Solar Racing Basics: Aerodynamics

Click to zoom / Image credit: Anthony Dekker (top three), Agoria Solar Team (wind tunnel)

Continuing the analysis of my Solar Racing Basics Poster (see this tag), perhaps the most important issue in solar car racing is aerodynamic efficiency. In the Challenger class, average power is limited by the size of the solar panel to about that of a microwave oven. This is about one hundredth of the engine power in a typical small car.

Solar cars must therefore eliminate as much aerodynamic drag as possible. Aerodynamic drag is the most important limiting factor on speed.

The aerodynamic drag force, which is given by the formula F = ½ C_d A ρ v², acts to slow the car down. At maximum speed, the drag force (plus also other factors) exactly balances the force of the motor, which of course acts to speed the car up. In the formula, v is the speed, C_d is the drag coefficient, A is the frontal area of the car, and ρ is the density of air (which we can’t change).

If F_max is the maximum force that the motor can deliver, then the maximum speed is given by rearranging the formula: v_max = sqrt (2 F_max / (C_d A ρ)). One way of speeding up the car is by making the shape more aerodynamic (that is, by reducing C_d). Challenger class teams should be aiming at drag coefficients C_d under 0.1. In the Cruiser class, values under 0.2 would be appropriate (for comparison, C_d in ordinary cars ranges from 0.25 for a modern streamlined sports car to 0.6 for an SUV).

 
Click to zoom / Image credits: Anthony Dekker (Electrum from Michigan, Green Lightning from Top Dutch)

We can also speed up the car by making it narrower (that is, by reducing the frontal area A). In 2019, the 1-metre-wide Electrum from Michigan finished ahead of the 1.2-metre-wide Green Lightning from Top Dutch, in spite of having had problems (79.6 km/h compared to 78.4 km/h). On the other hand, if you make the car too narrow, it will roll over (which means that the car fails pre-race scrutineering). Alternatively, we can reduce the frontal area A by making a “gap” for the air to flow through. If we can make both the drag coefficient C_d and the frontal area A one sixth of the values for a typical small car, then we can travel at 60% of the speed of that car, even though we have only one hundredth of the engine power.

In the past, successful Challenger class designs have included:

• Catamarans: double hulls, one of which holds the driver, held together by a “wing” on which the solar panel is fixed, with a “gap” between the hulls (this design has won every race since 4 wheels were made mandatory in 2013)
• Monohulls or “bullet cars”: long, narrow cars with a tapering rear like Electrum or Green Lightning (this design came second in both 2017 and 2019)
• Outriggers: like monohulls, but with the wheels outside the main body and more widely spaced for stability (this design has not performed quite so well, because of aerodynamic drag from the wheels)

Three wheels are now allowed in 2021. This allows slightly better monohulls (with two wheels inside the front of the body and one wheel just inside the tapering rear of the body). It also allows noticeably better outriggers (only two wheels need to be outside the main body). In addition, there are a number of new designs that teams have been thinking feverishly about for several months.

 
Click to zoom / Image credits: Anthony Dekker (a catamaran and an outrigger car, both Swedish)

During design, aerodynamics is typically assessed using computational fluid dynamics software, but “ground truth” is a wind tunnel or an actual race. In the illustration on the poster, Belgian team Agoria is using a green laser to reveal airflow around their car in a wind tunnel (see also the video here).

To read more about aerodynamics, see this brief post from 2018 and this 2015 Solar Car Conference presentation.

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Vesper Flights: a book review and reflection

Vesper Flights by Helen Macdonald

I have been waiting eagerly for a copy of Vesper Flights by Helen Macdonald. If you have read my review of her H is for Hawk, you will understand why. Early reviews of the new book were also positive – “powerful essays,” said The Guardian; “soul-stirring,” said USA Today; “a beautiful and generous book,” said npr. The Goodreads community gave it 4.2 out of 5.

I was fortunate enough to get a copy of Vesper Flights for Christmas. It is a collection of 41 essays, and Helen Macdonald writes “I hope that this book works a little like a Wunderkammer. It is full of strange things and it is concerned with the quality of wonder.” Many of the essays have an autobiographical component. Several moved me to tears.

