Sundials!

Above is an analemmatic sundial. The idea is to orient the sundial facing south, and then place a vertical pointer on the central figure-8 track, in a position corresponding to the date. The sundial above shows a simulated shadow for 2:15 PM yesterday. It can be seen that the sundial tells the time reasonably well, thanks to the inbuilt adjustment for variation in solar position.

For large-scale analemmatic sundials, like the one below, people can stand on the central figure-8 track and act as a human pointer. A sundial like this is fun to have in the garden.

Here are blank sundials for some Southern Hemisphere cities:

The ShadowsPro software will also generate sundials like these, if anyone is particularly enthusiastic.


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Lotus Blue: a book review


Lotus Blue by Cat Sparks (377 pages, published 2017)

I recently read, with great enjoyment, the hot new post-apocalyptic novel Lotus Blue by Cat Sparks. I’m a sucker for the genre, and this novel has shades of Dune, Mad Max, A Canticle for Leibowitz, and the works of Roger Zelazny – yet is not derivative. As a fan of the trans-Australia World Solar Challenge, I particularly liked the caravan of solar trucks on the cover. The cover also shows the falling satellite which marks the emergent threat to the world of the novel.

While opening with a solar-powered trading caravan, the novel has a few flashbacks to the three centuries of war that created the dystopian world of the story: “Mighty tankers were on the move, travelling in tight formation grids. Working together, not attacking each other. Not something you saw every day. Those mechabeasts had once roamed wild and free, following their own whims, their own flights of fancy. But something had changed. Something had gotten hold of their minds. Synchronous rhythm locked them into step. For Marianthe, the sight brought on a stream of flashbacks: glory days, when command and strategy spiked through her arteries like a virus. Like a drug. A platoon full of hearts beating in syncopation. You could feel your brother and sister soldiers, know they had your back, your breath, your sweat.” I’m trying to avoid spoilers, but of course that savage past collides with the protagonist’s present, and that’s where the adventure begins.

Some readers seem to have found the world, and the range of characters, somewhat confusing; I thought the level of complexity of the novel was just about perfect. I enjoyed both the characters and the world in which they were set. This book has had a fair bit of revision and polishing before hitting the shelves, and it shows (although a plethora of typos suggests some rather poor final editing). My only real complaint was that, although I liked Star, the 17-year-old protagonist, I would have liked to have seen more of her older sister Nene, the healer (why does Nene just vanish from the story?). With luck, this novel will have a sequel or two.

By the way, a blog post I read recently suggested that the protagonist of a young adult (YA) novel should:

  • Be aged between 15 to 18 years old (Star is 17)
  • Be autonomous from his or her parents (Star is an orphan)
  • Embark on a journey which has to do with coming of age or some sort of rite of passage (Yes, she does)
  • Learn something about who he or she is (Yes, in spades)
  • Have a ‘voice’ that readers can relate to (Yes again)

So OK, this is a YA novel, although it has not been specifically marketed as such. What that means is that it suits the age range from 14 up to and including adult (as opposed to, say, Great North Road, which is written for adults only). Having said that, for the benefit of parents of younger readers, I should point out that there is some bad language, but that the only mention of sexuality is 25 words on page 3: “Remy. Star should never have slept with him. He’d been hanging around her ever since, as if she would ever make the same mistake again.” And Star has quite a clear sense of what is, and is not, the right thing to do.

For me, this novel ended with a “Planet of the Apes” moment, since Cat Sparks has set part of the novel in the vicinity of her home town of Canberra, Australia. Calling one of the fortress cities “Nisn” was a clue I missed first time around – but I could hardly miss the reference to the Brindabella Range. I also finished this book with a strong sense of wanting to read more from this author. Lotus Blue was one of the best books I’ve read this year.


Lotus Blue by Cat Sparks: 4 stars


My favourite bookshops


I ♥ science books!

Even in the age of the Internet, there’s nothing like browsing real books. Here are some of my favourite bookshops in Australia for science books. All of them are worth a visit:


Abbey’s Bookshop, Sydney

Abbey’s Bookshop, in Sydney, is an excellent bookshop, with the entire back wall being devoted to science and mathematics.


Books Kinokuniya, Sydney (photo by “Jason7825”)

Books Kinokuniya, just a short distance from Abbey’s (in The Galeries Victoria), also has a good science collection.


Boffins Bookshop, Perth (photo by Boffins Bookshop)

Boffins Bookshop, in Perth, specialises in technical subjects, including science and mathematics.


The Book Grocer’s branch in Albury, New South Wales

The Book Grocer, in multiple Melbourne locations and elsewhere around Australia (including Canberra), is an excellent discount book chain. All books are $10 or less. The Book Grocer usually carries a range of interesting mathematics and science books.


ANU Co-op Bookshop, Canberra (photo by “Nick D”)

In addition to the bookshops listed, bookshops in major universities (such as branches of the Co-op) can be counted on to carry interesting stock in the areas of science and mathematics. Clouston and Hall Academic Remainders, in Canberra (not pictured), offer a range of interesting books at a discount, and a number of other bookshops, such as Readings and Reader’s Feast in Melbourne, also carry a reasonable stock of science and mathematics books.

So why not celebrate National Science Week by reading a book about science?

The analemma

If you photograph the sun at the same time every day (or every few days), you will find that the sun traces out a path in the sky, called the analemma. György Soponyai, in Budapest (Hungary), did exactly that at 8 AM each morning between 29 January last year and 6 January this year, to produce the wonderful photograph below (click to zoom):

More analemma photographs (by Anthony Ayiomamitis) can be found here. The shape of the analemma results from the fact that (1) the Earth is tilted on its axis by 23.5° and (2) the Earth orbits the sun in an ellipse, rather than a circle. The diagram below shows the calculated analemma for 12 noon at the Royal Observatory, Greenwich (latitude 51.48° N):

The concept of the analemma can also be used in constructing sundials. If an appropriate analemma is placed in the centre of the sundial, a gnomon placed at the right point on the analemma will correctly tell the time with its shadow (except for daylight-saving, of course).

Such sundials are popular in parks, because the viewer can stand on the analemma at a position corresponding to the current date, and his or her shadow will tell the time, without the need for additional time-of-year correction. I photographed the sundial above and below at Mt Stromlo Observatory in June 2012. It can be seen that the time was about 2:20 PM.

Questacon: the Australian National Science and Technology Centre


Questacon exterior (public domain photo)

Questacon, the Australian National Science and Technology Centre, is a science museum located in Canberra. It combines science with entertainment, and includes a number of interesting exhibits, such as a house undergoing a simulated earthquake, and a play area for the 0–6 age bracket.


Part of the periodic table display (my photo)

Questacon is open almost every day, and is one of Canberra’s major tourist attractions. However, it is not free. See the Wikipedia article and the museum website for more information.

Monitoring space debris from Australia

The NASA Orbital Debris Program Office has long worked on monitoring and managing the serious problem of space debris.

Now, a new Australian Collaborative Research Centre (CRC) for Space Environment Management based at Mt Stromlo Observatory will add to this effort. It will bring together the expertise of two Australian universities and two companies, together with US and Japanese partners. The photo below of the Satellite Laser Ranging (SLR) facility at Mt Stromlo is by Ian Sutton.