Take the glass of water. Sprinkle pepper all over the top of the water. Put several drops of detergent into the centre of the dish.
What happens to the pepper?
Is the same thing happening over the whole surface of the water, or is it just in the middle?
Click here to get to the index.
Oh, that's right, I was off finishing a book, and having done that, I took a break, moved house, and started thinking about an idea that hit me in 1993. It had its roots in a science fiction book I read in about 1960, plus or minus two, and you can read about that book here, and that link takes you to my big blog.
In 1993, I was setting up Sciencescape at the Australian Museum, and in Thinkers' Corner, we posed a puzzle: our civilisation is about to crash, you have one piece of indestructible metal on which to engrave a thousand words about the key ideas of science, things that will help our descendants get science going again, things like there is tiny life all around us, and wash your hands and boil the drinking water.
Not long after that, I came up with the idea of SPLATS, a much more fully developed set of golden rules in science, those key ideas that most scientists agree on, most of the time. Long before Twitter and Tweets, far earlier than X or Bluesky, I set a limit of 160 characters for each idea, though it was permissible to chain them together.
Here are some examples, relating to surface tension:
Now I want to introduce readers to primitive science, the notion of exploring deep effects, using stuff that should be around your home, and as you may have guessed, I will start with surface tension.
All of these shots were taken with a clip-on in the first couple of days after I got the first one in the mail.
When people get their first hand lens, they examine their hands, fingerprints and fingernails, and then they look at their hair. With clip-ons, the first time they set their device down on their lap while they move something, they see the detail in cloth.
 |
| Two views of one piece of cloth, probably satin. |
You will need some different types of clothes (or a ragbag of clean scrap material), and an embiggener. Shirts and blouses are usually woven cloth, t-shirts are typically knitted, and I know little more than that. There are some interesting images to be gathered, though. What you do from there is up to you. Discover something!
 |
| Three other cloth samples, but how many types of fibre can you see? |
Now look at the fibres in cloth samples, to see if they can both be distinguished in the fabric, or not. Here are two shots of cotton polyester at x15 and x60, then three of pure merino, at x15, then at x30 and x60. This exploration began when I wondered if you could see the different fibres in composite cloth like cotton polyester cloth. I think I can do that!
 |
But can you tell merino from cotton polyester without
labelling or a microscope? I don’t think I can do that!
This is one of the fun ones, but I suppose I would say that, because I was once an amateur numismatist, working in the Commonwealth Treasury Department, and used to answer all the odd public enquiries about money and other things. You will need a range of coins of different ages.
The best fun comes with pre-decimal coins (earlier than 1966), so ask your grandparents if they have any. There are fine details hidden away on coins, like the abbreviated Latin details around the sovereign’s head, but there are also mint marks and designers’ initials.
On the pre-decimal coins, look for the abbreviated Latin description around the sovereign’s head, but there are also mint marks and designers’ initials.
 |
| A 1951 sixpence, minted in London. In 1966, the sixpence became the new five-cent coin. |
Pennies and halfpennies have KG near the kangaroo, but it doesn’t mean KanGaroo, it reminds us that George Kruger Grey designed it (and also the shilling coin, which later became 10 cents).
 |
| A 1942 penny: the dots each side of .PENNY. tell you where it was minted. |
 |
| An old florin (two shillings, which became the 20 cents), minted in San Francisco. |
Most of the decimal “silver” was designed by Stuart Devlin (SD), and if you look at coins minted during World Wars I and II, you will find many foreign mint marks like S (San Francisco), D (Denver), I (for India, meaning Calcutta).
 |
| Spot the designer’s initials on the Australian 10 cent coin, between the lyrebird’s tail and foot. |
Of course, if you can’t get any of those older coins, there are still
plenty of other surprises, like gashes, scratches and other marks.
Now take a look at this image below: do you know where it came from? I came across the shot in my files, and even though it was one I had personally taken with a clip-on. I had to check where it came from. It is an Australian coin, but foreign coins have secrets as well.
Let the hunt begin! Clearly there are many more puzzles like the ones suggested here for you to explore!
The lower surfaces of most leaves are covered in stomates, and while they require a good microscope to see them well, we can take a cast of a leaf surface and look at that, using either a clip-on or even a hand lens!
The cast is usually called ‘a peel’, and last century, peels were made with stuff called collodion. Now, there’s a simpler way. All you need is some clear nail polish, some sticky tape and a glass slide. Choose a leaf: it seems that most leaves work, but not Camellia, and leaves without hairs on their lower surface are best (use the hairy ones for Looking at leaves!).
Using a small amount of clear nail polish, paint a thin strip on the lower surface, about 1 cm wide and 3 cm long (accurate measures aren’t really important).