A Wunderkammer painted by Domenico Remps around 1695 (click images in this review to zoom)

The essays in the collection are:

1. Nests – a reflection on bird’s nests
2. Nothing Like a Pig – coming face-to-face with a wild boar
3. Inspector Calls – a beautifully written and touching account of an autistic boy meeting a parrot
4. Field Guides – a visit to Australia, and praise for field guides

The hairpin banksia gets a mention in essay #4

5. Tekels Park – reminiscences of a childhood spent among nature in Tekels Park
6. High-Rise – a wonderful account of the surprising amount of life that can be found in the night-time sky
7. The Human Flock – about migration
8. The Student’s Tale – about a refugee
9. Ants – about nuptial flights in ants

A winged queen ant (photo credit)

10. Symptomatic – about migraines and impending doom
11. Sex, Death, Mushrooms – “Many toxic fungi closely resemble edible ones, and differentiating each from each requires careful examination, dogged determination and often the inspection of spores stained and measured under a microscope slide.”
12. Winter Woods – walking through woods in the winter
13. Eclipse – an eclipse is an emotional experience
14. In Her Orbit – with Nathalie Cabrol in the Atacama Desert, site of the now-defunct Carrera Solar Atacama (this chapter is based on a New York Times article)

San Pedro de Atacama, Chile (photo credit)

15. Hares
16. Lost, But Catching Up
17. Swan Upping – swan upping on the Thames as social commentary
18. Nestboxes – are they for the birds, for us, or both?
19. Deer in the Headlights – this essay highlights the problem of deer-vehicle collisions (the UK gets about 1 per thousand people per year); Australia has a kangaroo-vehicle collision problem of similar magnitude, but that issue is perhaps viewed a little differently
20. The Falcon and the Tower – about urban peregrine falcons, specifically in Dublin (see also this short documentary film)

The towers of the decommissioned Poolbeg Generating Station in Dublin, with a magnification of the western (leftmost) tower. These towers, around 207 m high, are home to the peregrine falcons described in essay #20 (photo credit)

21. Vesper Flights – the central and title essay, based on a New York Times article, is about swifts
22. In Spight of Prisons – all about glow-worms, Lampyris noctiluca
23. Sun Birds and Cashmere Spheres – golden orioles and bearded reedlings
24. The Observatory – “a swan had come towards me and offered me strange
    companionship at a time when I thought loneliness was all I could feel.”
25. Wicken – Wicken and other fens, which I imagine inspired the home of Puddleglum in the Narnia stories

A hide at Wicken Fen (photo credit)

26. Storm
27. Murmurations – “Words to accompany Sarah Wood’s 2015 film Murmuration x 10”
28. A Cuckoo in the House – about cuckoos and the man who inspired the character ‘M.’ Yes, that ‘M.’
29. The Arrow-Stork – the arrow-stork and the study of bird & animal migration
30. Ashes – on tree diseases
31. A Handful of Corn – as a famous song says: “Come feed the little birds, show them you care, and you’ll be glad if you do; their young ones are hungry, their nests are so bare, all it takes is tuppence from you.”

32. Berries
33. Cherry Stones
34. Birds, Tabled – a fascinating exploration of the morality of bird-watching versus bird-keeping and the class conflicts involved (a number of reviewers online have taken issue with this chapter, specifically)
35. Hiding
36. Eulogy
37. Rescue – a beautiful account of bird rescue and wildlife rehabilitation
38. Goats
39. Dispatches from the Valleys – a heavily autobiographical chapter, raising all kinds of spiritual questions (but not really answering them)
40. The Numinous Ordinary – “I kept trying to find the right words to describe certain experiences and failing. My secular lexicon didn’t capture what they were like. You’ve probably had such experiences yourself – times in which the world stutters, turns and fills with unexpected meaning.”
41. What Animals Taught Me – “When I was a child I’d assumed animals were just like me. Later I thought I could escape myself by pretending I was an animal. Both were founded on the same mistake. For the deepest lesson animals have taught me is how easily and unconsciously we see other lives as mirrors of our own.”

Not surprisingly, about half the chapters in this book are about birds, in some way or other:

At its best, this book is as good as the superb H is for Hawk, but is not consistently so (indeed, it scarcely could be). While some of the chapters are truly wonderful, others have a moralistic tone that I thought was a little more heavy-handed than it needed to be, and which became a little repetitive after a while. In the last chapter Helen Macdonald offers a corrective: “These days I take emotional solace from knowing that animals are not like me, that their lives are not about us at all.” Or, as C.S. Lewis once put it:

“Come out, look back, and then you will see … this astonishing cataract of bears, babies, and bananas: this immoderate deluge of atoms, orchids, oranges, cancers, canaries, fleas, gases, tornadoes and toads. How could you ever have thought this was the ultimate reality? How could you ever have thought that it was merely a stage-set for the moral drama of men and women? She is herself. Offer her neither worship nor contempt. Meet her and know her. If we are immortal, and if she is doomed (as the scientists tell us) to run down and die, we shall miss this half-shy and half-flamboyant creature, this ogress, this hoyden, this incorrigible fairy, this dumb witch.”

