How Does... With James May | BBC Science

[Music] how does glue work glue is actually a very simple concept it sticks things together and we've known about it for a very long time because there is evidence that Paleolithic man knew about glue 200,000 years ago when he used it to stick his collection of beer mats on his cave wall but given that gluing things together is such a simple notion explaining it is actually rather complex and a source of control controversy amongst boffins who chose to study glue rather than something simple such as particle physics firstly let's ditch the term glue because that could mean something abstract like the social glue techie types prefer the term adhesives so that's what we'll do here there are several categories of adhesive they can be reactive relying on a chemical reaction to make them Harden or non-reactive not relying on a chemical reaction to make them Harden there can be drying adhesives pressure adhesives contact adhesives multi-part adhesives and natural adhesives the first adhesives were of course completely natural and made from anything that happened to be sticky so beeswax Jam tar Bogies then came more complex chemical adhesives most famously animal glue and these were made by boiling up whatever was left on the slaughterous floor when everything else had gone into the food chain from from Posh sirloin staks right down to the rubbish that we call cat food so horses hooves for example in the Modern Age the chemical industry has produced sophisticated superglues such as acrylic or cyanoacrylic or most famously two-party poxy adhesives need to have adhesion the ability to stick to things and cohesion the ability to stick to themselves adhesion occurs at a molecular level and this is where theories are in conflict because some people say it is all down to Mechanical bonding but others say it's down to something called vanand deval's forces in simple Pub bluffers terms vaval forces come into play when molecules are polarized they have a positive and a negative end so they attract each other like billions and billions of microscopic magnets the problem is we know that vanand deval's forces only work when materials are in extremely close proximity actually about .1 nanom that's a 10 billionth of a meter so the Rival cam thinks that isn't what's happening at all when we glue things together at least not all of the time they say there must be an element of mechanical bonding more specifically something they call mechanical locking the theory here is that any apparently perfectly smooth surface surface a sheet of glass a pool ball David Cameron's face is actually very rough when viewed at a microscopic level the adhesive therefore works by flowing into these imperfections and locking into the imperfections on both sides and this explains why rough things stick together better than smooth things and it also explains why the instructions on many adhesives ask you to key I.E rough up the two surfaces to be joined the truth is adhesives probably work through a combination of several or even all of the things I've just described what we do know is that modern adhesives work extremely well indeed how does deodorant work you stink sorry to be so brutally honest about this but it's better that you hear it from me than by finding a growing pile of soap or perfume left for you by your work colleagues or your family members your natural Aroma is actually the result of various things including your diet your genetic makeup but the primary suspect is the aine sweat gland present in both your arm pits and what is delicately termed your genital region each of your pits contains up to 50,000 of these glands and the average human produces a liter of sweat every day but sweat itself doesn't smell strongly it's basically just water and various salts body odor is the result of billions of microorganisms that live on your skin mostly bacteria the majority of these are not harming you and may even offer positive benefits like stimulating your Skin's immune system but some of these especially members of the Corin bacterium Clan manufacture enzymes that break down your honest hardworking sweat into a variety of acids many of which including propic and butc acids and especially trans3 methyl hexi omic acid stink your armpits and your pubic region are also likely to contain thousands of thin wiry hairs broadly similar to the ones that Jeremy Clarkson has on his head and these act to Wick this pungent mixture exposing more of it to the air to help it spread further and faster and potentially enabling you to clear out a whole room by the simple Act of walking into it humans aren't alone having a tendency to make strong smells many animals have serious Bo too and in the wild it can be a huge Advantage marking out territory attracting mates or repelling enemies or even in the case of those creatures that Fain death to avoid getting eaten to persuade potential predators that they are already rotting and not very palatable but for humans smelling strongly is rarely regarded as a good thing and another problem is that our favorite way to clean ourselves through the use of soap can actually intensify this natural Aroma naturally our skin tends to be slightly acidic but