Crafty, Physics, Together with sis

Physics Experiments: Slime for Science

We had such a genuinely rewarding homeschooling experience yesterday when we took up Physics Girl’s challenge to recreate the Weissenberg effect – a phenomenon that occurs when a spinning rod is inserted into a solution of elastic (non-newtonian) liquid.

Our first attempts to make slime following Physics Girl’s recipe (1/2 cup PVA glue, 1/2 water plus 1/4 tsp borax dissolved in another 1/2 warm water) failed so we returned to the department store to get starch, a different type of glue and anything else that might help. Did we use the wrong glue? What is borax (originally, we thought it was the same as the salt used to clean the dishwasher)?

After we started asking around, the shop assistants threw in a couple of handy tips (like getting some fluid used for cleaning your contact lenses as it contains something like borax, borate buffers, and mixing that with glue and shaving cream). At the drug store, we got warned about the dangers of pure borax powder if used in large quantities (skin burns), but did manage to get a tiny bottle of the stuff after we assured that it was for an adult supervised experiment. With all this useful info and terribly tired, but fully equipped we returned home and resumed our attempts at mixing perfect slime. You can see for yourself in this unlisted video how we went about it.

Eventually, we ended up adding twice (in not thrice) the amount of borax to finally froth up the right consistency non-newtonian fluid and it just worked!

(Instead of being thrown outward, the solution is drawn towards the rod and rises up around it. This is a direct consequence of the normal stress that acts like a hoop stress around the rod).

Simon wrote: In this video, I make slime “climb” up! It’s because of the “viscoelasticity” of the slime.

Correction: I’ve made a mistake when I said “times H2O”. The dot in the formula didn’t mean “times”, it meant ion.

The borax formula was indeed what Simon called “a mouthful”: Na2[B4O5(OH)4]·8H2O where the dot refers to the elements in square brackets all forming the [B4O5(OH)4]2− ion.

So what is borax? It’s a mineral, a salt of boric acid, also called (di)sodium tertaborate, usually possessing a crystal water content (although the commercially available borax is partially dehydrated).

Thanks to more borax, check out how high our fluid rose – it came out the other side of the straw!

Crafty, Experiments, Geometry Joys, Murderous Maths, Physics, Simon teaching, Simon's sketch book, Together with sis

Physics Experiments: The Color Wheel and Mind Blending

Inspired by Physics Girl, here come a couple crafty color wheel experiments involving what Physics Girl calls “mind blending” (it may not be the real name) – mixing color wave lengths in your mind. Simon has already studied the way our brain perceives blended/ moving color before, in the several optical illusions he programmed. This time, however, he decided to observe how simple paint can produce the same effect.

CORRECTION by Simon: You can’t actually even see the entire visible spectrum. You only see red, green and blue (I couldn’t think of that in the video).

The rotating green and red disk look more yellow in this extra 2 sec of footage taken by a different camera:

Simon prepared the props himself, with some help from his sister New (who painted one of the disks) and me (I helped cutting the hard cardboard). We couldn’t figure out a way to get the disks to spin fast and tried several options (like straws, pencils and even a dismantles giroscope). Eventually, we decided to use a small drill from a children’s woodworking set and it worked!

Making the fourth disk was the most difficult part as Simon wanted to divide the circle into 12 equal sectors. He came up with this elegant solution: he drew a hexagon and then bisected every angle (see below).

Experiments, Physics

Physics Experiments: Levitating small spherical objects and air pressure

This is Simon’s favourite self-made toy at the moment: a straw and a ball made of foam clay. He is continuously experimenting with trying to levitate the ball with rising air, also after he tilts the straw and the air is blown sideways, a phenomenon dominated by the Coanda effect.  Above is another variation of this experiment with a blow drier. Simon is also interested in acoustic levitation, but we had to admit to ourselves that building an acoustic levitation set at home is to advanced for us, at least for the time being.

Experiments, Notes on everyday life, Physics, Together with sis

Physics Experiments: Vortices

Simon learned about this experiment from Physics Girl and tried several variations with a number of plastic plates and frisbees. He even got kicked out of a fashionable pool in Southern France for doing weird stuff with a plastic plate in the water. “Are you stupid or something?” the guard yelled at me when I tried to explain that it was a science experiment.

