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Podcast TranscriptThe Naked Scientists: Science Radio & Science Podcasts |
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Mosquitoes make sweet music together
We normally think of a mosquito’s buzz as being an overture for biting, but in fact it’s more like a lover’s aria. At least, if you’re another mosquito.
Writing in the journal Science, Lauren Cator, from Cornell University in the US, has found that male and female Aedes aegypti mosquitoes harmonise their buzzing just before mating, creating what must be the world’s most irritating duet.
The scientists carried out some very fiddly experiments involving mosquitoes tied to pins, moving one past the other to simulate courtship. Females beat their wings at a frequency of around 400 hertz (roughly a concert A, for any musicians listening), while males beat at a higher-pitched 600 hertz (that’s about a fourth higher). But just before they mate, they adjust the resonance of their thoraxes to produce a buzz of 1,200 hertz – a harmonic that’s about an octave and a half above the female mosquito’s pitch. And they could even get mosquitoes to harmonise with a simulated tone played through an earphone.
What’s interesting about these findings is that they overturn the conventional wisdom that male mosquitoes can’t hear anything above 800 hertz, and that female mosquitoes are completely deaf. They discovered this by taking careful electrical readings from the insects’ antennae and Johnston’s organs- the mosquito equivalent of our ears.
But there’s also something more important at stake. The mosquitoes that Cator and her team studied spread nasty – and even fatal – diseases like yellow fever and dengue fever. Dengue fever affects 50 million people around the world.
The researchers found that female mosquitoes who had just mated were much less likely to harmonise with male tones, suggesting they’re not really up for it again.
So the scientists suggest that releasing lots of sterile males into areas plagued by the mosquitoes might lead to female mosquitoes mating with them, which would not result in baby mosquitoes. And then the females would be less likely to go on to mate with fertile males. So it could help to control the population.
References | |||||
| - Cator et al, Science (2009), published online 8th January 2009 | |||||
11th Jan 2009
Sowing the Seeds of Cancer
Nine out of ten cancer deaths are due to tumours spreading from the original site, the primary tumour, to form secondary tumours in places like the lungs, liver or brain. Scientists call this metastasis. Now new research from scientists in the US, UK and Canada has revealed an important molecule called LOX is involved in metastasis, which could lead to new treatments for cancer.
To explain why LOX is important, we need to go back a bit. Secondary tumours don’t just spring up anywhere. In the same way that the ground needs to be right for a seed to grow, cancer cells need the right conditions. Back in 2005, scientists found that special cells move from the bone marrow into organs like the lungs, forming little bundles called pre-metastatic niches. And it’s in these niches that spreading cancer cells grow.
Now Janine Erler and her colleagues have found that a protein called LOX, or lysyl oxidase, plays an important role in forming these niches. LOX acts a bit like a craftsman, gluing together proteins that form the extracellular matrix – the jelly-like stuff that surrounds our cells. The researchers think that LOX glues together certain proteins, forming the right kind of environment to attract bone marrow cells, and therefore the right kind of environment for cancer cells to spread into.
Firstly, the team transplanted mice with normal breast cancer cells, or breast cancer cells that had been genetically manipulated so that they didn’t contain any LOX. The scientists found that the mice carrying cancer cells without LOX had far fewer secondary tumours than those with the unchanged cancer cells. And the LOX-free cancer cells also failed to recruit bone marrow cells.
It seems LOX might also be important in human cancer cells. The scientists took 95 samples of secondary tumours taken from cancer patients, including people with breast, bowel, stomach and oesophageal cancers. And in more than half of the samples, there were high levels of LOX, and clusters of bone marrow cells.
So now that we know LOX is important for this process, scientists can start searching for drugs that might block its actions, which could potentially be used to treat cancer – or even stop it from spreading at all – in the future.
References | |||||
| - Erler et al, Cancer Cell (2009) vol 15, pp 35-44 | |||||
11th Jan 2009
Strange forces on Martian rocks
The Spirit and Opportunity Mars rovers, which have recently celebrated their 5th anniversary on the red planet, seem to have discovered a strange force that is pushing rocks around the Martian surface.
If you look at the photos of the Martian surface, it is strewn with small rocks ranging in size from pebbles to cobbles, but interestingly, none of them are touching. The rocks are all evenly spaced as if something was pushing them away from one another. The surface of Mars is very windy, but because the atmosphere is about a hundredth as dense as it is on Earth, the wind is nowhere near powerful enough to move this size of rock.