soap is alkaline and using it repeatedly encourages more alkaline loving bacteria to flop to us which is where deodorant comes in killing or suppressing the bacteria through being mildly acidic and usually also carrying some perfume elements as well to make a smell nicer it's not a new idea naturally a occurring deodorizing salts have been used for thousands of years but it took the marketing Departments of big cosmetic companies and the threat that your Bo was turning you into the office bogeyman to see the idea really take off because modern deodorants don't just make you smell fractionally fresher they also serve as antiperspirants reducing the amount you sweat the modern antiperspirant was invented in the 1940s by a man with the spectacularly French name of Je tener sadly from the point of view of me now making a cheap gag about the French buying less deodorant than any other developed country moner was actually from Chicago so we can't do that antiperspirants contain an active ingredient to reduce the amount you sweat and therefore the amount of stink fuel available to the bacteria on your skin this is almost always an aluminium compound aluminum for our American viewers this will usually be alum aluminium chlorohydrate and aluminium zirconium TR chlorid Rex either of which will react with the electrolytes in your sweat to create a thick gel that effectively blocks the top of your sweat glands and which also acts as stringently to cause your pores to contract both of which will reduce the amount you sweat and therefore the amount you smell but is this a good thing there have been several Health scares over the years about anti persin and they were briefly banned in America in the 1970s over concerns about the long-term effects of inhaling some of these aluminium compounds but more importantly the antiperspirant is also trying to prevent your body from doing something it does naturally and for good reason to help regulate your body temperature it's also treating an effect rather than a cause research suggests that even extreme body odor can be reduced through changes in diet and by doing more exercise but deodorant could also be preventing more than just a few sodn shirs there's evidence that they can reduce the effect of your pheromones the chemical markers that we excrete and which help us to attract mates or even just casual sexual partners we're stinky for a reason High karate and Old Spice never worked as well as good honest sweat how does radar work there are are few greater Joys than shouting rude words very loudly at a cliff not only do you get to hear yourself saying something that would shock your mother bollocks is my favorite but you also get to hear it a second time and maybe a third or a fourth because as the sound waves produced by your voice reach the surface of the rock face they come bouncing back to you this phenomenon obviously is an echo and once you've substituted radio waves sound waves it also pretty much explains how radar Works see bollet because as you'll have noticed if you stand further away from the cliff you're shouting at then the noise will take longer to get back to you indeed if you pick your location carefully to be different distances from a variety of cliffs the same word will come back to you multiple times from all over the place radio waves had barely been discovered before it was realized that like sound or light waves they too would reflect from solid objects initially this was more of a problem than a solution The shipboard Operators of the early SP Gap transmitters noticed that other vessels passing between them and the radio operator they were trying to communicate with caused interference but it wasn't long before boffins realized the principal could be used to detect things and the tel mobos scope was born okay so the name didn't catch on radar appeared later as an American near acronym for radio detection and ranging and although patents had been filed in 1904 nobody did much to develop radar for several decades a French Cruise liner being the first ship fitted with an obstacle locating radio system in the 1930s it was the military that really spotted the potential of radar with America Britain Germany and the Soviet Union all rushing to develop systems as things looked set to kick off in the 1930s there were some obvious strategic advantages in being able to detect enemy ships and especially airplanes the British chain home system didn't look like modern radar equipment used a fixed antenna array to send out a wide beam of radar energy with returns then read by receivers nearby the time between the signal and its return based on the known velocity of the radio waves which is the speed of light enabled distance to be worked out and using multiple angled receivers and comparing the different Returns on each one enabled both the position and height of the target to be roughly calculated we almost certainly wouldn't have won the Battle of Britain without Radar's ability to tell us where the L waffer was a massing the dirty Radar's utility was obvious and more powerful systems were developed including the familiar rotating array that pulses a signal and then listens for its return before pulsing another but the principle Remains