Saturday Science: What is it all about ?

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Thanks for joining us here ! When we learn physics, we spend most of our time on theory. Which is great, but practical science projects should also be a substantial part of learning: it leads to deep learning, especially. So this website is about actually doing stuff, ‘getting your hands dirty’ with practical science and engineering projects.

As well as this website there is more: the Saturday Science books, go to the menu symbol Ξ above left to see about them (1 is free to download).  And there are the 46 articles in the magazine Engineering & Technology.  Some of the projects have videos which have links on them.  They will likely be more this year.  You can also go directly my 1 or 2 minute video shorts demonstrating many projects.  There are 45 or so, so far – access by going to YouTube, searching for Neil A Downie and clicking on the circle with my face on it for the recent ones.   Some  are filed as ‘shorts’, longer ones as ‘videos’.

Take a look at any real thing, a really close look, and you uncover many layers with more physics in each layer. Take a vehicle, like a train. It rolls along a track, it can’t be that difficult, after all its not rocket science. But not so fast ! How does the train roll ? Why doesn’t it skid ? Friction maybe ? Why doesn’t the track wear out ? What about axles ? Plain bearings & ball bearings. How do those work ? Corners, when the outer wheels have to roll further than the inside ones. Why doesn’t it stop rolling because of friction ? Steam, or diesel engines. One burns fuel outside the cylinder, one inside. But not all the fuel energy becomes driving energy. Carnot engine efficiency depends upon gas getting hot and then being cooled. How cooled ?… and so on.

Learning from practical projects is ‘pull’ learning, not ‘push’ learning: you want to figure out why something worked in a surprising way, or maybe didn’t work in a surprising way ! So you look up things, you think more deeply about things. Science clubs can offer a way of getting into more practical science projects. So go to a science club – or set one up if you don’t have one !

Press on the menu button with the triple ‘ = ‘ symbol Ξ above to get the menu/ navigation. There you will find sections about science projects and experiments you can make yourself.

Before diving into the dozens of projects on this website you might like to take a look at a video or two . The first one gives some answers to the question “Why do science projects”, while the second one shows some slightly crazy ways to literally launch a book. The third one is from the launch of my last book, The Ultimate Book of Saturday Science, which we made at Isaac Newton’s old house Woolsthorpe, where you can still see where he lived, and re-try some of his experiments in optics and mechanics.

As well as science projects, experiments and demonstrations there is a section called the Half-Bakery, where there a some half-baked projects – bright ideas that are half-tried, or worked but need further innovations. You’ll also find some tips and tricks on making things, and analysing what is going on. There is even a short section on innovation: brainstorming in teams and inventing new stuff. You might also find it interesting to take a look at the ‘blog’ below, at science and gadgets that are currently being worked on. As in the Half-Bakery section, though, you will find physics that is incomplete and projects that maybe don’t quite work – but maybe you can fix that !

NEW ! ! ! Christmas 2022 STEM Challenges in Engineering & Technology Magazine

There’s a couple more of my IET STEM projects for Christmas:

  1. Aerosleigh: how Santa will be able to get to those good children to give them a nice Christmas present – even if Rudolf and his pals are too busy and even if global warming means that there’s no snow for his sleigh to slide along.
  2. How to make a Santa Claus (or elf) detector, to see when someone’s landed on our roof, been down your chimney or passed through the door that goes to where your Christmas stockings are hanging up. All you need is a multimeter and some croc clips. Now you can get a heads-up to lean out of your window to see the magic of Christmas night.

Summer 2022 STEM Challenges in Engineering & Technology Magazine

The IET invited me to do 6 more pieces with them over the summer. Hope you have all had a look, but if you haven’t, do give them a click…

  1. Laser Gargoyles: light up the monsters at the bottom of your garden, with their scary LED eyes, using a laser pointer and the simplest imaginable circuit.
  2. Smoothwheel steamboats – sail your steamer along without paddles.  Just a smooth spinning disk like a CD or two – it’s a bit like the blower invented by the famous Mr. Tesla.
  3. An Invisible Car. With drive wheels on its roof.  How does that work?  Read all about the Subrugmarine.
  4. Cable Yachts: trim their sails and they’ll whizz along down a cable.
  5. The Digital Siphon Water ClockYou will be flushed with success if you build this siphoning clock, with its symphony of siphons big and small.
  6. The Fountain Boat: a jet of water can drive it along – even out to sea if you like.  It can sail along for hours – over the sea on a calm day.  And be environmentally friendly – because it’s solar powered.  As usual, the pieces have lots of pictures and a short video clip to make clear how they work.

