Blowing young minds with quantum mechanics

This morning I had my next visit to Loreto Kirribilli for mentoring with my four students there. They’re learning about waves at the moment in their science class, and the teacher suggested I talk about something related to light.

I started by asking them if they had any questions and one girl asked about sonic booms. I explained that by drawing diagrams to show how an object moving faster than sound creates a shock wave. Along the way I also mentioned the Doppler effect, since it’s closely related.

Then having started with sound waves I moved on to talk about interference, explaining destructive and constructive interference. I talked about how interference is used in noise-cancelling headphones and how they work. Then I went into an explanation of the double slit interference pattern, framing it first in terms of sound waves, building on the example of the headphones to explain the pattern of loud and soft areas.

All right, now we were ready to talk about light—also a wave. And if we take a single-wavelength light source like a laser and shine it on double slits, we get the same interference pattern as bright and dark spots of light. And if you change the wavelength, you change the spread of the pattern. So far, so good.

Then I switched tracks and started talking about electrons, which we had discussed at length last time. I explained how you can create a beam of electrons, by ionising something and accelerating them in an electric field. One girl asked if this was related to cathode rays, so we took a bit of a diversion into that and why they were called cathode rays historically. And how old cathode-ray TVs and displays worked.

Then I asked a question: What if we fire this beam of electrons at a double slit?

I could virtually see the wheels turning in the girls’ heads as they pondered why I was asking this question, and what the answer could possibly be. I didn’t keep them in suspense too long. I said you’d see an interference pattern, exactly as if it was a beam of light. This is what’s actually observed if you do the experiment. I explained that electrons are not “particles” in the way we think of macroscopic particles like marbles or grains of sand. They don’t behave in the same way as macroscopic particles. They behave like waves. I tied this back to last time’s discussion of electron orbitals in atoms, and explained that this wave behaviour is what’s behind the strange shapes of the orbitals, as the electrons are essentially interfering with one another.

I also mentioned that if you change the speed of the electrons (by changing the voltage of the electric field in the beam generator), then you change the spread of the interference pattern—exactly as if you were changing the “wavelength” of the electrons.

At this point the teacher reappeared. I asked him how much longer we had, and he said about three minutes. I said, “Great. That’s enough time. I’m just about to blow their minds.”

Okay, I said, so we get this interference pattern when we fire a whole bunch of electrons at a double slit. What if we slow it down? What if we fire one electron at a time; say one per day? Today we fire one electron. Where will it land?

Again, it was obvious the gears were turning in their heads. I said, “Well, it might end up here, right in the middle.” And I drew a dot. “Tomorrow, we fire another electron. Where’s that going to land? Maybe not the same place. It might end up here.” And a I drew a dot off to one side. “And the next day?” I kept adding more dots, one at a time, faster and faster, talking through that each electron was being fired once per day, so they couldn’t possibly be interfering with each other, but that over time as the dots accumulate you see exactly the same interference pattern emerging.

A single electron passing through double slits will have a chance of landing in different positions depending on the interference of its wave nature. We have no way of predicting where any individual electron will land, but we know it will have this shape built up over many electrons. Which slit does a single electron “go through”? We don’t really know. It acts like it goes through both at once. Matter at small scales like electrons and atoms doesn’t behave at all like macroscopic objects. It exhibits this mixed wave/particle nature that seems odd to us.

I looked from the whiteboard I was drawing on to the girls and they were all staring at me wide-eyed, absolutely rapt.

And the bell went off, and it was the end of our time together for the day. It was really cool. This was our last lesson for this term. They have a mid-year break, and then in the new term after the break the teacher needs to organise plans for the rest of the year. So it’ll be a few weeks before I see them again. But definitely looking forward to it!

After the lesson I took Scully to Maggio’s bakery for a slice of pizza, and I picked up another one of their award winning apple pies, to take home for dessert tonight. Back home, I packed a bunch of cards for sending to eBay buyers:

Packages

Then I had to drag them all up to the post office for mailing. It was quite a task carrying all of them and handling Scully at the same time, even though I drove most of the way there.