Helen Macdonald has a genuine talent for showing the reader what she saw, and the reader of a book like this will feel appropriate things in that situation. Perhaps the more moralistic tone is the inevitable, and possibly appropriate, nature of an essay written for a newspaper or magazine. The fact that this book is a collection of such essays would then explain why it feels a little repetitive at times.

My recommendation: buy this book, but only read a few chapters each week. And think about them.

Vesper Flights by Helen Macdonald: 4 stars

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That Russian Cyberfarm video

This fantastic Russian video by birchpunk has taken the world by storm. I thought I’d collect up some highlights (see also the screenshots below).

• 0:00, QR code: this goes to the Twitter profile of Dmitry Rogozin, the Director General of Roscosmos.
• 0:28, Izhevsk Dynamics Corporation: a play on Boston Dynamics, but one of the factories in the city of Izhevsk was responsible for the AK-47.
• 0:42, We don’t need them: an apparent Back to the Future 2 or 3 reference.
• 0:44, We suffer from air turbulence: that is what the road sign says.
• 0:50, Two years by Post of Russia: Russian Post has a reputation for delays, although of course they are justified in this case. The dropping parcels may be a reference to incidents like this one.
• 1:06, We took it apart for металлолом (scrap): may be a reference to incidents like this one.
• 1:08, Cyberfolk song: see this subtitled version.
• 1:38, Poster: the poster shows the face of Dmitry Rogozin and says “Let’s Make the Red Planet Green.”
• 2:39, РАССАДА ERROR: something is wrong with Nikolay’s seedlings.
• 2:46, Fractal cucumber: fractals are a real thing, and some strange conjoined cucumbers exist, but this is one of my favourite flights of fancy.
• 2:58, Genetically modified: this is kombucha, which was popular in Russia long before it became a fad in the West.
• 3:31, We have Netflix: notice the two moons, this one and that one.
• 3:45, But network is not so good: I haven’t heard that dial-up modem sound in years.

Oh, and don’t miss the New Year Special sequel.

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Solar Racing Basics: Classes

Click to zoom / Image credit: Anthony Dekker (top), Solar Team Eindhoven (bottom)

Beginning the analysis of my Solar Racing Basics Poster (see this tag), there are two main classes in the World Solar Challenge. The Challenger class is easiest to understand: highly aerodynamic single-occupant cars scored only on the time taken for the race from Darwin to Adelaide (with no external charging allowed, other than an initial full battery). The Challenger class cars show us the limits of what current technology can achieve.

The Cruiser class consists of more realistic multi-occupant cars, with proper doors and interiors. Some teams field two-seater cars, and some four-seater “family” cars. The Cruiser class cars show us options for what commercial solar cars might look like. Cruisers are scored on distance travelled, time taken, passengers carried, external charging along the way (if any), and “practicality” judging. A rather complex formula combines all those factors. To read more about Cruiser class scoring, see my previous posts:

• A simplified view of Cruiser scoring
• 2019 Cruiser scoring

 
Click to zoom / Image credits: Anthony Dekker (Challenger class car from Agoria and Cruiser class car from Eindhoven, both winners in 2019)

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Solar Racing Basics Poster

I have constructed a poster summarising the basics of solar car racing, with a focus on the 2021 World Solar Challenge, but with an eye on the other solar car races planned for 2021 as well. A series of ten follow-up posts will explain the poster (see this tag).

Click to zoom / Image credits: Agoria Solar Team (wind tunnel), American Solar Challenge (chassis), Solar Team Eindhoven (Cruiser car), mostdece.blogspot.com (battery & motor), Vattenfall Solar Team (race strategy), public domain (lower right 3), Anthony Dekker (remaining 7).

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WSC 2021 preliminary teams list

It’s still early days, but here is a list of the 31 cars (from 18 countries; 23 Challengers and 8 Cruisers) most likely to attend the Bridgestone World Solar Challenge in October this year (I have included some interesting newcomers, and I also expect several Japanese cars). There have been some quite radical rule changes in the Challenger class, and this will make for some interesting design choices this year.

In the Cruiser class, there is continued debate as to how to deal with the tough scoring formula. Also, after building four “solar family cars,” Solar Team Eindhoven have promised something radically different that doesn’t involve Australia, so the Cruiser class is wide open this year!

Of course, Covid-19 still casts a shadow over the event. See this page and this blog tag for my past coverage of the event, and the official race social media at        (click on the icons).

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2    University of Michigan Solar Car Team 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Michigan came 9^th at WSC 13; came 4^th at WSC 15; came 2^nd at WSC 17; came 3^rd at WSC 19; won ASC 14; won ASC 16; came 2^nd at ASC 18; and won Abu Dhabi 15. Their team number (2) is a long-standing tradition.

