s the stuff that makes oranges and lemons smell orangey and lemony.  So, if you take an orange and you scrape the peel a little bit and smell your fingers, it’s that very intense orangey citrus smell, isn’t there?

Don -   Yeah.

Chris -   And that is the limonene.  The orange peel contains huge amounts of it.  It’s a very big organic molecule.  It’s lots of carbon and hydrogen atoms stuck together in giant ring structures.  And in fact, we did an experiment on The Naked Scientists a little while back.  Dave did it as a Kitchen Science where you actually blasted some of the limonene through a candle by squeezing the peel of the fruit and you spurted the limonene into the flame.

Dave -   That’s right.  You produce a sort of aerosol of limonene into the flame and limonene is really flammable and so, it catches fire.

Chris -   But the reason that fruit makes it is because it’s also quite nasty for things other than humans who haven’t got fingers to peel an orange.  If you try to borough through the peel of an orange, you’d have to eat the peel and the peel doesn’t taste too good.  Limonene is mildly toxic and being organic and unpleasantly tasting as it is, it puts off insects and that’s a way that the tree uses of keeping its fruit in good condition.

Don -   Okay.  I find it also in my shower gel.  Why is it in there?

Chris -   Sure.  Well the answer is rather than trying to invent artificial flavours and colourings and things which would do the same job as a molecule which is already doing the job very well in nature, sometimes it’s easier just to use the natural product and then you can also have a marketing benefit because you can say, “Hey!  This is a natural product.  It’s got limonene in it.”  So, rather than having to use orange flavored stuff or a small molecule that smells the same, then you can just use the natural product and then you get two bangs for your buck.  So, what it’s doing in your shampoo is contributing a nice orangey aroma and which also, because it’s fatty and oily, it will stick to your skin quite well.  It won’t get washed off by the water and it leaves you smelling vaguely with a faint aroma of oranges.  Have you noticed that?

Don -   Yeah.  I have.

Chris -   Then we’ve got the answer right.  Thank you very much, Don.

Chris -   The point he’s making is that a black hole is a collapsed star.  So, all the mass of the star ends up in the black hole.  So, if light can come out of the star in the first place, given that there’s no more mass now in the black hole when it’s collapsed, what’s changed that now light can’t get out?

Dave -   That’s right.  When you take a star and convert it into black hole, you actually normally lose an awful of mass.  It involves all sorts of explosions and lots of energy given off so that black hole normally weighs an awful less than the original star did, but that mass is much, much closer together - it’s much more dense.  The force of gravity even the Newtonian force of gravity is essentially proportional to the inverse square.  So, if you’re twice as far away from it, the force gets four times weaker.  So, if you take a star and squash all that mass very close together and then you stand on the surface of it, apart from being burned up and everything, you stand on the surface  of it then you’re going to be a lot closer, a lot more mass.  So the gravity is going to be much, much stronger.  And once you go into relativity and general relativity then that mass can bend space enough that light always gets bent around and it can never escape at all, ever.

Chris -   So, if the black hole blew up again and you took the same mass and put it back to something that was the original size of the star – so in other words, the density was low again then it would start to emit light again.

Dave -   Yeah then light could escape no problem.

Peter -   Hello.  Well, my question is fairly complicated, so you have to bear with me  a little bit.  We start off with the refrigerator.  Now, the refrigerator, actually, you get more benefits than the energy you put in.  In the sense that you put a certain amount of electricity and to move heat from the hot to the cold or pump heat away from the cold areas.  And you can pump significantly more heat in the energy you put in.  So, you got sort of reverse efficiency where you can move several times and probably, I don’t know three or four times.  I don’t know the exact figures.  The energy reacted in…

Dave -   That depends on the temperature you’ve – the difference in temperature which the fridge is working across.

Peter -   Yeah, so you’re actually moving physically more heat than the energy you’re putting in.  Now given that, can’t we do the same thing in reverse and use the fact that we’ve created a heat differential to power a heat engine to generate the electricity back again.  And now, one or two things will happen.  Either will get more electricity out than we should in a sense that we’ve got an efficiency which is greater than the factor…   For an example, let me say, if we pump in four times as much heat and to convert the heat back to electricity, we need only 25% efficiency or better to actually win in the game.

Chris -   So, this is worth making tons of free electricity just by running your fridge for cooling your beer down, Dave.