Back at home I did another section of the Lego D&D set. First, photos of stage 16 which I did yesterday. Skeletons!

Lego D&D set, stage 16

Lego D&D set, stage 16

And the roof frame is completed, awaiting the next storey to be placed on top. And today’s stage 17 was just this cool displacer beast:

Lego D&D set, stage 17

Lego D&D set, stage 17

Which fits into the room like this:

Lego D&D set, stage 17

This evening I restarted my critical thinking/ethics classes, with the new topic on “The Countryside”. One notable response I got was to the question “How important is it for children from the city to experience the countryside?” I expected answers like it’s good to see farms where your food comes from, or to see wildlife. But one student said that it was a good idea because there’s no Internet connectivity there and kids can spend time off their devices!

Oh, and one kid was joining from a new country: Lebanon. He’s normally in Dubai, but is travelling, and took the time to still connect to my class. But someone joining from Lebanon brings my country list up to 53.

New content today:

Finished marking, oh my

I had a full day today, five ethics classes. And in between during the afternoon I finished marking all of my university Data Engineering student project reports and presentations.

It was a bit of a slog, because most of the reports were not particularly high quality, with some fundamental mistakes and misunderstandings of how to apply statistical tests and present graphical data. The last report I had to mark was a final breath of fresh air though, as they had actually done the statistics correctly and achieved a decent result for their experiment.

They wanted to determine if brand awareness had an influence on people’s judgement of photo quality. They got a series of photos of the same scenes taken by an Apple and a Samsung phone camera, and made surveys where they showed them side by side and asked people to pick which photo they preferred. In one survey they showed the photos labelled simply as “option 1” and “option 2”. In a second survey with different people they labelled the photos as “Apple” or “Samsung” respectively. And then in a third survey they switched the labels so that the Apple photos were labelled “Samsung” and vice versa. I thought this was a really clever bit of experiment design.

The results showed that out of 200 responses to survey 1 (20 people judging 10 photo pairs each), 96 favoured the Apple photos, and 104 favoured the Samsung. This established a baseline for comparison, which was pretty even. In the second survey, they found 111 favoured the “Apple” labelled photos (which actually were Apple), while 89 chose “Samsung”. And in survey 3, 112 favoured “Apple” labelled photos (which were actually Samsung), while 88 chose “Samsung” (actually Apple). This is a pretty cool result! It really suggests that some people are swayed towards photos that they think were taken with an Apple phone, even if they weren’t. They did a chi-squared test on the numbers, but the p-value was 0.12, meaning there was a 12% chance of this discrepancy happening by random chance. We usually expect a value of 5% or less before we say that it was likely not random, but 12% is pretty close. The problem for this analysis is they didn’t quite have enough data – if they’d received the same proportions with more data it would have been more significant. Anyway, it was a really nice experiment and project and write-up.

The other thing I did today was take Scully for a long walk to Botanica Cafe for lunch. I started working my way down their all-day breakfast menu, from the first item, a “breakfast bowl” of tapioca and chia seeds with preserved mangoes, coconut, and fresh figs and berries. It’s delicious and cinnamony, but a large sweet meal for lunch really filled me up for the afternoon and I was craving something savoury afterwards. I waited for the minestrone that my wife made for dinner, using yesterday’s leftover vegetable soup.

New content today:

Games class and marking

This morning I wrote my class for this week’s critical and ethical thinking topic on games. I have all new questions from the games topic I ran last year, asking the kids what actually is a game, and what aspects of games can make them fun for people to play. And what can be good or bad about games.

I also started marking the university Data Engineering course final reports and videos. I need to get this finished by Friday. Hopefully I’ll have it done tomorrow.