Jon D. Pelletier from the University of Arizona has worked out what is most likely causing this rock spacing, and it is an effect that will make sense to anyone who has every tried to dam a stream on a sandy beach.
If you put a rock in the stream, you may have noticed that the sand gets eroded away where the water is moving fastest - in front of and to the sides of the rock, where the water must accelerate to get around the blockage. If you leave the rock for long enough it will fall upstream into the hole that has been created.
Something similar appears to happen on Mars. If you have two rocks touching, the wind will be slowed between them but faster going around the opposite sides. This means that the wind will tend to move the sand they are sitting on from in front of the rocks, and deposit it between them. So like the stream eventually they will roll apart. This gives the appearance that the rocks repel one another and spread out, and no little green men are involved at all.
References | |||||
| - Pelletier et al. Geology 37 (1): 55. | |||||
11th Jan 2009
Stem cells for three blind mice
We’re often talking on the Naked Scientists about research into stem cells, which could have the potential to treat many different ailments. This is because they can be persuaded to change into a wide range of cell types. Now researchers at the University of Washington in Seattle have used human embryonic stem cells to restore some sight, or at least light responses, to blind mice.
The researchers were using mice that were lacking a gene called Crx, which means they are blind from birth as they don’t properly develop photoreceptors, the cells that sense light. They grew human embryonic stem cells in the lab, and treated them with certain chemicals and growth factors that encourage the stem cells to change towards being retinal cells – cells found at the back of the eyeball.
Then the scientists injected these modified stem cells into the eyeballs of mice. They found that the cells settled into the back of the eye, forming organised layers. And when the cells were injected into the eyes of the Crx-deficient mice, they started to turn into photoreceptors. When the scientists tested the mice’s responses to light, they found that these new photoreceptors had some response to light flashes, compared with eyes that hadn’t been injected, which showed no response to light at all. And the eyes with the biggest areas of transplanted cells had the biggest responses.
The researchers also tested transplanting the modified stem cells into albino mice, whose photoreceptors are very sensitive to light and break down. The stem cells also integrated into the retinas of these mice, and were more resistant to breaking down than the cells that were already there.
This is exciting because it suggests that human embryonic cells could be a good replacement for damaged photoreceptors, and maybe in the future could be used to restore sight to people whose eyesight is damaged, or even to those who have been born blind.
References | |||||
| - Lamba et al. Cell Stem Cell I(2009) vol 4, pp 73-79 | |||||
11th Jan 2009
Making your own Aspirin
Gwen Baxter, Dumfries and Galloway Royal InfirmaryChris - Scientists in Scotland have discovered that humans and possibly many other animals make their own anti-inflammatory chemicals. The person who’s made that discovery is Dr Gwen Baxter. She’s from Dumfries and Galloway Royal Infirmary. She’s here to tell us a little bit more about that. Hello Gwen, thank you for joining us. What are the Chemicals that you’ve discovered that humans make that are their own aspirin?
Gwen - It’s linked to the finding that salicylic acid can be produced from benzoic acid which hasn’t been reported in experiments before.
Chris - Tell us a little bit about salicylic acid. What is it?
Gwen - Salicylic acid’s a very simple compound. It’s been around for a long time. It’s recorded as being used as a therapeutic agent from about 3000BC when it was used to relieve pain and as an anti-inflammatory agent, if you like and to help reduce temperatures in fevers.
Chris - If we have it in our body already, why do we need to take more of it?
Gwen - What we’ve discovered is that we seem to be able to produce it ourselves and that’s a novel thing that we’re reporting. Previously we had assumed it was something that people took in, in perhaps diet. Now we’ve found that it’s produced in people.
Chris - What do you think it’s actually doing in the people though?
Gwen - We’re thinking it’s a bit like considering your endorphins. I think people are familiar with that fact that they can be up-regulated. You can increase the amount circulating should you require to do so in times of stress. It’s very close to thinking what happens to salicylic acid in plants. In plants it does act as a responder to stress such as attack by a pathogen. We’re saying that humans are possibly in a position to do that same thing because we have shown that we can produce it.
Chris - You can make the same stuff from aspirin. In fact, when you put aspirin into the body it eventually turns into salicylic acid. Do you think that what you’ve discovered is basically the way in which aspirin or part of the way aspirin works is achieved?
Gwen - Well, I think that if we just go back a wee bit that salicylic acid was used for the things that aspirin is used for. The effect aspirin has on platelets and stops them sticking together which is a therapeutic use of aspirin that salicylic acid doesn’t have in the same way although it does act as an anti-inflammatory. More recently it has become involved as the original agent itself, if you like.
