Ariane 5 on the launch pad. Photo Credit: (NASA/Chris Gunn) Public Domain via Wikimedia Commons.
If you spent billions of dollars on a gadget you’d probably like it to last more than a minute before it blows up. That’s what happened to a European Space Agency rocket. How do you make sure the worst doesn’t happen to you? How do you make machines reliable?
A powerful way to improve reliability is to use redundancy: double things up. A plane with four engines can keep flying if one fails. Worried about a flat tyre? You carry a spare in the boot. These situations are about making physical parts reliable. Most machines are a combination of hardware and software though. What about software redundancy?
You can have spare copies of software too. Rather than a single version of a program you can have several copies running on different machines. If one program goes wrong another can take over. It would be nice if it was that simple, but software is different to hardware. Two identical programs will fail in the same way at the same time: they are both following the same instructions so if one goes wrong the other will too. That was vividly shown by the maiden flight of the Ariane 5 rocket. Less than 40 seconds from launch things went wrong. The problem was to do with a big number that needed 64 bits of storage space to hold it. The program’s instructions moved it to a storage place with only 16 bits. With not enough space, the number was mangled to fit. That led to calculations by its guidance system going wrong. The rocket veered off course and exploded. The program was duplicated, but both versions were the same so both agreed on the same wrong answers. Seven billion dollars went up in smoke.
Can you get round this? One solution is to get different teams to write programs to do the same thing. The separate teams may make mistakes but surely they won’t all get the same thing wrong! Run them on different machines and let them vote on what to do. Then as long as more than half agree on the right answer the system as a whole will do the right thing. That’s the theory anyway. Unfortunately in practice it doesn’t always work. Nancy Leveson, an expert in software safety from MIT, ran an experiment where different programmers were given programs to write. She found they wrote code that gave the same wrong answers. Even if it had used independently written redundant code it’s still possible Ariane 5 would have exploded.
Redundancy is a big help but it can’t guarantee software works correctly. When designing systems to be highly reliable you have to assume things will still go wrong. You must still have ways to check for problems and to deal with them so that a mistake (whether by human or machine) won’t turn into a disaster.
The World Health Organisation currently estimates that around 1.3 billion people, or one in six people on Earth, “experience significant disability”. Designers who are creating devices and tools for people to use need to make sure that the products they develop can be used by as many people as possible, not just non-disabled people, to make sure that everyone can benefit from them.
Disabled people can face lots of barriers in the workplace including some that seem simple to address – problems using everyday ICT and other tech. While there are a lot of fantastic Assistive Technology (AT) products unfortunately not all are suitable and so are abandoned by disabled people as they don’t serve their needs.
One challenge is that some of the people who have been doing the designing might not have direct experience of disability themselves, so they are less able to think about their design from that perspective. Solutions to this can include making sure that disabled computer scientists and human-computer interaction researchers are part of the team of designers and creators in the first place, or by making it easier for other disabled people to be involved at an early stage of design. This means that their experience and ideas can contribute to making the end product more relevant and useful for them and others. Alongside this there is education and advocacy – helping more young computer scientists, technologists and human-computer interaction designers to start thinking early about how their future products can be more inclusive.
An EPSRC project “Inclusive Public Activities for information and Communication Technologies” has been looking at some practical ways to help. Run by Prof. Cathy Holloway and Dr. Maryam Bandukda and their wider team at UCL they have established a panel of disabled academics and professionals who can be ‘critical friends’ to researchers planning new projects. By co-creating a set of guidelines for researchers they are providing a useful resource but it also means that disabled voices are heard at an early stage of the design process so that projects start off in the right direction.
Prof. Holloway and Dr. Bandukda are based at the Global Disability Innovation Hub (GDI Hub) in the department of computer science at UCL. GDI Hub is a global leader in disability innovation and inclusion and has research reaching over 30 million people in 60 countries. The GDI Hub also educates people to increase awareness of disability, reduce stigma and lay the groundwork for more disability-aware designers to benefit people in the future with better products.