the Same shout listen okay there has been one big development Doppler radar this enables the system to detect the speed of a moving object without having to wait for two separate pulses to hit it and be bounced back which in the case of a really fast moving jet fighter or missile might take too long this is where the Doppler effect comes in this is the way in which the pitch of a wave changes according to the relative speed of the object it bounces off it sounds complicated but it isn't imagine you've installed a very loud mate a mile away and told him the variation of our obscene Echo experiment to yell rude words at you for exactly a minute his voice is carried at the speed of sound let's call it a nice round 600 MPH meaning that 6 seconds after he starts screaming the sound waves reach you and 6 seconds after he's finished the sound stops easy but now we're going to install him on the back of a pickup truck one so quiet you can only hear him shouting the truck is traveling towards you at exactly 60 MPH or to simplify the maths a bit for anyone who drags their Knuckles numerically that that means it will take him exactly 1 minute to complete the mile he starts to shout as the truck passes the one mile Mark and speeds towards you as before it takes 6 seconds for the first sound to reach you and you'll also notice that his voice sounds a little bit higher pitch than usual which you initially put down to him being a bit of a Jessie 60 seconds later the truck passes you just as your mate finishes shouting so what's happened because he's been traveling relative to the speed of sound which is serving as an unbreakable absolute here he's been shouting for a minute but you've only been listening for 54 seconds the sound waves have therefore been squeezed their frequency increased and as a Doppler radar knows the frequency of the radio wave it sends out the velocity of which is limited by the unbreakable speed of light it can work out through the change in frequency coming back whether the object detected is moving towards it or away from it and at what speed it's how police radar guns work of course radar doesn't always work if it doesn't find anything to bounce off then it won't be able to give a return which is how stealth systems work and like any wave it's possible to cancel it by overlaying it with the opposite wave or jamming it should we save that for another time how does a quartz watch work historically all time pieces have always relied on something oscillating in the case of a grandfather clock it's a pendulum swinging to and fro in the case of a mechanical wrist watch or a small alarm clock it's a sprung balance wheel swinging one way and then the other because the time taken for one complete swing or one complete oscillation of the wheel is constant the period as it's known to physicists then this can obviously form the basis of a timekeeper the same is true for a quartz watch a tiny tiny quartz crystal you can think of it as an especially small piece of silicon dioxide or a grain of sand is an oscillator it vibrates as long as you know the rate at which it vibrates you can use it to form the basis of a clock fortunately quartz has what are known as piso electric properties that is if you squash it or bend it it generates a small electrical current and extreme cases piso electrics are what are used to create the spark in those barbecue lighter things as is often the case in physics and with electrical things in particular the piso electric effect also works in Reverse if you pass current through a piece of quartz then the piece of quartz will deform and if you pass a particular amount of current through a very carefully shaped piece of quartz it will vibrate it will oscillate Bingo you have the beginnings of a timekeeper look inside a quartz watch ideally under very strong magnifying glass and you will see a tiny little metal cylinder this contains the quartz crystal usually shaped a bit like a tuning fork and cut very accurately with a laser and it's it's minute when the current from the watch battery is passed across this it vibrates it oscillates and in most quartz watches it's designed to oscillate at 32,768 times per second you will notice that if you have this number 15 times in succession you will arrive at the the number one this is exactly what the electronics in the watch do harving the 32,768 vibrations per seconds to arrive at a convenient one vibration per second or one Hertz so the quartz crystal and its electronic minders are now delivering regular pulses separated by exactly 1 second and that is why the second hand on a quartz watch moves in 1 second steps rather than smoothly and continuously like the second hand on a mechanical watch it's now a simple matter to arrange gears from that second hand to drive the hour hand and the minute hand in the correct ratio we've known how to do that bit for centuries the basics of quartz timekeeping have been known for over a 100 years and by the 1930s this method was being used to measure things like tiny variations in the rotational speed of the Earth but these instruments were massive and very very expensive it was dur during the electronics revolution of the 1960s that courts technology finally made its way into