Chris - How do you get the salicylic acid made in the body and does everyone make it and do some people make it more than others?
Gwen - That’s another interesting thing. We’ve done lots of work over the years with people who would have salicylic acid in their body because they perhaps eat it so obviously vegetarians do have higher levels. No surprises there. We’ve also looked at people who have been fasting and they still maintain it so obviously it’s not coming from diet which was the starting point of ‘where is it coming from?’ We’re thinking that if we can find the store for it – it must be somewhere in the body or some precursor such as benzoic acid, which is a product of lots of other metabolic pathways that we have already recorded in our body – it can be used as a bio-regulator and help with some gene protection. As for, ’does everybody make it?’ Well, we’ll have to find that out. Certainly, in our work we’ve discovered that not everyone can metabolise the salicylic acid. Perhaps there is a relationship there to do with gene expression. I think the bottom line there is that it regulates biological systems and a lot of people are working on how small amounts of salicylic acid can modulate gene expression. It may be that if you’re good at making it you’re protected better than people who can’t.
January 2009
Drop Magnifier
Make the cheapest microscope in the world, using a piece of plastic and some water. And find out what it has to do with sneezing on your TV screen!
What you need
| A little water |
| Some transparent plastic from a lemonade bottle or some packaging |
What to Do
Cut a small piece of transparent, thin (but still stiff) plastic like you find at the sides of a lemonade bottle. Make it about 2cm wide and 4-5cm long.
Using your finger or something like a pencil, dab a small droplet of water onto the plastic. For best effect, you want a nice circular droplet about 5-6mm across.
Try looking at things through it. You may have to get quite close to get good results.
What may Happen
You should find that the droplet magnifies what you are looking by a factor of 5-10. The smaller the droplet the more the magnification, but also the harder it is to look through.
What is going on?
The droplet is acting as a very powerful magnifying glass. The water droplet acts as a lens, this bends the light so that it approaches you eye as if it was coming from a much larger object, so it looks magnified.
Microscopes on this principle were state of the art in the 17th century. They were perfected by Antonie van Leeuwenhoek, using tiny glass lenses a similar shape to your water droplet. Because he could make a small almost spherical lens much more accurately than a larger one he could make a much better small microscope than a large one. The problem was that they were very difficult to use, so although he could make a microscope that would magnify up to 200x very few other people could use it. This meant that he wasn't believed for a long time when he saw bacteria, which was unfortunate for medicine over the next 200 years until Pasteur came up with the germ theory of disease.
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Antonie van Leeuwenhoek | Leeuwenhoek's microscope, a tiny glass lens with a point to hold the object to be viewed. |
Why does it magnify anyway?
First of all the way that you see the size of something is to do with how large an angle it makes on your eye. The larger the angle the larger the object looks.
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A small object makes a small angle with your eye. | A large object a larger one. |
Light travels more slowly in water than in air, so when the light moves from one to the other it will bend or refract. The light will bend more near the edges of the lens than at the centre because it is more curved there
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A drop is shaped so that light hitting the edges is bend more than the centre © Dave Ansell |
This means that if you look at an object on the centre, the light relfected from the object will go through a less curved piece of water than the light going through the sides. This means that the light looks like it is coming from a larger object, and appears magnified.
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The light reflected off the object is refracted by the water droplet. | Your eye sees this as if it were a larger object, and it appears magnified. |
The Science of Sneezing on a Screen
When you spray polish on a TV screen, use a mobile phone in the rain or sneeze on your monitor (which is not very hygienic, by the way), you may see strange colours, or a grid seem to appear in the droplets on the screen. This happens because you are putting many tiny blobs of water onto the screen, and each of these blobs acts like a lens to magnify the pixels underneath. Screens are made up of a grid of tiny pixels, and so you may see the individual pixels magnified in exactly the same way that the droplet of water on clear plastic does above.