Saturday Science has Moved!

We’ll be in Hexham, Northumberland from – but we’ll still be in London regularly.

We moved in August to Hexham, near Newcastle-on-Tyne. With the fast trains on the east coast – and lots of things going on with Highgate School, with the Institute of Physics and with Exovent, we’ll be down south pretty often. We’re closer to Scotland – so we will be popping up in places like Bute (last week) and elswhere in Scotland more often. And with accommodation near the sea in Northumberland, maybe we will do more projects involving beaches and the sea – like the sea-going (just!) Fountain Boat above.

Christmas 2021 STEM Challenges in Engineering & Technology Magazine

The IET carried on with a couple more of my STEM projects for Christmas:

  1. A Christmas Roundabout – driven by eddy currents – perfect coffee table ornament for stimulating ‘how on earth does that work’ discussion.
  2. Stepper Dice: all you need is a scrap stepper motor from an old printer and an low voltage AC supply to make your own motorized dice. Avoids arguments in those Xmas holiday games.

Summer 2021 STEM Challenges in Engineering & Technology Magazine

The IET is carried on with my STEM projects with another 6 over the summer:

  1. Whack-A-Rat and Rat-O-Matics: non-intuitive Ratty experiments to challenge your science
  2. The Vacuum Engine: we make a model of the engine that launched the Industrial Revolution and made the modern world
  3. Fire from water: a water lens sitting in a bowl of cling-film can really focus a lot of solar power !
  4. The Art of Heat: how to make pictures with thermal paper
  5. Water Battles: converting bike pumps to water rifles and a water-howitzer, the Single Helix pump
  6. Vacuum Pile Driver: use you vacuum cleaner to power your garden pile-driving.
  7. The Armstrong (Vacuum) Crane (no messy water required to pick things up and move them around)
  8. The Bernoulli Bearing and the Upside-Down Ceiling Hovercraft

And an update on the E&T magazine series: it has won a prize ! Look at , and you’ll see that my work with Crispin and Tim at the IET has won the bronze award for how-to articles.

Lockdown Challenge II January 2021… The UK Lockdown for Coronavirus continues

Another coronavirus / Covid-19 lockdown has descended on the UK. Which is a great opportunity for us all to get on with some home science projects ! Once again, Saturday Science has stepped up to the plate to do projects with friends and kids at home and on Zoom, with the help of the IET and Engineering and Technology magazine editor Tim Fryer. You can read all about it, see the pics and the video clips, on as before. As before too, do let us know about projects you did, how you did them, what you changed from our suggestions. Here is the latest 14 2021 Lockdown Projects to choose from just complete this month with Mole Radio:

1.Pykrete: Ice and Cushion Stuffing

2.Dancing Tubes on Hair driers

3.Holes without Drills

4.Whirlpool Toddy Lifters

5.Dead Reckoner from a Microbit

6.Eiffel Ice Tower

7.Swanee Banana Mystery

8.Paperclip Clocks

9.Forever Marbles

10.Safe Descender

11.Saxotron the electric saxophone

12.Breathing monitor + graph with noise & chest movement

13.Ski jumping for Rice and Beans

14.Mole Radio

AND here are all the projects Saturday Science did with IET in 2020:

1.The Vacuum Bazooka

2.Polarised Light: Art and Engineering Meet

3.The Eiffel Brick Tower

4.The Very Remote Control and Secret Agent Message System

5.Whirling Dervish Hosepipe Pump

6.Megawatt Sunbeam Balloon Exploder

7.The Sound of Drums and Trumpets

8.Microwave Steam and Glue

9.Go into Battle with Blunderspuds

10.Dodge those icebergs with a mobile phone radar

11.One pound Cable Cars

12.Time from Tissue Paper

13.Sundials on your ceiling and electric sundials

14.The Biggest Bang since The Big Bang

July 2020 … Lockdown Challenge I… Great projects for lockdown with IET

The UK Lockdown for Coronavirus continues, although with some increases in what we can do safely. But the good news is: the IET Engineering & Technology Magazine is continuing with the Lockdown Challenges. Saturday Science has contributed one of the two articles each week for the last 6 weeks. As well as the Vacuum Bazooka, we now have