An activity that the UCL team ran in February 2024, for schools in East London, was a week-long inclusive ICT “Digital Skills and Technology Innovation” bootcamp. They invited students in Year 9 and above to learn about 3D printing, 3D modelling, laser cutting, AI and machine learning using Python, artificial reality and virtual reality experiences along with a chance to visit Google’s Accessible Discovery Centre and use their skills to “tackle real-world challenges”.
What are some examples of Assistive Technology?
Screen-reading software can help blind or visually impaired people by reading aloud the words on the page. This is something that can help sighted people too, your document can read itself to you while you do something else. The entire world of audio books exists for this reason! D/deaf people can take part more easily in Zoom conversations if text-to-caption software is available so they can read what’s being said. That can also help those whose hearing is fine but who speak a different language and might miss some words. Similarly you can dictate your clever ideas to your computer and device which will type it for you. This can be helpful for someone with limited use of their hands, or just someone who’d rather talk than type – this might also explain the popularity of devices and tools like Alexa or Siri.
Web designers want to (and may need to*) make their websites accessible to all their visitors. You can help too – a simple thing that you can do is to add ALT Text (alternative text) to images. If you ever share an image or gif to social media it’s really helpful to describe what’s in the image for screen readers so that people who can’t view it can still understand what you meant.
*Thanks to regulations that were adopted in 2018 the designers of public sector websites (e.g. government and local council websites where people pay their council tax or apply for benefits) must make sure that their pages meet certain accessibility standards because “people may not have a choice when using a public sector website or mobile app, so it’s important they work for everyone. The people who need them the most are often the people who find them hardest to use”.
“DIX puts disability front and center in the design process, and in so doing aims to create accessible, creative new HCI solutions that will be better for everyone“
You might have come across UI (User Interface(s)) and UX (User Experience), DIX is Disability Interaction – how disabled people use various tech.
Careers
Examples of computer science and disability-related jobs
Both of the jobs listed below are CLOSED and are just for your information only.
[CLOSED] Islington Council, Digital Accessibility Apprentice (f/t), £24k, clos 7 July
Are you interested in web design and do you want to help empower disabled people to become fully engaged within the community? This is a great opportunity to learn about the rapidly growing digital accessibility industry. Qualified and experienced digital accessibility specialists are sought after.
This role is focused on maximising comms-based engagement across the GDI Hub’s portfolio, supporting GDI Hub’s growing outreach across project-based deliverables and organisational comms channels (e.g. social media, websites, content generation).
We’re occasionally asked by school pupils, their parents and teachers about where young people can find out about work experience in something to do with computer science. We’ve put together some general information which we hope is helpful, and there’s also information further down the page that might be useful for people who’ve finished a computing degree and are wondering “What’s next?”.
Work experience for school students
(This section was originally published on our website for teachers – Teaching London Computing).
Supermarkets – not in the store but in the office, learning about inventory software used to manage stock for in-store shopping as well as online shopping (e.g. Ocado etc).
Shops – more generally pretty much every shop has an online presence and may want to display items for sale (perhaps also using software to handle payment).
Websites – someone who’s a blacksmith might not use a computer in their work directly, but the chances are they’d want to advertise their metal-flattening skills to a wider audience which is only really possible with a web presence.
Websites involve technical aspects (not necessarily Python types of things but certainly HTML and CSS / JavaScript) but also making websites accessible for users with visual impairments, e.g. labelling elements helpfully and remembering to add ALT TEXT for users of screenreaders. Technical skills are important but thinking about the end-user is super-important too, and often a skill that people pick up ‘on the job’ rather than being trained about (though that is changing).
Usability – making websites or physical products (e.g. home appliances, cameras, phones, printers, microwaves) easier to use by finding out how easily users can interact with them and considering options for improvement. For computing systems this involves HCI (human-computer interaction) and UX (user experience – e.g. how frustrating is a website?).
Transport – here in London we have buses with a GPS transponder that emits a signal which is picked up by sensors, co-ordinated and translated into real-time information about the whereabouts of various buses on the system. Third-party apps can also use some of this data to provide a service for people who want to know the quickest route to a particular place.
