Sunset on a flat earth

Earlier, I wrote a post on why people know that the earth is round. Evidence such as star movement, the obscuring of distant objects by the earth’s curvature, and aircraft flight times shows that the earth is not flat:

In this post, I want to temporarily put on the “hat” of a flat-earther. They claim that the sun is a “spotlight” which travels across a circular flat earth like this:

That is at least a well-defined model, crazy though it might be, and therefore can be tested. Here is a computer render of the spring sun at sunset on that assumption (as seen from, say, San Francisco, at the moment that the sun disappears from view):

Three obvious problems with the flat-earth model are visible in this picture:

  • The sun is much too small: only 40% of its noontime diameter (because it is 2.5 times as far away as at noon)
  • The sun appears oval, rather than circular, because the “spotlight” is being seen obliquely (click to zoom if you can’t see the shape)
  • The sun is much too high in the sky (24° above the horizon)

In reality, of course, the sun at sunset is a circular disk that gradually slips under the horizon. Oops. No, the earth is not flat.


Looking back: 1982

In 1982 (35 years ago!) I finished my basic undergraduate degree, majoring in Mathematics and Computer Science (after sniffing around the job market, I continued my studies for an honours year). This was the year that the compact disc and the Commodore 64 computer came out:

Also that year, Stephen Cook won the Turing award for his work on computational complexity theory. The then Soviet Union landed two spacecraft in the hellish inferno that is Venus, and took photographs:

It was also a year of conflict – Argentina started a war with the UK over the Falklands Islands, and Israel invaded Lebanon. On a more positive note, there were several movies which became cult classics, such as Tron, E.T., and Conan the Barbarian. The superb science fiction movie Blade Runner stood out from the crowd (even with the flaws in the original cinema release):

In literature, Isabel Allende published her debut novel, as did Kazuo Ishiguro. In music, The Alan Parsons Project released their album Eye in the Sky and Australian band Icehouse (originally Flowers) released their classic single “Great Southern Land”:

Overall, it was a great year (apart from the wars).

Australians know that the world is round

Following up on my earth-measuring post, people have known for more than 2,000 years that the earth is round. In 350 BC, Aristotle wrote “The evidence of the senses further corroborates this [that the earth is spherical]. How else would eclipses of the moon show segments shaped as we see them? As it is, the shapes which the moon itself each month shows are of every kind straight, gibbous, and concave-but in eclipses the outline is always curved: and, since it is the interposition of the earth that makes the eclipse, the form of this line will be caused by the form of the earth’s surface, which is therefore spherical. Again, our observations of the stars make it evident, not only that the earth is circular, but also that it is a circle of no great size. For quite a small change of position to south or north causes a manifest alteration of the horizon. There is much change, I mean, in the stars which are overhead, and the stars seen are different, as one moves northward or southward. Indeed there are some stars seen in Egypt and in the neighbourhood of Cyprus which are not seen in the northerly regions; and stars, which in the north are never beyond the range of observation, in those regions rise and set. All of which goes to show not only that the earth is circular in shape, but also that it is a sphere of no great size: for otherwise the effect of so slight a change of place would not be quickly apparent.” (On the Heavens, II, 14).

Around the year 700, Bede wrote “We call the earth a globe, not as if the shape of a sphere were expressed in the diversity of plains and mountains, but because, if all things (terrestrial) are included in the outline, the earth’s circumference will represent the figure of a perfect globe. Hence it is that the stars of the northern hemisphere appear to us, but never those of the southern; while on the other hand, the people who live on the southern part of the earth cannot see our stars, because the globe obstructs their view.” (De Natura Rerum). Australians verify his statement about stars every night.

I have commented previously on how the medieval poet Dante described time zones on a round earth:

In more recent times, we have pictures from space:

Aristotle and Bede mention the stars. Not only do the visible stars vary with latitude, but in the Northern Hemisphere they rotate around Polaris, while in the Southern Hemisphere they rotate around the South Celestial Pole, as in this photograph taken in Chile:

Sailors at sea have long known that the earth is round. From a vantage point 20 metres above sea level, one can see a complete ship 17 km away. Beyond that, the distant ship goes “hull down,” and only the upper parts of it are visible (from 34 km away, the lower 20 metres of a distant ship will be hidden). Closer to sea level, the distance is much less. This photo, taken in Spain by “Santifc,” shows the phenomenon (and similar observations can be made at some Australian beaches):

And, of course, the aircraft flight times to and from Australia can only be explained by the fact that the earth is round:


World Solar Challenge: doing media right

I’ve often pointed out that a solar car team is more like a startup company than anything else. A little like the early days of Google, really. The main product (the solar car, the search engine) is a gigantic money sink, and any cash coming in relates to something else (sponsorship, advertising). Overall success requires multiple skill sets working together. In particular, making sponsorship work requires an excellent media team (as well as a car fast enough to generate lots of good news). A number of teams have a track record of doing this well – Twente, for example, and Punch.

Deufol Technics packs Punch’s car and gear yesterday

An important example of sponsorship relates to transport. Here, the team acts as a kind of giant billboard for a tricky logistics problem handled well. This year, Punch provided a textbook example of superb media handling on this topic:

‘Voor mij is het de eerste keer dat ik voor zo een uitdaging sta,’ zegt logistiek manager Pieter Galle uit Leuven. ‘Het batterijpakket versturen is de grootste uitdaging voor het team. De batterijcellen die wij gebruiken zijn vaak niet toegelaten op vluchten. Om deze toch te kunnen versturen moeten er veel veiligheidsmaatregelen getroffen worden. Gelukkig heeft DHL Global Forwarding, in samenwerking met Deufol als verpakker van de goederen en batterijen alles tot in de puntjes kunnen regelen, zodat wij ons met het team volledig op het wereldkampioenschap konden concentreren.’” (Translation: “‘It’s the first time I’ve faced a challenge like this,’ says logistics manager Pieter Galle from Leuven. ‘Transporting the battery pack was the biggest challenge for the team. The batteries we use are often forbidden on flights. To be able to send them, many safety measures need to be taken. Fortunately, DHL Global Forwarding, in cooperation with Deufol our packer, has managed all the details, making it possible for us to focus our attention on the world championship.’”)

