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Podcast TranscriptThe Naked Scientists: Science Radio & Science Podcasts |
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| 1st Nov 2009 | < Previous Show | Next Show > | |||||||||
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Million frames a second camera
There are many processes in physics chemistry and biology which are very interesting but happen very quickly so they are hard to study. There are many forms of high speed imaging but they work by making conventional cameras faster, which normally involves expensive mechanical systems and they often have a limited light sensitivity because their exposure time is so short. So if you are not careful you have to illuminate the sample so brightly that the light levels will damage it, and they are useless if you are looking at light emitted by a process.
The Megaframe project had just built a camera capable of 1 million frames per second 
by approaching the problem from a different direction. They have taken sensors called Single Photon Avalanche Diodes, which, as the name suggests, can detect individual photons, making the camera far more sensitive than a converntional camera. These detectors are then connected to timers which can tell you when the photon arrived to within 100ps and be ready to receive another photon 32ns afterwards. They have then made arrays of these detectors up to 128 square, which is a long way from HD video, but immensely better than the alternative of using individual detectors.
The precise measurement of when each photon gets to the detector makes this camera particularly means that it can be used for a variety of forms of imaging which need to know very precisely when the photons arrive at your detector.
This makes the camera useful in a variety of ways, not least, because the rate that 
some dyes (Oregon Green Bapta-1 ) emit light after they have been given energy by a laser is dependent on the concentration of calcium around them. Calcium is used in the firing of a nerve cell so this means that they have been able to make a video of an indivdual nerve cell firing and as they get more pixels on their detectors, they should be able to video groups of cells interacting.
References | |||||
| - Megaframe project | |||||
1st Nov 2009
Speedy strides due to heel size
When you think about building the perfect sprinter, you might think of long legs and powerful muscles. But new research published in the Journal of Experimental Biology suggests that it's the size of an athlete's heels that might also be important in giving them the edge.
This is research by Stephen Piazza and his team in the US, who was approached by an American Football star to find out if they could help them get the edge over the competition. When a sprinter pushes off the ground, their acceleration depends on the leverage that they can generate by the calf muscles pulling on the back of the heel, pulling it up and pushing the toes down.
Piazza figured that the best sprinters would have a long distance between the ankle and the back of the heel – making a longer, more powerful lever and pulling the heel up a long way. But when they actually measured how far the athlete's tendon actually moved while pulling up, they got a surprising result.
The researchers discovered that this particular footballer's tendons moved a much short than average distance. So they measured the tendons of a number of elite sprinters and long jumpers, and compared them with the legs of non-sporting people. And they found that on average, the distance athlete's tendons moved with 25% less th
an those of non-sporty types, suggesting they actually had a shorter “heel lever”.
When Piazza looked into this, he discovered that sprinters compensate for this by contracting their calf muscles comparatively more slowly than those of non-sprinters, generating much more force when accelerating. This is a similar design to many sprinting animals. And the scientists also found that sprinters toes were on average a centimetre longer, meaning they stay in contact with the ground longer as the sprinter pushes. So although it appears on first glance that short heels might not help you to sprint, short heels combined with long toes and powerful muscles actually help to generate more power.
References | |||||
| - Lee, S. S. M. and Piazza, S. J. (2009). Built for speed: musculoskeletal structure and sprinting ability. J. Exp. Biol. 212, 3700-3707. | |||||
1st Nov 2009
Liquid identification
If you have travelled by aeroplane recently you will probably have been annoyed by the rules limiting the liquids you can take onto the plane. 
The problem is that there are various liquids that can be used to make explosives or just a fire, which are hard to detect quickly and easily in the security check.
A group for Julich in Germany think they may have a solution. They are looking at the frequencies reflected in the GHz to 10 THz region of the spectrum, which is the frequency of your mobile phone and upwards. Different liquids have different spectra so you can detect which one is in a bottle, however these frequencies are difficult to deal with and conventional spectrometers are very slow, or they only use a single frequency.
Their solution is to use a Josephson junction, which is a small gap between two pieces of superconductor. The relationship between the voltage across the junction and the current flowing through it changes when you apply GHz and THz frequencies. So they have been able to shine a variety of different frequencies onto a suspicious liquid and the focus the reflections onto the Josephson junction and work out what frequencies were reflected.
At the moment they have only distinguished 5-6 liquids including water and a variety of alcohols, ketones and water but there is no reason it shouldn't work for more, and they can take a spectrum in a second or so which getting towards a practical speed for testing baggage.
References | |||||
| - 2009 Supercond. Sci. Technol. 22 114005 | |||||
1st Nov 2009
Bad news for dinosaur fans
A paper in this week's edition of PloS One is disappointing news for small boys and palaeontologists, or anyone who's a dinosaur fan. According to a study by Mark Goodwin and Jack Horner, it appears that we may have significantly over-inflated the number of different dinosaur species.
Goodwin and Horner have been looking at dome-headed dinosaurs from North America, known as pachycephalosaurs – they have heads like bowling balls. They've been collecting fossils in Hell Creek, Montana for 11 years, doing a detailed analysis of different species of dinosaur fossils, using techniques like CT scanning and analysis of bone structure.
Horner and Goodwin compared fossils of pachycephalosaurus with another domeheaded dinosaur found in Montana, and a dragon-like skull unearthed in South Dakota, named Dracorex hogwartsia – yes, after Harry Potter's school.
The scientists think that rather than being three different species, the dinosaurs are all actually from the same species, but are just at different stages of sexual maturity. They confirmed their findings by looking at another 17 dino skulls from North America.
This suggests we need to have a drastic rethink about what actually constitutes a dinosaur species. It seems that much of the confusion has crept in because juvenile dinosaurs can look quite different from grownups of the same species, due to the development of head ornaments like horns, domes and spikes. But scientists may have confused these superficial features with more important underlying similarities between fossils, missing the fact that they are actually the same species.
Horner and Goodwin reckon that up to a third of all named dinosaur species may actually never have existed, and may just be juvenile forms of another species. Other scientists have also suggested this, as a species called Torosaurus was recently dismissed as being a juvenile version of another species, while a number of duck-billed dinosaurs and the fantastically named Nanotyrannus – thought to be a mini T rex – may not be separate species.
So sadly for dino-fans, some of those wonderful names may have to be consigned to the taxonomic dustbin.
References | |||||
| - Horner JR, Goodwin MB (2009) Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus. PLoS ONE 4(10): e7626. doi:10.1371/journal.pone.0007626 | |||||
1st Nov 2009
Scientists turn stem cells into germ cells
With a discovery that will help to shed light on the grey area of human reproductive biology, scientists in America have developed a technique to convert stem cells into germ cells - the precursors of sperms and eggs.
The process through which humans produce these gametes, which contain only half the amount of DNA found in a normal cell, is poorly understood and cannot be faithfully reproduced in animals, making it very difficult to study. This means that for patients suffering from infertility, research has progressed very slowly in this area.
But now, writing in Nature, Stanford University scientist Renee Reijo Pera and her colleagues have found a way to make germ cells in the dish. The researchers began by incubating human embryonic (ES) stem cells with various growth factors known to encourage them to specialise into reproductive-type cells. They then picked out those cells - about 5% of the total - that had begun to express certain chemical markers associated with germ cells.
The team then confirmed that the resulting cells were doing something else very germ-cell-like - demethylating their DNA. This is where chemical markers called methyl groups that are added to DNA to control gene expression are stripped off to "reset" the DNA to the state seen in sperm and eggs.
Next, to find out what was controlling the process of germ cell production the team repeated the earlier steps but blocked the actions, individually and together, of three different genes called DAZ, DAZL and BOULE, which had previously been linked to the formation of germ cells. These, they found, are critical for stimulating unspecialised stem cells to turn into germ cells.
Even better, when the team used a genetic technique to boost the levels of these genes in the stem cells, they found that they could increase significantly the number of germ cells produced. And when the team examined the DNA contained within the resulting cells they found that a proportion of them contained only half the normal amount of genetic material, just as in mature sperm and eggs.
This means that this new technique can provide scientists with a powerful tool with which to study the previously inpenetrable process of human gamete formation, as well as to test the impact of factors like pollution, toxins or infections, thereby shedding light on some of the factors that underlie infertility.
1st Nov 2009
The most distant object ever discovered
Professor Nial Tanvir, University of LeicesterChris - Now also in the news this week, two international teams of astronomers have described what we can only describe as the most distant object ever discovered. What they've seen is the gamma ray burst of the star that died when the universe was just 640 million years old. That’s less than 5% of its present age. The universe would’ve been only about 9% of its present size and that means the light from that star has been going across space, coming towards us for over 13 billion years. And one of the people who manage to see was Professor Nial Tanvir who’s at the University of Leicester and is with us now. Hello, Nial.
Nial - Yes, good evening.
Chris - Welcome to the Naked Scientists. So, tell us first of all, how did you make this observation?
Nial - So, these gamma ray bursts are actually quite tricky to observe because their
main characteristic is a short flash of gamma rays and of course, the gamma rays don't penetrate the earth’s atmosphere. So, we have to observe them initially with satellites and the current sort of work-horse satellite doing this stuff is one called Swift and that’s the satellite that the UK is partially – built part of the satellite so has an interest in. So, Swift finds about, on average, two gamma ray bursts every week and it reports the positions on the sky of these events down to the ground within a matter of seconds or minutes so that observers on the ground like myself can make follow up observations using a variety of different large ground-based telescopes. And it’s by analyzing the information that we get from those ground-based telescopes that we ascertain things like the distance and in this case of course found that it was a record breaker.