Dave -   Okay, so basically you’re asking if a fridge can pump far more heat than the energy you put in, that’s definitely true.  In fact, if it’s pumping for very small temperature difference it can pump 100 times more heat than the energy you put in.  Can you make a heat - temperature difference with that and then use that temperature difference in order to generate electricity?  We can use that temperature difference to generate electricity, we do use temperature differences to generate electricity all the time.  Essentially by using a heat engine - something like a car engine is a heat engine.  And basically they can produce high quality electrical energy by moving heat from a hot place to a cold place.  But a fridge is essentially just a heat engine running backwards and again with a normal heat engine the amount of energy you can get out compared to amount of heat you can move is to do with the difference between the two temperatures.  The bigger the difference in two temperatures, the more efficient it is.  And so you’ll never, ever going to get more energy out by going around to the circle like this.

Chris -     You’ll just be violating the laws of physics basically, it’s just not going to happen.

Dave -   Yeah, there’s a really, really fundamental law of physics.  Which essentially says you can’t generate useful energy from nothing and this would violate it completely…

Chris -   It’s an analogous question to, if I have a propeller on my car as I drove along, could I connect that to some kind of generator.  And then power the car with the generator, it’s kind of getting a free lunch isn’t it?  And it just doesn’t happen, energetically speaking it’s just not going to happen.

Dave -   Yeah, and I think actually with this one it would be far, far worse than, it would work far less well than that.

Chris -  I’d say, it’s the placebo effect, wouldn’t you?  I think it’s just because you automatically think it’s nicer because it’s in glass.

Diana -   Yeah, having lived, sort of six years on and off as a student, I think it starts to taste the same after a while anyway.

Dave -   A lot of what you experience from a meal food is to do with the surroundings which is why restaurants spends so much money on having pretty stuff in the room not just on the food.

Chris -   The answer is probably not.  But I did a bit of poking around, in fact we have covered a story on the Naked Scientists a couple of years ago by Scientists (the reference is Meh Jong Jong) who is a crop researcher over in South Korea.  And published this in the journal of Molecular Breeding.  So it’s a peer reviewed  journal but I'm not sure how robust the science is.  But what they did was to, for some reason - and they don’t say why in their paper, they were playing classical music to different plants.  And they tried 14 different types of classical music to see what effect this would have on the plant growth.  And the plants, not surprisingly, did not respond at all.  

So then they thought well perhaps it’s a mixture of tones and perhaps plants are sensitive to a range or specific set of tones.  So then they started playing sounds at specific discrete frequencies at plants and monitoring gene expressions.  So they would grind up the plant and see which genes have been turned off or turned on in response to the presentation of a tone over a period of time.  When they played certain plants a tone at 50 Hz, a series of genes went down, turned off.  When they played the same species of plants some sounds of 150 Hz, 125 Hz or 250 Hz, the same genes increase their activity.  And when they use the molecular machinery, the bits of genetic sequence that turned those genes on and off and link them to another gene, that made the cells change colour, that’s called a “reporter gene” they could, by playing certain sounds to the plants, get these plants to change colour.  Suggesting that plants are are sound sensitive, so maybe in the case of cereals we know they have ears, so maybe they are sensitive to sounds and therefore maybe, there is some validity in saying you should talk at them.  I think it’s more likely though, that the CO₂ that you are emitting in your breath when you talk to your plants is going to have a bigger effect than the range of frequencies.  But maybe Bloke’s voices being more low frequency dominate it would have a better effect than women’s voices, I don’t know.

Diana -   So, Prince Charles was right then?

Chris -   Maybe Prince Charles is right, maybe.

Dave -   Are plants vibration sensitive?  Because when wind blows past them they’ll vibrate, and if it’s windy then they’re going to want to have all sorts of different settings, than if it’s not..  

Chris -   Yeah, plants definitely response to being moved around.  Because they realize that this is bending them and they therefore need to strengthen and so they deposit more growth related products and then they turn on growth related genes in the other side of the stem to the one in which they are bending.  So they strength from the side that they are bending away from.  So in other words, it makes it stiffer on that side.  And that’s why trees can look a little bit bent but still stand up despite say an on shore breeze or something. So that’s why.