New content today:

Mentoring students, meeting 2

I visited Loreto Kirribilli again today to meet with the four Year 9 students I am mentoring. Since the previous meeting, the science coordinator had sent me some questions the girls wanted to know more about:

  • Does thinking of electrons in clouds (as briefly discussed two weeks ago when I mentioned that the model of electrons as tiny particles they were being taught was not the most accurate model) rather than as small particles have any impact on understanding chemical interactions?
  • How did we discover these details of atoms?
  • Explain the effect that when astronomers look back to the distant universe, objects can appear larger than if they were closer.

I prepared some answers and some images to show the students on my iPad, and went through those in the meeting today, also drawing a lot of diagrams and sketches on the whiteboard. We started with some discussion of the philosophy of science, and how it builds models and refines them over time to account for more complicated phenomena. Then put this into context with the atomic models we were discussing. And finished with an explanation of the galaxy size effect.

The students were very interested and engaged, although I did most of the talking. Hopefully as they get more used to our meetings they will open up more and the discussions can be more two-way. I feel today’s meeting was more successful than the previous one.

I picked up Scully from my wife’s work on the way home and we drove over to Naremburn for lunch at Cornucopia bakery. I had a Moroccan lamb pie and a small chocolate cake since I felt like spoiling myself a bit.

This afternoon my wife had to deal with a bit of a family health issue, which I don’t want to go into any details about here. But it meant I was rather distracted all afternoon, waiting to hear news and for her to come home. She was home in time for dinner and I made spaghetti with a tomato and fennel sauce.

While I was in the middle of the mentoring lesson at the school, our new neighbours next door phoned me, but I let the call go to voicemail, and then I was too distracted to ring back until after dinner. They are inviting us over on Saturday evening for some pre-dinner drinks and to socialise a bit, which is very nice of them. We’ve accepted, so will head over there on Saturday.

New content today:

Starting marking, restarting parking

Today I downloaded the student final assignments for Data Engineering, which I need to mark over the next few days. One team submitted their video in MKV format, which is not supported by MacOS. But fortunately I have some third party video playing software which can handle it – otherwise I would have had to download something just for this. I sent a message to the professor saying maybe we should specify acceptable video formats next time.

At lunch I took Scully for a walk. I decided to mix things up a bit and walk down to Bob Campbell Oval and the “Stairs of Cirith Ungol”, which I’ve mentioned a couple of times before (with photos each time).

When we reached the top of the steep street leading down to the Oval, I saw a large sign indicating the oval was closed for redevelopment work. I believe the council has a plan to replace the natural grass with artificial turf, so presumably this is that work now underway. When we got to the bottom of the hill, the entire area around the oval was fenced off. It looks like they’re demolishing and rebuilding the amenities there as well and redoing the car park and other works.

Bob Campbell Oval construction

Fortunately the Stairs of Cirith Ungol depart from the road just before the temporary fence, so we could climb up them to the street above and continue our circuit home.

A total of five ethics classes today took e late into the evening. Now it looks like Irregular Webcomic! and Darths & Droids have not updated to new comics for today, but oddly Square Root of Minus Garfield and Comments on a Postcard and iToons have. But I can’t log in to the server to fix things – it’s rejecting my attempts to use SSH for some reason, and I can’t connect using SFTP either. I don’t know what’s wrong, so I’ve submitted a support ticket to the webhost. Hopefully things will be running properly again by morning.

New content today:

Engineering the taste of beer

It was another busy day. I worked on a Darths & Droids comic for tomorrow, which I had to get done today so it will be ready for publication in time. Then a bit before 11am I had to leave to head into the university on the train for today’s last Data Engineering tutorial session.

The students’ final projects are due on Friday, so today was the last time they got to sit in class and work on it, and ask us any questions about their projects. One team is doing an experiment to try to determine relationships between amount of hops, boiling time, and perception of bitterness in pre-brewing beer solutions. And today they brought in their samples and were getting people in the class to taste them and answer a survey.

I did the survey. The first survey question was “How much do you like bitter drinks?” (1-10 scale). I said 8, since I like beer and stuff like Campari and herbal bitters. Then I tasted the four samples and rated them as bitterness levels 2, 5, 4, and I think 6 (out of 10). Then the professor did the same test, saying 5 for how much he liked bitter drinks. His ratings of the bitterness levels of the samples was about 3 or 4 points higher than mine.