Chris - What actually causes the gamma ray bursts in the first place?
Nial - That’s a good question. It’s something that is still enshrouded in a certain amount of mystery, but we think actually, there are a number of different kinds of objects in the universe that can give rise to these sorts of flashes gamma rays. But in particular, the one that seems to be most frequently are seen are related to the collapse of a very massive star. So, we have a star that’s maybe 20, 30, 40 times the mass of the sun. At the end of its life, ceases to create energy in its core and no longer supports nuclear reactions. And so, the star just collapses on the under gravity there’s no pressure, radiation pressure to keep it up. Now, that’s a reasonably common and fairly well understood process but it seems that in certain rate situations, instead of just producing a normal supernova which is what we would expect normally to happen, such a star can also produce an extremely energetic and highly relativistic jet of material that pierces its way after the star. And if you happen to be sort of lying and looking along the line of site, down the barrel of this jet as it were then you see this phenomenon of the gamma ray burst.
Chris - Why is it that we’ve not seen one that’s this old before? Because presumably, the universe has had stars forming and ploughing themselves to pieces and producing gamma ray burst like these for a long time.
Nial - Yeah. The problem really boils down to just rarity. It seems that it’s only very exceptional stars that explode in this way. And therefore, even in the whole universe, as I say, Swift sees a good chunk of the universe in a sense as it scan off the sky every day, and yet, it still only detects in the whole universe a couple a week. So really, it just boils down to the fact that we needed to wait a long time until we were lucky enough to spot one at this sort of distance. If we carry on observing, we may getting more sensitive satellites and scan even more of the sky then the hope is in the future that we’ll find more at this sort of age.
Chris - What can you learn from the fact or what can you infer from the fact that there was a star burning 600 million years after the Big Bang when the universe was created? What’s written into that gamma ray burst in terms of the signature and the chemistry that can inform you of the structure of the early universe around that time?
Nial - Right, okay. Well, I should say that in this particular instance, gamma ray burst and what – the initial flashes is very bright in the gamma rays, but then the object will then sort of track through the ground-based telescopes is a sort of fading ember. It’s what we called the afterglow of the burst. And in principle, the afterglow can give you a great deal of information about the local chemistry and the conditions at the time and in the vicinity of the burst. And so, that’s very important for example if we find that there is a lot or a certain amount of elements heavier than hydrogen and helium. So for instance, oxygen, carbon, iron, all the things that we’re familiar with. If we find that those are present at this time, we know those could’ve only been cooked in the senses of stars. And so, it gives a very important clue, not just to what’s happening there and then, but what must have happened at even earlier times to produce those heavier elements.
Chris - Are they there?
Nial - So that’s the principle. But on the other hand, the problem is that with the GRB afterglows, they come in a sort of great range of different brightness. And really, if we’re going to find that sort of information from a gamma ray burst afterglow, it needs to be a particularly bright afterglow and unfortunately, this one wasn’t a particularly bright one. I mean, it was fairly bright, but it wasn’t bright enough. I mean, we didn’t really – at the end of the day, manage. If we had been very lucky with the kind of data that we’d got, then it’s possible we would’ve done it. But with these things that they go from random times and so, you have to live with whatever telescopes can make the observations at that time and we’ve made the first observations in fact, using telescopes in Hawaii which we sort of triggered from the UK. But conditions weren’t great in Hawaii that night, so you see the problem. We obtained enough data to prove that we got this record breaker, but we unfortunately didn’t manage to get good enough data to sort of take it to the next step to do those sort of, you know, refined pieces of analysis.
Chris - I see. And just to finish off, Nial. Can you tell us? What does this tell us about the structure of the universe at that time, the fact that there was this big star burning at that time? How does this inform our understanding of the early universe?
Nial - Well, it tells us that there’s at least one star and of course, one who seems that there were more and we hope in the future, by building up statistics of these things, we’ll be able to really sort of measure the rates of star formation in the universe, even at those very early times. The other thing it does is it pinpoints the position on the sky presumably, it’s galaxy that hosted this stars. So, stars forming galaxies and we’d like to know, not only about the properties of stars at this time, but also the properties of galaxies. And so, the galaxy is going to be far, far fainter than the gamma ray burst because gamma ray bursts is stupendously bright and galaxies only have, you know, a few hundred million stars in them or something like that. So they're much fainter. But we can now know the position and knowing the distance, we can go away with all the other facilities that we have without disposal like the Hubble Space telescope, and look really hard for the host galaxy. And so, that’s certainly something that we haven’t yet achieved, but we hope to do next year is to really search very hard and see if we can find this host galaxy and therefore, for the first time, learn something about the properties of the galaxies which existed at this really early era.
November 2009
National Pathology Week
Suzy Lishman, Royal College of PathologistsKat - Now this week, there are events running all over the country as part of National Pathology Week. This is giving people a chance to look into the work and the lives of pathologists. And on the line now, we have Suzy Lishman from the Royal College of Pathologists to tell us more about this. So hello Suzy.
Suzy - Good evening.
Kat - Thanks for coming on the show. Now, do tell us to start with, what on earth do pathologists do? I have this vision that they're all in the lab wearing coats, cutting up dead people. What do pathologists do?
Suzy - Well, you're quite right there. Research has shown that most people get their information about pathology from the television, watching things like CSI and Silent Witness. And I'm afraid it’s just not really like that. There are over 6,000 pathologists and 20,000 scientists working in 18 different pathology specialities. And less that 1% of those people actually work in forensics, the bit you tend to see on TV. So, there’s no typical day for a pathologist because they all do completely different things. For example, I'm a histopathologist, a member of the largest specialty and I study disease by examining tissue with the naked eye and under the microscope, and that might be a biopsy, a small piece of tissue that’s removed during an operation, anything up to a whole organ like a breast or a kidney or a limb. So, I’m then involved in a team, deciding the best treatment to offer the patient according to what I can see when I have a look at that tissue. But then, other big specialties include haematology, the study of diseases of the blood and the bone marrow, medical microbiology, looking at the diagnosis, management and control of all sorts of infections, clinical biochemistry, the diagnosis and treatment of disease through analysis of body fluids like blood and urine.
Kat - So, you're pretty much covering the whole gamut of biology and medicine there with pathology?
Suzy - That’s right. In fact, over 70% of all diagnoses in the NHS involve pathology in some way and over 700 million tests are done every year in the U.K. That’s an average of over 14 for every man, woman and child in the country.
Kat - Impressive stuff. So, tell us about National Pathology Week. What sort of stuff are you focusing on this year? It’s the second year, isn’t it?
Suzy - Yes. Last year we just had a general year when we said, “Pathologists and scientists, get out there and promote what you’re doing.” We thought to give it a slightly different angle this year. We’ve chosen the theme of the heart and out strapline is Pathology, the heart of modern health care. So we’re focusing on the diagnosis and treatment of all different types of heart disease by members of all the different pathology specialities.
Kat - So what sort of things do pathologists find out about heart disease? What sort of things would you be looking at if someone comes to you with heart problems?
Suzy - Well, pathologists are involved in even preventing heart disease developing in the first place which is a very important role so, for example, diagnosing and treating diseases like diabetes, keeping the blood sugar under control, checking people’s cholesterol level to making sure that that doesn’t build up because cholesterol is a risk factor for developing heart disease. And also, genetics, geneticists are also pathologists and they can look at inherited diseases and enable people to be treated for heart disease before they even know they’ve got it.
Kat - Fantastic stuff - so tell us about some of the heart-based events that you’ve got going on.
Suzy - We’ve got an Awareness Day at the Royal College on Monday. It’s called Think Heart: Save the Baby’s Life. And what we’re trying to do is raise awareness of some of the heart pathology that can present in the first week of a baby’s life so that parents, midwives, and GPs can be aware of what to look out for because a lot of these disorders, although very serious, can be cured if they’re picked up quickly enough. There are also events around risk factors. People have the opportunity to learn about some of the risk factors for heart disease like, high cholesterol, which I’ve mentioned, high blood pressure, poor diet, and do some interactive events to try and find out what various factors are.
Kat - And I understand you’re also having a heart – the anatomy of a heart attack. Looking at heart attacks.
Suzy - I’m particularly looking forward to this one. It’s at the Royal Institution and I grew up watching their Christmas lectures so it’s going to be real treat to organize an event in there. Yes, we’re going to have a virtual autopsy, with a model who’s going to play the body and we have a pathologist Ali Winstanley who’s going to come in and talk us through on autopsy and what we would do to look – what we would look for in somebody who has died of a suspected heart attack. Ali’s then going to dissect a pig’s heart, for obvious reasons we can’t dissect a human one, just to show a bit of the anatomy on what it is pathologists would look for at an autopsy. And then we’ve got illustrations of what the diseased heart would look like so you can see the damage that is done.
Kat - That sounds absolutely fascinating. How can people find out about all these events and where to go?
Suzy - We have a website www.nationalpathologyweek.org and that has a full program. We have now over 420 events taking place around the country, in schools, hospitals, shopping centres, libraries—absolutely everywhere. So, do have a look. They’re arranged by regions so there should be something near you.