Council services – it’s possible to pay parking fines, council tax and other things online, also utility company bills. The programs involved here need to keep people’s private data secure as well.
Banks – are heavy users of ‘fintech’ (financial technology) and security systems, though that might preclude them taking on people in a work experience setting. Similarly GP surgeries have dedicated IT systems (such as EMIS) for handling confidential patient information and appointments. Even if they can’t take on tech work experience students they may have other work experience opportunities.
Places that offer (or have previously offered) work experience
TechDevJobs website Our ‘jobs in computing’ resource (homepage) should give you an idea of the different sectors which employ all sorts of computer scientists to do all sorts of different things (see the list of jobs organised by sector). There are about 70 80 jobs there so far; it doesn’t cover everything though (that’s almost an impossible task!).
There are obvious computing-related jobs such as a software company looking for a software developer but there’s also a job for a lawyer-researcher (someone who is able to practise as a lawyer if necessary but is going to be doing research) into Cloud Computing. For example there are all sorts of regulatory aspects to computing, some currently under consideration by the UK Government on data leaks, privacy, appropriateness of use and how securely information is stored, and what penalties there are for misuse.
Possibly a local law firm is doing some work in this area and might be open to offering work experience.
Other resources for recent graduates
The TechDev Jobs website (listed above in Other resources) is a great place to start. The jobs ‘advertised’ are usually closed but the collection lists several organisations that are currently employing people in the field of computer science (in the widest sense) and we are adding more all the time. Finding out about jobs is also about finding out about different sectors, some of which you might not have heard of yet – but they are all potential sources of jobs for people with computing skills.
Recent graduates or soon-to-graduate students may be able to help newer students get to grips with things in the Year 1 modules. Sometimes it’s not the computer science and programming that they or the lecturers need assistance with but really practical stuff like logging on and finding the relevant resources.
The Find A Job website from DWP (https://findajob.dwp.gov.uk/search) can be filtered by location and keyword too. Put in a keyword and see what pops up, then filter by salary etc.
Further study: if you’re interested in continuing your studies you might consider a Masters degree (MSc) in computer science and see the panel below for information on studying for a PhD, for which you are usually paid.
The Entry Level Games site isn’t a jobs board but if you’re interested in games design then it gives you a really helpful overview of some of the typical roles, what’s needed to do those roles and information from people who’ve done those jobs.
If you are interested in creating assistive technology or making computing more inclusive you might be interested in the work of the Global Disability Innovation Hub.
Networking is also a good idea to build up contacts and hear about different roles, some people find LinkedIn useful as an online version of networking and as a great place to hear about newly-opened vacancies. You can also take part in local hackathons, or volunteer at code clubs etc. This sort of thing is useful for your CV too.
There are probably organisations near you and it’s fairly likely that they’ll be using computers in one way or another, and you might be useful to them. Open up Google Maps and navigate to where you’re living, then zoom in and see what organisations are nearby. Make a note of them and if they have a vacancies page save that link in a document so that you can visit it every so often and see if a relevant new job has been added. Or contact them speculatively with your CV.
If you have a Gmail account you can set up Google Alerts. Whenever a new web page (e.g. a new job vacancy is published) that satisfies your search criteria you’ll get a daily email with a summary of what’s been added and the link to find out more. This is a way of bringing the job adverts to you!
Digitally stitching together 2D photographs to visualise the 3D world
Composite image of one green glass bottle made from three photographs. Image by Jo Brodie
Imagine you’re the costume designer for a major new film about a historical event that happened 400 years ago. You’d need to dress the actors so that they look like they’ve come from that time (no digital watches!) and might want to take inspiration from some historical clothing that’s being preserved in a museum. If you live near the museum, and can get permission to see (or even handle) the material that makes it a bit easier but perhaps the ideal item is in another country or too fragile for handling.