And then I saw them have a woman in the class do the survey. She said she didn’t like bitter drinks. She tasted the first sample, and said “Oh my god! That’s horrible… yuk!!!” And she ended up rating them all in the 8-10 range for bitterness. And immediately ran out to get some water as soon as she was done.

The students said one of the things they were trying to determine was if a taster’s preference for bitter drinks affected how bitter they perceived the solutions to be. Looks like that’s a positive correlation!

On the way home I went via the game shop where I still had some store credit to spend. I found a copy of Kids on Bikes, which I snapped up, as I’ve been trying to get my hands on it for some time. That left me only about $30 credit left, which I used to buy some card sleeves and hard plastic top loaders for safely sending Magic cards through the mail. I’ve been using quite a few selling my cards, so a few extra boxes won’t go astray.

Tonight I started the new ethics class topic on Arguments. Had a couple of new students, and things went smoothly.

New content today:

Science mentoring meeting

Today I visited Loreto Kirribilli school to meet with four Year 9 students who the teachers there have selected for mentoring in science. They are advanced students with a strong interest in science. I introduced myself and briefly described my career from university degrees to industrial research, then asked the students what areas of science they were interested in and what they hoped to learn in our mentoring sessions.

They have a diverse range of interests in terms of topic: physics, biology, chemistry, astronomy, computer science. But one thing I found out was they have a common desire to obtain a more rounded and deeper understanding of science than they are taught in classwork. Actually understanding what the science is, rather than just learning ways to solve problems that will be on their exams. They were a little reserved but hopefully will get more enthusiastic as they get used to the mentoring sessions.

We finished up our time (we had 50 minutes) with a discussion of atomic theory, going a bit deeper into quantum physics than they get at a Year 9 level. It ended up a bit rambly, because there are so many interesting digressions I can make along the way! Hopefully the next session (in a fortnight) will be a bit more focused. Th girls have been given some homework to come up with some specific questions they are interested in, either about science topics or careers.

In other news, there was a strange meteorological phenomenon today. Th sky was a weird blue colour and there was a strange ball of light in it. Yes, the rain has finally ended, after beginning on 30 April. It was so nice to be out and about without getting wet.

The dampness left behind a nasty legacy though. I mentioned the mould spots in the house yesterday. Today I went around with some mould killer and treated all the areas I could see. It’s horrible, but hopefully stopped before it gets too serious.

All of this meant I didn’t have a lot of time to write my ethics class for the new week. I dashed it off quickly after dinner. The topic is “Arguments”, as in heated disagreements, not logical arguments. What causes arguments? How can an argument get out of control? How does it feel to be in an argument? What strategies can you use to stay more calm and reasonable in an argument? What’s the difference between healthy debate and harmful argument? And so on.

New content today:

Marking done

Today I did the marking for the first experiment planning report for Data Engineering. I had four teams’ reports to mark. I think the quality is definitely better than last year, though there was still some significant variance overall.

There was more heavy rain this morning. It’s been raining every day since 1 May, and the forecast is for rain every day until at least 13 May. I needed to go to the post office to try to get them to reroute the lost package back to me, rather then continue delivering it to Canada, as I refunded the buyer all of the money. In the channels where I’m selling these cards, reputation is everything, and I’d rather take the hit on refunding the money than get a negative seller reputation that would make it difficult to sell more cards. But the post office said there was no way they could do that. So, I have to trust that if the buyer eventually does receive the package that he’ll let me know and be reasonable about sorting things out fairly from there. I do have reasonable trust that he will, since as I said reputation is prime in these circles and the guy has a positive rep that he won’t want to tarnish too.

Anyway, I decided to drive up instead of walk in the rain. It doesn’t save much (if any) time, but it does mean about a kilometre less walking in the wet. But by the time I got there, the rain stopped and the sun came out!

Since I had the car out by now anyway, I decided to drive over to Maggios’ Bakery at Cammeray for lunch, where I got a slice of pork sausage pizza and a pistachio chocolate scroll. And tonight for dinner we have minestrone, to round out the Italian food day.

New content today:

Tale of a missing package

I’ve been selling my old Magic: the Gathering cards piecemeal over the last 4 years, and as indicated here recently I’ve started a renewed effort to sell more of them. I’ve ever had a problem with shipping them to all corners of the globe. Until now.

On 24 April I sent a package of cards to a buyer in Victoria, British Columbia, Canada. This morning he sent me a message indicating he hadn’t received them yet. I always send the packages with tracking, so I checked the tracking info on Australia Post’s website and discovered that the only update on there was that the package had been received at my local post office where I lodged it. The next step should be “Cleared and awaiting international departure”, but that wasn’t there. Apparently the package is still in Australia somewhere.

I went to the post office and talked to someone there about it. They brought up the tracking details in their system, which has more info recorded than shown on their tracking website. The delivery address was correct, except for some reason it didn’t display “Canada”. I’m not sure why – I filled out the customs form online and it did auto-completion of the address, so it should know that it’s in Canada.

My theory: I guess the bar code has been scanned and it just shows a street address and Victoria (the city in British Columbia), without Canada, so it got sent by domestic mail to Melbourne, in the Australian state of Victoria. Presumably it’s sitting there somewhere, waiting for someone to figure out that it can’t be delivered, actually read the handwritten address, and realise it’s meant to go to Canada.

So… maybe it will get to international post handling eventually, and from there it should be smooth sailing to the destination in Canada. But… the problem is that the buyer wanted some of those cards specifically because he’s meeting the artist at a tournament on Wednesday next week, and he wanted to get them signed. Even if they figure the parcel out tomorrow and get it on a plane, it’s not going to be delivered to the final address in time.

Also today there was a bit of an incident in my Data Engineering course at the university. The professor and I had to defuse a situation with some members of one of the student teams having a disagreement. I don’t want to go into details, but it was rather uncomfortable and I felt like some lines were crossed. Hopefully we resolved things and nothing similar will happen again.

New content today:

Problems with Instagram

Okay, so I deactivated my Facebook account a few days ago. Something I’ve been wanting to do for years. Today I wanted to use Instagram and… it wouldn’t show me my normal feed. I couldn’t post a photo. I went into the Account Settings to try to log out and back in again, and it wouldn’t load the account info page.

I figure this must have something to do with my Facebook account being deactivated, because they’re both owned by Meta. But I switched to Scully’s Instagram account (yes, she has one), and that was working fine. But Scully doesn’t have a Facebook account. So clearly Instagram can work without an associated Facebook account. So why is mine now completely broken?

I’ll have to look into this another day, because today was very busy and I’ve just finished three ethics classes in a row, after spending the middle of the day at the university doing tutoring for the Data Engineering course. We’re approaching the end – only two more weeks to go. But I’ll have marking of student reports and videos to do.

This morning I also had to dash up to the post office to mail some more Magic cards to people. The weather was rainy again today, and I got sprinkled on, but it wasn’t heavy. It would have been miserable taking packages there in heavy rain.

In other teaching news, I heard back from Loreto Kirribilli and now that it’s second term of the school year, they have organised a group of four Year 9 students for me to mentor. We’re going to do fortnightly sessions this term, and then maybe organise something different in third term. I go to visit the school to begin in two weeks. I’m looking forward to this -it should be fun, and also hopefully really inspiring for the students.

Oh, and finally, last night I had a big panic when Wednesday’s Irregular Webcomic! wasn’t ready in time for the automated update, and I quickly assembled the comic, uploaded it, and forced a manual update. It was only when I woke up in the middle of the night that I realised it was Tuesday, not Wednesday, and I’d therefore manually published Wednesday’s comic just an hour after Tuesday’s one!! So to correct for this, there’s no new comic tonight – since tonight’s comic was actually published yesterday.

New content today: