One of the biggest challenges to any town or city based amateur visual astronomer is the pollution due to street and business lighting.  This ’second hand light’ basically wrecks the night sky for a considerable distance around most UK cities, although some local authorities are finally realising that reducing light pollution is good for their energy bills as well as being good for people’s experience of the natural environment.

For some people, though, it’s their well-being that is also suffering with 50% of respondents to a recent CPRE / BAA survey on the impact of artificial light reporting disturbed sleep.

I was gratified to see this report and hope that local authorities will start treating light pollution like noise pollution and other forms of disruption to our enjoyment of the natural world.

This is a fine example of what’s possible on a small budget with some ingenuity and determination.  Taking photographs of the Earth from the edge of space using digital cameras taken up on weather balloons, all on a shoestring budget.

Congratulations to Mr Harrison and his ‘Icarus’ project!

Apparently even NASA have been in touch to see how this was done – perhaps the budget there is tighter than we think…

Or, as we Brits call them, biscuits!

Not strictly speaking a scientific experiment, but this scientifically inspired recipe for biscuits based on the energy states of the hydrogen atom has to be worth a quick look!

http://www.evilmadscientist.com/article.php/atomiccookies

Plastics are an example of a chemical compound called a polymer - a material made up of long chains of smaller identical molecules that are linked together.   Although the term polymer is often associated with plastics, it also describes a number of biological molecules, such as starch and cellulose, as well as more complex molecules such as DNA.

Level : Simple

Time Required : 30 minutes (plus drying time)

You will need

• Some milk – not necessarily fresh, a cup full will do.
• A small saucepan to heat the milk in.
• A wooden stirring spoon or spatula
• Vinegar – either white vinegar or malt vinegar will do
• Colander / Sieve
• Paper towel
• Cooker – may require adult supervision
• Rubber or plastic gloves

What to do

Line the sieve / colander with a paper towel.  If you have them available, a coffee filter is a better proposition, but with care a paper towel works fine.

Pour the milk in to the saucepan and gently heat it to bring it up to a simmer – don’t let it boil.  Pour a little vinegar in to the milk, and keep the milk simmering whilst you stir the milk / vinegar mixture.  As your pour more vinegar in, you’ll see a white fluffy material appear in the milk, and the liquid remaining will become clear.  After a while, the addition of more vinegar will result in no more change in the milk, which will now consist of a suspension of a white, fluffy precipitate. This is Casein,  a milk protein that cannot stay in solution in acid – hence the use of vinegar.

The precipitate now needs to be drained off.  You can start this by carefully pouring off the clear liquid, then pouring the liquid containing the precipitate in to the paper towel in the sieve.  Allow the liquid to drain through the paper, leaving the precipitate behind.  You can gently press the precipitate to squeeze the fluid out – just don’t tear the paper.  This is also a good time to rinse the precipitate with clean water to get rid of excess vinegar.

Once you’ve drained as much liquid off as possible, you’ll end up with something like the photo below:

Using the gloves, you can squeeze remaining fluid out of the polymer, and knead it until it becomes more ‘doughy’ .  You can shape the ‘plastic’ with your fingers and mould it in to a ball, or use a pastry-cutter to cut out a particular shape. 

You can then leave the plastic to harden – this will take a couple of days in a warm place.  If you try speeding up the process in the oven, don’t put the heat up too high or you’ll burn the plastic.  Once it’s dry, you can paint the shape you’ve created.  Just don’t eat it….

Further Experiments

When the plastic is still in solution, you can try adding food colouring to the solution to get a coloured precipitate out before moulding and drying. 

You may notice a similar effect to this if you ever try heating milk for a hot drink that is on the edge of curdling.  The first stages of milk going sour is the creation of mildly acid conditions in the milk, which, as we’ve seen, causes the precipitation of the Casein protein from the milk.  Under normal conditions, you smell the milk as ‘off’ before you witness the precipitation, but if you heat souring milk you get the reaction that we’ve witnessed here.  I know this because I’ve done it more than once…

Level : Simple
Setup Time: 5 minutes, then 5-10 minutes to get the results.

This experiment demonstrates how heating can cause permanent chemical changes in materials – and also makes simple invisible ink!

You will need:

• A sheet of plain, white paper.
• A small amount of milk
• A small amount of lemon juice
• A fine paintbrush
• An oven – pre-heated to Gas Mark 4 or there abouts (CARE – children should get an adult to help here)
• A baking tray big enough to take the paper

What to do

Using the paint brush, draw some images or letters on the sheet of paper using the milk and / or lemon juice.  The easiest way to do this is to draw with lemon juice, then wash the brush, then draw with the milk.  Don’t use too much liquid.  It can be very difficult to see what you’re writing – after all, we are using invisible ink – but a strong light shining from one side will allow you to see what you’re doing.