References | |||||
| - National pathology week | |||||
November 2009
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Why don't electrons stick to protons if there’s electrons whizzing around the outside of an atom and the protons are the positive bit in the middle? Why don't the two just collapse in on each other? Sarah Rogers |
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Okay. In a very simple sense, they do stick to protons as much as they can. They're attracted to protons and so, they form atoms. So an atom is essentially an electron stuck to proton. What you really ask is why don't they get any close than they do? It’s all basically to do with the fact that electrons – in fact, everything- has wave properties. And the electron’s wavelengths are about a similar sort of size of atom and that’s the reason why atoms are that sort of size over the order of the wavelength in electron. And so, you can't really compress a wave any smaller than one or few wavelengths. And so, the electron can’t get any smaller than that without actually changing its properties entirely. So, it can't actually get any closer to the proton in the centre of the nucleus than it does and so, it’s stuck as close as it can. You can cause – if at very high pressures-, you can cause electrons essentially to react with protons and turn into neutrons and this is what happens in neutron stars. A neutron actually isn’t stable just lying around, in the atmosphere or in a vacuum. It decays in about 14 minutes into an electron and proton sort of forms into a hydrogen atom. |
November 2009 |
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Sarah Raphaella Rodgers asked the Naked Scientists: I'm a 16 year old Chemistry student. My Chemistry class has been focusing on the periodic table recently. I know that protons are positively charged, neutrons are neutral, electrons are negatively charged and that atoms are mostly empty space. I also know for magnets opposites attract. So why don't electrons stick to protons instead of flying around the nucleus? Magnets do it, so why can't atoms? What do you think? - Sarah Raphaella Rodgers - 26th Oct 09
It has to do with the uncertainty principle. Because the electron cannot have a defined position in the nuclei of atoms means that it must occupy every other space within the atom in a wave of possibilities. If the electron was positioned with great certainty within the nuclei of atoms, their momenta becomes infinitely uncertaint. But instead, they seem to have energy-orbits inside of atoms which determine the chemical struture of the universe. Another interesting thing to note is that electrons could not be in the center of atoms, because if they where, matter would drastically sink in size. We already know of nature objects which undergo this process, and they go by the name of neutron stars. In classical mechanics, electrons couple so strongly with protons that they should collapse all the time; and would in classical physics mean that every nucleus of every atom would gobble up the electrons in about 100 microseconds. - Mr. Scientist - 26th Oct 09
When I was 16 people like Einstein and Schrodinger were reassuring us that we need not worry; the Copenhagen interpretation and Quantum Theory were too weird to make any real difference. Now we are a half century into Physics becoming Quantum theory to the exclusion of reality even. Causality was abandoned because Quantum theory can't survive if we insist upon it. There is a cause for quantum phenomena just as there is a cause for uncertainty. Philosopher David Hume trashed causality with his view that no matter the times we observe an event and its precursor we can never be certain that such an event will follow a future precursor of the same nature. Philosopher Emanual Kant insisted that there is a cause for every event, however; it is just that we may never know that cause with certainty. Edit: The cause of all quantum phenomena is that the electric and magnetic amplitude that space can support is a finite value; all photons peak at this value. Max Planck observed this. But because we did not demand causality, we imagined the Quantum nature of the universe without even considering its cause. Uncertainty has been boiled down to the statement that it is impossible to know both the position and the momentum of anything absolutely. The more you know about the position of something, the less you can know about its momentum. Books have been written about the implications of this. The link describes the cause of uncertainty. The quote below is the meat of it. Edit: I should point out that the causes mentioned are my speculation; you won't find them in physics books. - Vern - 27th Oct 09
The present state of physical science does not allow "why" questions. Any answer will have to be speculative. I have an answer to the question that works well for me. There has never been found any substance of an electron that is smaller than its electromagnetic radius. This radius is much larger than a proton. So if observations are correct, and electrons only exist at their electromagnetic radius, they would consist of a hollow shell about 12 times larger than a proton. The electron would engulf the proton and form a dynamic dance with the proton's charges. This is speculative, but it explains the observations. - Vern - 27th Oct 09
I'm afraid not. It's actually a result of two physical phenomena. 1) Pauli exclusion principle This states that two fermions must be distinguishable i.e. you can always tell them apart. In practice, this means they must have at least one different quantum number. This restricts electrons into their shell structure. For example, consider hydrogen. The first shell (s- shell) has quantum numbers (1,1,1) and (1,1,-1). This is why two electrons, at most, can occupy the s- shell. These number combinations are easily derivable by solving the Schrodinger wave equation for hydrogen. 2) Entropy Processes in physics tend to increase the entropy of the universe. Energy likes to go from ordered states to disordered (like how a ball wants to roll down a slope). A proton and an electron is more energetically favourable than a neutron. The decay of neutrons this way is known as beta decay. In order to 'squash' together a proton and an electron into a neutron you need to supply a large amount of energy, as well as overcome the electron degeneracy force (as you're probably going to try it with a large collection of atoms rather than waiting millions of years for a single electron to pair up). This occurs inside neutron stars. - Homely Physicist - 1st Nov 09
Principles do not cause things; principles merely describe the happenings. We tend to think of principles and theories as causes; they can not be causes; their use is in describing the happenings. I'm just trying to keep folks honest.
- Vern - 1st Nov 09
I'm afraid not. It's actually a result of two physical phenomena. 1) Pauli exclusion principle This states that two fermions must be distinguishable i.e. you can always tell them apart. In practice, this means they must have at least one different quantum number. This restricts electrons into their shell structure. For example, consider hydrogen. The first shell (s- shell) has quantum numbers (1,1,1) and (1,1,-1). This is why two electrons, at most, can occupy the s- shell. These number combinations are easily derivable by solving the Schrodinger wave equation for hydrogen. 2) Entropy Processes in physics tend to increase the entropy of the universe. Energy likes to go from ordered states to disordered (like how a ball wants to roll down a slope). A proton and an electron is more energetically favourable than a neutron. The decay of neutrons this way is known as beta decay. In order to 'squash' together a proton and an electron into a neutron you need to supply a large amount of energy, as well as overcome the electron degeneracy force (as you're probably going to try it with a large collection of atoms rather than waiting millions of years for a single electron to pair up). This occurs inside neutron stars. I am sure Hawking himself said the Uncertainty Principle had something to do with it. Either way you're wrong, the pauli explusion principle has nothing to do with electrons falling into the nuclei of atoms. It's a process which eliminates one fermion energy level to another. This happens everywhere, not only inside an atom. And entropy also has nothing to do with it. - Mr. Scientist - 1st Nov 09
Just in case you would like an example of the exclusionary principle ordinary in nature, it even happens when two electrons come close to each other in space. It's closely related to the wave function, which is actually one main reason why the electron does not fall into the nuclei of atoms; specifically because they are not located to any particular region of space, which would induce a collapse of their superpositioned states. They are ''arranged'' within their superpositioning because of energy levels. But the exclusion principle is not the prime cause of either the wave function or the fundemental reason why particles do not fall into the nuclei of atoms.
- Mr. Scientist - 1st Nov 09
I knew i was right. I came across this convo on the net: If these particles are attracted to one another, shouldn't electrons be pulled into the nucleus? I gather the reasoning is because of the strong force? If thats the case i need to understand this "strong force" better.. Mizzuno This question is actually addressed in the Feynmann lectures, which are linked to in the physics napster thread in the General Physics forum. The answer is: What keeps the electrons from simply falling in? : If they were in the nucleus, we would know their position precisely, which would require them to have a very large, but uncertain, momentum, i.e., a very large kinetic energy. This would cause them to break away from the nucleus. They make a compromise: they leave themselves a little room for this uncertainty and then jiggle with a certain amount of minimum motion in accordance with this rule. It wasn't really the answer I was expecting. I was previously under the impression that the uncertainty relations were only an expression of our own limitation as subjective observers of a subatomic event, but apparently they are actually an expression of a fundamental principle governing the behavior of small particles. If you're curious, the relation used here is: \Delta x \Delta \rho \geq \frac{h}{2\pi} Where x = the position of the particle, \rho = the momentum of the particle, and h = Planck's constant - Mr. Scientist - 1st Nov 09
If you like to think that Quantum theory represents reality you have to invent excuses. Quarks can not exist outside nuclei, for example. Electrons dance to the uncertainty tune, etc. To me it is much easier just to accept reality as it presents itself.
- Vern - 1st Nov 09
But it seems that we hve experimental evidence for these conclusions. If anything, i think reality has shaped physics for the larger part, not so much intentionally the other the way.
- Mr. Scientist - 1st Nov 09
But we really don't. I started looking for experimental evidence for wave function collapse years ago. I'm still looking. None found. We have a habit of reporting our conclusions as experimental results. Sometimes it is hard to find the actual results that led the experimenters to their reported conclusions. In every case where I have searched out the actual experiment the evidence was not there. The POS thought experiment Einstein and company proposed is still valid. - Vern - 1st Nov 09
We can measure decoherence, which is the gradual collapse of the wave function in wave-states of matter. We may not be able to directly observe the transformation because in doing so we disturb the p-field ''probability-field''. But, we know the collapse must occur as an actual transition from having matter acts as waves and then suddenly not.
- Mr. Scientist - 1st Nov 09
But this is what we don't know; this is the idea in contention. Does the observed state happen at the time of observation as in wave function collapse, or does the observed state happen at the time of creation of the particles, as in the POS experiment? - Vern - 1st Nov 09
But there is very little else that can happen. Given the intantaneous change from wave to particle-nature means that there is little room other than to say there is a sudden collapse. All models have agreed with observation.