And Pieter Galle wasn’t just engaged in hyperbole there – transporting lithium battery packs really is tricky. In 2015, and again this year, there have been horror stories involving battery packs. I should also point out that some good photos really help the sponsorship game too, like these from Twente this year, or this one from Michigan, or this one from Nuon in 2015:

Nuon’s 2015 flightcase being loaded (photo: Jorrit Lousberg)

Another important sponsorship category relates to the team’s university. Here Western Sydney provides an excellent example, with their 2015 car being part of a major university rebranding exercise:

Western Sydney University’s 2015 car (photo: A. Dekker)

Michigan always does a great job of this during the American Solar Challenge. Their media team generates local news coverage everywhere they go. And the University of Michigan can afford to take the long view. If a 12-year-old boy or girl somewhere in rural America gets excited by the car, and decides to study engineering at Michigan one day, that’s a win. And not just for the university – if the sponsorship money keeps rolling in, the cars keep rolling on, and the fans can keep watching.


Killer robots: it’s not the AI that’s the problem

In a recent open letter, Tesla’s Elon Musk and others called for a ban on autonomous weapons, saying “Lethal autonomous weapons threaten to become the third revolution in warfare. Once developed, they will permit armed conflict to be fought at a scale greater than ever, and at timescales faster than humans can comprehend. These can be weapons of terror, weapons that despots and terrorists use against innocent populations, and weapons hacked to behave in undesirable ways. We do not have long to act. Once this Pandora’s box is opened, it will be hard to close.

Yet autonomous weapons are already with us, after a fashion. And artificial intelligence isn’t actually the biggest problem.

A bullet, during the second or so that it is in flight, autonomously follows the laws of physics. But the world is not likely to have changed much during that time. If shooting the bullet was appropriate, that will still be true when it hits. A cruise missile can fly for several hours, and home in on a precise spot, specified by GPS coordinates – although things may have changed during those hours of flight.

Smarter again is a heat-seeking or radar-guided missile, which can home in on an aircraft, even one doing it’s best to evade the threat – yet it cannot distinguish passenger aircraft from military aircraft. The next step up are systems guided by IFF, which can distinguish friend from foe. After that comes the kind of AI that Elon Musk is talking about.

The ultimate extreme is the “Menschenjäger” of Cordwainer Smith’s 1957 short story “Mark Elf.” The Menschenjägers were built by the “Sixth German Reich” to seek out and kill their non-German enemies (whom they could infallibly detect by their non-German thoughts). Being virtually indestructible, the last Menschenjäger had travelled around the planet on this mission 2328 times by the time the story is set. Since no Germans were alive at that point, there was nobody left to shut it down.

The real problem with the Menschenjägers was not their AI, but their persistence in time. A similar problem arises with that most stupid of autonomous weapons, the landmine. Sown in their tens of millions, landmines continue to kill and maim for decades after the war that buried them is over.

It isn’t really a matter of whether the weapon has AI or not – it’s whether the weapon has an off switch or a self-destruct mechanism. No weapon should keep on pointlessly killing people.


When the towers fell

The World Trade Center towers (photo: Carol M. Highsmith)

I continue to see bizarre and ill-informed conspiracy theories on the Internet about the 2001 collapse of the World Trade Center towers (above). This is in spite of the detailed investigations of, and voluminous reports on, the event.

Steel softens at temperatures well below the melting point of 1400°C

In fact, it has long been known that structural steel buildings like the World Trade Center can collapse due to fire. In 1967, the structural steel roof of McCormick Place in Chicago collapsed because of softening due to a fire. This collapse began only about 30–45 minutes after the fire was reported.

The World Trade Center under construction (photo: Eric Shaw White)

In the case of the World Trade Center, this fundamental problem with structural steel was combined with building-specific design flaws. Still, in my view, concrete construction is simply safer. Concrete resists fire far better than steel, and locating fire escapes inside a thick concrete core assists evacuation, should that be needed. The 9/11 conspiracy theories are just silly, though.

A concrete tower under construction in Australia (photo: Erin Silversmith,)


Gender and glaciers?

There has been some controversy about the 2016 NSF-funded paper “Glaciers, gender, and science: A feminist glaciology framework for global environmental change research” (see here for a detailed analysis). The paper refers, inter alia, to the Forbes/Tyndall debate of the century before last (although I believe it is misinterpreting that saga). But, interesting as that episode was in the history of science, it has little to say about the epistemology of modern glaciology. In the 1800s, observing glaciers required extensive (perhaps even “heroic”) mountain climbing. Today, remote sensing methods and computer models are also important, and we understand glaciers much better than either Forbes or Tyndall did.

I don’t think that the gender studies lens adds anything to our understanding of glaciers. And I suspect that Elisabeth Isaksson, Moira Dunbar, Helen Fricker, Julie Palais, Kumiko Goto-Azuma, or Jemma Wadham would not think so either. Nor are race relations particularly important in studying ice. And as to “alternative ways of knowing,” I would prefer to stick with the scientific method – it’s worked very well so far (didn’t we just have a march against “alternative facts”?). Indeed, to subordinate science to the modern politicised humanities would be to abandon the concept of scientific truth, and to make it impossible to gain widespread agreement on the crises currently facing humanity.