a wristwatch and the very first one the Seiko Astron of 1969 was also very expensive the equivalent in today's money of about $8,000 us but as with everything else electronic the price of the inits tumbled to the point of disposability the great advantage of quartz is that it's incredibly accurate compared with old school mechanical watch technology ology even a really cheap quartz watch can be accurate to within 5 Seconds a month whereas an officially certified Swiss chronometer is only guaranteed to be that accurate over a day time as we know is money but thanks to quartz it's a lot less money than it was is there Plasma in a plasma TV yes there is [Applause] the bigger question is what exactly is plasma and how does it help you to watch Strictly Come X Factor out of here in glorious high definition well the technology behind the television barely evolved for the first 60 years of its existence it relied on the cathode ray tube basically a device that could fire out a stream of electrons onto the back of a fluorescent screen the parts of the screen being hit by electrons would then glow and the beam of electrons would run across the screen in a series of parallel lines multiple times each second this happened so quickly that our eyes looking from the other side of the screen see a steady image early televisions had only one of these electron guns meaning their images were in what was called black and white actually green and gray for anyone old enough to remember but then color television was invented giving a new best thing since to replace sliced bread and that was was by using three separate streams of electrons to create red blue and yellow which could then be combined to enable people to finally make sense of televised snooker but as our appetite for bigger TVs and sharper images developed so the humble cathod ray tube screen started to hit problems televisions were already heavy electricity hungry things but as the size of screens increase they had to become deeper as well so that the CRT tube could reach each corner of the screen the number of pixels that a CRT could support was also limited by the need for it to scan the whole screen 50 or 60 times a second this was clearly a problem in need of a solution the concept for the plasma display had been invented as long ago as the 1930s with a single color plasma display being produced in the 1960s and 1970s especially for early computers the principle is very simple instead of using a beam of electrons to create life the plasma screen uses what are in effect tiny quick acting fluorescent light cells to form a picture in a modern color plasma display each pixel has three of these fluorescent lights one in each primary color and fires them intelligently to create the desired color in the picture LCD televisions the sworn enemy of plasma systems according to the bloke in the T shop use individual LCD shatters for each pixel to create a similar effect but what is plasma a plasma is basically just an electrically conducted gas that contains both free flowing ions positively charged atoms and electrons which are negatively charged if you introduce more electrons by putting a voltage through this gas then these will begin to collide with atoms knocking off other electrons and turning them into ions then negatively charged particles will start to move towards the positively charged area and vice versa this causes the atomic equivalent of a Motorway pil up with particles smashing into each other and with the Zenon and neon gases used in plasma screens releasing photons or light as we'd call it most of this light is ultraviolet which is invisible but by coating those tiny cells with phosphoric material this can be changed into visible light when it hits the side of the cells which it does a lot a modern high definition display with 1,920 pixels across and 1,80 up has over 2 million individual pixels each being fired dozens of times a second to produce different colors the result is that plasma displays are far more shallow than the old CRTs you can stick them on the wall but also that they can be scaled up simply by adding more pixels and enough Computing Firepower to run them plasma TVs have been produced in sizes up to 152 in that's the diagonal measurement across the screen large enough for even the most Discerning rap star to watch himself waxing misogynistic in glorious high definition but now settle down with the Blu-ray release of Ghostbusters and remind yourself how important it is to never ever cross the streams now if you haven't already gone what my mother would have called Square eyed through watching all this stuff about television why not go over to number Hub and find out just how many pixels can be squeezed into the world's largest TV do that by [Music] clicking here how does a bulletproof vest work in many ways the idea of bulletproofing is older than bullets the notion that you could protect yourself against your enemy's weapons goes all the way back to the plate armor and chain mail of the medieval knights further back than that in fact it goes back to the leather armor of Roman soldiers all this stuff was quite good against swords and battle axes trouble was as Weapons became more powerful and more accurate so