This is where 3D imaging can help. Photographs are nice but don’t let you get a sense of what an object is like when viewed from different angles, and they don’t really give a sense of texture. Video can be helpful, but you don’t get to control the view. One way around that is to take lots of photographs, from different angles, then ‘stitch’ them together to form a three dimensional (3D) image that can be moved around on a computer screen – an example of this is photogrammetry.
In the (2D) example above I’ve manually combined three overlapping close-up photos of a green glass bottle, to show what the full size bottle actually looks like. Photogrammetry is a more advanced version (but does more or less the same thing) which uses computer software to line up the points that overlap and can produce a more faithful 3D representation of the object.
In the media below you can see a looping gif of the glass bottle being rotated first in one direction and then the other. This video is the result of a 3D ‘scan’ made from only 29 photographs using the free software app Polycam. With more photographs you could end up with a more impressive result. You can interact with the original scan here – you can zoom in and turn the bottle to view it from any angle you choose.
A looping gif of the 3D Polycam file being rotated one way then the other. Image by Jo Brodie
You might walk around your object and take many tens of images from slightly different viewpoints with your camera. Once your photogrammetry software has lined the images up on a computer you can share the result and then someone else would be able to walk around the same object – but virtually!
Photogrammetry is being used by hobbyists (it’s fun!) but is also being used in lots of different ways by researchers. One example is the field of ‘restoration ecology’ in particular monitoring damage to coral reefs over time, but also monitoring to see if particular reef recovery strategies are successful. Reef researchers can use several cameras at once to take lots of overlapping photographs from which they can then create three dimensional maps of the area. A new project recently funded by NERC* called “Photogrammetry as a tool to improve reef restoration” will investigate the technique further.
Photogrammetry is also being used to preserve our understanding of delicate historic items such as Stuart embroideries at The Holburne Museum in Bath. These beautiful craft pieces were made in the 1600s using another type of 3D technique. ‘Stumpwork’ or ‘raised embroidery’ used threads and other materials to create pieces with a layered three dimensional effect. Here’s an example of someone playing a lute to a peacock and a deer.
“Satin worked with silk, chenille threads, purl, shells, wood, beads, mica, bird feathers, bone or coral; detached buttonhole variations, long-and-short, satin, couching, and knot stitches; wood frame, mirror glass, plush”, 1600s. Photo CC0 from Metropolitan Museum of Art uploaded by Pharos on Wikimedia.
Using photogrammetry (and other 3D techniques) means that many more people can enjoy, interact with and learn about all sorts of things, without having to travel or damage delicate fabrics, or corals.
*NERC (Natural Environment Research Council) and AHRC (Arts and Humanities Research Council) are two organisations that fund academic research in universities. They are part of UKRI (UK Research & Innovation), the wider umbrella group that includes several research funding bodies.
Other uses of photogrammetry
Examples of cultural heritage and ecology are highlighted in the post but also interactive games (particularly virtual reality), engineering and crime scene forensics and the film industry use photogrammetry, an example is Mad Max: Fury Road which used the technique to create a number of its visual effects. Hobbyists also create 3D versions (called ‘3D assets’) of all sorts of objects and sell these to games designers to include in their games for players to interact with.
What is photogrammetry? (12 November 2021) Great Barrier Reef Foundation “What it is, why we’re using it and how it’s helping uncover the secrets of reef recovery and restoration.” [EXTERNAL]
Even if you’re the best keyboard player in the world the sound you can get from any one key is pretty much limited to ‘loud’ or ‘soft’, ‘short’ or ‘long’ depending on how hard and how quickly you press it. The note’s sound can’t be changed once the key is pressed. At best, on a piano, you can make it last longer using the sustain pedal. A violinist, on the other hand, can move their finger on the string while it’s still being played, changing its pitch to give a nice vibrato effect. Wouldn’t it be fun if keyboard players could do similar things.
Andrew McPherson and other digital music researchers at QMUL and Drexel University came up with a way to give keyboard performers more room to express themselves like this. TouchKeys is a thin plastic coating, overlaid on each key of a keyboard, but barely noticeable to the keyboard player. The coating contains sensors and electronics that can change the sound when a key is touched. The TouchKeys’ electronics connect to the keyboard’s own controller and so changes the sounds already being made, expanding the keyboard’s range. This opens up a whole world of new sonic possibilities to a performer.
