Category: Science

New discoveries, the scientific method, and all matters relating to the scientific study of the physical world

Climate change and wildfires

Through a variety of mechanisms, anthropogenic climate change is worsening wildfires. For instance, warm winter temperatures were a key factor in British Columbia’s apalling mountain pine beetle epidemic, and trees killed by the beetles may be more susceptible to fire. More directly, high temperatures dry out forests and raise fire risks.

Page 44 of the divestment brief summarizes some of the research on climate change and wildfires.

Fires also contribute to the worsening severity of climate change, both by releasing large amounts of carbon dioxide and by producing dark soot which absorbs energy from sunlight.

Gabor Maté on addiction

“Nothing sways them from the habit—not illness, not the sacrifice of love and relationships, not the loss of all earthly goods, not the crushing of their dignity, not the fear of dying. The drive is that relentless… If human life was so simple that people learned from negative consequences, well then human history would be very different… The drugs solve problems in people’s lives, in the short term. Of course, they create problems in the long term… When you stress animals, they’re more likely to engage in addictive behaviours… Our whole social policy’s based on stressing the addict—and then we hope to redeem them—which flies in the face of science, not to mention human compassion… We’re punishing people for having been abused in the first place.”

Morally intolerable climate change impacts and risks

Sometimes convincing moral arguments take the form: outcome X is unacceptable, and since it arises from behaviour A then behaviour A can no longer be allowed to continue.

This is implicit in many of the hundreds of posts I have written about climate change, but I thought it would be good to have an open thread specifically listing credible impacts and risks associated with climate change which are so severe they compel us to discontinue behaviours that make the problem worse, such as fossil fuel production and development.

For example: Parts of South Asia could be too hot to live in by end of century

That’s a risk so morally intolerable that it torpedoes competing moral arguments, such as the claim that people can legitimately do anything to maintain their financial livelihood, or that political jurisdictions have an unrestricted right to exploit resources in their territories.

Grating coupler arrays as cameras

A recent Economist article describes a novel camera design with the promise to be far thinner than those that exist now, with some novel features:

Not only do Dr Hajimiri’s cameras have no moving parts, they also lack lenses and mirrors—in other words, they have no conventional optics. That does away with the focal depth required by today’s cameras, enabling the new devices to be flat.

…

To mimic the image-making role of the optics in conventional cameras, the OPA manipulates incoming light using electrons. Dr Hajimiri compares the technique to peering through a straw while moving the far end swiftly across what is in front of you and recording how much light is in each strawful. In the OPA this scanning effect is created by manipulating the light collected by the grating couplers electronically, using devices called photodiodes. These place varying densities of electrons into the amplified light’s path through the OPA, either slowing it down or speeding it up as it travels. That shifts the arrival times of the peaks and troughs of the lightwaves. This “phase shifting” results in constructive interference between waves arriving from the desired direction, which amplifies them. Light coming from other directions, by contrast, is cancelled through destructive interference. Change the pattern of electrons and you change the part of the image field the OPA is looking at. Scanning the entire field in this way takes about ten nanoseconds (billionths of a second).

…

To zoom in for a close-up, the device selects a specific part of the image and scans it more thoroughly. To zoom out for a fish-eye, it scans the entire optical field, including light from the edges of that field. To change from zoom to fish-eye takes nanoseconds.

Doubtless, such cameras will have some interesting applications. Unfortunately, that will certainly include further entrenching the surveillance state — increasingly using devices too small to see.

Basics of gas centrifuge uranium enrichment

[U]ranium enrichment is the process that separates U-235 from U-238 in order to increase the proportion of the former isotope. Separation is measured by the kilogram separative work unit (SWU), representing the amount of uranium processed and the degree to which it is enriched. The gas centrifuge exploits the mass difference between these two isotopes (three neutrons) by spinning uranium hexafluoride gas (UF6) at extraordinarily high speeds (twice the speed of sound), forcing the lighter U-235 to the center, where it can be “scooped off” at the top. These centrifuges must be arranged in cascades, or groups of centrifuges, as each cascade enriches the material only slightly before feeding it into the next. Although this process may sound fairly simple, the specialized materials and precision engineering necessary are very difficult to achieve.

The necessary ingredient for the enrichment process, UF6, must be free of any impurities, as impurities may condense and trigger blockages in the valves and piping of the cascades, causing the centrifuges to crash. Once this gas is produced with the highest degree of purity, it is then ready to be fed into the centrifuge, a machine made of many complex parts. The main components are (1) rotor and end caps; (2) bearing and suspension systems; (3) electric motor and power supplies; (4) center post, scoops, and baffles; (5) the vacuum system; and (6) the casing. The first challenge is to acquire the specialized materials for these parts. High-strength, corrosion-resistant materials, such as maraging steel, aluminium alloys, titanium, glass-fiber resins, or carbon fiber, are essential for most of the aforementioned components. Maraging steel specifically provides not only protection but also the capacity for faster rotor speed.

The second challenge is to construct a perfectly balanced centrifuge rotor (an almost impossible task) that can rotate at supercritical speeds (about 100,000 rpm). In addition to the complex engineering necessary for the construction of other centrifuge parts, a method must be devised to control the temperature and convection in the vacuum. Now imagine replicating this precision engineering in cascades of about three thousand centrifuges.

Khan, Feroz Hassan. Eating Grass: The Making of the Pakistani Bomb. Stanford University Press; Stanford. 2012. p. 142

Open thread: additive manufacturing

I was surprised to see that I don’t seem to have ever put up a post about 3D printing, despite the variety of ways in which it’s interesting.

The Economist has recently printed a few articles:

I’ve done a little 3D printing myself, making one of Bathsheba’s free designs at the Toronto Reference Library. It would be great to be able to print in something more durable than the biodegradable plastic they offer.

Lots of significant climate news

CPSA is keeping me busy, but there have been some interesting news stories in the last few days:

Overall, recent developments are worrisome. We know how short a window there is for action capable of hitting the Paris Agreement’s targets, and yet we continue to make contradictory policy choices.