 
Left: credit / Right: Anthony Dekker (click images to zoom – OLD PICS)

3    Vattenfall Solar Team (Delft) 

Challenger (new car: Nuna11) – this year’s attempt to regain the trophy will be the last year that Delft partners with Vattenfall.

Previously, Delft won WSC 13; won WSC 15; won WSC 17; came 12^th at WSC 19; won SASOL 14; won SASOL 16; and won SASOL 18. Their team number (3) is a long-standing tradition.

 
Left: Anthony Dekker / Right: Anthony Dekker (click images to zoom – OLD PICS)

4    Antakari Solar Team 

Challenger (new car: Intikallpa VI) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Antakari participated in the WSC 13 Adventure class; came 10^th at WSC 17; and came 7^th at WSC 19.

 
Left: credit / Right: credit (click images to zoom – OLD PICS)

6    Top Dutch Solar Racing 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Top Dutch came 4^th at WSC 19 and came 3^rd at iESC 20.

 
Left: credit / Right: Anthony Dekker (click images to zoom – OLD PICS)

7    Adelaide University Solar Racing Team 

Challenger (new car: Lumen III) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Adelaide came 21^st at WSC 15; participated at WSC 17; and came 16^th at WSC 19.

 
Left: credit / Right: credit (click images to zoom – OLD PICS)

8    Agoria Solar Team / KU Leuven 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Agoria came 6^th at WSC 13; came 5^th at WSC 15; came 3^rd at WSC 17; won WSC 19; came 3^rd at Abu Dhabi 15; came 2^nd at iESC 16; came 6^th at iESC 18; came 1^st and 6^th at iESC 20; and won Carrera Solar Atacama 18. Their team number (8) is a long-standing tradition.

 
Left: Anthony Dekker / Right: Anthony Dekker (click images to zoom – OLD PICS)

10    Tokai University 

Monohull challenger (Tokai Challenger) – they are hoping to attend both the South African event and the WSC.

Previously, Tokai came 2^nd at WSC 13; came 3^rd at WSC 15; came 4^th at WSC 17; came 2^nd at WSC 19; came 7^th at Abu Dhabi 15; came 2^nd at SASOL 16; and came 2^nd at SASOL 18.

 
Left: credit / Right: credit (click images to zoom)

15    Western Sydney Solar Team 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, WSU came 11^th at WSC 13; came 10^th at WSC 15; came 6^th at WSC 17; came 20^th at WSC 19; and won ASC 18.

 
Left: Anthony Dekker / Right: Anthony Dekker (click images to zoom – OLD PICS)

16    Stanford Solar Car Project 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Stanford came 4^th at WSC 13; came 6^th at WSC 15; came 9^th at WSC 17; and participated at WSC 19.

 
Left: credit / Right: Anthony Dekker (click images to zoom – OLD PICS)

18    EcoPhoton Solar Car Team (UiTM) 

Challenger (new car) – I am not sure what their plans are, exactly.

Previously, EcoPhoton came 26^th at WSC 15; participated at WSC 17; and participated at WSC 19.

 
Left: credit / Right: credit (click images to zoom – OLD PICS)

21    Solar Team Twente 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Twente came 3^rd at WSC 13; came 2^nd at WSC 15; came 5^th at WSC 17; came 17^th at WSC 19; won iESC 16; came 1^st and 2^nd at iESC 18; and came 2^nd and 4^th at iESC 20. Their team number (21) is a pun and a wish for success in the race (“Twente-One”).

 
Left: credit / Right: Anthony Dekker (click images to zoom – OLD PICS)

22    MDH Solar Team 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, MDH participated at WSC 17 and participated at WSC 19.

 
Left: credit / Right: credit (click images to zoom – OLD PICS)

23    Halmstad University Solar Team 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, HUST participated at WSC 19.

 
Left: credit / Right: credit (click images to zoom – OLD PICS)

35    University of Minnesota Solar Vehicle Project 

Four-seat cruiser (new car: Freya I) – they are America’s Cruiser class pioneers. They are building a new car, but raced their old car at WSC 19 (read their race report here). I am not sure if they will attend WSC 21.

Previously, Minnesota came 4^th in the WSC 13 Cruiser class; came 5^th in the WSC 15 Cruiser class; participated in the WSC 17 Cruiser class; came 5^th in the WSC 19 Cruiser class; came 2^nd at ASC 14; came equal 10^th at ASC 16; and came equal 2^nd in the ASC 18 Cruiser class. Their team number (35) is derived from the Interstate 35 highway.

 
Left: credit / Right: Anthony Dekker (click images to zoom – OLD PICS)

41    Australian National University 

Three-wheel challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, ANU participated at WSC 17 and participated at WSC 19.