The sensors can follow the position and movement of your fingers and respond appropriately in real-time, extending the range of sounds you can get from your keyboard. By wiggling your finger from side-to-side on a key you can make a vibrato effect, or you change the note’s pitch completely by sliding your finger up and down the key. The technology is similar to a phone’s touchscreen where different movements (‘gestures’) make different things happen. An advantage of the system is that it can easily be applied to a keyboard a musician already knows how to play, so they’ll find it easy to start to use without having to make big changes to their style of playing.
They wanted to get TouchKeys out of the lab and into the hands of more musicians, so teamed up with members of London’s Music Hackspace community, who run courses in electronic music, to create some initial versions for sale. Early adopters were able to choose either a DIY kit to add to their own keyboard, wire up and start to play, or choose a ready-to-play keyboard with the TouchKeys system already installed.
The result is that lots of musicians are already using TouchKeys to get more from their keyboard in exciting new ways.
Jo Brodie and Paul Curzon, Queen Mary University of London
Earlier this year Professor Andrew McPherson gave his inaugural lecture (a public lecture given by an academic who has been promoted) at Imperial College London where he is continuing his research. Watch his lecture.
World Emoji Day is celebrated on the 17th of July every year (why?) and so we’ve put together a ‘Can you guess the film from the emoji’ quiz and added some emoji-themed articles about computer science and the history of computing.
An emoji film quiz
Emoji accessibility, and a ‘text version’ of the quiz
Computer science articles about emoji
Emoji are small digital pictures that behave like text – you can slot them easily them in sentences (you don’t have to ‘insert an image’ from a file or worry about the picture pushing the text out of the way). You can even make them bigger or smaller with the text (🎬 – compare the one in the section title below). People use them as a quick way of sharing a thought or emotion, or adding a comment like a thumbs up so they’re (sort of) a form of data representation. Even so, communication with emoji can be just as tricky, in terms of being misunderstood, just as with using words alone. Different age groups might read the same emoji and understand something quite different from it. What do you think 🙂 (‘slightly smiling face’ emoji) means? What do people older or younger than you think it means? Lots of people think it means “I’m quite happy about this” but others use it in a more sarcastic way.
1. An emoji film quiz 🎬
You can view the quiz online or download and print from Word or PDF versions. If you’re in a classroom with a projector the PowerPoint file is the one you want.
2. Emoji accessibility, and a text version of the quiz
We’ve included a text version for blind or visually impaired people which can either be read out by someone or by a screen reader. Use the ‘Text quiz’ files in Word or PDF above.
More generally, when people share photographs and other images on social media it’s helpful if they add some information about the image to the ‘Alt Text’ (alternative text) box. This tells people who can’t easily see the image what’s in the picture. Screenreaders will also tell people what the emojis are in a tweet or text message, but if you use too many… it might sound like this 😬.
This next article is about the history of computing and the development of the graphical icons for apps that started life being drawn on gridded paper by Susan Kare. You could print some graph / grid paper and design your own!
In 1977 NASA scientists at the Jet Propulsion Laboratory launched the interstellar probe Voyager 1 into space – and it just keeps going. It has now travelled 15 BILLION miles (24 billion kilometres), which is the furthest any human-made thing has ever travelled from Earth. It communicates with us here on Earth via radiowaves which can easily cross that massive distance between us. But even travelling at the speed* of light (all radiowaves travel at that speed) each radio transmission takes 22.5 hours, so if NASA scientists send a command they have to wait nearly two days for a response. (The Sun is ‘only’ 93 million miles away from Earth and its light takes about 8 minutes to reach us.)