Written by Dave Ansell
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Do we give out 'flirty' frequencies?Do we send out frequencies like this to make people get attracted to us? Pooky Amsterdam |
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Chris - Yes we do, because we speak to them. Scientists have shown that men who have deep voices tend to be more attractive to women who fancy men, obviously. Voice is down to the level of testosterone – the more testosterone you have the lower your voice and so it can be a sign of a well-testostero-genised man. Also there was a study recently that showed women who are at their peak fertility tend to use higher tones in their voice than at other times of the month. Women speak with a high pitch when they’re more fertile. This is maybe another subtle clue that women are using to give away their fertility to men. |
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January 2009 |
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Can earthworms fly?I was cleaning the roof of my garage, sweeping falling leaves and branches away. There was all this decomposing matter there that had reached critical mass that was making soil on the roof. As I cleaned it off I was surprised to find healthy earthworms in the soil. How did they make it up there? Brian |
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Kat - This is an interesting one but my prime suspect in this case would be birds. There is some evidence that worms can crawl but I doubt that big earthworms can crawl that far. I reckon that a bird has got mud on its beak or is maybe carrying another earthworm that’s got mud on it that’s got tiny earthworm eggs and they’ve got deposited up there. It’s a nice environment, it’s nice and damp. If you’ve got soil, organic matter up there then those dropped worm cocoons, the eggs in a bundle have started to grow. I reckon they’ve been dropped up there by birds. Chris - I agree because when I was little I got into trouble with my parents for putting a worm in my brother’s hair which I absolutely did not do. Because he reached into his hair and found a worm and got told off for it. Actually a bird had just gone over and I think a bird dropped the worm on my brother’s head. I didn’t do it honest. |
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January 2009 |
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Why does a bike stay up more easily when it’s moving?Why does a bike stay up so much more easily when it’s moving? It’s very hard to balance when the bike isn’t moving. Jim |
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Dave - It is very hard to balance when a bike’s stationary. There’s two effects. One of them is if you tip a bike to the left you’ll see the front wheel tends to turn into the left as well because the front forks are leaning forwards. It’s more stable if the handlebars tip to the left. Once the handlebars tip to the left then you tend to steer into the corner and the wheel works its way back underneath you. Chris - So it’s like if I give you the old trick of a broom handle you can balance the broom handle in the palm of your hand. Just by moving your hand around you can hold the broom handle vertically. It’s because when the broom starts to fall in one direction you can move your hand to go effectively into the direction of fall and that’s what keeps it stable. The bike’s doing the same thing. Dave - The bike’s doing the same thing automatically. There’s also a gyroscopic effect that can help. Chris - Because the wheels are spinning and so because the wheels themselves are turning they have a gyroscopic moment. It’s obviously difficult to make it deviate. Given that it’s most unstable when it’s moving slower you can still balance. You probably get more stable when you speed up? Dave - You do and it’s easier to ride when you’re going faster. If you imagine a spinning top it starts to fall over it starts to rotate round and round in circles and the same thing starts to happen to your bike wheel. As you start to turn over it starts rotating and turns into the corner as well. |
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January 2009 |
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How do clouds form electricity for lightning?How do clouds form electricity for lightning? How is the energy stored? Is it dynamically generated? John, Orange County |
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Chris - The answer is we don’t 100% know. Clouds are made of billions of tiny particles, ice crystals. They’re called hydrometeors and these particles rub against each other in the cloud because the clouds are full of big currents of air. There are big ones and small ones. In exactly the same way as you take a balloon or a comb and run it through your hair it will transfer charge from one thing, your hair, to the balloon or comb. This enables you to have static electricity. The same thing happens with these particles in a cloud. By a mechanism that no one understands that well for some reason the big ones get a negative charge and the small ones get a positive charge. The small ones get pushed to the top of the cloud and are upcurrents, more than the bigger ones. That’s how you get this distribution of charge within the cloud. Some people speculate it might be something to do with the solar wind which is this charged stream of particles coming from the sun, past the Earth’s magnetosphere. That aside, what you end up with is a big aggregation of static energy within the cloud which is separated, according to its charge. The bottom of the cloud is very negative. The Earth, therefore, feels an electric field pushing towards it and this repels any negative charge in the surface of the Earth because the negatives can move away, leaving the surface of the Earth net positive. This intensifies the electric field and the result is that eventually the potential difference that builds up overcomes the natural insulation or the inherent resistance of the air and it begins to ionise. This is where you strip electrons away from gas molecules in the atmosphere and because electrons can move they can conduct. You begin to carry a current and so you get a few feelers come down. When you’ve got a sufficient and contiguous connection between cloud and ground you’ll get a full-on strike. The lighting comes zipping down. The actual discharge is only about the size of a five pence piece and it lasts for a billionth of a second, microseconds at best. The actual current that flows down it is something like 20,000 Amps and it’s discharging between 1 and 10 billion joules of energy which is, in fact, enough to light a 100W bulb for 100 days. It’s not a huge amount but is enough to make a big bang. The reason that the lightning’s nice and bright is that, as the electricity goes smashing though the air it causes the electrons in the atoms to get very excited. They then fall back to their original energy positions, giving us some light in the process. They also get very hot and because of the thermal expansion you get a shockwave. It’s like a gun going off. |