 
Left: credit / Right: credit (click images to zoom – OLD PICS)

46    JU Solar Team 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, JU came 20^th at WSC 13; came 15^th at WSC 15; came 8^th at WSC 17; and came 10^th at WSC 19. Their team number (46) is the Swedish national telephone prefix.

 
Left: Anthony Dekker / Right: Anthony Dekker (click images to zoom – OLD PICS)

51    Chalmers Solar Team 

Three-wheel (tadpole) challenger (new car: Sköll) – they were the first Challenger-class team to reveal a render.

Previously, Chalmers came 21^st at WSC 19.

picture credit (click image to zoom)

70    Sonnenwagen Aachen 

Challenger (new car) – this team did very well in 2019, in spite of being blown off the road.

Previously, Aachen participated at WSC 17; came 6^th at WSC 19; came 3^rd at iESC 18; and came 5^th and 8^th at iESC 20. Their team number (70) is the number they raced with in 2017.

 
Left: credit / Right: Anthony Dekker (click images to zoom – OLD PICS)

75    Sunswift (University of New South Wales) 

Cruiser (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Sunswift came 3^rd in the WSC 13 Cruiser class; came 4^th in the WSC 15 Cruiser class; participated in the WSC 17 Cruiser class; and came 2^nd in the WSC 19 Cruiser class.

 
Left: credit / Right: credit (click images to zoom – OLD PICS)

77    Blue Sky Solar Racing (Toronto) 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, Blue Sky came 8^th at WSC 13; came 12^th at WSC 15; came 11^th at WSC 17; came 11^th at WSC 19; and came 3^rd at ASC 16.

 
Left: credit / Right: credit (click images to zoom – OLD PICS)

82    Kookmin University Solar Team 

Challenger (new car) – there is not much news on what they are up to, but this indicates that they plan to participate.

Previously, KUST came 15^th at WSC 13; came 20^th at WSC 15; participated at WSC 17; and came 19^th at WSC 19. Their team number (82) is the Korean national telephone prefix.

 
Left: KUST / Right: KUST (click images to zoom – OLD PICS)

84    Solar Team Solaris (Dokuz Eylül University) 

Asymmetric challenger (S10) – they did some testing before ESC (which they were sadly unable to attend). They have not mentioned building a new car.

Previously, Solaris participated in the WSC 13 Adventure class; came 25^th at WSC 15; came 18^th at WSC 19; came 9^th at iESC 16; came 2^nd at Albi Eco 18; and came 2^nd at MSRC 19.

 
Left: credit / Right: credit (click images to zoom)

101    Éclipse – Véhicule solaire de l’ÉTS 

Asymmetric challenger (Éclipse X.1) – they raced in Australia in 2019 as number 92, finishing 2^nd among North American teams. They are favourites to win ASC 2021.

Previously, Eclipse came 18^th at WSC 13; came 9^th at WSC 19; came 10^th at ASC 14; came 8^th at ASC 16; came 4^th at FSGP 17; and came 3^rd at ASC 18.

 
Left: credit / Right: Anthony Dekker (click images to zoom)

900    PUT Solar Dynamics (Poznań University of Technology) 

Two-seat cruiser (new team with car: Klara) – they were making good progress on construction, although Covid-19 seems to have slowed this down. This (Polish) video describes their project.

 
Left: credit / Right: credit (click images to zoom)

910    Universidad Autónoma del Estado de México SRT (Hyadi) 

Two-seat cruiser (new team with car: Quetzál) – this new team from Mexico are planning to build a great-looking Cruiser.

picture credit (click image to zoom)

920    Solaride  

Two-seat cruiser (new team) – this new team from Estonia hopes to build a Cruiser.

picture credit (click image to zoom)

932    Solar Electric Vehicle – Cairo University Team 

Two-seat cruiser (new team with car: Horus) – this team has been building a Cruiser for quite some time.

 
Left: credit / Right: credit (click images to zoom)

940    EMUAI 

Challenger (new car) – this team from UAI (Universidad Adolfo Ibáñez) previously won the two-seater hybrid category of the 2018 Carrera Solar Atacama. Their team logo is an Australian emu, so they should do well in the Australian Outback.

picture credit (click image to zoom)

950    Orion Solar Car 

Three-wheel (tadpole) challenger (new team) – they have posted a timeline for construction.

picture credit (click image to zoom)

960    Deakin University / ACCIONA (Ascend) 

Two-seat cruiser (new team with car: Ascend) – they are developing a dash display.

picture credit (click image to zoom)

970    University of Canterbury Solar Team 

Cruiser (new team) – this team from New Zealand was building a Cruiser, but they have posted nothing in the last 12 months.

public domain photo

This page last updated 11:39 on 17 January 2021 AEDT.