When you’ve completed your message, put the sheet of paper on one side for a while until everything is dry.  With luck, you’ll have a sheet of paper that looks like that below – look, no words!

Now put the sheet in the oven, in a baking tray, and ‘cook’ for 5 minutes.  Note that the baking tray is pretty important – otherwise hot air will blow the sheet of paper around the oven, especially a gas oven!!  Take the sheet out of the oven.  You should now have a sheet of paper with your messages revealed – like that below.  If the ‘developing’ isn’t yet complete, put the sheet of paper back in for a while longer, and perhaps turn the heat up a little.

How does it work?

The heating in the oven actually burns the chemical compounds that make up the lemon juice and the milk, and discolours them.  For this to work, the decomposition temperature of the chemicals must be below that of the paper.  For Citric Acid – the ‘active ingredient’ for our purposes of the Lemon juice, this temperature is 175′C.  A similar principle applies to the milk.  The heat decomposes the ingredients in the milk and lemon juice and the resultant products are the brown colour that we see on the paper.

Further Experiments

You might like to try other fruit juices to see whether they work as well as the Lemon Juice.  Prisoners of War used to make their own invisible inks out of their saliva and sweat – these would then be ‘developed’ in a similar way to the process we’ve used here by the recipients.

This has to be an encouraging turn of events; anyone who’s read Ben Goldacre’s book ‘Bad Science’ (most recent edition) will remember some of the stories of legal pressure he told.

In this story, Simon Singh has succesfully defeated a libel claim from the British Chiropractic Association.  It’s a triumph for freedom of expression, but doesn’t absolve anyone involved in science writing – at any level – from getting our facts and evidence in order.

It’s now fortunately harder to sue you for doing good science!

How very true!  According to this piece of research, science teachers in the UK are doing fewer practical based sessions than they used to due to the demands of the curriculumn or testing.

 I have to say that as an ‘outsider’ this has been my perception based on anecdotes told to me by teachers – perhaps Hands On Science can help stay this trend by making easy experiments available to all?

Level: Simple    
Setup Time: 5 minutes
This simple demonstration shows how to make a battery out of easily available kitchen materials. 

You will need:

• A piece of aluminium foil, about 6cm x 6cm.
• A square of kitchen towel.
• A 2p piece.
• Some lemon juice or vinegar in water.

The basic ingredients are shown below, along with a voltmeter to measure the output of our battery.  A digital voltmeter is suggested – these are easily purchased for a few pounds from Maplin or similar shops. 

What to do

The coins used should be reasonably clean.  A coin will provide one of the electrodes of the battery.  The second electrode is provided by the piece of aluminium cooking foil.  To provide the electrolyte,  mix some lemon juice or vinegar with some water – you won’t need too much a mixture of half and half in an egg-cup will provide more than enough for this experiment. 

To do the experiment, turn the set the voltmeter to a DC Voltage range of 1 or 2 volts.  Moisten the square of paper towel with the electrolyte – be careful handling it when wet, as it may well tear if handled roughly. Put the paper towel down on the aluminium foil, and then lay the coin on top of the paper. NOTE – the coin and aluminium foil should not be in contact with each other dircetly, only through the electrolyte soaked paper.

That’s it!  Now, place the negative probe from the voltmeter on to the foil, and the positive probe on to the top of the coin.  You should see a voltage generated of about 0.5 to 0.6 volts.  Unfortunately, you’re not in a position to put Ever Ready out of business yet – this simple battery can supply next to no electrical current, which means that whilst it is generating electricity, as shown by the presence of a voltage, it is incapable of doing any useful work.

How does it work?

Ever chewed on a piece of silver foil from a chocolate bar and felt a tingle as it touched a filling?  That’s the same principle here.  In your mouth, your saliva provides the electrolyte, the filling is the equivalent of the copper coin used here and the aluminium foil is the same in both cases!

The principle here is – Dis-similar metals bought in to contact in the presence of an electrolyte’.  So, that begs a question.  What is an electrolyte?  In this field of science – electrochemistry - an electrolyte is a usually a solution of a chemical compound in a solvent which conducts electricity.  This conduction is made possible by the fact that soem chemicals split in to positive and negatively charged ‘ions’ when dissolved in an appropriate solvent – water, or a weak acid, for example.  These ions allow the solution to conduct electricity, and also allow the electrolyte to be used in the generation of electricity.