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January 2009 |
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Why do you get white blooms on refrigerated chocolate?Why do you get white blooms on refrigerated chocolate? I was recently given a block of chocolate from a friend and to avoid it melting, as it’s currently summer here in Australia, i put it in the fridge. Finally got round to eating it today. When I unwrapped it I noticed there were white spots all over the place. William Isdale |
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Kat - I’ve been doing a life time of research into chocolate and yes, you’re right. Bloom on chocolate this kind of white stuff you see in it is not harmful. You get two types of bloom on chocolate. You get cocoa butter bloom which is when the cocoa butter comes to the surface of the chocolate. You can tell if you’ve got cocoa butter bloom because it kinda feels a bit oily and greasy. You can get sugar bloom and that’s when sugar crystals come out of your chocolate and that feels kind of granular. What’s causing it? Well, chocolateers think that what causes bloom is when you get temperature changes, big changes in temperature to chocolate. As it’s been hot in Australia and now you’ve put your chocolate that’s been in the fridge to keep it cold you’ve put it through quite a big temperature differential and then got it back out of the fridge again. That’s caused the bloom. It’s probably best to keep your chocolate at a cool, stable temperature – not necessarily in the fridge. |
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January 2009 |
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Indoor Snow
Richard Shears, Milton Keynes SNO!ZoneMeera - Yes, it is the season that many of use decide to go skiing to various resorts around the world. But this week I’m at a place that you can ski that’s in the UK and also inside. I’m at the Milton Keynes SNO!Zone, part of the Xscape Leisure complex in Buckinghamshire. In front of me there are 3 snow slopes. Two which are up to 173m long and 20m wide. The best bit is that all of these slopes are actually made of real snow. What does it take to create the snow that’s in here and fill basically a big dome like this with tonnes and tonnes of snow? Here to tell me all about it is Richard Shears who’s the facilities manager at Snowzone.
Richard - The temperature here at the moment, Meera, is -2, -3 degrees. Up above us are some large radiators. Within the radiators there are six large fans. These large fans blow air across a radiator and the radiator is cooled down to -16 degrees with an antifreeze mixture inside it. When we’re running at full capacity with 100% fans we’ll it down to probably -6 degrees. That’s the temperature that we make the snow.
Meera - Can you describe the actual structure here of the slope?
Richard - Underneath the snow is a large concrete slab stretch from the base of the slope, right up to the top. The concrete slab is covered with an insulating material and on top of the insulating material is lines of 20mm pipes. These 20mm pipes contain the antifreeze mixture which is cooled down to -16 degrees. Each time we run water over the pipes it freezes and gives us a depth of ice down to 30-40mm thick of ice. We have an ice layer under the snow.
Meera - To find out how the snow’s actually made we’re going to head up to the snow bar which is on the second floor and looks out over the snow slopes so we can actually see the sprayers that the snow is created form. Let’s head up there now because I can’t feel my fingers at the moment!
Now Richard, you create up to 1500 tonnes of snow here, all with these sprayers that seem to be located at different positions around the room. How do these actually go about creating the snow?
Richard - The snow’s created by using high-pressure water and air which runs through what we call a snow gun. The water and the air are broken up into fine particles and then blown out at high pressure into the atmosphere of the ski box. When the mixture hits the atmosphere it freezes into a fine mist which lands onto the ground, which forms real snow.
Meera - What other conditions need to be maintained to get the maximum snow created here?
Richard - During the night we can drop the temperature of the ski box to -6/-7 degrees. Providing the humidity is right within the box we can make the snow that temperature. Obviously the higher you can drop the snow from the snow guns the longer it has to form, the better the snow can be made.
Meera - How does this compare to the snow we get outside? Is it the same?
Richard - The structure of the snow is a little bit different where you have nice snowflakes outside and they’ll probably fall 30,000 feet. We’re falling from 40-50 feet. The ice crystal doesn’t have that time to actually form. Outside every snowflake that your get is different. If you put them under a microscope you’ll see the shape is different. In the snow we get here, because it’s a controlled environment it’s an ice crystal that comes out but they’re all formed in the same structure.
Meera - What do the actual crystals look like? Are they quite spherical then?
Richard - Yes, they’re round. If you put them under a microscope they’re all uniform. They’re all round.
Meera - We’ve been talking so much about snow and I can see all these skiers in front of me that I really need to go and try it out for myself....
January 2009
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Why does one get cramp? |
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Chris - Cramp is a muscle spasm and we don’t actually know what cramp is. We just know that if people have regular cramps – and it tends to happen quite often at night and it tends to happen in younger people more often than older people and it tends to be relieved with quinine, the same stuff that makes tonic water taste nice. A muscle spasm is when some of the muscle fibres – because a muscle isn’t just one homogeneous giant thing. It’s actually made up of lots of individual little muscle fibres. Some of those muscle fibres go into a spasm. In other words, the contract more than they should and they lock in a contracted state. Surprisingly, muscle actually takes energy to relax, not to contract. When a body of a person dies, they go into rigor mortis because the cells in their muscles run out of energy and their muscles can’t relax and they stay rigid. That’s why a person gets rigor mortis. If you leave them a bit longer then the rigor mortis goes away again when the muscle breaks down and starts to relax. What cramp could be is for some reason that clutch of muscle fibres don’t have enough energy in them, perhaps because there’s been a reduction in blood flow that’s insufficient for the muscles needs. Therefore the muscle runs a little bit short of energy and this trips its inability to relax properly and you get a cramp. Rubbing a muscle and massaging it to get the blood through it can make it better. Zanzibar Rothschild, in Second Life - Bananas are good for cramps. Could it be down to potassium? Chris - could be but I don’t know for sure. I know that if you don’t have enough potassium then you can end up with excitable cells in that way and this can lead to muscle spasms so that’s a possibility. |
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January 2009 |
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Why does my car windscreen mist up only when it rains? |
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Dave - What’s happening when your car windscreen mists up is you’ve got lots of moisture in the air inside your car. If the car windscreen is cold enough then it will be below the dew point and below the temperature at which water can condense on it. You will get condensing on the windscreen until eventually you get little droplets making it hard to see through. There’s various things which will affect this. One of them is the amount of moisture in the air. If you’ve got rain it’s very humid and you’re probably wet. You’re probably heating up water and it’s evaporating off you so it makes the air very moist. The other big one is how cold the glass is. If it’s raining then rain’s probably hitting the glass, taking a lot of the energy out of it and cooling it down. Probably two reasons: one is that there’s more moisture in the air and the other is that it’s cooled down. To try and stop this from happening, you should try this Kitchen Science Experiment! - www.thenakedscientists.com/HTML/kitchen-science/exp/stopping-fogging/ |
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January 2009 |
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What are the spasms that occur as you fall asleep?What about spasms that occur all over the body when you’re asleep? Vanbar Pontchartrain |
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Chris - I think what you’re thinking of is a hypnic jerk. When people fall asleep and you can notice this yourself you suddenly jerk violently. Often enough to wake you up again and certainly anybody who’e sleeping next to you. If you’re on a bus with someone and you don’t know them it scare the hell out of them because I’ve done that to people. This is a hypnic jerk and it’s to do with the part of the nervous system that paralyses you when you go to sleep. When we go to sleep and we dream you don’t want to be acting out your dreams because that could have unfortunate consequences. There’s a region of the nervous system called the sub-cerulean nervous system in your brain stem which receives information about when you’re going to dream and it also has the ability to switch off the flow of motor systems going down to your spinal cord. It can paralyse your body when you’re going to sleep. When you’re switching in this system, sometimes it gets a bit carried away. You get these jerks as the system is turning on. |
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January 2009 |
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Why do rockets not 'burn up' on the way up?Why do rockets go up without resistance into the stratosphere and yet come back with resistance and have heat shields and stuff like that? Meteors experience the same thing so why does that happen? Jack, Corbeth |
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Dave - Basically, does a burn up on the way down but not the way up? The amount of heat you’re generating is all to do with how fast you’re going and how thick the atmosphere is. The thicker the atmosphere and the faster you’re going the more heat you generate. Although space rockets can go several times the speed of sound they do get some heating on the way up. It’s not that much because they’re going fairly slowly while they’re near the ground and the air’s fairly thick. They get faster up in much thinner air so there’s less heating. On the way down they’re going really fast and they’re still going fast through the thin air. As the air gets thicker they’ve still got lots of energy. Chris - The escape velocity’s 13-14,000 miles an hour or something ridiculous, isn’t it? They have to have a way of dissipating heat. Dave - They can’t dissipate all that energy in the upper atmosphere. They have to dissipate it lower down. |
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January 2009 |
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Why is urine yellow?Why is urine yellow? Is it usually yellow in most species, just mammals? It’s mostly water so why is it yellow? Israel, USA |