armor had to become tougher and that meant heavier by the time the first gunpowder muskets had reached Europe it had all got a bit out of hand and the average weight of armor went up from 15 kg in the 15th century to something like 25 kg by the late 16th century eventually we arrive in the late 19th century and the homemade armor used by Ned Kelly and his gang each suit weighed around 45 kg which means that one Outlaws energy was almost entirely consumed humping his own protective kit around none of it left for robbing bulletproofing didn't need to be heavier it actually needed to be a bit cleverer in fact it needed to be softer a bit of physics a bullet works by concentrating a great deal of energy all the energy from its speed and its momentum into a very small Point that's why it can punch its way through apparently impenetrable surfaces like brick walls and yet remarkably you can stop one with fabric this was worked out by some Koreans in the 1860s who realized that you had to increase the area that the bullet works against bullets intended for soft targets such as animals and indeed Korean soldiers work by deforming on impact this increases the bullets area and allows it to do more damage but it's also the bullet's weakness as the Koreans worked out whilst being shot at by the French they worked out how to make lightweight protection from layers of folded cotton causing the bullet to deform just before it reached flesh and blood and causing the energy to be dissipated as it tried to force its way through the lower levels when the Americans fought the Koreans quite soon afterwards they captured one of these vests and took it home for analysis it worked and the idea quite quickly spread interestingly Arch Duke Ferdinand of the austr Hungarian Empire was wearing one of these bulletproof vests when a nationalist Serbian assassin shot him in 1914 unfortunately for the arch Duke the Assassin had the good sense to shoot him in the neck thus starting the first world war by the 1920s bulletproofing was positively hip in America where organized criminals adopted these Gangsta vests to protect themselves against rival gangs and of course the feds this led to a sort of arms race with more powerful ammunition being developed to penetrate better bulletproof vests leading ultimately to the development of the notorious Magnum round providing protection against relatively slow handgun bullets isn't such a problem it's reckoned that since 1973 over 3,000 us police officers have been saved from serious gunshot wounds by Ballistic vests the problem is trying to provide protection against High velocity rifle rounds and bits of shrapnel as found on the battlefield fabric vests simply aren't good enough for this so modern body armor incorporates metal or ceramic plates as well so now once again we come up against the age-old problem of weight a modern body armor vest can weigh as much as 15 kg or if you remember exactly the same way that your medieval Knight had to cart about how the noise cancelling head head phones work if you're wearing a pair of headphones on a long airplane flight there are two sounds of interest to you whatever it is you're trying to listen to and the tiresome drone of the engines the sound of the engines is coming from outside the headphones girls allow from within the genius of noise cancelling headphones is that they can get rid of the sound of the engines without interfering with the so-called music all sound is really just compression and rif faction of the air around us when you fire a starting pistol the air around the gun is compressed then it thins out again then it's compressed again and so on imagine an infinite number of slinkies stretching away in all directions and the sound Rippling along them these are known as longitudinal waves but for the purpose of illustration we can represent them with sine waves with Peaks and troughs like ripples in a pond the engines of the aircraft produce a sound wave of constant amplitude that is the height of the Peaks and the depths of the troughs and constant wavelength that is the length of the entire wave and if you produce another sound with the same amplitude and wavelength but opposite phase that is it has a peak where the original sound has a trough you have something called an antiphase the two cancel each other out and the result is silence weirdly you add two things together but arrive at but nothing but think of it as adding plus two to minus two so noise cancelling headphones incorporate a tiny microphone that listens to the ambient noise in this case the jet engines their internal Electronics then measure this and work out an antiphase but of course you don't hear the antiphase you hear nothing and because these microphones aren't listening to The Sounds inside the headphones your music is unaffected noise cancelling headphones are much better at dealing with continuous noise like jet engines than they are at coping with sudden or abrupt sounds so they don't work very well in a gunfight or prime minister's question time when you switch your noise cancelling headphones on you will notice a very short delay before they take effect this is the electronics measuring the Ambient sound and coming up with the antiphase