Saturday, September 16, 2017

Thoughts on Stewart's Calculating the Cosmos: Astronomy as a motivator for math (eg mechanics, chaos, relativity)

I found Ian Stewart’s Calculating the Cosmos to be an interesting work that gives one a sense of how mathematics has been used in astronomy over the ages. The book provides a fairly traditional survey of all the astronomical elements -- the planets, the sun, asteroids, and comets -- and then continues to describe galaxies and the creation of the universe. The book highlights how key bits of mathematics are important for understanding these elements; for instance, angular momentum is crucial in creating disc- and spiral-shaped planetary systems and galaxies, and many-body dynamics is essential to understanding the motion of planets and how Lagrangian points around them confer special status.

The book explains why a lot of important mathematical concepts such as Gaussian curvature and Riemannian manifolds manifest themselves in general relativity. A lot of the things we take for granted just do not hold true in the world of black holes. I particularly liked the description of how chaos arises from small perturbations in initial conditions and how this manifests itself in terms of the overall motions of planetary bodies and the dynamics of systems. Furthermore, it is notable how astronomers used the deviation from what they expected as a way of finding Neptune and eventually Pluto, although the latter in a sense was a mistaken find.

Overall, this was an interesting read and put a lot of mathematics into perspective. I enjoyed it very much and would highly recommend it.
Calculating the Cosmos: How Mathematics Unveils the Universe
by Ian Stewart (Author)


Tuesday, September 05, 2017

Letters commenting on the safety of bikers (& drivers & pedestrians), given the recent increase in urban cycling

Letter #1

I read the recent Times article on the upswing in cycle commuting with
great interest. Certainly, from the perspective of a technocratic
transportation planner, this is a great thing. However, it cannot
relieve the terror one feels at night when a lightless bike zooms by,
narrowingly missing a collision, or when one has to wrench the
steering wheel and swerve almost into another car, to avoid a cyclist
going the wrong way down a street. There must be a way to fix this.
Perhaps give licenses to cycle commuters? Or maybe technology can
help: Trackers on bicycles or cameras monitoring sidewalks to flag bad

Letter #2

I read with great interest the recent Times Op. Ed. about a
65-year-old pedestrian killed by a cyclist. I sympathize as I am often
terrified walking down sidewalks by careening cycles, coming out of
nowhere. Also, there's the scary situation of the driver who swerves,
nearly getting into an accident, to avoid a cyclist going the wrong
way. A fundamental issue underlying cyclists' unsafe behavior is that
it's often ambiguous -- from their perspective -- whether they are
motorists or pedestrians. It's often better for the cyclist to ride on
safer sidewalks than on more perilous roads or to ride through a red
light to keep momentum. What can be done? A cyclist needs to be given
clear rules, and they need to be enforced. If a bike becomes a loose
canon, perhaps it is possible to take it away before damage is done.

Unpublished letter in response to:

Wheels of Misfortune -

More New Yorkers Opting for Life in the Bike Lane - The New York Times

Sunday, August 27, 2017

Thoughts on Dataism by Steve Lohr - Vignettes on Data Science, entertaining specifics but are they representative?

I read Steve Lohr's book Data-ism with keen interest. The author is a noted reporter for The Times that writes on technology. I was looking forward to the book and found it an interesting read. However, it's a bit patchy in certain places and tends to focus specifically on one point or illustration. I'm not sure it gives a balanced view of the emerging field of data science. That said, I particularly liked the way it talked about how data science is revolutionizing farming -- how the putting together of many sensors enables one to get an overview of the field much more so than one could get normally.

Data-ism: The Revolution Transforming Decision Making, Consumer
Behavior, and Almost Everything Else
by Steve Lohr (Author)


Sunday, August 20, 2017

Thoughts on Levitin's Weaponized Lies & A Field Guide to Lies - Good reads on how statistics can deceive

With great interest, I read Daniel Levitin's recent books "Weaponized Lies: How to Think Critically in the Post-Truth Era" and "A Field Guide to Lies: Critical Thinking in the Information Age." Both of these books give a good primer to deal with statistics, going over such things in detail such as Bayesian analysis in terms of a 2x2 table. Levitin also talks a bit about how people sort the truth by simply making false graphs with unlabeled axes or how there are more subtle aspects such as subtly changing the denominator (eg when talking about individuals versus families). Altogether I found these extremely useful reads. One thing that was a little troublesome to me was that they were fairly similar books. I think it does make sense for the author to repurpose his text into more current times where we talk about fake news and so forth but I still found the overlap between the two books disconcerting.
A Field Guide to Lies: Critical Thinking in the Information Age Audio CD – Audiobook, CD, Unabridged
by Daniel J. Levitin
Weaponized Lies: How to Think Critically in the Post-Truth Era Reprint Edition
by Daniel J. Levitin (Author)



Sunday, August 13, 2017

Thoughts on the Sonnenburgs' Good Gut - Great combo of hardcore microbiome science & practical tips for your diet