- Mr. Scientist - 1st Nov 09
We don't know that there is an instantaneous transition from wave to particle. We know that there is an instantaneous transition of a previously unknown state to a known state at the time of observation. We have not yet figured out how to know the state of the previously unknown state. In the simple case of a photon striking a target, my speculative model has changing fields driving two points of maxima of the fields. Interaction always occurs very close to the points of maxima; the fields determine the trajectory. Edit: Bolded text was edited for clarification. - Vern - 1st Nov 09
Though, we have what we need to know about this state, and that is it acts in every way like a particle when its not being observed.
- Mr. Scientist - 1st Nov 09
I can't argue with the success of Quantum theory. It is the only theory I know that demands a change in reality when reality does not agree with it.
- Vern - 1st Nov 09
I meant a wave by the way in the passage above - oops.
- Mr. Scientist - 1st Nov 09
I don't mean to be contrary. I just need to explore every possibility that might offer experimental evidence that my vision of a photon is not reality. As far as I can determine the double slit experiment supports the vision. If I did not have the photon defined so that it must produce the observed results by cause and effect, I might fantasize some magical wave-particle duality. The anatomy of a photon: A photon consists of two half cycles of electric and magnetic fields that drive points of maxima through space. The fields exist in a spatial area around the points. The changing amplitude of the fields drive the points and determine their path through space. Photon interaction happens at the points of maxima. So any observation will see the points. Edit: It is not my definition; it is Maxwell's definition. What perplexes me is that folks don't seem to understand that. Is it that I just can't put the right words together? Here's a schematic of the vision. It looks just like those that were in the text books when I studied electronics and nuclear instrumentation back in the 50's. - Vern - 2nd Nov 09
I wouldn't be as bold as to suggest you cannot explain physics, if indeed it is the correct description of a photon. Physics is not easy to explain, whether it being a pet-theory or not.
- Mr. Scientist - 2nd Nov 09
I have to keep reminding myself what my goal is here in this forum. It is not to point out weaknesses in Quantum theory, and it is not to promote my pet concepts. It is simply to remind folks when common misconceptions are promoted. In this case it was the misconception that there is experimental evidence that quantum states occur at observation time.
- Vern - 2nd Nov 09
Fair do's.
- Mr. Scientist - 3rd Nov 09
It would really be interesting if there was experimental evidence; maybe a last instant change in one of the states that is reflected in the other. I know that has been tried. All the attempts I know about failed.
- Vern - 3rd Nov 09
Vern - You wrote: "There is a cause for quantum phenomena just as there is a cause for uncertainty." I agree. SOMETHING caused an individual Uranium atom to decay. We just do not know what the hell it is. Perhaps it is a simply some sort of harmonic in the electron field that works a bit like "The Buterfly" effect. Personally, I have become increasingly convinced our four dimensional world is entangled with one, or probably several other "Dimensions". In our universe NOTHING transits from point A to point B through an infinite number of points. I am unaware of ANY motion that does not pop in and out of our universe according to the various Plank Units. Perhaps our universe has time movement, but not particle movement. As time progresses paricles move in and out of a timeless 'holding' dimension producing an effect something like a motion picture. - litespeed - 3rd Nov 09
Vern I have a couple of observations concerning Quantum Mechanics that may or may not be relevant. First, the Drake Equation shows that entangled particles are not a local phenomena. That means that entangled particle A and entangled particle B do not change polarity symultaneously because they were both 'programed' at the time of separation. I see no possible way to explain this other then to accept some sort of extra dimensional involvement, that theoretically could communicate faster the the speed of light. I send a series of entangled particles in your direction, followed by a similar sequence of non entagle particles. You notice the diference, and work out some sort of Morse code with the senders. Almost instantaneously you have joined a universeal communications exchange. Of course the signal SENT to you travels at light speed. The subsequent communications is instantaneous. - litespeed - 3rd Nov 09
I think you're making a huge assumption here. I know of no experimental evidence that movement is quantized. - Vern - 3rd Nov 09
I have seen several attempts to show that this could happen. As far as I know they have all failed. I have never seen a proof for wave function collapse in the Copenhagen sense. - Vern - 3rd Nov 09
Vern, I agree it is a big leap. Howver, the Heisenberg Uncertanty priciple seems to support the notion. Further, I would like your discussion on Plank Units. IMHO, these seem to support a kind of granularity in our universe. For instance, there is a minimum distance between A and B that can not be subdevided. Similarly, Plank time seems to support a minimum unit of time that can not be subdevided. Of course my understanding of Plank Units is very likely flawed. However, I have actually seen explanations of the Big Bang that include things like Plank Zero is null, Plank Two is such and such proportion of the inflation etc etc. My basic point is that it seems to me nothing in our universe EVER moves. It simply moves in and out of time. Just me rambling.... - litespeed - 3rd Nov 09
I have not yet signed on to quantum units other than the quantum of light. That is because I have a speculative cause for How Come The Quantum that assigns the cause to a property of the photon. I guess when you dwell on a subject for a long time it kinda sets in your mind and makes it difficult to contemplate another scenario for the action in mind.
See the whole discussion | Make a comment- Vern - 3rd Nov 09
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Why do car wheels appear to move backwards when you view them under streetlights sometimes? Dan Bolton |
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Dan - I'm just wondering why car wheels sometimes appear to be going backwards when you view them under streetlights sometimes? Chris - I think I've seen it. As you're driving along, the car next to you is accelerating away and it looks like their wheels are going backwards in the streetlights, illuminating the wheels of the car. Dan - Yeah, that’s right. Chris - Yeah. It’s actually a stroboscopic effect. If you've been a fan of Westerns, if you were a big John Wayne fan and you used to watch those early Westerns where the cart would pull away from the scene and the wheels would initially go forwards and then appear to start going backwards. Did you see those? Dan - Yeah. I've seen that before. Chris - Yeah. It’s the same phenomenon. In the case of the cart, it’s because the camera is taking X number of frames. In other words, pictures every second. In the case of the car driving down the road to where next to you, it’s the streetlight flashing on and off about 120 times a second because mains electricity is 60 hertz. So the light goes on and off 60 times a second. So as a result, you're seeing 60 flashes or illuminations of the car wheel per second. Now if the car is accelerating, if you imagine the – say you drew a line on the car wheel, a chalk mark and you watched that go around, it would go around in a circle. But you only see it in the dark when it’s illuminated by the street light. Now say, the street light flashes on, you see the chalk mark pointing straight upwards, the light goes off and the wheel turns around a bit, agree? Dan - Yes. Chris - Light comes back on, the chalk mark is now in the new position, agree? Dan - Okay. Chris - Now as the car wheel speeds up the distance of the chalk mark makes it around the wheel will change according to how fast the car is going, yeah? Dan - Yup. Chris - There will therefore be a speed at which the wheel will go when it doesn’t look like it’s moving at all because the chalk mark is starting going all the way around and finishing before the light comes back on again. Dan - Okay. Chris - Once it speeds up a bit more, the chalk mark will go right the way around and then a bit further. So it will look like that it was going faster, faster and faster. Eventually, you’ll get to a speed where it’s actually going right around and back on itself again. So it looks like it’s actually going backwards a bit because it’s doing more than one complete revolution a bit more. So it looks like it’s going backwards and it’s because of acceleration. Once it reaches the constant speed, that effect would stop. But it’s stroboscope, that you're seeing flashes of light, illuminating the wheel and your eyes sees it, doesn’t see it for a fraction of a second and then sees it in the new position. And when the speed is right, it looks like it’s going backwards. |
November 2009 |
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Dan Holton asked the Naked Scientists: Hello Why do car wheels sometimes appear to move backwards when illuminated by street lights, even though the car is going forward? Dan Holton in Bristol, UK What do you think? - Dan Holton - 28th Oct 09
It's usually a stroboscopic effect called the wagonwheel effect, (nothing to do with the oversize biscuits ) However if it was a boy-racer, pimp-my-ride, type car it could actually be spinning hubcaps ... http://en.wikipedia.org/wiki/Spinner_%28wheel%29 - RD - 28th Oct 09
The streetlights are not emitting light continuously, but normally pulsed in 100Hz flashes (50Hz electricity countries) or 120Hz (60Hz countries).