Leave the nail polish to dry for about 10 minutes, and then lay a strip of clear sticky tape over the nail polish. When you lift the tape off, the polish will come with it, and there will be a perfect cast of the leaf surface on the lower side. When you attach the tape to a glass slide, you are ready.
The tape, loaded with nail polish, is ready to go on the microscope slide.
Above, you can see two views of a peel from the lower surface of a bay leaf, at x100 and x400 (the inset).
Stomates let carbon dioxide in and oxygen out. They also let water vapour escape, so plants need to control their stomates, which are very tiny, about 0.05 mm (1/20 mm) across, so you won’t see them with the naked eye. Still, once you know what you are looking for, you can see them with a good hand lens, but only as closely-packed dots.
Sometimes research is just trying out ideas, and that was the case when I tried looking for stomates on fishbone fern. They are indeed there, but another form of scientific research involves reading ‘the literature’, the things other scientists have seen, noticed or discovered. That revealed that other people had already seen fern stomates. I found it has clear stomates on the under-side.
Another literature search told me that the very best plant for this exercise is Tradescantia pallida, a garden favourite with purple leaves, and one that grows easily from cuttings. Here on the left is what you can see of Tradescantia pallida with a clip-on at x15 and x65 (in the inset). Then I reached for a microscope, and the results are on the right. The same ‘peel’ is now seen through a high-end monocular microscope, at x40, x100 and x400. This is better!
Once you see this, the clip-on and hand lens views will make sense. Each stomate looks like two fat sausages (or lips) lying side by side: when they curve around, the stomatal pore opens and gases go in and out. The stomate is made up of two guard cells: these are the ‘lips’ of the ‘mouth’, but in Tradescantia pallida, there are two other cells, one at each end, making a rectangle.
It turns out that you can see the stomates on the plant’s actual leaf with a clip-on, if you know what you are doing! The shot above is not a peel: it is the actual plant that is under a clip-on. The first shot is with no digital zoom, the second is with full zoom. Look for the pale squares. This view is looking at the leaf itself, with reflected light. The stomates are the pale square shapes. The stomates are very visible at x60, but you can even see them with a hand lens offering x10, if you know what you are looking for.
Almost all the flowering plants have leaves. A few have phyllodes or cladodes, types of stem that work like leaves. Apart from that, there is a huge amount of variation to look for. They also have a few things in common. Most of the photosynthesis in a plant, the work of food-making, happens in the leaves.
The pictures above show a member of the pea family called Bossiaea (pronounced ‘bossier’). They are hard to find where I live, and these are the best shots I have. Notice how the leaves are reduced to little scales, poking out from the sides of the flattened stem, which is called a cladode.
Leaves also have openings called stomates, which we will come to later. Most leaves are green because of the chlorophyll in them. Chlorophyll is the molecule plants use to capture the sun’s energy to drive photosynthesis. Some leaves are coloured because they contain other pigments that hide the chlorophyll.
Old leaves get their colours because plants break down the chemicals in the leaves and try to take back as much goodness as possible before the leaves fall off. The autumn colours are leftovers. Most leaves have different upper and lower surfaces, but try to find a top or a bottom on a gum leaf!
Most leaves are free to wave around in the breeze, catching as much sunlight as possible, but gum leaves hang down vertically, which is why the two sides are identical.
Image credit: based on a Wikipedia Commons image, Leaf Tissue Structure by Zephyris.
You would never see the picture above under the microscope: it is built up from different views under high-powered microscopes. Ignore the names, but note that there are openings into the leaf, and air spaces inside. The chloroplasts inside the cells are the places where photosynthesis happens.
She-oak 'needles' are really stems that have the leaves stuck onto them. At each 'joint', there are leaf tips sticking out. Some leaves have hairs on them
There are other leaves that are furry.
And then there are the stomates...
This is my review of a neat little toy that I came across while writing this book. I went into some technicalities which I think are sufficiently explained, but they aren’t essential to readers here. I have my reservations about this gadget as a tool, but I recommend it as an informative toy for youngsters.
Mine seems to have no brand, but it is a camera, sold by various suppliers as a “digital microscope”, and it comes with a USB cable. Mine cost me about $26 on eBay, and it came minus the software, but the suppliers promptly gave me a link so I could get amcap.exe (for Windows). On my MacBook, I just use Photo Booth to capture the images.
I got another one from Amazon, but there seem to be many versions out there: just enter USB microscope into your search engine.
A few technicalities here: the camera only delivers 640 x 480 pixels, and the images are reported to be at 96 dpi (dots per inch), which means the images ought to be about 170 x 128 mm, but setting my simple software program to “actual size”, I get an image that is 200 x 150 mm on the screen. This is near enough, and it means that the images above show magnifications of x18 and x40, near enough.
Trust me, this is ab out surface tension. You need a glass of water, a pepper grinder, and a tiny amount of detergent. Take the glass of wat...