FDS – The Flight Data System
The Voyager 1 probe has sensors to detect things like temperature or changes in magnetic fields, a camera to take pictures and a transmitter to send all this data back to the scientists on Earth. One of its three onboard computers (the Flight Data System, or FDS) takes that data, packages it up and transmits it as a stream of 1s and 0s to the waiting scientists back home who decode it. Voyager 1 is where it is because NASA wanted to send a probe out beyond the limits of our Solar System, into ‘interstellar space’ far away from the influence of our Sun to see what the environment is like there. It regularly sends back data updates which include information about its own health (how well its batteries are doing etc) along with the scientific data, packaged together into that radio transmission. NASA can also send up commands to its onboard computers too. Computers that were built in 1977!
The pale blue dot
‘The Pale Blue Dot’. In the thicker apricot-coloured band on the right you might be able to see a tiny dot about halfway down. That’s the Earth! Full details of this famous 1990 photo here.
Although its camera is no longer working its most famous photograph is this one, the Pale Blue Dot, a snapshot of every single person alive on the 14th of February 1990. However as Voyager 1 was 6 billion miles from home by then when it looked back at the Earth to take that photograph you might have some difficulty in spotting anyone! But they’re somewhere in there, inside that single pixel (actually less than a pixel!) which is our home.
As Voyager 1 moved further and further away from our own planet, visiting Jupiter and Saturn before travelling to our outer Solar System and then beyond, the probe continued to send data and receive commands from Earth.
The messages stopped making sense
All was going well, with the scientists and Voyager 1 ‘talking’ to one another, until November 2023 when the binary 1s and 0s it normally transmitted no longer had any meaningful pattern to them, it was gibberish. The scientists knew Voyager 1 was still ‘alive’ as it was able to send that signal but they didn’t know why its signal no longer made any sense. Given that the probe is nearly 50 years old and operating in a pretty harsh environment people wondered if that was the natural end of the project, but they were determined to try and re-establish normal contact with the probe if they could.
Searching for a solution
They pored over almost-50 year old paper instruction manuals and blueprints to try and work out what was wrong and it seemed that the problem lay in the FDS. Any scientific data being collected was not being correctly stored in the ‘parcel’ that was transmitted back to Earth, and so was lost – Voyager 1 was sending empty boxes. At that distance it’s too far to send an engineer up to switch it off and on again so instead they sent a command to try and restart things. The next message from Voyager 1 was a different string of 1s and 0s. Not quite the normal data they were hoping for, but also not entirely gibberish. A NASA scientist decoded it and found that Voyager 1 had sent a readout of the FDS’ memory. That told them where the problem was and that a damaged chip meant that part of its memory couldn’t be properly accessed. They had to move the memory from the damaged chip.
That’s easier said than done. There’s not much available space as the computers can only store 68 kilobytes of data in total (absolutely tiny compared to today’s computers and devices). There wasn’t one single place where NASA scientists could move the memory as a single block, instead they had to break it up into pieces and store it in different places. In order to do that they had to rewrite some of the code so that each separated piece contained information about how to find the next piece. Imagine if a library didn’t keep a record of where each book was, it would make it very hard to find and read the sequel!
Earlier this year NASA sent up a new command to Voyager 1, giving it instructions on how to move a portion of its memory from the damaged area to its new home(s) and waited to hear back. Two days later they got a response. It had worked! They were now receiving sensible data from the probe.
Voyager team celebrates engineering data return, 20 April 2024 (NASA/JPL-Caltech). “Shown are Voyager team members Kareem Badaruddin, Joey Jefferson, Jeff Mellstrom, Nshan Kazaryan, Todd Barber, Dave Cummings, Jennifer Herman, Suzanne Dodd, Armen Arslanian, Lu Yang, Linda Spilker, Bruce Waggoner, Sun Matsumoto, and Jim Donaldson.”
For a while it was just basic ‘engineering data’ (about the probe’s status) but they knew their method worked and didn’t harm the distant traveller. They also knew they’d need to do a bit more work to get Voyager 1 to move more memory around in order for the probe to start sending back useful scientific data, and…
Success!
… …in May, NASA announced that scientific data from two of Voyager 1’s instruments was finally being sent back to Earth and in June the probe was fully operational. You can follow Voyager 1’s updates on Twitter / X via @NASAVoyager.
Did you know?