See the whole discussion | Make a commentThen see this thread of a few months ago: http://www.thenakedscientists.com/forum/index.php?topic=20619 - techmind - 31st Oct 09
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It has been discussed on your show about genes being turned on and off through things like genetic engineering and I’ve got a picture in my mind a sort of a big double helix with old-fashioned light switches sticking out the sides of it, which I seriously doubt is correct. And I was just wondering what is actually meant by genes being turned on off? Catherine, Bromley |
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Catherine - I just got a quick question for clarification really. It has been discussed on your show about genes being turned on and off through things like genetic engineering and I’ve got a picture in my mind a sort of a big double helix with old-fashioned light switches sticking out the sides of it, which I seriously doubt is correct. And I was just wondering what is actually meant by genes being turned on off. Kat - That is a great question and actually, your mental image is a fairly good analogy for it. So, if you think about – imagine a long string of DNA. Catherine - Yes. Kat - Now, a bit of that will be the actual gene and genes are basically instructions that tell a cell to make a particular protein. So you have kind of the recipe bit. And then around that, you have sort of instruction bits. So, these are regions of DNA that attract proteins that come and sit on them and tell the gene to be on or off. So these are called transcription factors and they attract the kind of molecular machinery that actually churns through the instructions and tells a cell to make a particular protein. So, you have all these different proteins sitting on different bits of the DNA and some protein’s transcription factors tell a gene to be switched off and some transcription factors tell a gene to be switched on. So really, you do have these molecular switches. You also have another aspect of that ,and Chris mentioned this a little bit earlier on the show, is that you have kind of things called epigenetic switches as well. And these are things that are over and above what’s in the DNA. You get little molecular, almost like post-it notes or tags stuck to the DNA and stuck to the proteins that are wrapped around the DNA that have more information about when a gene should be used, for example during development. You know, you should turn on this gene for a bit while you're making hands and then turn it off again or should this gene be permanently switched off or permanently switched on. So really, there’s this whole array of little molecular switches that are telling the DNA to be on or off in a particular cell at a particular time. Catherine - Very clever, isn’t it? Kat - Yes, it is. Dave - Can't you also get bits of DNA which are folded up so the chemistry can't get at it. Kat - Yes. So, a lot of these sort of epigenetic factors. When a cell has decided that this gene should be permanently off, that gene gets all compressed up and squished up so that the molecular machines can't actually get to it. So we know that genes that are off are really compressed and wrapped up really tightly. Whereas genes that are very actively used are much more open so all the machines can get into there and read the genes. |
November 2009 |
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catherine wells asked the Naked Scientists:
Hi,
You often talk about genes being switched on and off. I have in my head a picture of a double helix with lots of old fashioned light switches sticking out of it - but seriously doubt this is correct. What actually happens when genes are switched on and off.
Many thanks,
Cath
What do you think?
- catherine wells - 14th Oct 09
hi cath.. u ask "What actually happens when genes are switched on and off." actually genes are turned of and on during the embryonic level to start or cease the specific funtion of that gene.gene of and on is related to its expression.U start to think like that in every cell there is complte information of each and every thing in the form of genome but some cell converted to eye cell,other into liver cell and so on...this all is controlled by the gene on and of.When some genes turned on in specfic cell,that cell will be concverted into its specfic kind...... hplfuly u got my point khurrum - khurrum - 18th Oct 09
Hi Cath Commonly, genes are controlled by chemicals called "transcription factors", which are proteins, usually phosphate-bearing proteins, which lock onto specific regions of the DNA and alter its shape or chemistry in such a way as to make an adjacent section of the DNA more or less accessible to the miniature machines (polymerase enzymes) that read the DNA code and turn it into gene products. Other modifications can also turn genes on and off including hormones - thyroxine from the thyroid gland binds directly to DNA to activate certain genes - whilst other enzymes can add or remove chemical groups (usually methyl or acetyl groups) from the proteins around which DNA is wound. This alters the shape of that section of the genetic code, making it more or less readable by the cell. Using these mechanisms cells can achieve both short and long-term control of gene expression in a highly dynamic way. Chris - chris - 18th Oct 09
Gene expression is controlled by regulatory factors. For example, to turn on Ras gene, it requires GTPase, meaning that GDP is phosphorylated to GTP, thus activating Ras pathway. It can be turned off by sensor molecules and other regulator factors.
- Jonathan Madriaga - 25th Nov 09
This is not right. The Ras protein is activated/deactivated by exchange factors GAP and GEF. However, the Ras gene itself is not directly turned on or off. One should make a distinction between the _gene_ and the _gene product_ (or protein), as it pertains to the question of OP. - kmiller755 - 30th Nov 09
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I've always been taught, an early age, that if meat has been frozen and thawed, you shouldn’t re-freeze it because of food poisoning. But why is this? Ian Mellor |
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Well the answer is that some bacteria don't actually get to be bad for you because they infect you. They actually put things into the food that are toxins and the toxins are not broken down by heat. So, the bacteria multiplying in the food leads to the accumulation of toxins in the food which will then make you ill even though the bacteria may be long gone by reheating the food. So if you keep cooling and warming the food, the food might spend enough time at a certain temperature which encourages the bacteria to grow and put toxins into the food whilst not themselves actually really posing much of a threat. That’s one way. Another way is that if you keep on warming up and cooling down food, some bacteria will just end up flourishing and they’ll go from being at very low level in the food, where they're not growing very fast because the temperature is low, to getting to a very high population in the food where that might be an infectious dose. So to catch Salmonella for example, you actually need to eat about a million organisms, 106 particles of Salmonella. That’s an infectious dose. Other bacteria infect you at much lower doses. So it really depends on what the pathogen is and what the way in which it makes you sick is – but the bottom line is, if food spends time at higher temperatures, there’s a higher chance that bacteria will grow and therefore, make you sick. So, the best advice is to either cook it and eat it, cool it and eat it, but don't keep reheating it because that could be bad. |
November 2009 |
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Ian Mellor asked the Naked Scientists:
A question for you:
We are always taught from an early age that if meat has been frozen and then thawed, we should not re-freeze, because of the danger of food poisoning.
But what is the scientific reason for this?
My understanding is that freezing slows down the replication of bacteria, so what goes wrong the 2nd time the meat is frozen?
Regards
Ian
What do you think?
- Ian Mellor - 29th Oct 09
I do not offer this as a scientific reason but while the meat is unfrozen, it picks up additional bacteria and they multiply to the point that, the second time it is thawed, it would be possibly very harmful. Joe L. Ogan
See the whole discussion | Make a comment- Joe L. Ogan - 22nd Nov 09
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In an article I read this week, they said that the coldest spot in our solar system was a crater on the south pole of the moon. The temperature’s about - 238 degrees. I realise this is close to absolute zero. But if absolute zero is the coldest temperature we can achieve, is there a limit to how hot you can make the temperature? Cee Jai Bernard, Canada |
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Temperature is basically a measure of how much energy each particle has got or each direction a particle moves in. And so, you can pretty much all the energy away from something and you can't take any more energy away, and so, there’s a minimum temperature as an absolute zero. But certainly, in any normal idea of physics, anything we know, definitely there’s no maximum amount of energy you can give particles. So there’s no maximum temperature. You can keep on giving more and more energy and the temperature will keep on going up. There could possibly be a maximum temperature. You might find a maximum energy, you can give things due to some bizarre bit of quantum mechanics, but as far as we know, we haven’t found this solid one yet. |
November 2009 |
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Cee Jai Bernard asked the Naked Scientists:
Hello,
My name is Cee Jai (CJ) I'm from Canada and I'm a big fan of your show. I do have a question though. In the news his week, I read an article that the coldest spot in our solar system has been found in a crater on the south pole of our moon with a temperature of minus 238 degrees Celsius.
I realize that that is very close to absolute zero, but why does this bother the scientists?
Also, absolute zero is the coldest temperature we can achieve, is there a limit to how hot it can get as in the highest temperature possible?
Thanks
CJ
What do you think?
- Cee Jai Bernard - 29th Sep 09
Theortically-speaking, there is no upper limit to tempearature.
- Mr. Scientist - 29th Sep 09
Absolute zero, or zero Kelvin, as it is otherwise known, is a theoretic temperature which, according to the laws of thermodynamics, cannot be attained.
- rhade - 29th Sep 09
Re the hottest temperature possible: there is the Planck Temperature, of 1.416785(71) × 1032 K, beyond which current physics theory breaks down. Then there is also the speed of light 'c' limit when considering temperature as the kinetic energy of atoms/molecules in a medium. - LeeE - 29th Sep 09
Could be misunderstood to mean that this is the highest temperature we can go. In all due respect, this is not what the theory states. - Mr. Scientist - 29th Sep 09
Well, I didn't say that the Planck temperature is the highest temperature that 'we can go', just that the Standard Model doesn't currently work above it. So basically, if you want to work with higher temperatures than the Planck Temperature you need to use a different model (atm). - LeeE - 30th Sep 09
Temperature = kinetic energy content.
See the whole discussion | Make a commentLightning = a whole lot of energy Electric energy of lightning dissipated as heat - Nizzle - 5th Nov 09
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Can vaccines can be given together? I know someone that just received four vaccines at once. Can they wear out the immune system and not produce as good a response? Steve Junk |
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Chris - The answer is both yes and no actually. When you give vaccines to people, what you're aiming to do is get the immune system to respond so that it can recognize that pathogen in the future and protect you either with antibodies or cells that kill viruses in cells. Now, one way of vaccinating people is what’s called Live Attenuated Vaccine. This is where you grow viruses in culture for many generations and through the effects of mutation, they lose the ability to make you ill, but they nonetheless remain infectious. So, with the MMR, Measles, Mumps and Rubella, for example, you put the virus into the person. It doesn’t cause severe disease, but what it does do is to display to the immune system the entire repertoire of viral genes, viral proteins. And what that does is it makes a very broad immune response, involving making both antibodies and cells that can attack virally infected cells. That way, your body is very powerfully primed to recognize and prevent you from getting that virus in the future. The problem is that when you go into that state of infection, what it does is to release large amounts of a signalling hormone called interferon, Alpha interferon in fact. And what that does is put all the cells in the body into this antiviral state where the cells are undergoing surveillance. They increase the surface markers, they displace the immune system so that they're more likely to get killed if they’ve got a virus in them, they degrade genetic material that they think might be viral, and they become much harder to infect for viruses. Now that means if you've had one virus, that’s attenuated vaccine, about a week or two before, your body makes load of this interferon. If you then come along and then try and infect yourself with another attenuated virus, for instance another vaccine, it won't work very well because it doesn’t get into the cells, and the body kills it really quick before it has a chance to prime your immune system. So live vaccines, if you don't have them at the same time, but you have them all together is a bad thing to do. Having them all together is fine because the immune system works by discriminating very powerfully between different epitopes that different viruses display anyway. So that’s not a problem. For the present situation we’re in now though, people are asking me, “What about flu vaccines?” Because lots of people had a seasonal flu vaccine but then they're also saying, “Well now, we need to have a swine flu vaccine. Will the fact that I had the seasonal vaccine about two weeks ago make a difference for me having the swine flu vaccine now?” And the answer is not in that circumstance. No, because the flu vaccine is a killed vaccine. You're just putting in bits of dead virus, shrapnel if you like which the immune system then learns to recognize. This doesn’t trigger the same interferon response so it doesn’t make you feel ghastly in the same way. It doesn’t actually prevent you getting infected with other viruses in the same way. Dave - Is this interferon response, the reason why I still feel really quite shattered now, two weeks after I had the flu? Chris - Yeah and the reason that flu makes you feel so rotten, despite the fact that the virus is only confined to your respiratory tract, nose and throat, and sometimes lungs if you get a very severe infection, you probably had symptoms that were nonetheless across your whole body. Muscle aches and pains, tiredness, very bad headache, temperatures, just feeling ghastly. That’s because of these hormones, the interferons that the body produces in response to the infection which then turn all of your cells into this very antiviral prime state. So, exactly right, yeah and that’s why after some vaccines that do provoke lots of interferons to be released, you have a day of feeling a bit rotten. It’s not because you’re infected, although you might be. It’s actually the interferons – it’s your body’s own hormones that are making you feel like that. |
November 2009 |
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Steve Junk asked the Naked Scientists:
Hi Dr. Chris,
I listen to your podcast on my long commute. My question is, How many vaccines may be given to a patient at one time? Are there certain combinations that may be particularly problematic?