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Chris - The yellow colour is because of the stuff that makes your blood red. When we break down red blood cells which last about 120 days the haemoglobin makes a protein which has a iron atom at the centre. That protein gets broken down into something called bilirubin. Bilirubin is dumped out of the body by the liver. The liver metabolises the bilirubin bit by adding sugar to make it dissolve in water, puts in bile and your bile then gets squirted into your small intestine to help it reabsorbs fats. The bilirubin, because it has sugars stuck on it becomes broken down by bacteria. The bacteria metabolise the molecule and they turn it into something which is called urobilinogen. Urobilinogen gets reabsorbed further down the small intestine. Unlike bilirubin, which is not very soluble in water urobilinogen is very soluble but it’s a brown colour. The urobilinogen goes round the blood stream again but when it goes round in your blood stream again but when it goes through you kidney, because it’s soluble in water, it moves out through the kidney in the same way as the other things that go into urine do and it goes into your urine. Because your urine is a concentrate of plasma you take water back but leave the products that have got filtered behind and it builds up in the urine and adds this brown colour. So urine goes darker and darker. The more dehydrated you are the darker it is because the concentration is higher. Kat - It may be a bit of it’s riboflavin as well because if you take a lot of B vitamins you just wee them out. I think, riboflavin, when it’s dissolved in water is very yellow as well. |
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January 2009 |
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Life from Outer Space?Have they found any life in the rubbish that falls to Earth from outer space? John Wilson, Netherlands |
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We put this to Dr Vic Pearson from the Open University:
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January 2009 |
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Depends. Give me a definition of life:) What they have found is organic molecules such as sugars and amino acids. Now scientists think that they've found "complex organic chemicals used to make self-replicating molecules that are genetic ingredient of all known lifeforms – DNA and RNA - inside a meteorite, life originating with the aid of extraterrestrial molecules that might have come from space more than 3.6 billion years ago.' But I don't know of any 'living' organisms found from outer space. The times they've though they found such, it most probably has been 'contaminated' from Earth. Or have they? - yor_on - 27th Dec 08
Of course not. At least the way we know life is. But we may have certainly come across some organic molecules. Who knows maybe life has been triggered on earth through these fallen debris ? There was a news that a fossil of a bacteria was found in the rocks fallen from mars. - kancha - 27th Dec 08
If they've found any, the secret agencies are not telling.
- Chemistry4me - 28th Dec 08
If they fall on our planet.. And it comes at great speed... It is like a fireball.. So all the organisms would have burnt to death anyway Just my theory - seanahnuk - 6th Jan 09
And those life forms that make it to the ground are obviously very hot, as a result jump off the rock, and scatter to find water to cool their jets. No wonder we cannot find any. Karsten - Karsten - 7th Jan 09
A valid theory which has been tested. Some resarchers simulated the effects of riding a meteor into the Earth on some bacteria. The vast majority of them were burnt up, but a very small percentage survived. Which is all you need. The inside of a meteor doesn't always get that hot when entering the Earth's atmosphere. Bacteria can be pretty hardy, some have been found growing inside nuclear reactors. Dr Pearson is talking about a hypothesis called psuedopanspermia, which is that as she say some of the building blocks of life may have come from meteorites and comets. The more controversial panspermia hypothesis is that life (bacterial) itself fell from space. Few researchers in the area hold to the theory (and the ones that do tend to be a little strange), but I see little reason to rule it out. I met some people from the SETI institute at an origin of life conference once and they assured me that if they or NASA had evidence of life from space they would be the last people wanting to keep it secret. It would mean a massive boost to their funding. But would other government/military agencies try to stop them? - bryan - 14th Jan 09
I suppose it would depend on what they find - Chemistry4me - 15th Jan 09
Where do you think we all came from?... (cue in sinister laugh) we didn’t originate in this planet... this is just a Petri dish that is being watched closely –very closely. Sshhhhh - Emilio Romero - 15th Jan 09
If you insist Emilio Romero ! - Chemistry4me - 16th Jan 09
Hmmm, That would explain 'the eyeballs in the sky'. http://www.theauthenticperishers.co.uk/mainmenu/eyeballs.htm - Don_1 - 16th Jan 09
It's not that slim. Matching the elemental makeup of meteorites that landed in the Antarctica a great many years before mankinds appearance on the evolutionary scale had what are called polycyclic aromatic hydrocarbons. This particular hydrocarbon makeup is in fact the perfect ingredients for microbe-like life. Also metreorites can act like life-sustaining capsules over long periods of time, as though preserved in their frozen environment. So, i disagree. Whilst it being not only probable, it's also possible that the theory of Panspermia is an excellent theoretical description of how the first prokaryote of life appeared from which all eukaryotic lifeforms evolved from. - Mr. Scientist - 12th Nov 09
My ex wife is clearly from outer space. More then that, I truly believe she was deliberately expelled for reasons I will not elaborate. It might endanger the entire planet.