Both Voyager 1 and Voyager 2 carry with them a gold-plated record called ‘The Sounds of Earth‘ containing “sounds and images selected to portray the diversity of life and culture on Earth”. Hopefully any aliens encountering it will have a record player (but the Voyager craft do carry a spare needle!) Credit: NASA/JPL
References
Lots of articles helped in the writing of this one and you can download a PDF of them here. Featured image credit showing the Voyager spacecraft: NASA/JPL.
*radiowaves and light are part of the electromagnetic or ‘EM’ spectrum along with microwaves, gamma rays, X-rays, ultraviolet and infra red. All these waves travel at the same speed in a vacuum, the speed of light (300,000,000 metres per second, sometimes written as 3 x 108 m/s or (m s-1)), but the waves differ by their frequency and wavelength.
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EPSRC supports this blog through research grant EP/W033615/1.
The Ancient Egyptians, Romans and Greeks used dice with various shapes and markings; some even believed they could be used to predict the future. Using just a few invisible dice, which you can easily make at home, you can amaze your friends with a transparent feat of magical prediction.
The presentation
You can’t really predict the future with dice, but you can do some clever magic tricks with them. For this trick first you need some invisible dice, they are easy to make, it’s all in the imagination. You take your empty hand and state to your friend that it contains two invisible dice. Of course it doesn’t, but that’s where the performance come in. You set up the story of ancient ways to predict the future. You can have lots of fun as you hand the ‘dice’ over and get your friend to do some test rolls to check the dice aren’t loaded. On the test rolls ask them what numbers the dice are showing (remember a dice can only show numbers 1 through 6), this gets them used to things. Then on the final throw, tell them to decide what numbers are showing, but not to tell you! You are going to play a game where you use these numbers to create a large ‘mystical’ number.
To start, they choose one of the dice and move it closer to them, remembering the number on this die. You may want to have them whisper the numbers to another friend in case they forget, as that sort of ruins the trick ending!
Next you take two more ‘invisible dice’ from your pocket; these will be your dice. You roll them a bit, giving random answers and then finally say that they have come up as a 5 and a 5. Push one of the 5s next to the dice your friend selected, and tell them to secretly add these numbers together, i.e. their number plus 5. Then push your second 5 over and suggest, to make it even harder, to multiply their current number by 5+5 (i.e. 10 – that’s a nice easy multiplication to do) and remember that new number. Then finally turn attention to your friend’s remaining unused die, and get them to add that last number to give a grand total. Ask them now to tell you that grand total. Almost instantly you can predict exactly the unspoken numbers on each of their two invisible dice. If they ask how it you did it, say it was easy – they left the dice in plain sight on the table. You just needed to look at them.
The computing behind
This trick works by hiding some simple algebra in the presentation. You have no idea what two numbers your friend has chosen, but let’s call the number on the die they select A and the other number B. If we call the running total X then as the trick progresses the following happens: to begin with X=0, but then we add 5 to their secret number A, so X= A+5. We then get the volunteer to multiply this total by 5+5 (i.e. 10) so now X=10*(A+5). Then we finally add the second secret number B to give X=10(A+5)+B. If we expand this out, X= 10A+50+B. We know that A and B will be in the range 1-6 so this means that when your friend announces the grand total all you need to do is subtract 50 from that number. The number left (10*A+B) means that the value in the 10s column is the number A and the units column is B, and we can announce these out loud. For example if A=2 and B=4, we have the grand total as 10(2+5)+4 = 74, and 74 – 50= is 24, so A is 2, and B is 4.
In what are called procedural computer languages this idea of having a running total that changes as we go through well-defined steps in a computer program is a key element. The running total X is called a variable, to start in the trick, as in a program, we need to initialise this variable, that is we need to know what it is right at the start, in this case X=0. At each stage of the trick (program) we do something to change the ‘state’ of this variable X, ie there are rules to decide what it changes to and when, like adding 5 to the first secret number changes X from 0 to X=(A+5). A here isn’t a variable because your friend knows exactly what it is, A is 2 in the example above, and it won’t change at any time during the trick so it’s called a constant (even if we as the magician don’t know what that constant is). When the final value of the variable X is announced, we can use the algebra of the trick to recover the two constants A and B.