Someone I know just received four vaccine injections in one office visit. All is well, but it "begs the question". Can the immune system become "preoccupied" or otherwise degraded as a result of work it is doing "computing" or manufacturing an antibody for one pathogen, such that countermeasures against a second, third or fourth pathogen may produce ineffective antibodies or even decremental effects?
Does the name cold sores imply this effect? Having the HLA-b27 gene, and having gone through a bout with reactive arthritis triggered by C. jejuni, I know our immune system can be a powerful adversary as well as an essential guardian. Can the immune system be overwhelmed by the diversity and numbers of pathogens - has a limit been identified?
P.S. What's Dr. Karl really like?
Steve
Irvine California
What do you think?
- Steve Junk - 2nd Oct 09
Hi Steve The evidence is that the body can respond to more than one vaccine at once but they should be given simultaneously and not when a person is already suffering from another infection. This is because when the immune system responds to a foreign agent, including an infection or a vaccine, it produces signalling hormones called interferons. This place cells all around the body into an antiviral state whereby they degrade genetic signals that appear to be foreign and also upregulate cell surface markers that indicate viral infection. Therefore, if you administer a new vaccine once cells have already been primed in this way, the vaccine - particularly if it's a live vaccine like MMR, chickenpox, yellow fever - might struggle to gain a toe-hold and therefore the amount of immunity it triggers will be reduced. Chris P.S. Dr Karl is a great guy, incredibly clever and an inspiration to us all. I've never met anyone who can write so well and so prolifically - he's published over 27 books now - and I strive to be as good as he is! C - chris - 3rd Oct 09
The body can respond to several vaccines at once; of course it can. The body doesn't know that the vaccine is "medical" it just treats it as a potential threat. If it couldn't cope with a handfull of vaccines at once how could it cope with thousands of different bacteria at once? Since it does that every day... - Bored chemist - 3rd Oct 09
One thing I should probably add is that the interferon-induced state resulting from exposure to a viral infection or a live vaccine will have an impact on the administration of another live vaccine while this is taking place.
See the whole discussion | Make a commentBut exposure to killed vaccines - which are effectively just bits of protein - are less likely to be compromised in this way and may safely be given in a staggered fashion. This very question has surfaced a bit lately with people who have recently received a seasonal flu vaccination and are now being offered a swine flu vaccination a week or two later. There's no problem with this pattern of administration. Chris - chris - 5th Nov 09
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Is the Earth getting heavier owing to plant photosynthesis converting energy into mass. And if so, does this affect the Earth’s spin? Sam, Hitchin |
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We have actually looked at this in the past and the answer is actually, yes. Because E=mc2, Einstein’s famous equation, (E) energy equals (m) mass, times (c), the speed of light squared. So, if you increase the energy in the system then the mass must also increase. The Sun is adding energy to the Earth’s system in the form of chemical energy; this arrives as light and is converted into chemical energy by photosynthesis. Therefore, the Earth is gaining a little bit of weight in the form of the entrapment of that energy within plant chemistry. But, compared with the 40,000 tons of dust and material that rains in on Earth from space every year, it’s quite literally a drop in the ocean. So, on the whole, the Earth is gaining a bit of weight as plants in the biosphere capture energy coming from the Sun. |
November 2009 |
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If I have a torch and I put three batteries in it and two are fully charged and one is fully drained, will the torch still produce light? Jesse, USA |
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I think that very much depends on the chemistry of your batteries. A battery is essentially a chemical reaction which is split into two halves and the only way – and let’s say you got part half A and half B, the whole lot’s got to happen to be driven in any way that can happen is quite passing electron through your circuit. And eventually, the battery runs out because you run out of all the chemicals you need for the chemical reaction. Now, basically you're saying, if we apply a large voltage and carry on pushing electrons through the battery, what’s going to happen? That would depend on what other the chemical reactions go on to move charge through the electrolyte in the battery. Normally, that’s often quite inefficient. If you’ve got have something like a lead acid battery which is symmetrical, it will just start up in the wrong direction. Certainly a very simple that acid battery will – and so, it will turn into battery but pointing the wrong direction. If you have other chemistries of batteries, it could cause all sorts of havoc and it will depend on the exact chemistry. It will certainly become a very high resistance. It will work for a bit but eventually, it’s going to run out of – it will either stop or it could do all sorts of strange things to your battery, it’s certainly going to damage a rechargeable battery. |
November 2009 |
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Jesse asked the Naked Scientists:
Dear Naked Scientists,
I have a question. If I have, say, a torch, and I put three batteries in it, two fully charged and one drained, will the torch still produce light?
Thanks,
Jesse
Ithaca, NY, USA
What do you think?
- Jesse - 2nd Nov 09
With a traditional torch it is common to connect batteries in series. Putting a run-down battery in the torch will prevent you getting a bright output. This is because the net voltage output will be lower (the total voltage output is the sum of the battery voltages) so the current, produced from this voltage across the light bulb's impedance, will be lower. Also run-down batteries start to have a higher internal impedance than when charged so this also reduces the net current and will also waste power from the good batteries. In some electrical items (and some more modern torches) the batteries may be in parallel. Here it is also important not to put in a run down battery with good batteries. In this case the good batteries will try to charge the run down one. This again wastes power and will reduce the available current to power the light. It can also be hazardous because there can be a lot of heat generated. The actual behaviour will also depend on the type of batteries used, but it is fair to say that it is generally not a good idea to mix run-down batteries with good ones. - graham.d - 2nd Nov 09
Wow! That's a new one. No isolating diodes or anything? Sounds like a scheme invented by battery manufacturers to make us buy more batteries! - Geezer - 2nd Nov 09
Wow! That's a new one. No isolating diodes or anything? Sounds like a scheme invented by battery manufacturers to make us buy more batteries! Some of the high power LED torches have them in parallel. The combined voltage would be the same as a single cell but the current drain would be shared between the cells so they would last longer. - that mad man - 2nd Nov 09
That's OK as long as all the batteries have exactly the same potential, but if they don't (as Graham.D points out) the cell with the greatest potential (voltage) will try to "charge" the cell with the lower potential. As a result, the energy in the cell with the higher potential will be dissipated without doing any useful work. At least, that's what theory says. Perhaps the effect is minimal with modern alkaline batteries. - Geezer - 4th Nov 09
You will find that equipment manufacturers will say in the instructions (I never read them either) that you should never mix batteries of different types or mix old and new batteries.
See the whole discussion | Make a comment- graham.d - 4th Nov 09
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Does a supernova, in other words, the death of a star clear out a planetary system completely of everything that used to orbit the star? Sharon Wade |
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The answer is yes. It’s the death of the star. The star’s gravity is what holds things in orbit around it and if the star blows itself to pieces, then it will completely decimate the material which is in that system and that would destroy unfortunately any planets. Eventually, our sun will blow up like a red giant. The one that should go supernova, I think it’s a bit too small but it will cook us but it won't blow apart. But there are stars which do blow themselves to pieces and they could take things with them. |
November 2009 |
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Why is it that the sun warms us up on Earth while it remains cold above us despite the fact that above us is really closer to the sun and at some point closer to the sun it’s probably really hot so at what point does it become freezing cold? Aaron Hurwitz |
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Chris - If you have a gas, which is, say, in an aerosol, says the contain you’re going to spray into your armpit with your deodorant, there’s a gas under pressure in there. When you spray it in your armpit, it feels very, very cold. What’s happened? Well the gas has expanded. I thought about simply if you imagine there’s some kind of piston, inside the aerosol can, when the gas expanded it effectively pushed on the piston, it’s done some work, let’s say. If something has does some work, it must have less energy, after it’s done the work than before it did the work. Since temperature is proportional to the energy in the particles, if somebody’s got less energy, is therefore going to lower the temperature so the temperature must fall and that’s why we think that when a gas expands, the temperature goes down. Dave - OK. And now this is actually very related to why mountains are cold. Okay. The temperature of things on Earth is sort of balance between the amount of heat which is getting either from the sun or from heat moving around the world and the amount of heat it can lose by radiating into space or radiating anything at room temperature, radiating heat and infrared really quite well. And so, basically the only things which can absorb sunlight very well tend to be at the ground. The atmosphere is transparent so the heat is going into the ground and heating it up and then that heats up the air above it. And now, the tops of mountains are very, very small. So basically, what’s the temperature of the atmosphere at 30,000 feet? 10,000 meters, or 9,000 meters? And the reason why that’s very cold is because if you have pockets of air which is being warmed up on the surface of the Earth and then it lifts up by convection, it’s moved upwards, the pressure drops about half the pressure it was before, which means that gas expands and as gases expand, they get cold so the air gets very, very cold. So, the air around the mountain is very, very cold and also anything which is pointy like a mountain has got lots – can emit infrared light in lots more directions and the flat thing has got more surface area compared to mountain sunlight which hits it. So it cools down better during the night and emits light into the space very much better so it tends to be very cold. |
November 2009 |
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Aaron Hurwitz asked the Naked Scientists:
Hi Dr. Chris and crew,
Love your show.
