Drawing vision diagrams

Today I relaxed a bit after yesterday’s manic work at the market. By “relaxed”, I mean I went for a 5k run first thing in the morning. I tried running the loop at the halfway mark in the opposite direction today, which meant uphill sections on either side of a downhill, rather than vice versa. I don’t know if it made much difference overall, but my time today was 20 seconds slower than last week.

After the run, I got stuck into drawing some diagrams for my planned class on human vision and colour perception for Outschool. I need to draw my own diagrams to avoid using copyrighted images. Here’s my take on the layers of the human retina:

Retinal structure

I got most of the diagrams I need done, but still have a couple of tackle tomorrow. But now I can at least make a title image for my class to upload to Outschool, and start signing up students!

New content today:

Looking for birds

So as mentioned on 27 December, I’ve been getting into using eBird to record my bird sightings as I walk around the neighbourhood. I’ve been recording lists of sightings every day, which is training me to keep an eye and ear out for birds as I walk around.

Up to today, I’d recorded a total of 25 different species of birds. But today as I was out walking Scully I spotted the 26th, and a rather surprising one it was – an Australian pelican! They’re common along various Sydney ocean beaches and coastal strips, but I’m inland on the harbour shore, where they don’t often come. I don’t think I’ve ever seen one on the ground in this area – and in fact today’s was flying overhead. But as soon as I saw it I recognised it and was astonished that a pelican was flying so far from the sea. I watched it circle on a thermal over the harbour shore for a few minutes, wishing it would come closer so I could get a definite ID. After a while it did come close enough that yes, I can confirm with surety that it was a pelican. Cool!

Today I assembled the comics from the photos I took yesterday. It was a marathon effort, taking about six hours of solid work. The next step is writing the annotations, which I’ve made a start on, but will have to finish off another day.

The other thing I wanted to mention today is that I’ve been noticing a few discussion threads on reddit lately about colourblindness or other aspects of colour science. And I’m dismayed by how much misinformation there is and downright incorrect assertions that people make. I would be happy to provide correct explanations of things about colour and human vision, since this is part of my professional expertise, but it feels futile fighting against such a tsunami of misleadingly incorrect text. So it’s a bit depressing. I guess I should just stop reading anything about colour on reddit.

In COVID news, the Sydney outbreak seems to be being held under control, although there are still thousands of people under self-isolation orders. The number of actual new detected infections has been low the past few days, with testing numbers high. So if this continues, it looks like we have avoided an exponential spreading event. Fingers crossed!

New content today:

Sourdough and Conjunction

This morning I began making my first sourdough loaf. I started by taking 100 grams of my new starter culture:

Making sourdough, step 1

I added 310 mL of water, 500 g of flour, and 10 g of uniodised salt, and mixed to form a dough:

Making sourdough, step 2

The dough seems to have a good consistency. I covered the mixing bowl in cling film and have left it to rise overnight. By this evening it’s already risen a lot, I’d say doubled in size easily. But I’ll bake it in the morning.

The other good news today is that the clouds obliterating Sydney’s view of the grand conjunction of Jupiter and Saturn for the past week finally lifted today. Only they lifted higher into the atmosphere, forming a thin haze over the sky. Nevertheless, I went out tonight with my camera to see what I could, and managed to get a few photos. Here’s the best one:

Grand conjunction: Jupiter and Saturn, 23 Dec 2020, Sydney, Australia

You can see Jupiter, all four Galilean moons, and Saturn. Saturn looks elongated by the rings, but you can’t really tell they’re rings. Here’s the same photo labelled:

Grand conjunction: Jupiter and Saturn, 23 Dec 2020, Sydney, Australia - labelled

It was a pretty crappy view, honestly. Always through cloud haze, and sometimes the planets would disappear altogether as thicker cloud wisps drifted across. But it may be the best I get, because the forecast for tomorrow is more evening rain, and then rain every day for the next week. But at least I got to see it.

New content today:

No conjunction for you!

I’m sitting here just after sunset and wondering if maybe tonight’s the night I get to see the Jupiter/Saturn conjunction…

But no, the cloud cover is about 90% at the moment. I’ll give it another hour or so, by which time it’ll be too late. I’m not confident though.

I spent most of today working on the Secret Project, making good progress, but of course I can’t talk about it. I also fed my new sourdough starter, in preparation for beginning a loaf tomorrow.