Other ways to do the trick
Of course there are other ways you could perform the trick using different ways to combine the numbers, as long as you end up with A being multiplied by 10 and B just being added. But you want to hide that fact as much as possible. For example you could use three ‘invisible dice’ yourself showing 5, 2 and 5 and go for 5*(A*2+5) + B if you feel confident your friend can quickly multiply by 5. Then you just need to subtract 25 from their grand total (10A+25+B), and you have their numbers. The secret here is to play with the presentation to get one that suits you and your audience, while not putting too much of a mental strain on you or your friend to have to do difficult maths in their head as they calculate the state changes of that ever-growing variable X.
How can you tell if someone looks trustworthy? Could it have anything to do with their facial expression? Some new research suggests that people are less likely to trust someone if their smile looks fake. Of course, that seems like common sense – you’d never think to yourself ‘wow, what a phoney’ and then decide to trust someone anyway. But we’re talking about very subtle clues here. The kind of thing that might only produce a bit of a gut feeling, or you might never be conscious of at all.
To do this experiment, researchers at Cardiff University told volunteers to pick someone to play a trust game with. The scientists told the volunteers to make their choice based on a short video of each person smiling – but they didn’t know the scientists could control certain aspects of each smile, and could make some smiles look more genuine than others.
One of the ways that computers could be more like humans – and maybe pass the Turing test – is by responding to emotion. But how could a computer learn to read human emotions out of words? Matthew Purver of Queen Mary University of London tells us how.
Have you ever thought about why you add emoticons to your text messages – symbols like 🙂 and :-@? Why do we do this with some messages but not with others? And why do we use different words, symbols and abbreviations in texts, Twitter messages, Facebook status updates and formal writing?
In face-to-face conversation, we get a lot of information from the way someone sounds, their facial expressions, and their gestures. In particular, this is the way we convey much of our emotional information – how happy or annoyed we’re feeling about what we’re saying. But when we’re sending a written message, these audio-visual cues are lost – so we have to think of other ways to convey the same information. The ways we choose to do this depend on the space we have available, and on what we think other people will understand. If we’re writing a book or an article, with lots of space and time available, we can use extra words to fully describe our point of view. But if we’re writing an SMS message when we’re short of time and the phone keypad takes time to use, or if we’re writing on Twitter and only have 140 characters of space, then we need to think of other conventions. Humans are very good at this – we can invent and understand new symbols, words or abbreviations quite easily. If you hadn’t seen the 😀 symbol before, you can probably guess what it means – especially if you know something about the person texting you, and what you’re talking about.
But computers are terrible at this. They’re generally bad at guessing new things, and they’re bad at understanding the way we naturally express ourselves. So if computers need to understand what people are writing to each other in short messages like on Twitter or Facebook, we have a problem. But this is something researchers would really like to do: for example, researchers in France, Germany and Ireland have all found that Twitter opinions can help predict election results, sometimes better than standard exit polls – and if we could accurately understand whether people are feeling happy or angry about a candidate when they tweet about them, we’d have a powerful tool for understanding popular opinion. Similarly we could automatically find out whether people liked a new product when it was launched; and some research even suggests you could even predict the stock market. But how do we teach computers to understand emotional content, and learn to adapt to the new ways we express it?
One answer might be in a class of techniques called semi-supervised learning. By taking some example messages in which the authors have made the emotional content very clear (using emoticons, or specific conventions like Twitter’s #fail or abbreviations like LOL), we can give ourselves a foundation to build on. A computer can learn the words and phrases that seem to be associated with these clear emotions, so it understands this limited set of messages. Then, by allowing it to find new data with the same words and phrases, it can learn new examples for itself. Eventually, it can learn new symbols or phrases if it sees them together with emotional patterns it already knows enough times to be confident, and then we’re on our way towards an emotionally aware computer. However, we’re still a fair way off getting it right all the time, every time.
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