This video is a rather short visual summary of what two connected
vortices actually look like.

If you want to hear Simon explain the Physics behind the phenomenon, check out this longer video:


And here is yet another video with Simon trying (not extremely successfully) to add food colouring to emphasise the vortices’ shape. We actually set up a huge inflatable kiddy pool specifically for that last try. Anything for science!




chemistry, Exercise, Experiments, Good Reads, Milestones, motor skills, Murderous Maths, Notes on everyday life, Physics, Simon makes gamez, Simon's sketch book, Together with sis, Trips

Looking back at the vacation

Although vacation is a vague notion in our family, where days are devoted to doing favourite things 365 days a year. For Simon, that means that his days are filled to the brim with science experiments, practicing math and devouring books and videos on quantum mechanics, also when he is on vacation (away from home). The past three weeks in Southern France and Spanish Sitges also involved a lot of swimming and enjoying the outdoors of course, but science remains Simon’s top priority. He also felt like he had grown unaccustomed to the beach overkill (while at home, we only went to the beach something like once a week max) and couldn’t bear the sand sticking to his wet feet for a while. By the time we settled at our Spanish Airbnb he gradually got acclimatised to this continuous sensory ordeal though and I was happy to see him relax at the seashore, especially on the last day of our stay. He had spent about two hours in the water (experimenting with vortices, swimming after a ball and just playing silly), and  didn’t even want to get the sand off his feet anymore. We just sat there on the beautiful retro beach in Sitges, hugging and watching the sea, in absolute tranquility. Simon had even forgotten that Daniel Shiffman’s live stream was due that evening!

dsc_06646749091631384876171.jpgMade a lot of “binary calculators” (above)

dsc_08098571406704053720752.jpgHelped little sis learn fractions

dsc_07972979319674618445058.jpgIntroduced little sis to infinite fractions

dsc_06271192208290101593530.jpgChecked out his new lathe tools and tried sawing

dsc_06877459075749954970581.jpgExperimented a whole lot (with surface tension, forces, water and gases)


dsc_07585635002843708540665.jpgYet another experiment

dsc_08371515643779040846973.jpgFollowed tutorials by Physics Girl, Up and Atop, PBS Space Time, Veritasium, Reactions, PBS Infinite Series




Loved his new Larry Gonnick Calculus book and did quite a lot of… Calculus. It was quite funny when a restaurant owner noticed Simon differentiate at dinnertime and was very impressed. He trend out to be a former high school science teacher. Interesting how Simon’s giftedness is usually only openly appreciated by those who have some understanding of the subjects he elaborates upon. People with less understanding show less tolerance, like a guard at the French swimming pool who told us off and snatched Simon’s (clean) plastic plate away, not allowing Simon to carry out his beloved vortices experiment in the public pool (resulting in a huge meltdown and Simon being afraid the pool would close or change rules every day).











dsc_09612735924853232773240.jpgLaunching propeller rockets on the beach

dsc_09071976964664774880504.jpgSimon’s first chemical equations. He first thought they worked like linear equations 🙂

dsc_08943237920924875579728.jpgMore Physics Girl inspired experiments

dsc_09108778766156185324596.jpgFavourite one: burning matches in a glass results in all the water in a shallow plate getting sucked into the glass (water level rising). Has a physical and a chemical explanation!

dsc_08732805749892983265193.jpgFavourite evening activity

dsc_09114093660143972351481.jpgLoving the waves

Coding, Java, Physics, Simon's Own Code

Optical Illusions in Processing (Java)

Simon created three optical illusions in Processing (Java) playing with color. For better effect, you can download Simon’s code on GitHub:

The Part 1 video is about the first two illusions. The third (and the coolest) illusion is in Part 2.


Simon writes:
Illusion 1: A checkerboard with blue and yellow squares, but if you move away from it, you see white.
Illusion 2
Mode 1: A disk with red and green, but when you spin it, it becomes yellow.
Mode 2: A disk with red and cyan, but when you spin it, it disappears.
Illusion 3: A rainbow of colors, but when you pause it from flickering, you only see red, green, and blue.

If Illusion 2 Mode 2 doesn’t work, change the background from 255 to between 128 and 135.
If any of the other illusions don’t work, try doing them on a different screen.

Inspired by Physics Girl videos.