  • adventures with polarized light (put a banner up on a TV that only someone with 3D cinema glasses can see
  • Eiffel Brick Towers: build a tower out of toy bricks TO THE CEILING!! And then play Jumbo Jenga with it
  • Very Remote Controllers: take over your neighbour’s TV from 100m away ! And send secret messages like James Bond
  • Whirlish Dervish Hosepipe Pump: Water the garden or pump out your sinking boat !
  • Megawatt per square meter Sunbeam Balloon Exploder

Here is a link to the whole set of 9 weeks published so far. Another 5 are just being finished and will appear in the next 5 weeks. Watch this space – and Engineering & Technology Magazine for more after that !

May… Vacuum Bazookas for IET Engineering & Technology magazine.

Saturday Science is now also what the IET are calling ‘Lockdown Challenge’, projects and challenges for everyone to have a go at that involve some science, some engineering, some stuff you probably have lying around your house or garage – and LOTS OF FUN !

The first episode of the series from me is on the famous Vacuum Bazooka – now an official Wikipedia website, the subject of my book with Princeton University and built and enjoyed on every continent on Planet Earth. (No reports of Vacuum Bazookas on Antarctica or in space yet, though). Click on the website .

April… Exovent breathing machines forge ahead to help patients with Covid-19 and other lung disease

Saturday Science has been very busy making more prototypes of negative pressure assistance machines for the Exovent Task-Force, and testing them in all sorts of ways. The machines are based on vacuum cleaners or other centrifugal blowers pulling a slight vacuum on a vessel which goes around the torso of a patient who has difficulty breathing. The vacuum can either be continuous (called continuous negative extrathoracic pressure or CNEP), Alternatively, the pressure can be cycled from from low to high negative pressures to help a patient breathe. Discussions sometimes go on up until midnight, while every day sees technical developments. The Exovent group now includes dozens of people, doctors and other clinicians, engineers and scientists and people from other walks of life.

As the project forges ahead, Saturday Science will set up a ‘page’ (which will be dozens of screen pages) which will give more details of some of the most interesting science behind the Exovent, with a different perspective to the Exovent website. That website, gives more information – and is just about to be expanded and updated.

February and March… Negative Pressure Breathing Assist for Covid-19. Covid-19 cases in the UK fit an exponential model. Girls measure moisture with ultrasonics.

Saturday Science has been working with a wider team to come up with simple but unusual scheme to provide breathing assistance to those who have breathing difficulty due to the virus disease Covid-19. In less than two weeks we have made 3 prototype ventilators and will be making another this week. Look at for more information.

A simple model of the cases recorded by the WHO would appear to fit the data nicely, as seen on the log-y graph versus date above, at least in the first 20 days. So in just a few days, the UK will have 10,000 cases, which is very serious, but now cases are heading beyond, but the growth rate is slowing. The growth in the cases for 20 days looks almost precisely exponential, with a growth factor of 0.3 per day in the formula:

Cases = 10 * exp (days since 27th Feb *0.3)

There is an important lesson to be learnt here which is quite general: the valuable insight into data that plotting a log graph offers. With a log-lin graph you can instantly see in the current epidemic what is really going on. Each new person who gets the virus is passing it on to a few others, and this means that after a week or two, the growth in the number of people who have or have had it will increase ‘geometrically’, i.e. by the same multiplication factor every day.

N1 = No x 1.35

N2 = No x 1.35 x 1.35 = No x 1.82

N3 = No x 1.35 x 1.35 = No x 2.46…

Nd = No x (1.35)^(no. days) OR

log10 Nd = log10 No + (days*1.13)

So the log of the number of cases increase linearly with the number of days, which of course means a simple straight line on a graph. The log graph shows clearly that the growth in cases is now growing more slowly – something that is not clear in an ordinary linear plot.