Why is it that the sun warms us on Earth while it remains cold above us, despite 'above us' being closer to the sun? I assume that right around the sun it is indeed hot. At what point does it become freezing cold?
Also, was Mt. Everest always the world's tallest mountain? Is it still growing? If yes, by how much every year? Is it's growth rate been steady over thousands of years?
Thanks,
Aaron Hurwitz
Jerusalem, Israel
What do you think?
- Aaron Hurwitz - 30th Oct 09
By 'above us' I assume you mean in the space between Earth and the Sun, ie outside our atmosphere, in which case, the reason is because there is nothing to heat outside our atmosphere. In answer to your second question, no, Everest has not always been our tallest mountain. In fact it isn't our tallest mountain now. There are sub oceanic mountains taller. Everest is our highest mountain though and yes, it is getting higher. The rate of growth will change from day to day, week to week, year to year etc. One day it will begin to erode faster than it is being pushed up, if it indeed continues to be pushed up. Perhaps in a few million years it will be no bigger than an ant hill. That's the day I'd climb Everest and not before. - Don_1 - 30th Oct 09
The earths atmosphere traps the heat.
- latebind - 30th Oct 09
We are a cloud of mass, in a void of space just within a remarkably unique distance from an irradiating body. Radiation is by definition, massless, as so are the least of the particles predicted by the standard model. Energy, according to the translation of quantum mechanics, is when particles reach high velocity in quite a large collection. The result is simply that the material they compilate begins to get hotter. If something gets really hot where molecules move at high speeds relative to the other ''brother'' particles which make an object, it may glow due to a certain heat density. We find that atoms can ''vibrate'' when thermal energy is received from an outside source - in effect, the system becomes more operative towards thermal decay in the form of electromagnetic radiation. Since radiation has a frequency and a wavelength means it can quantum mechanically-couple to ordinary mass (the kind of mass that makes the earth like a ball of gas. In fact we are not unique in this sense, because many of the planets in our solar system are giant gas balls which are more efficient at trapping photon energy, than let's say our thin breathing air. As you progressively reach spacetime from airspace, the atmosphere literally becomes less compactified by radiation (heat). Since the air pressure decreases as you move higher up means that the air that is rising is in fact expanding. It is said that temperature of the scale of three degrees fahrenheit is accounted for every ascent or decent within airspace. - Mr. Scientist - 31st Oct 09
What? So low velocity particles in a small collection don't have energy then? Every ascent or decent of how far? Try to remember the motto of The Naked Scientists is "stripping down science", which means trying to present scientific information in a way that can be easily digested. The question asked needs no answer that involves quantum mechanics. Your post was hard enough for me to decipher, and I like to think i'm rather scientifically literate. - Madidus_Scientia - 31st Oct 09
All due respect, but if it is not allowed a quantum physical description (which isn't hard to involve when talking about subjects like radiation, then it shouldn't be in the quantum physics and cosmology section. It should be in general sciences, if anyone protests.
- Mr. Scientist - 31st Oct 09
quote author=Mr. Scientist link=topic=26446.msg281315#msg281315 date=1256988543] if it is not allowed a quantum physical description (which isn't hard to involve when talking about subjects like radiation, then it shouldn't be in the quantum physics and cosmology section. It isn't. - Bored chemist - 31st Oct 09
It's really nice answer to the question but very tricky or confusing though.
See the whole discussion | Make a comment- Mr.american scientist - 26th Dec 09
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Why are valleys colder than areas that are higher up? Aaron Hurwitz |
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Okay. There’s a secondary effect. The world is far more complicated than you’d like to think. That tends to be because cold air falls. So, the valleys at low places on average are warmer. But if you got somewhere which is high up and the air can cool down on the tops of mountains, it’s then denser around it and it falls downwards and if it’s not falling very far it doesn’t compress very much, doesn’t get very much hotter so you get, locally very cold air is in bottoms of valleys but globally it’s warmer low down and colder higher. |
November 2009 |
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Why can you see the moon during the day? Alan, Waterbeach |
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Why shouldn’t you be able to see the moon during the day? The moon is orbiting around the Earth. It takes the moon about 28 days to go right away around the Earth, come back to where it started. The Earth turns. Obviously, it does a complete evolution in one day, 24 hours, since so you would expect to see the moon go across the sky every day, pretty much. At some point so it might not be visible on some occasions so much but it should be there. So that’s not so unusual |
November 2009 |
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Why do magnets have healing properties? - If they do, that is... William |
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The answer is they don’t. It’s basically good old-fashioned quackery as far as we know. There’s this idea that if you wear copper bracelets or magnetic bracelets in some way, it can help with things like arthritis. Research has shown that this is absolute bunkem There isn’t really any truth in there. There’s some recent results published in October where they did a rigorously controlled trial looking at magnetic or copper bracelets compared to plastic bracelets so people didn’t know what it had, and really they found that it was just a placebo effect if you tell someone they’ve got a magnetic bracelet they think it’s doing them some good but there’s actually there’s no science supporting it. But it’s a multimillion-pound industry so, you know, maybe worth it, if you’re making them. |
November 2009 |
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Does water weigh less when it’s boiled? My kettle feels lighter when water is boiled than when it’s cold. Les, Catfield |
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Well, Les, if your kettle is open at the top than it would have evaporated a bit of water so it may have lost weight purely through evaporation but if the kettle is a sealed unit then E=MC2 says, If you add energy to the kettle when it’s hot, therefore, it should weigh slightly more than the water’s hot than the water is cold. |
November 2009 |
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Light from the stars travels millions of miles away but this is a continuous beam? Also, if you’re in, for example, Australia would you see the same light as somebody who’s in the UK? Michael, Newmarket |
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You won’t see the same photons of light, the individual particles of light but the properties on either side of the earth are going to be very, very similar. |
November 2009 |
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I would like to know where socks go when they put some into the washing machine? I made some observation that I put matching socks into the washing machine and I get only single socks back. Yes socks are not quantum mechanical entities. Where are the socks going? Stephan Gyoery |
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Kat - I think you have to give up some socks as a sacrifice to the “God of Washing”. I don’t know. Maybe they didn’t end up as pairs in the washing machine when you put them in. Chris - I’ve got a theory of this actually. I think what happens is that socks, very often, glue themselves to the inside of the machine so you remove the washing but you might leave one glued to the top so it gets separated from its counterpart. You then go to the washing, hang washing up, process it, put it all back in your bedroom all ironed and stuff and now you got an oddsock. You find the other one and that gets processed separately but by then you’ve got this odd sock in the bedroom and you think “Oh I must have forgotten to wash this one” so I put back in the wash. Its counterpart is probably – or in the wash then the other one comes back from the wash having been found later but by then its counterpart is now in the wash and the two remain separate forever. I think that’s what it is. Kat - (Laughing) Yeah that’s the same circulating odd socks. Chris - Actually I just got an email from Drew Merchant and he says 'I had to take apart my wasjing machine recently and I found 3 socks stuck in the drain tube, so this is where I think they end up'. |
November 2009 |
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Stephan Gyoery asked the Naked Scientists:
Hello Naked Scientists,
I am enjoying your show from Switzerland listening to the podcast (I'm slowly catching up with the present).
I think I have one of the fundamental questions of mankind: where do socks go when they vanish in the washing machine?
I thought that this phenomenon of single socks returning without partner is limited to white tennis socks (experience dated from the 80's), but I can now attest that the same happens to black dress socks as well: once in a while (~20%) one out of a pair of socks "vanishes" when washing in a washing machine. First I thought that Black Holes are made up of lost socks, but...
Okay, quite seriously: would there be statistic evidence for this observation? And would there be an explanation (mathematical/probability)?
Cheers
Stephan
What do you think?