I read with great enjoyment Justin and Erica Sonnenburg’s book, The Good Gut. This is a rare work that combines solid science with practical help on dieting and wellness. On the scientific front, the book provides information about the bacteria that live in our gut (the microbiome), how they were first discovered, and how various properties were ascribed to them. It talks about the process of digestion and how the bacteria in the gut feed on molecules that are indigestible in the framework of human metabolism, in particular long-chain oligosaccharides, and how they produce short-chain fatty acids (SCFAs), which we can combine with oxygen to get small amounts of energy from. Furthermore, the bacteria in the gut are very important for tuning our immune system; they are also connected, in a sense, to our nervous system and to making us feel good. The book gives practical strategies of how we can help these bacteria do their job better. In particular, it talks about the distinction between probiotics, prebiotics, and symbiotics, with the former consisting of bacteria (eg in yogurt), the second, the food to feed these bacteria (eg leafy vegetables), and the later being great combinations of these two – eg yogurt with an inulin-containing banana. Finally, it discusses how we can intelligently expose our children to microbes, for instance, by letting them play in the dirt (but still washing their hands after touching door knobs and handles that are exposed to urban germs). Altogether, I found this a great read that talks about hardcore science in a practical context.

The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-term Health
by Justin Sonnenburg (Author), Erica Sonnenburg (Author)


Sunday, April 23, 2017

Fun things about liquids illustrated by simple kitchen mixtures of oil & water: hydrophobicity, diffusion, surface tension, &c

I did my PhD partially on liquids, analyzing the hydrophobic effect. Recently, I stumbled across an account describing simple things that you can do with home kitchen ingredients to illustrate properties of water and other liquids (see reference at bottom). The basic idea, of course, is just to mix oil and water in a container. However, there are many flourishes that you can easily add - for instance, you can add syrup (a very thick liquid) at the bottom, which forms a third layer separated to some degree from the water unless you vigorously mix it.

You can then put lots of things into this three-layer stack that go to the different characteristic layers depending upon the density -- for example, corks or toothpicks, which float to the very top, or blueberries, raspberries and some other vegetables, which go to the oil-water interface. Then there are things such as light plastic beads and pasta that go to the water-syrup layer. Finally, coins or metal objects sink to the bottom. Tightly crumpled paper vs a flat piece will also go to different levels, illustrating Archimedes'.

There are other neat things you can do such as pouring little bits of dye into the mixture and then watching it go through the oil and slowly mix with the water. Or even putting small amounts of salt in and watching them clump together and eventually pass through the oil before dissolving into the water. The differential aspects of pouring and mixing illustrate the physical concepts of diffusion and viscosity.

To some degree, one can also see the differences in surface tension of water and oil when one looks at objects at the oil/water boundary and also floating on top of the oil. The surface tension of the water is illustrated by the curved shape of the oil/water boundary (where the blueberry sits) in contrast to the top of the stack on the oil (where the cork or the duck sits).

Finally, if one leaves the preparation for enough time, the syrup mixes with the water. Of course, the oil and the water will stay separate. Eventually, if you wait long enough, you will see a small layer of bacteria at the interface, which is kind of interesting to watch grow, presumably getting considerable energy from the hydrocarbons in the oil.

Altogether a lot of fun: I have taken many pictures of the mixing and so forth and I would encourage people to do the same at home.

Pictures and Movies of the oil-water separation

Playful Separations: photos of oil-water mixtures in bottles, some with a 3rd layer and suspended objects ( and
Time-lapses: at first fast; then slow to equilibrium

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Lisa Burke,

Things illustrated

Diffusion and viscosity
Viscosity and diffusion
Capillary Action and Surface Tension
Hydrophobic Effect
Archimedes' principle

Sunday, March 12, 2017

Thoughts on Harari's Sapiens: An encompassing history of humankind, with non-intuitive insights - eg on our post-Neolithic quality of life)

I read Yuval Noah Harari's Sapiens: A Brief History of Humankind with great interest. The book covers the broad arc of human history all the way from prehistory and prehumans to the current day. It gives one a good feeling for a lot of things that we take for granted in organizing modern life but which are of course essential. In particular, the book talks a lot about how important shared myths and ideas are with things such as what is a company, what is money and how important that is to structuring society? The book also has a fascinating take on a lot of key events in history. For instance, it does not necessarily portray the agricultural revolution and domestication of animals in an entirely positive light, pointing out that while it led to a huge population boom for humans, it made the average person much more miserable, much harder working and much more susceptible to diseases. Likewise, we have a very romantic view of the notion of domestication of animals, but in a sense, it is a cruel practice. While, of course, it led to a great multiplication of certain animal species, it provided individuals of each species a potentially awful life to live -- e.g., think of the cooped-up chicken. The book has further interesting discussions about energy and how we have been able to ever more efficiently extract it from the environment over time, culminating in the industrial and then atomic ages. There are further interesting views on colonization and so forth. Overall, I found this a great read and would highly recommend it.

Sapiens: A Brief History of Humankind (9780062316097): Yuval Noah Harari