The Light Tunnel project on this website (and in my book Ink Sandwiches) provides another example, where an exponential pops up in the data that comes out of a highly unusual sensor.

Meanwhile, away from the medical hurly-burly, at the Innovative STEM Sessions organised (with students from several schools) at Highgate School, the third session saw all the groups successfully building a rig, making measurements and gathering data to analyse. One team, Team HAK has now successfully measured the surprising effect of moisture on ultrasonic reflectivity. Other groups successfully measured colour precisely with a rig of their own design and measured carbon dioxide with an ingenious electronic twist on the lime-water reaction. Further south in London school teams gathered at Sutton Grammar School to further brainstorm their inventions ready to start building and testing later in the month (Coronavirus-willing !). They are aiming to used ingenious types of Light Tunnel (on this website) to measure flow, measure water, provide assisted braking of a bike and even operate a musical instrument !

November: Ancient Greek Inventions, weather on Mars and the Liquid Nitrogen Ping-Pong Ball Turbine

October saw Diane and I holidaying in the warm autumn sun of the largest of the Greek islands, Crete. Crete was one of cradles of civilization, and a new museum, the Kotsanas Museum in the island capital, Heraklion, celebrates the technology side of this. The museum has a large number of hand-made replicas of the ancient machines, covering all sort of science from the motion of the planets to water pumps which were used for putting out fires. Thomas Petrakis showed us around, and he and his colleagues set many of the machines working and explained how they worked. thanks Thomas ! We got talking about the replica of the Hero Turbine, invented 2000 years ago.

This reminded us of a great liquid nitrogen demonstration: the Ping-Pong Ball Turbine. Look at the Liquid Nitrogen page to find out more.

Early in October, I was at a couple of Institute of Physics meetings for teachers in the North East, meeting up with teachers and the excellent IoP crew there. I enjoyed a chat with Paul Hardaker, CEO of IoP, about weather. It wasn’t just passing the time of day. Paul was a senior scientist at the Met Office and gave us a superb lecture on the huge strides that weather forecasting ! As I knew well from my friend the late Sue Ballard, with the aid of HUGE computer models, forecasting has gotten much, much better. And they work just as well on other planets – weather on Mars is now forecast !

After that, Bernard Taylor got us all to work making ‘particle accelerators’, actually glass bowls supplied by a Van der Graaf generator which can set suitably conductive balls zinging around the bowl with the aid of aluminium tape electrodes. Thanks Bernard !

The Odiham cosmology study group looked at Dark Energy and Dark Matter in the universe. They’ve both got to be there, it seems, but both are deeply mysterious. Next month we need to look at more (even bigger) mysteries. Inflation faster than the Zimbabwian Dollar, the assymetry in baryons (why you won’t be meeting an alien made of anti-protons and positrons any time soon), and, gulp, quantum gravity.

Carrying on with ultrasonics, I now have a very simple self-tuning oscillator – just six parts costing pennies – that can power up a continuous oscillation anywhere from just a few kHz to 500 kHz. Students can build these very quickly – even without soldering – and get going on measuring ultrasonic waves effects. More on this soon !

A chance remark then led to me testing out electrothermal oscillation as a subject for study. An example of such an oscillator is the common or garden thermostat: with a constant heat loss from a room, a thermostatted heater will switch on and off in a regular cycle. But how fast can this work ? Can you switch from mechanical devices and to tiny volumes to get a thermal ‘clock’ ? The answer… I don’t know yet ! Watch this space…

September… Ultrasonic Adventures

The manifold possibilities of ultrasonics popped up in discussion when someone asked how many ways there were of measuring the molecular weight of a gas. Well, to cut a long story short, I pulled out a drawer marked ‘Ultrasonics’ and started thinking – and playing. What can you do with ultrasound ? Well, you can measure transit time of pulses – distance measuring on a smaller scale but similar to GPS. The speed of ultrasound itself is useful, of course (tells molecular weight), you can reflect off things do radar, like bats do, you, you can check absorption – in gases, liquids or solids – at frequencies from 20kHz up to MHz. And of course in solids you don’t just have longitudinal (pressure) waves – there are transverse and surface waves too ! And what about waves up tubes ?