- litespeed - 5th Jan 10
Very interesting. Thanks for the share.
See the whole discussion | Make a comment~sam all inclusive vacations - SamTHorn - 20th Apr 10
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The likelihood of finding life in meteorites is probably pretty slim. There was, in the 1990s, a big debate on whether or not NASA scientists had identified nanobacteria, so very small bacteria only identifiable using very powerful microscopes in meteorites that had come from the surface of Mars. This has pretty much been debunked now. That’s not to say that the building blocks of life may not have been brought in meteorites because meteorites themselves contain biogenic elements such as sulphur, nitrogen, phosphorous. Also, carbon-based molecules or organic molecules which are required for life on Earth and elsewhere in the solar system: these are things such as amino acids, carboxylic acids, sugars – all of which make up living systems on the Earth and all of which are the backbone of the organic molecules that make up our own DNA. The chances of being able to find life elsewhere in the solar system is also a lot stronger by the fact you can find the organic molecules. Whether or not you can actually get life itself from meteorites is probably very unlikely.
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Does my iPod get heavier as I add more music to it? |
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Dave - The only way that actually adding music to your iPod could increase its mass could be if you were somehow increasing the energy of it. The way modern iPods tend to store music is in what’s called flash memory. This has lots of tiny cells inside it. You tend to trap the electrons, maybe a few hundred electrons in the little gap. That affects how current will flow through a wire until you can read it again. This is going to store some energy and maybe a miniscule amount. Probably 1/1000th of a joule at most inside your iPod. That’s for the 1s so the 0s wouldn’t store any energy – so half of that. According to E=MC2 it will increase the mass ever so slightly. That’s a tiny amount but that’s far less that the increasing mass. Perhaps when you charge up the battery but that’s less than the mass of a greasy fingerprint you put on top of it. Chris - So the answer is yes if you put some energy into the iPod – if whatever you do to it means it gains some energy because Einstein says E=MC2 it has to go into mass but the amount is going to be tiny. |
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January 2009 |
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How long can cancers grow before detection?Is it true that adult cancers when they present at late stage by the time it’s been detected in you has it been growing for more than 10 years and could have spread somewhere else? Brenda Herbert |
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Kat - Absolutely not at all. Then screening wouldn’t work. Things like the breast screening and the bowel screening that we have now. Some cancers, yes, they are advanced and that’s why the government’s trying to do a lot through an initiative called the early detection and awareness initiative to try and catch cancers earlier. Bowel cancers you can spot them when they’re just a little polyp. You can take them away and cancer will not have grown anywhere. In the case of breast cancers, breast screening picks up very small tumours that really haven’t spread far so it’s not necessarily true for all types of cancers that they will have spread around the place. Chris - Could she mean that cancer’s a multistage process where you slowly build up and acquire changes of your DNA which eventually mean you get cancer and you could have spent a lifetime building up those changes? Kat - That’s kind of true because we do pick up all kinds of damage to our DNA just in the hurly burly of life within our cells. Cancer is a disease that usually takes a very long time to happen. There is also and idea that we do, everyone has tiny cancers all over us but it’s our immune system that’s constantly patrolling our bodies and keeping these under control. What happens when cancer really starts to grow is that it started to evade this immune suppression and really start going for it. There’s a lot we don’t understand about how cancer really gets going. |
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January 2009 |
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Why do we get goosebumps when we’re scared?Why do we get goosebumps when we’re scared, especially when we’re told stories about ghosts? Briana |
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Chris - Goose bumps or goose pimples are the bulges produced by your piloerector muscles. These are the muscles that can make your hairs stand on end. In other animals like mice, cats, dogs; making your hair stand on end is a good thing. If you’re cold you trap more air next to your body and it thermally insulates you. If you’re scared it makes you look much bigger. If you look much bigger then you’re scary to other animals and they’re less likely to attack you. We’re obviously derived and related to all these other mammals that do this but have less hair. It doesn’t serve a useful purpose in us, it’s just a sort of evolutionary vestige. |
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January 2009 |
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