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Happy Solar Car New Year!

The American Solar Challenge is on again in July/August 2021 (hopefully), and the World Solar Challenge in Australia follows in October 2021 (again, Deo volente). As the pictures above from Canadian team Midnight Sun/Waterloo illustrate, chassis/suspension + aerodynamics/electrics = a solar car.

How that equation works out in practice can vary. The World Solar Challenge has now allowed three-wheeled cars again, and Chalmers Solar Team from Sweden is taking advantage of this to build a sleek tadpole three-wheeler called Sköll (render below). Other teams are still frantically designing new cars. The big-name teams hope to reveal completed cars in July. Good luck and Happy New Year to all!

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History, geography, and the Western genre

Once Upon a Time in the West, Rio Grande, High Noon. We know the films – and the many books.

“The bray of a lazy burro broke the afternoon quiet, and it was comfortingly suggestive of the drowsy farmyard, and the open corrals, and the green alfalfa fields. Her clear sight intensified the purple sage-slope as it rolled before her. Low swells of prairie-like ground sloped up to the west. Dark, lonely cedar-trees, few and far between, stood out strikingly, and at long distances ruins of red rocks. Farther on, up the gradual slope, rose a broken wall, a huge monument, looming dark purple and stretching its solitary, mystic way, a wavering line that faded in the north. Here to the westward was the light and color and beauty. Northward the slope descended to a dim line of canyons from which rose an up-flinging of the earth, not mountainous, but a vast heave of purple uplands, with ribbed and fan-shaped walls, castle-crowned cliffs, and gray escarpments. Over it all crept the lengthening, waning afternoon shadows.” – Zane Grey, Riders of the Purple Sage (1912)

But why are the films and books all set in the United States? Didn’t the very similar continent of Australia have similar stories? Well, up to a point.

Click map to zoom

If we want to know why things are the way they are, the answers often lie in history and geography (Jared Diamond makes an especially strong case for geography in his Guns, Germs, and Steel). European settlement in the US began several centuries ago. The Appalachian Mountains (rising to 2,037 m or 6,684 ft) formed a barrier to westward expansion, but hardly in insurmountable one. The eastern US is also blessed with many navigable rivers, especially the Mississippi and tributaries such as the Ohio, Missouri, Platte, and Arkansas. The eastern US is also blessed with good rainfall.

Click map to zoom

Western expansion in the US constantly outran organised government. This created a degree of chaos that lasted for a surprisingly long time. The Oklahoma Panhandle, for example, was “No Man’s Land” from 1850 until 1890 – not part of any state or territory. The western part of the Minnesota Territory had the same status between 1858 and 1861. In addition, some of the organised territories in the contiguous US (Arizona and New Mexico) did not become states until 1912.

One tool for dealing with this situation was the resurrection of a thousand-year old English law enforcement strategy: posse comitatus or “power of the county.” Law enforcement was provided by a sheriff, who was authorised to call on armed citizens as needed. Part of the drama of Western stories lies in the sheriff deciding when this was actually needed.

Click map to zoom

In contrast to the US, Australia is significantly drier. The Great Dividing Range in the east is somewhat loftier than the Appalachians, with the highest point being Mount Kosciuszko (2,228 m or 7,310 ft). A significant part of the water falling on the west of the range winds up underground in the Great Artesian Basin, a vast bed of porous sandstone holding up to 64,900 cubic kilometres (15,600 cubic miles) of water, capped by an impermeable layer of rock. In places, the basin is 3 km (2 miles) deep. The basin was discovered in 1878, and only after that date did cattle stations or sheep stations in certain parts of the country become feasible, thanks to water from deep bores.

Click map to zoom

Politically, the Australian situation was quite different from the US as well. The entire continent east of 135°E was initially part of the British colony of New South Wales, and by 1829 all of the continent had been claimed. Colonial boundaries shifted several times before Federation in 1901 (and the Northern Territory was transferred to federal control in 1911), but the US situation of unorganised territory was nonexistent.

Law enforcement in Australia was initially military, and early police forces were composed of military personnel. In 1853, Victoria was the first colony to merge law enforcement into one colonial police force. However, law enforcement was never decentralised, as it was in the US.

Mounted police escorting gold, 1852 (British Museum)

The vast size and relatively small population of Australia meant that there was plenty for law enforcement to do, of course. Stage coaches and gold miners were robbed, and what Americans call “rustling” also took place. In 1870, a daring theft of around 800 head of cattle took place at Bowen Downs Station in Queensland. Harry Redford and four accomplices overlanded the stock to outback South Australia, where the brands would not be recognised (a distance of about 1,300 km or 800 miles). Employees of Bowen Downs successfully tracked the herd, but Redford was acquitted by a working-class jury who didn’t much mind rich graziers being robbed.