August… Adventures in China – the Water Kingdom and Chinese characters for physics

For most of August, Diane and I toured the east coast and some of the other major cities of China with. Science and engineering was in evidence, of course, from the ancient to the absolutely modern. We came across modern marvels like the Three Gorges Dam, with its 22GW capacity the biggest in the world, more than the comparable Itaipu Dam of Brazil/Paraguay. The scale is simply stunning – the size is comparable to many of the hills in the area – a reminder of how much flowing water you need – and what a geologically large scale of dam you need – to make a power station.

We saw lots of historical China, temples, palaces, walled towns and, of course, the Great Wall itself. In the ancient category came small boats, actually bamboo rafts made from giant 15cm diameter bamboos, propelled by outboard motors, but also by punt-pole on small waterways. And the Chinese language, a venerable systems quite different to the alphabetic and phonetic languages like English.

Could Chinese characters – the simpler ones at least – be useful in algebra ? The extra characters would extend and diversify the characters we use from the English and Greeks ones we use generally in maths and science. Because a single character can have a meaning, unlike in English (or Greek), they even have the chance to be used more meaningfully. Once readers know that a symbol means, for example, big, or middle, or sky, then they won’t have to cross-check a list of symbol definitions so often.

July… Check out Sonic Molecular Mass Meters

This month we had a whole bunch of Sonic Molecular Mass Meters being road-tested by students at the British Physics Olympiad ‘camp’ in St. John’s College, University of Oxford. Read all about they work – and how you can make one – on the Saturday Science Projects page.

Saturday Science Bazookas at Big Bang Fair London South 12th July

We were at the Big Bang Fair at Sutton Grammar School with a smorgasbord of Vacuum Bazookas.  We blasted projectiles at a big target, measuring their speed, measuring the pressure, and trying different projectiles to get the last metre per second out of them.  We showed off Vacuum Engines too, and one method to measure Vacuum Bazooka projectile speeds.  And students brainstormed nearly 30 more methods to measure its speed ! 

Some more Saturday Science projects will be popping up on the website too, from ingenious new rotameters to measuring the sun with a marble !

June… IoP Rugby Meeting went with a Boyle’s Law Bang !  

May… Escape Chutes, Microbits Blowing in the Wind, Curved Space & Quantum, Free 295-page E-book

There is a free ! e-book on the website – a full downloadable printable copy of the Exploding Disk Cannons book, a paperback and hardback book, 295 pages with history, analysis, projects, tips and tricks and a ton of science that you won’t find anywhere else. There is a link to download it on the Saturday Science Books page. (Do let me know if you have problems with this).

Travelling this month both by ship and by jet plane, we noticed the escape chutes available in both. The physics and engineering of escape chutes is something on which lives can depend. Not widely known about, but they are interesting – they can be both sloping at different angles, even right up to vertical. We’ve started looking at a model chute using a Microbit with its acceleration sensor, and have the first data. And we are using the Microbit and acceleration sensor for measuring wind… its incredibly simple – but not quite working ! We’ll tell you how just as soon as we have some good data.

Finally, there’s a whole new section (‘page’), Curved Space & Quantum, which goes into the maths and algebra behind Stephen Hawking’s book Briefer History of Time. It has all the weird stuff that happens when you have things that move at incredible speed, near the speed of light, when you have enormous things like black holes, and when you move to the quantum world of the very small.

April… British Physics Olympiad in China, Magic Chinese Water Paper and more… more projects this month !

Being in China, we were reminded of the ‘magic’ paper which is used by Chinese children to learn to write the complex calligraphy of the ancient tradition of Chinese writing system. And discussing physics always involves collisions, and collisions gets you to thinking about marbles. We’ve now put up some examples of the serendipitous combination of marbles and Chinese magic water paper – now in the Marbellous section, of course.

We were also busy playing around with glow-in-the-dark gadgets like phosphorescent emergency signs charge by light and those ingenious chemical Glow Sticks which glow in the dark when the glass tube inside is broken by bending them. We monitored the light coming out versus time, with both a multimeter and also ‘intelligent’ data gathering using a Microbit computer. Interestingly, the glow seems to follows a double exponential curve, not a simple single exponential curve. A Chinese student knows something about these – we’ll report back: this is all on the Optical Realities page.

March… 6 more projects this month

This month, there is another 6 projects – Waltzing Tube in 3 Minute Sat Sci, Wet Solar Cells in Optical Realities, Pneumatic Drums in Sat Sci Projects, Light Tunnels in the Microbit Sat Sci section, Air Juggling (using a hair drier) on the Appliance of Sat Sci page, and Balloon Biceps on the Subtle Sat Sci of String page. Click on those sections to see what they are all about.

As well as all this, there has been some more exploration on the February’s ‘Latest’ posting – how kitchen hand blenders can ‘suck’ a cup or small bowl up. Then it’ll go onto one of the main pages, maybe on the 3-minute Saturday Science section.

February… Kitchen Blenders also suck

Following a tip from Esther Redhouse White (thanks Esther !), Diane and I have been playing around with how hand blenders – those electric kitchen gadgets handy for making soup out of vegetables – can actually lift up cups /small bowls of water. Really ? you might think. It may be weird but it really happens. If you don’t believe us, grab a blender and just try it yourself.

But how, why does it happen ? What is the physics behind this ?

I thought that this might be down to some kind of Bernoulli effect, because Bernoulli is often causes weird surprising effects. But now I think it might be basically down to the blender working like a peculiar sort of ‘cut-away’ centrifugal pump.

A proper centrifugal pump produces a basic pressure P given by

P = ρv2 / r

where ρ is the density, v the speed of the blade tips, and r the radius. Now it turns out that if you put some numbers in, you get forces like 10N, or 1 kilogram lift force. Could this be right ?

Well Diane had a nice idea for how to prove it: she taped a length of plastic straw to the side of the blender, going down to the centre at the bottom. There are probably some other effects going on – I am not sure what – but I think that this is 80% of the explanation of how lifting blender works. Now watch the video to see how Di’s ingenious modification works.

January… bent-pipe control

I’ve been playing around with the idea of something that gets you flow control using the bending of a tube. Most of us have stopped a garden hose by bending over to 180 degrees. In fact, though, the effect is not used in flow control – crushing the tube is preferred. Flow stopping by crushing a tube is a long established technology, used, for example, in peristaltic pumps, where a roller squeezing down on a tube pushes liquid inside it along. We’ve all seen those little plastic adjustable clips, or metal clips with a little screw that adjust flow by crushing a tube: there are thousands of them in every hospital, regulating flow of drips, for example. I’ve often thought that it would be useful to know the ‘law of pipe crushing’. What formula does flow in a crushed pipe follow versus, for example, the distance between the crushing bars in a screw clip ? Its probably fairly complicated. You can see with some tubes, for example, that the free cross-section goes smoothly from circular to oval, then, often, to a kind of elongated dumb-bell shape.


Simply squeezing the tube works fine with ultra-flexible PVC tubing of relatively small diameter. But you can also get great flow control of bigger, nominally rigid pipe, leastways reasonably thin-walled slightly flexible pipe polypropylene pipe by bending it. You can monitor the control you are getting by looking at the angle of the bend. And it has the advantage of needing no equipment other than Mk I Human Hands. We’ve used this for a while now to control the flow of air to a vacuum cleaner in vacuum-based projects. But the the pipe is really difficult to bend at first, then – OOoops ! – it bends down flat and nearly shuts off the vacuum cleaner.

Above shows the ‘Dee’-shaped cross section of the pipe – clearer in the back-lit pic on the right – which forms as it is bent against the fulcrum post. The Dee narrows as the angle of bend increases, decreases the flow. The pipe is 32mm bore, 1.5mm wall thickness polypropylene. We think that we’ve uncovered ways of making this more usable which still needs some more work… more coming soon !

ri talk question

The most exciting phrase in science is not “Eureka !”  but ‘That’s funny” – Albert Einstein  Neil A Downie doing Saturday Science at the Royal Institution, London