The two metals used – copper in the coins and aluminium from the kitchen foil – have different affinities for electrons.  Copper attracts electrons more than Aluminium does, and the electrolyte solution allows this transfer of electrons to take place.  When we connect the electrodes of our ‘cell’ (in electrical terms, a battery is made up of several of these simple cells) an electrical circuit is completed and the electron flow is completed.

 This sort of electrical cell is known as a Voltaic or Galvanic cell – dissimilar metals in contact with each other in the presence of an electrolyte.

Further Experiments

Here are some ideas for further investigations.

1. What happens to the voltage as time passes?
2. Is the voltage produced dependent upon the strength of the scid solution?  What happens with neat vinegar or lemon juice, rather than a dilute solution?
3. What happens with the same metals (e.g. two coins)  rather than a coin and aluminium foil?
4. What happens to the voltage with other combinations of metals?  You might find looking at the Electrochemical Series will give you some ideas.

There are some more complex experiments discussed here.

In my computational youth, I designed and built several ‘interface cards’ for Z80 based systems, as well as made full use of the excellent interface capabilities of the BBC Micro.  When PCs came along I have to say that I did less work with interfaces, but in recent years I’ve become more and more inteersted in getting back in to this field.

On a recent trip to Maplins I encountered a rather nice looking ready built circuitboard from Velleman that provided digital and analogue inputs and outputs interfaced to a USB connection.  The price was a reasonable £25-00 – not bad for a ready made piece of kit – and whilst it was clear that the board wouldn’t be suitable for fast conversions of data I concluded that it might work nicely for basic recording of experimental data and experiments in control technology.

Construction

The board comes as a ‘bare’ printed circuit board, nice little rubber feet for table top use and the inputs and outputs are made available via screw connectors.  The board also features a host of LEDs displaying outputs, and some push buttons and a couple of preset ersistors used for the analogue input setup.   The illustration belows shows the board and the major components on it.

Quality of build is good, and the USB socket is soldered to the board with a couple of good sized lugs – it’s not just held down by the connections for the interface itself.  As sockets are often a major point of failure, this was good to see.  As can be seen, chips are socketed (and identifiable!) and there are no surface mounted components; the board looks fixable!

The two illustrations above show closer up views of the input and output sections of the board.  I was particularly pleased to see built in LEDs and pushbuttons here, and to see the outputs at least slightly protected with 1k resistors, as it allows you to start playing with the board ‘out of the box’, rather than having to go digging around for bits and pieces!  The outputs are Open Collector.

The board draws power from the USB socket – I had no problems using the board with a laptop and a desktop, with all outputs on, and with other USB devices in use.  Quoted consumption is 70mA.  The board comes with a USB cable about a metre long.

My only grumble was with the positioning of the USB socket on the board.  If you sit it on your bench ‘logically’ – that is, writing right way up, inputs to left, outputs to right – then the USB socket is at the front of the car, which can get in the way a little when the cable’s connected.  But that was my only grumble with the build.

Software and Information

The board comes with a miniature CDROM containing a series of directories for various Velleman products.  Basically, all you need is in the K8055_VM110 folder.  This contains a PDF leaflet about the product which has some basic technical information on it, and a series of folders, of which your first port of call can be the ‘Kit Assembly and Info’ and ‘Software Manual’ folders where you will find good documentation.  The documentation is provided as PDF files in multiple languages – for English speakers look for the _UK ones.  The hardware documentation contains a schematic diagram and also circuit component values.

In sofwtare terms the first step is to install the Demo program.  This installs the DLL that supports communication with the Interface board, and provides a very basic demonstration of the capabilities of the board.  This is to be found in a folder called ‘Demo PC Soft Install’ and runs on Windows 98SE, ME, Windows 2000 and XP.

Source code samples are suplied in Visual BASIC 6.0, VB.NET and VC.NET.  All versions require the DLL supplied with the board to handle the USB communication.

The sofwtare isn’t thrilling , but is adequate to demonstrate that the board is working.  The source code samples supplied are adequate for anyone with a basic knowledge of programming to create their own applications.

In terms of performance, commands are executed within 20mS.  This puts a limit on the frequency of signals that can be measured via the inputs, but the board is perfectly adequate for doing experimental recfording, simple robotics and control technology, exploring assistive technologies, etc.

I’ll be using this board regularly – I’ll post applications and experiments as I do them!