they can't do it immediately headphones like this were first devised in the 1970s but by then the technology was already well understood noise cancelling systems had already been Incorporated in the cockpits of aircraft and helicopters more recently it's become popular with car makers not only can active noise cancellation make a car quieter by playing an antiphase through the stereo speakers it can actually improve the sound a sophisticated system can replace engine noise with something nicer so you can drive around in a dreary 4- cylinder diesel hatchback but enjoy the soundtrack from a V12 Ferrari racing car this sort of thing is expensive but then again a Ferrari 250 GTO recently sold for $35 million how do digital cameras work the camera is one of those wondrous inventions that change the world before it arrived the only way to make a picture was to draw it or paint it which obviously removed a fair amount of the spontaneity when you were trying to knock off a quick selfie of yourself giving epic duck face while eating a Macky D with your Bei mates it's probably why rembrand always looks so depressed in his self-portraits anyway the camera made it possible to make an instant picture in a fraction of a second but the process involved in getting the image out of the camera and printed was a complicated one the light sensitive film had to be carefully removed sent to processor get developed turned into a negative and then printed onto photographic paper in the dark which was a problem with the rise of the digital age and the internet and your pressing need to upload a picture of fluffy that my cat looks like Hitler web for him but while the microprocessor Revolution started to transform many parts of our lives from the 1970s onwards the digital camera was a relatively late invention arriving after the video camera the mobile phone the laptop computer and even the Billy big bass singing plastic fish this was because the technology that lies at the heart of it the sensor chip is unbelievably complicated in a film camera light is sent through a lens and a shutter onto photosensitive film which with a subject shot in normal light needs just hundredths of a second of exposure to capture the image the front end of a digital camera works on exactly the same principle light is focused through the lens and controlled by a shutter and a variable aperture but instead of film there's a light sensitive sensor chip that has to record all of the data in a very short space of time there are different ways of doing this but we're going to concentrate on the CMOS or complimentary metal oxide semiconductor sensor that now sits in the majority of digital cameras from those integrated in phones to fairly chunky dslrs that's digital single lens reflex in the jargon they're the sort that look like real cameras the camera sensor is covered with tiny individual light sensitive cells Each of which can measure the amount of light that falls on it as the digital camera has evolved so have the number of these pixels on the surface of the sensor 10 years ago you'd struggle to get a digital camera capable of delivering much more than a single megapixel of resolution a million total pixels or a grid 1,200 by 900 but these days 12 or even 16 megapixels are common place among topspec pruma and professional cameras that's enough to enable you to produce images the size of a magazine cover with no loss in perceived quality the sales act like the photosensitive C chemicals on old-fashioned film reacting to the light that falls on them and then reporting that to the camera's microprocessor brain that would be fine for the sort of Moody black and white shots favored by gothy Instagram users but because most of us want to post pictures of our lunch to Facebook in color it's also necessary to split the light seen by the camera into the three primary colors which can then be used to create an accurate image there are different ways of doing this some expensive cameras will employ three different filters but most CMOS sensors will use what's called a Bayer filter this is a grid of colored filters that sits over the sensor with red green and blue elements over individual pixels and they will only allow their respective light color through because the human eye is most sensitive to Green Light which largely determines how bright an image looks there are twice as many green pixels as red or blue ones the filters are arranged in a clever mathematical pattern which means that the camera's brain can interpolate using a demosaicing algorithm yes really or slightly pler language the camera doesn't just look at an individual pixel on the sensor it also looks at the pixels around it to come up with an informed guess of what the true color of that pixel is although even the most advanced sensors in the world still struggle with the increasingly unlikely color of Richard Hammond's hair

Channel: BBC Earth Science

Views: 258,454

Keywords: bbc earth lab, earth lab, science, chemistry, physics, why, biology, space, BBC Earth Science, How Does... With James May, James May, glue, camera, bulletproof vest, deodorant, plasma, tv, radar, watch, headphones

Id: ArH1PY8IkB0

Length: 34min 45sec (2085 seconds)

Published: Sun Apr 28 2024