Tom Roberts, Bailed Up (1895)

The Western genre tells stories of human drama and resourcefulness on the frontier, and in that it resembles the science fiction genre. But to a large extent the Western genre is also a celebration of the land. To quote one of my favourite contemporary short stories (a Christmas story, actually), from novelist Elisabeth Grace Foley:

“A million diamonds glinted in the smooth, untouched white curve of snow in the basin, struck out by the sun that pierced the bright silver-white sky. The bitter wind whisked across it, kicking up little powdery swirls. Cal Rayburn turned up the collar of his sourdough coat with one hand, hunching his shoulders a little so the collar half covered his ears. He squinted at the blinding-bright landscape, and one side of his cold-numbed lips twisted back a little in a half-smile.” – Elisabeth Grace Foley, “The Bird of Dawning”

Australians may have lost contact with the land to a greater extent than Americans have, so that the genre of Australian colonial stories has largely faded away. Australia was formed as a collection of colonies with coastal capitals (and with the national capital only 100 km or 60 miles inland). That, together with the dryness of the interior, facilitated a drift to the cities, so that 70% of the population now lives in the 8 capitals.

In contrast, the US has many landlocked states which seem to retain a greater connection to the land. The state flag of Kansas, to pick just one state, seems to tell an entire story, including Indians hunting bison on the Great Plains, a steamboat on one of the navigable rivers, a settler ploughing his field, and a wagon train heading west. There is scope for all kinds of literature and cinema right there (as Laura Ingalls Wilder, Louis L’Amour, Howard Hawks, John Sturges, Clint Eastwood, and many others have shown). Let us hope that people will keep telling those stories.

Flag of Kansas

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World Solar Challenge Cruiser scoring

Having participated in some recent discussions about the World Solar Challenge Cruiser Class, I thought I would explore the scoring again. Scoring in the WSC is based on a multiplicative formula (see reg 4.4.7), but as we all learned in high school, multiplying is equivalent to adding logarithms.

By appropriate scaling of logarithms, the chart above breaks down the various components of the multiplicative formula into additive points (black bars are negative numbers).

For example, on this system, in 2019 Eindhoven received a total of 67 points:

• 100 points for completing all three stages
• +12 points for an average of 2.6 people in the car
• −53 points for 71.2 kWH of external energy
• −0 points for no lateness
• +8 points for a practicality of 93.1%

Lateness refers to arrival at stage stops after the “soft cutoffs,” which in 2021 will be Sat 15:30 in Tennant Creek, Mon 16:30 in Coober Pedy, and 11:30 Wed in Adelaide (there are also “hard cutoffs” leading to elimination, of 17:00, 17:00, and 14:00 respectively). According to reg 4.4.8, teams are ranked by the number of completed stages, and then by score.

In 2019 Minnesota received a total of 39 points:

• 86 points for completing only one stage (thus also ranking after all the finishers)
• +9 points for an average of 2 people in the car
• −40.5 points for 25.7 kWH of external energy
• −21 points for 165 minutes of lateness
• +5.5 points for a practicality of 76.3%

Suppose a larger battery and a longer race had increased Minnesota’s external energy use to 128 kWH (an extra −20 points), but this had removed the lateness factor (an extra +21 points) and allowed achieving all three stages (an extra +14 points). Minnesota would then have been 15 points ahead, for a total of 54. This would have put them neck-and-neck for second place with Sunswift.

This example makes clear how the rules create an incentive for large batteries. It also highlights the difficulty of the second stage from Tennant Creek to Coober Pedy – I wonder if an extension to the “hard cutoff” is possible there?

Technical note: I am multiplying natural logarithms by 12.48 (so that 3020 gives 100), and I have also doubled practicality, and thus the total score (this doesn’t, of course, give practicality any extra weight). Sanity check for Eindhoven: 12.48 × ln(104×2) = 67.

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A planetary conjunction and a Christmas greeting

It’s time for a Christmas blog post, and there’s really only one thing to write about. On 21 December, there will be a great conjunction, in which Jupiter and Saturn will appear very close together in the early evening sky. Look for them near the western horizon, as they get closer and closer over the next two weeks. The diagram below (from fourmilab.ch) shows what the solar system will look like at conjunction. A line from Earth to Jupiter continues on to Saturn, but skims by the Sun (which is why the “kissing planets” are only visible in the early evening). These two giant planets have not appeared so close for several centuries.