That’s about it. COVID numbers were 8 new cases in Sydney today, continuing yesterday’s downward trend. No cases of mysterious origin. Hopefully this cluster is contained and the cases will die out over the next week. The real issue is that nobody knows what sort of restrictions will be in place in Sydney for Christmas Day. The NSW Government has indicated that if it weren’t for Christmas, we’d already be in a lockdown extending over that date, but they’re leaving any such decision to the last possible minute in an effort to keep things as open as medically advisable for Christmas. So we continue to wait and see.

New content today:

Kicking off sourdough

I got into a discussion with a friend today about baking, since I was baking some bread this morning, and he’s been doing a lot of experimenting with sourdough ever since COVID restrictions began. My loaf was just using a prepared bread mix from the supermarket, which comes with yeast. I’ve made this a few times and it’s not difficult. Here’s what today’s loaf looked like:

Home baked loaf

I said I might try starting some sourdough at some point, and my friend offered to bring over some of his sourdough starter. I said that’d be great, but no rush, but he said he was looking for an excuse to get out of the house and go somewhere different. So he brought some over!

Bébé Fett

Yes, he named it Bébé Fett. He also typed out some instructions for me on how to feed it and pointed me at a couple of YouTube videos for how to bake bread with it. So I’ll try it out some time in the next few days (when we run out of the loaf I baked today).

In other news, my wife is back to working from home following the new COVID restrictions and advice here in Sydney. We had 15 new cases today, but the NSW Government hasn’t announced any big changes to restrictions. I suspect they’ll wait until Wednesday before announcing that the Northern Beaches lockdown and other restrictions will have to be extended over Christmas.

While staring out the window, she called me to look at a kookaburra that had perched on a tree outside. I grabbed my camera and took a few photos:

Laughing Kookaburra

Finally, in today’s grab bag of stuff, I’m disappointed that I haven’t been able to get a look at the amazing conjunction of Jupiter and Saturn… because it’s been raining here in Sydney every day for the past week, and it’s been overcast every single evening. Right now as I type this it’s evening and would be a great time to go out and see it… except it’s raining again. And the forecast is basically for rain for the next week. 🙁

New content today:

Not being bored

On reddit today I came across a very interesting explanation of why we get bored (versus why lizards can sit there all day doing nothing, apparently without getting bored):

Most organisms are in a constant struggle for energy. Obtaining energy is dangerous, you have to leave your safe burrow or go risk injury in a hunt. That’s why many organisms develop strategies for minimising the risks they need to take. And one of the most popular strategies is simply having simple, low demand physiologies, slow metabolisms and generally low energy needs.

Warm blooded animals are fairly unique. We’re like a car with the engine constantly running. That means we’re ready to go from zero to 100 right away but we’re also guzzling gas constantly, even if we’re standing still. That’s why warm blooded animals need to constantly eat.

[Boredom is] really just another evolutionary adaption. There’s no advantage to boredom if your survival strategy relies on doing nothing. Boredom is essentially the inability to articulate what is a meaningful activity for you right now. It motivates you to change whatever it is you’re doing and find something meaningful or productive to do.

That lizard isn’t questioning what it should be doing. It’s surviving by doing nothing and not wasting energy. Humans on the other hand have so many needs that doing nothing is nearly always the wrong thing to do, so you get bored.

(My emphasis.) Anyway, I thought that was pretty cool.

I got up early this morning and went to the nearest golf course at 6:30, playing my now usual two simultaneous balls on each hole. I scored a par on the very first hole, and thought it might be a good day, but things went a bit downhill after that. My totals were 50 and 58 – the 50 is good, but 58 is not as good as I’ve been scoring lately.

When I got home, before 9 am, I was so hot and sweaty that I had to have a cold shower. The weather has been warm this week, but mostly ridiculously humid. It’s not actually too hot – but once you do anything you start sweating and it just doesn’t evaporate. I guess the “cooler, wetter” La Niña conditions for the summer are here.

I continued today working on Darths & Droids writing. I’ve been doing a lot of story planning this week, and it’s starting to pay off with the next few strips I’m having to write, because I know exactly what plot elements they need to touch on.