Dave -   Well, yeah.  Star, it’s not actually the fusion which is holding the stars up directly.  It’s actually their temperature.  If you had a gas, the hotter it is the more pressure it will exert, the harder it would push out.  So stars are basically supported, they’re basically made out of very, very hot gas - plasma that are supported by their temperature.  So if a star gets hotter it will expand, star cools down it will shrink.  A planet doesn’t have to be supported like that, planets are made out of solid, lumps of things they’re basically supported by the repulsion between atoms and molecules, in the same way as the table is supported or you’re supported.  So they are not big enough for the need the temperature to support them and basically just molecules and atoms are strong enough.

Chris -   Because planets like Jupiter are just around the threshold of what we call brown dwarfs, aren’t they, they’re failed stars are not quite big enough to squeeze themselves enough to trigger a fusion to actually get going.

Dave -   Yes, small stars it can also be supported just by this molecular strength basically.

Diana -   That’s a good question actually.   And now, Dr. Karl Kruszelnicki has worked a bit on on this and he actually did win an IgNobel Prize for his lint research.  But he says that for both belly button fluff and laundry lint, is actually an average of all the colours of your clothes.  So all the stuff that comes off even your white laundry, will end up being sort of slightly grayish, bluish, horrible colour.  And if you think about even if you do have a lot of black clothing, and I'm sure most people will have at least one item of black clothing, will tend to sort of fade to grey and those are the bits that are more likely to disintegrate and fall off and become lint.

Dave -   It’s not always blue.  I once washed a bathroom mat from the floor, which was already fluffy and bright red.  And that shed completely, it jammed up the whole washing machine and the lint that came out of that was definitely red.  

Chris -   And the other slights a bit of additional information or perhaps you might or might not wants to know about Dr. Karl’s study, he actually invited to send in their belly button fluff, to see that colour that was.  I think it came out pretty much the same, didn’t it?

Diana -   Yeah, the IgNoble people told him to never, ever do research on this again.

Dave -   No, this is perfectly normal.  In fact we did a Kitchen Science on this a couple of years back.  Basically polyester is a polymer which is quite good at charging up.  So if you rub that against your hair or against other sheets it would tend to, as it touches the sheets it would slowly get electrons transfer to it (or away from it, I’m not sure which way with polyester) and so it gained a charge.  This means if you move it near a fluorescent tube, a fluorescent tube is basically hollow tube with some very low pressure mercury gas in it.  Some of that mercury gas will be ionized, it would’ve lost electron, you move a charged thing near that some of those ions will move towards or away from the charged thing, will accelerate along, will hit other mercury atoms and knock electrons off those and then you’ll get a cascade effect.  And get a little bit of electric current flowing through the tube one way, when you take it away then it will flow back again, and that will transfer energy to the mercury atoms some of that they will release as ultraviolet light.  This will hit the sort of white coating inside of the tube and that will emit visible light, which you can see as this flash of light.

Chris -   So there’s nothing radioactive about your bed, it’s okay then, you’re okay.

Chris -   I wish I knew the answer to that.  It’s actually just simple numbers.  There are two reasons for this.  One is to be immune to something, your immune system has to see it in the first place.  So you have to be infected with the thing, so you then learn to neutralize it in the future.  Now, that would be simple if there was one virus, but in fact there are hundreds.

If you look at the rhinovirus family, which is the cause of the common cold, around most of the year, there is about a hundred of those.  If you look at the enterovirus family, there’s about a hundred of those.  There is 50 or 40 adenoviruses, many of which cause upper respiratory and eye infections.  Then there are the corona viruses, the parainfluenza viruses, the influenza viruses and to add insult to injury, these viruses also mutate.  So not only are there hundreds of them around for you to get your immune system’s head around but also they are moving target.  They are changing their molecular appearance, so even if you have learned to recognize it, there’s no guarantee that you’ll recognize it again the next time.  And given that there are all these hundreds of viruses and the average person gets about two or three colds per year, that’s three life times worth of cold infections before you’ve actually got any chance of being immune to all of them, by which time they probably have changed.

So, I don’t think there’s really any prospect of ever being able to cure the common cold with the exception that what scientist including Steven Legit who is a researcher of University of Maryland had done, is they’ve sequenced genetically all of the rhinoviruses so far.  And they know how they divide up to a little subfamilies and it might be that if you a made a vaccine based around some members of some of those subfamilies, then every time you immunize someone who gets one of the subfamilies you are protected against all the other members of that family.  So you could make a vaccine but it would have probably be based around lots and lots a different members and probably be unfeasible.  Who knows, let’s hope though that we come up with some kind of common cold cure soon because since you have children you’re into a whole different ball game.