The Christmas connection relates to the Magi mentioned in the Bible: “After Jesus was born in Bethlehem in Judea, during the time of King Herod, Magi from the east came to Jerusalem and asked, ‘Where is the one who has been born king of the Jews? We saw his star when it rose and have come to worship him.’” (Matthew 2:1–2, NIV)

One theory as to what the Magi might have seen was a set of similar conjunctions of Jupiter and Saturn in 7 BC (the great astronomer Johannes Kepler was the first to suggest this – and yes, thanks to a calendrical error 500 years later, Jesus was born around 7–4 BC). There were three such conjunctions in 7 BC: in May, in late September, and again in December. Here is a view of the September one, as seen from Ctesiphon in Parthia (from fourmilab.ch again). The planets Jupiter (♃) and Saturn (♄) would have risen just before sunset, and been visible in the evening twilight (and then throughout the night):

The Babylonians and Persians had an elaborate system of seeing omens in the sky. For example: “If Jupiter becomes steady in the morning: enemy kings will be reconciled. … If Jupiter passes Regulus and gets ahead of it, and afterwards Regulus, which it passed and got ahead of, stays with it in its setting, someone will rise, kill the king, and seize the throne.” So a conjunction is the sort of thing that would have gotten the attention of star-gazers in the Parthian Empire (the planet Jupiter was associated with the god Marduk and with kingship). Others have suggested a nova recorded in China in March of 5 BC. Yet others have suggested that a sequence of astronomical events led the star-gazers to search for a newborn king specifically in the frontier province of Judaea:

Countless paintings show the journey of the Magi across the desert (the one above is from James Tissot). If they were sensible, they would likely have travelled along the trade routes via Palmyra and Damascus. “A cold coming we had of it” wrote the poet T.S. Eliot (adapting lines from a 1622 homily by Lancelot Andrewes), “Just the worst time of the year / For a journey, and such a long journey.”

The real danger was Herod, of course. He had murdered his own sons Alexander and Aristobulus in 7 BC (and was to murder a third son, Antipater, in 4 BC). According to Macrobius (Saturnalia Book 2, IV, 11), Caesar Augustus had quipped “Better to be Herod’s swine [Greek hus] than his son [huios],” making a Greek pun referencing Herod’s Jewish religion and its prohibition on pork. Naturally, a man like that would be less than thrilled at the suggestion that another heir to the throne might exist:

“When King Herod heard this he was disturbed, and all Jerusalem with him. When he had called together all the people’s chief priests and teachers of the law, he asked them where the Messiah was to be born. ‘In Bethlehem in Judea,’ they replied, ‘for this is what the prophet has written:

“But you, Bethlehem, in the land of Judah,
are by no means least among the rulers of Judah;
for out of you will come a ruler
who will shepherd my people Israel.”’ [a summary of Micah 5:2–5]

Then Herod called the Magi secretly and found out from them the exact time the star had appeared. He sent them to Bethlehem and said, ‘Go and search carefully for the child. As soon as you find him, report to me, so that I too may go and worship him.’” (Matthew 2:3–8, NIV)

This is the kind of trouble you get when you mix star-gazing boffins and international diplomacy (I have been to enough international scientific events to know how that works). The gospel account makes a further confusing reference to the “star” and mentions the famous gifts of “gold, as to a king; myrrh, as to one who was mortal; and incense, as to a God”:

“After they had heard the king, they went on their way, and the star they had seen when it rose went ahead of them until it stopped over the place where the child was. When they saw the star, they were overjoyed. On coming to the house, they saw the child with his mother Mary, and they bowed down and worshiped him. Then they opened their treasures and presented him with gifts of gold, frankincense and myrrh. And having been warned in a dream not to go back to Herod, they returned to their country by another route.

When they had gone, an angel of the Lord appeared to Joseph in a dream. ‘Get up,’ he said, ‘take the child and his mother and escape to Egypt. Stay there until I tell you, for Herod is going to search for the child to kill him.’” (Matthew 2:9–13, NIV)

This “Flight into Egypt” has been a common subject of Christian art. The painting above, by Adam Elsheimer (1609), includes a beautifully painted Milky Way.

Egypt, of course, was a logical destination. We know first-century Alexandria primarily as the scientific and mathematical centre of the world of that time, but it also had a thriving Jewish community, with hundreds of thousands of Jews living in the city, and hundreds of thousands more in the rest of Egypt. The Hellenistic Jewish philosopher Philo was still a boy at this time, as was the Greek scientist Heron, but the Musaeum was fully active. Eventually, Alexandria was also to become one of the most important Christian cities, and the statement “gold, as to a king; myrrh, as to one who was mortal; and incense, as to a God” was from Alexandria. An active Coptic Church is still there (though suffering hardship).

But troubled as the world of 2020 may be, let me wish all my readers a Merry Christmas, and a better 2021!

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