- Stephan Gyoery - 26th Oct 09
Ah ha! (Don's his deerstalker and lights his pipe) The case of the disappearing socks. Elementary, my dear Watson Stephan. It is usually the case that the missing sock never entered the washing machine in the first place. However, it might be, where the sock was indeed put into the machine, that it now resides within a duvet cover. (Just to add to your problem, how is it that duvet covers often manage to turn themselves inside-out in the washing machine?) So, if the sock was not put into the machine, where is the absconder? In the case of those who unfortunately suffer from ***ahem***, dare I say? Yes I dare..... Foot odour, I believe the offending garment may, seeing its opportunity, 'make for the hills', so to speak. Alternatively, a passing animal (either 4 legged or 2) with a (whispers) foot fetish, may perloin the said garment for their perverse delectation. I also believe that there is a mysterious place within every home to where many a missing item goes to fox us all. In this place, should one ever be found, there will be the missing socks along with numerous coins, earrings, screws (from something you set out to repair and could never reassemble), nail clippers, pens and a host of other objects which seem to have a knack of eluding us. "Watson!" "Yes Holmes, my dear chap?" "Call a Handsome Cab. Our services are required in Switzerland." "Switzerland Holmes? Isn't that where Swiss Rolls come from?" "Buffoon, Watson." - Don_1 - 26th Oct 09
Being the owner of many washers, and also the main repair person in my home I have had the honor of finding the answer to that question!! On many occasions socks slip up over the top of machine tub and are lost that way I have found may socks stuck in the water pump of the washer and know that they can go through the pump and into the waste water drain... but many stuck in the pump and burn up the pumps..! If water level gets to high and machine is overloaded it can be swept over the side and get into the drain hose and pumped out with rinse water etc.. - Karen W. - 27th Oct 09
I'm a leg amputee. As it's hard to get my shoe on and off my fake foot, and because my fake foot doesn't sweat I don't often change it. All my socks match but I always get even numbers out of the dryer. I would suggest having one leg taken off of you want to keep your socks. Also you might be able to sell odd socks to amputees who don't use a fake leg. If there are other amputees here I'd like to know if you keep your socks. Perhaps an interesting kitchen science? - mountaineirc1969 - 5th Nov 09
Dryers can not only rearrange matter, they can teleport it too. Socks usually are turned into common metals. Dryers only being 220 volts can only teleport items short distances. That spare change in your sofa, yep, lost socks. And your lost remote control and keys, that's where the lint comes from in the dryer's catch filter. - AllenG - 5th Nov 09
Then how do you explain the loose change in MY sofa. Considering my dryer doesn't seem to eat my socks. Maybe it's the socks from next door. I'll start giving the change to her if that's the case.....now where are my keys...
- mountaineirc1969 - 5th Nov 09
Stone me!!! That's a bit drastic. Not that I have anything against you personally, nor any other amputees, but I'll pass on that solution if you don't mind. Now where's that woolly hat I put in the wash? ♪ ♪ ♪ding dong ding dong ♪ ♪ ♪ Who's that at the door? Aghhhh! Its mountaineirc1969 and he's got a guillotine I'M OFF!!! - Don_1 - 5th Nov 09
I've always found that duvet covers have a strong tendency to swallow up socks and underwear (and even T-shirts) in the wash. Talking of things lost, in the kitchen last weekend I pranged my mp3 player which was on my belt-clip. The player came partially out of its plastic holster and the AAA rechargeable battery disappeared never to be seen again. I spent ages spying under the fridge and under the washing machine with torch and mirror -the 'only' place it could have gone- and I can see no trace. I've checked all the pocket of the trousers I was wearing at the time of the disappearance. I've also checked inside the washing machine (the door was probably ajar at the time). - techmind - 5th Nov 09
having parts of your body removed to save socks is a bit extreme. It's entirely up to how badly you want to save socks. Personally I'd rather lose my socks if I could have me leg back.
See the whole discussion | Make a comment- mountaineirc1969 - 6th Nov 09
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Why does television signal improve when you hold the aerial? Andrew Hawthorn, Arkansas |
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We posed this question to Phil clark from the Particle Physics Laboratory in Edinburgh... Phil - Essentially when you grab the aerial, you’re typically increasing the size of the aerial and then to take your body sort of conducting electrolytes. And a good example of this would be in a laboratory if you have an oscilloscope and you look at the pick up from the main frequency, you can see a 50-Hertz signal which is to pick up from the resonance (circus) in the room. And if you hold the probe in your hand, the amplitude of the pickup increases dramatically and the same thing happens when you grab the TV aerial, you’re improving the pickup and it’s then using you to resonate within the circuit to produce the signal within the televisions. And the TV has to tune quite closely to the right frequency but when you touch the aerial it will improve the signal dramatically. The other thing is when you grab on to the aerial the connectivity between your fingers and aerial and tightly squeeze on the aerial or if your fingers are wet and the conductivity between you and the aerial will be improved. So it often depends on how hard you squeeze the aerial. Diana - And what about the difference between analog TV signals and digital? Phil - The digital signal effectively is a sequence of on and off bits that come down the aerial and effectively it will either be receiving those or it won’t and you may with the aerial built increase the chances of picking out 0’s and 1’s correctly but you have to get it all right for it to work. This is also why you need quite good signal for digital antennas to work correctly. |
November 2009 |
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Here's my idea, and it's only a slightly educated guess. I think when you hold the aerial you effectively be come part of it making it larger. The bigger your aerial the better. I've noticed the same effect when you touch the antenna of a radio.
- mountaineirc1969 - 28th Oct 09
This depends on many factors. Assuming the TV is operating in the UHF band then, if the signal improves when you touch the aerial, the aerial is not operating optimally. This could be because of a number of combined effects: the aerial is a low-gain aerial which is not very directional, the wrong aerial for the band being received, not functioning properly or in a position which is not conducive to good reception (ideally a UHF aerial should be directional - perhaps some sort of Yagi array to have some gain - and in direct line-of-sight to the transmitter). A properly setup, correct, aerial will usually result in a worse signal if you touch it.
- graham.d - 28th Oct 09
I used to think it was because your body was grounding static electricity that built up in the antennae
- Madidus_Scientia - 28th Oct 09
But what's actually happening when you do touch it?
- chris - 31st Oct 09
When you touch an aerial, your body becomes substantially electrically connected to it - your body effectively becomes part of the aerial. Unsurprisingly, this changes how well it receives signals. In "free space" (the chimney-stack or a small mast is a good approximation) the radio or TV signal is a nice plane wave, coming from a single source (the transmitter) with few significant reflections (the signal won't depend on position) and it's relatively easy to design an efficient aerial - such as your typical Yagi. With such an optimal aerial, if mounted on the rooftop you should find that if you were to touch it the reception will almost certainly get worse. Indoors, with TV signals (with a wavelength of about 50cm) the radiofrequency field can be very complicated, with many reflections off of walls and metallic/conducting objects (including people). These reflections will interfere constructively (increasing the signal) or destructively (weakening it) to different extents at every point in the room. (See also "standing waves".) The relative hotspots and deadspots will be of the order of half a wavelength distance apart, ie. ~25cm. People moving in the room can cause this mess of hotspots and deadspots to move around chaotically. Touching the aerial (changing its effective size, shape, and location) will change the mix of hotspots and deadspots it 'feels', and so may improve reception (but it could equally make it worse). I would also make the suggestion that if the reception was ok to start with, you probably wouldn't bother touching the aerial (and therefore you've indvertently dismissed the cases where touching the aerial makes things worse). Each station broadcasts on a different frequency, with a different wavelength, which means each has a unique pattern of hotspots and notspots - which is why you may need to reposition the aerial for different stations. - techmind - 31st Oct 09
I know that electromagnetic radiation is "bent" by going through matter. (For example, it's very difficult to catch a fish in a lake since the light bends in the water since it travels differently than it does in air.) So maybe as we are big bags of water, the waves are moving through you and are refracting the waves somehow. - Jessica H - 3rd Nov 09
Plenty of diffration effects occur with radiowaves around obstructions; refraction certainly can happen but I suspect it's not such a dominant effect in the context of the vaguaries of indoor TV reception. (Largely because of the salt and other ions which make the body substantially conducting.) There's an 'A' level physics practical where you use a big perspex prism to refract microwave (3cm wavelength) radiowaves. No doubt you could do the same with cleam water. - techmind - 3rd Nov 09
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Build your own helicopter
Build your own helicopter using just a piece of card, some tape and a few pencils.
What you need
Some stiff card from a cereal box or something similar | 3 pencils 2 short and 1 long | ||
some tape | scissors |
What to Do
Tape the three pencils together
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Tape the two short pencils either side of the longer one. | Cut a piece of card about 2cm by 10cm and then mark two holes either side of the centre. Then punch two holes at these points using another pen or pencil. |
.It is a good idea to put something soft under the card when you are doing the punching as otherwise you will probably either make a hole in your table or your hand.
Make sure the holes are quite loose on the launcher so the card can lift off easily.
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make two diagonal flaps on opposite corners of the piece of card, both pointing down. | Put the piece of card on the launcher and spin! |
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What may Happen
With any some luck and a bit of practice you should be able to get the helicopter to take off and fly for 3-4 seconds.
What is going on?
When you spin the piece of card, it moves through the air like a wing. As the air hits the flaps it is forced downward. Isaac Newton worked out that if you push something one way it will push you back, so the card pushing the air downwards means that the air pushes the card upwards.
Essentially you have built a rotating wing so the wing is moving through the air even if the card stays over the same place, so it can hover.
This is exactly the same principle as a helicopter, but a helicopter has added problems, because its engine is always pushing the rotor blade around, the equal and opposite force should cause the helicopter to spin in the opposite direction. This is why helicopters have to have a tail rotor to provide a balancing force.
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The helicopter is twisting the blade in one direction (red) however the equal and opposite force twists the helicopter in the opposite direction (blue) | The torque is canceled out by the tail rotor |
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