New content today:

The Australian Museum

I had a strange dream about baseball last night. I was part of an amateur Australian team who had travelled to the USA to play one of the professional Major League teams. The pro team was so much better than us that one of their batters scored 64 runs in one at-bat. Not a whole inning, just one at-bat (I know this is impossible by the rules of baseball, but nonetheless). The team figured this was plenty of runs, so they didn’t bother finishing their inning and let us bat (again, against the rules of baseball as far as I know).

I was now up to bat. The pitcher threw a ball, then another ball, with me being savvy enough not to swing the bat. The pitcher indicated to me that this next pitch would be right over the plate, so I better swing at it. He threw it well wide, and again I didn’t swing, and the umpire called it a ball.

I said, “As if I’d swing at a pitch like that!”

At this, the other team took offence and walked off the field, refusing to play because of this deathly insult. I was forced to apologise to the pitcher, the opposing coach, and to their entire team, before they would agree to continue playing.

Now, I know baseball and I know this is all extremely unrepresentative of how it’s actually played, but it in the world of dream logic it seems this was all perfectly reasonable. The dream ended at that point, so I don’t know what happened next.

After waking up and having breakfast, I took a train into the city to visit The Australian Museum, the largest museum of natural history in Australia. The’ve been closed for 15 months for major renovations, and only reopened a couple of weeks ago. I wanted to go check it out before summer holidays start for the schoolkids.

Queuing in the rain

It was a rainy day, but that’s no problem. There was a considerable queue to get in ten minutes before opening time. Entry used to cost money for the past couple of decades or so (it was free when I was a kid), but it’s now free again after the reopening. They had a special exhibit on dinosaurs for which you had to pay, and most of the visitors today were going in there first, so I had a very empty remainder of the museum to walk around in.

First Nations gallery

The First Nations gallery (above) has many examples of cultural artefacts from Aboriginal peoples and Torres Straits Islanders.

T. rex

This T. rex skeleton is part of the free permanent exhibits on dinosaurs, not part of the special paid exhibit on dinosaurs (that I didn’t see).

The Long Gallery

This is the Long Gallery, which was one of the original display galleries in the museum. I remember coming in here when I was a child, and this was always the most exciting part of the museum.

Opalised pliosaur

This is very cool. It’s the fossilised skeleton of a pliosaur, from the early Cretaceous period, about 110 million years ago. But it was fossilised in the place that would later become Coober Pedy, South Australia, which is one of the largest opal fields in the world. The same geological processes that created opals here mineralised the skeleton, turning it into opal.

Honestly, I was expecting more from the refurbishment, especially after more than a year. I’d assumed they were doing major construction work of some sort, but nearly all of the rooms and galleries were pretty much as I remembered, and even most of the exhibits were the same ones I’d seen many times in the past. What they’d done is given the whole museum a thorough cleaning and a new modern look – removing old faded signs, dusty cabinets, etc, and replacing them with brand new fittings. So it’s all shiny and new, but generally mostly the same stuff behind it. The did remove the old special exhibition space from what was a courtyard in the original building but is now enclosed space – it’s now a spacious interior foyer space. I didn’t see the new special exhibition space on the lower floors, so I suppose maybe that’s all new.

Anyway, it was fun looking around, and great to get free entry again to one of the best museums in the country!

New content today:

Late Friday catch-up

I missed Friday’s entry last night, because my wife and I went out for a nice dinner, and then when I got home my friends were keen to play skribbl.io and I spent the rest of the evening doing that. Our custom word list is working well – we’re getting more interesting and tricky things to draw, and the results are even more hilarious than the default word list.

I forgot to mention yesterday that on Wednesday night when I took Scully out for her pre-bedtime toilet, I was standing with her out on the grass and looking up at the stars, and I saw a meteor streak across the sky. Almost directly overhead, and heading south-west. Not particularly bright or noticeable – I was just lucky to be looking in the right spot at the right second. It’s not the first meteor I’ve seen when out with Scully at night either – this is about the third in a couple of years. As an astronomer I know that meteors are actually very common, and if you sit outside for half an hour or so just looking up at the night sky, you’re likely to see some – it’s just that most people never do this. But I have a habit now of looking up whenever I take Scully out (and the sky is clear), so I’ve been spending a significant amount of time doing this added up over the year.

Another thing I accomplished this week is finishing off reading book 6 of the Diary of a Wimpy Kid series in Italian: Si Salvi Chi Può (“everyone for themselves”, which is how they titled the Italian version of Cabin Fever). So that’s six complete books I’ve read in Italian now. They’re definitely getting easier and faster to get through as my vocabulary and grammar skills are improving. When I began, every page I’d have to stop and look up several words. Now I can often get through a page without needing to look up anything, except perhaps to confirm the meaning of a word which I can figure out by context. On to book 7!

New content today:

Filming a video for Science Week

It was mostly a lazy Saturday today. The main thing I accomplished was filming a short video for the school where I do my volunteer science visits. I haven’t been able to visit the school to talk to the kids in person since March or so due to COVID. I wrote to my teacher contact and said I’d be happy to do something remotely, like a Q&A session via Zoom or something. She suggested that with Science Week coming up next week maybe I could record a short video to introduce the week to the students.

The theme of Science Week this year is “Deep Blue” – basically looking at the science of the oceans and how to use them sustainably rather than damaging them. So today I drove out to the coast, specifically to the rock shelf at Freshwater, where I could set up a tripod and camera with the ocean as a backdrop.

My wife came to help me do the recording, and she did a great job of directing as well. My first take was very flat and lifeless, and she got me to add more movement and gestures and voice inflection, which really helped in the later takes. I ended up with just over 4 minutes of video, and although not super professional I thought it turned out pretty good. After getting home I checked the result and it was good to go with no editing. So I sent it to the teacher and hopefully it’ll be a hit with the kids on Monday.

New content today:


Today I started working on a new one of my “100 Proofs that the Earth is a Globe“. It’s the first one I’ve started for some time, because I’ve been distracted at home a lot with my wife working from home and haven’t been able to sit down knowing that I could work uninterrupted for several hours at a time. But today I just knuckled down and got started despite that. Normally I’d finish an article the same day I start, but I’m only about half way through, so hopefully I’ll be able to finish and post it tomorrow.

I took a break at lunch time to go do another 5k run. My fastest time for the 5k last year was 29:06, and last week I managed 29:16, so today my goal was to break 29 minutes. Unfortunately I miscounted laps and after sprinting the last couple of hundred metres and bending over exhausted to catch my breath while I checked my time on my phone, I discovered that I’d only covered 4.6 km! I still had a lap to go! I had to put the disappointment aside immediately and get the legs working again and set off on another lap…

But I managed it! My time for the full 5k today was 28:05. While running the last few laps I felt pretty exhausted and again really had to push through it mentally to avoid stopping, but now a few hours later my legs definitely don’t feel nearly as tired as last week.

I boasted to my friends on our online chat. One asked me if I was running laps of a street route, but I said no, the streets here are much too hilly for me to run, so I do laps of the nearby sports oval. And then this conversation happened:

Friend: Actually your run is consistent with orbiting a very dense object at the centre of the oval. #100ProofsGoreHillOvalIsABlackHole

Me: hmm…. I could calculate the mass, given the radius and speed… Damn, now I have to do it.

And I did. Approximating the oval as a circle and using the equation for a circular orbit: v = √(GM/r) gives the mass M of an object needed to cause me to orbit it at speed v and radius r. My speed was 5000/(28×60+5) = 2.97 m/s. I ran 11 full laps, totalling 5.14 km, so the radius of the oval is approximately (5140 m)/(11 laps)/(2π) = 74.4 m. Plugging the numbers in gives M = 9.81×1012 kg. Which is basically 1013 kg to any sensible degree of accuracy.

According to Wikipedia, 1013 kg is almost exactly the mass of comet 67P/Churyumov–Gerasimenko. Which is a little large to fit inside the oval. But never fear, for it’s also roughly the mass of two teaspoonfuls of degenerate neutron matter, which one could easily fit into the middle of a sports oval. If that much degenerate neutron matter had been in the middle of the oval, I could have stayed in orbit about it by running in a straight line. Although I suspect my orbit would decay rapidly after 5 km of running…

Friend: I’m so happy I nerdsniped you into doing this.

And just to include a photo: for dinner tonight I made a vegetable quiche, stuffed with potato, cauliflower, pumpkin, broccolini, onion, cherry tomatoes, eggs, and cheese:

Vegetable quiche

New content today: