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I really like a little book called This Blessed Mess by Patricia H. Livingston. It is my go to book when my stomach is tied up in knots, and I am having trouble sleeping. I open it up to a random chapter, and tend to find a story that makes me laugh or sometimes to cry a little. Then I can sleep in peace.

Livingston describes how life can be chaotic and uncertain, but how there is goodness throughout. She describes how turmoil in her life forced her to challenge her ideas of God and the world. The science of chaos theory gave her a fresh perspective to appreciate the unpredictable nature of our lives and to make sense of where God is in all of the mess. Her personal stories make these ideas relatable and alive.

I find Livingston’s story to be hopeful and inspiring. Faith and science are both really important to me, so I love it when Livingston talks about faith in a way that takes science seriously. Chaos theory is great too; learning about it in college was part of what inspired me to go to grad school and study soft matter physics. I find chaos theory to be attractive because it shows that life can not be predicted. There is something wild and free about that. Livingston helps me to remember that I am not alone in the wilderness, but God is mysteriously there with me, ready to create something wonderful and new.

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I have been thinking of pasta, and the wheat it is made from, as a commodity. In my mind, it is all pretty much the same, a convenient and tasty source of energy. Recently, I came across organic pasta, and I am curious to know if there is a real difference between the organic and regular. If there is a difference, what are the benefits of organic?

I do not have first hand knowledge about how food gets to the grocery store. From what I’ve read, organic food certified by the USDA follows strict standards including restrictions on herbicides and pesticides and requiring plants be non-GMO (Genetically Modified Organisms). See for example this post by the USDA. I learned recently that some organic farmers even use fire to kill weeds. In contrast, regular farming of commodity crops like wheat involves heavy use of herbicides like RoundUp and GMO crops.

Here are some ideas about ways the organic food could be better:

  1. Less pesticide/herbicide residue.
  2. Happier, healthier plants leading to better tasting food.
  3. Maybe the non-GMO plants are better in some way.

The first reason seems plausible to me. If some substance is so deadly for weeds or for bugs can it be that great for me? But on the other hand, humans may not be affected because our biology is different than bugs or weeds or we may not be affected if the dose is too small.

The second reason, happier, healthier plants, also seems reasonable even though it is more subjective. I think of the difference in taste between food grown in home gardens and food we buy in the store. It seems reasonable that plants will thrive in an environment designed for them, instead of in a chemical warfare battleground.

The third reason, GMO, I’m not worried about except with how it plays into the first two reasons. Selective breeding has been used for ages, and breeding modifies plant genes. From what I have read, genetic modification really seems to be fine. The only concern I have is that farmers might drench the hardy GMO crops in herbicide and pesticide to make it easier to handle weeds and bugs. It seems like that could lead to more pesticide residue and it might be rough on the plants as well.

Are these ideas about benefits of organic food accurate? Are there other benefits to organic food? What are reliable sources for answering these questions?

How does the organic food affect our health? It seems that more people have trouble digesting wheat than they used to. Could farming practices be partially to blame, and could organic wheat help?

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Parallel parking is hard. Many of us avoid parallel parking if we can help it, and yet there are a select few that seem to be able to parallel park with ease. How do they do it? Over the past three years, I’ve been forced to parallel park a lot since our apartment doesn’t have enough parking in the lot. All the practice has helped me get a lot more comfortable about parallel parking, but it has also got me thinking. Parallel parking is an iterative process; somehow by going backwards and forwards and turning the steering wheel back and forth you can shift your car into a spot. I realized there must be an algorithm, a simple set of rules, that will always move the car smoothly into the spot. So I figured out a way to do it, and want to share it with you today. Maybe knowing the rules will help our parallel parking!

Shift car into spot by shifting back and forth according to an algorithm.

The basic problem with parallel parking is to shift your car into the spot, as shown in the sketch above. It would be easy if the front and back wheels could rotate 90 degrees, but with a normal car you have to deal with only the front wheels able to turn. Here is an algorithm I found for parallel parking:

  1. Start with car lined up with front of spot (not optimal but easier to understand the algorithm).
  2. Turn wheel right and reverse about half the length of the spot.
  3. Turn wheel left and reverse to the end of the spot. The car should be straightened out.
  4. Turn wheel right and go forward about half the length of the spot.
  5. Turn wheel left and go forward to end.
  6. Repeat until car is close enough to curb.
The car tires draw out concentric circles as the car turns.

As I was figuring out how to sketch the process of a car parallel parking, I actually learned something about car steering. It turns out that the front wheels do not point exactly in the same direction during a turn. Instead they follow the Ackermann condition so that every wheel draws out a circle with the same center point, as shown in the sketch above. With this insight, I was able to trace out the motion of the car as it parallel parks. The images below break down the process:

  • Car about to park in spot
    Line up car with open spot.

So if you trust my drawings, following these steps solves the parallel parking problem. Give it a shot! It is a little unnatural at first following a series of steps, but is nice once you get the hang of it. I like knowing that I can always shift the car where I want it just by going forwards and backwards.

To really learn something, I think it’s important to mess around and try things. I played around with making the turns uneven and found that this can cause the car to be crooked or straighten it out after I make a mistake. The slides below explore how this works.

  • The tracks of the back tires make nice symmetric curves if you follow this parallel parking algorithm.

Thanks for reading my thoughts into how parallel parking works. I hope it was helpful and interesting. Part of my inspiration was a nice article I read about visualizing algorithms. Please let me know if you have and questions or comments!

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I have been wondering about the long term prospects for the economy as I am trying to get things like retirement accounts and a 529 savings account set up. All the investment advice talks about the wisdom of holding stock for the long term. This advice makes sense because for the past few hundred years, there has been continual exponential economic growth (see great exploration of the economic growth at Max Rosen’s Our World In Data site).

But I am skeptical of anything growing exponentially forever. Exponential growth is relentless; it keeps getting faster and faster. There are lots of things that grow exponentially for short amounts of time, most commonly populations whether they are bacteria, rabbits, or people. At some point something will limit the growth. Are economies different? Can they grow exponentially forever?

I have read articles arguing both ways. The optimists feel that we will keep on innovating our way to growth (see for example a Freakonomics post). The pessimists (or realists) argue that economic growth is tied in some way to energy use (for example see this blog post). Consequently if we kept economic growth going then at some point the earth would would burn up from the waste heat emitted from all of the energy use. The optimists counter that we can have immaterial economic goods so production does not have to be tied to energy.

I would argue that gaining and maintaining knowledge requires a significant amount of energy. While computers make it look effortless to spreading knowledge, in fact every web page that is visited costs a little bit of energy. It is hard to see how we could create an ever more impressive virtual world without increasing energy costs in the real world. So for now I side with the realists!

Of course even if the growth does stop someday it is hard to know when it will stop. I have given up predicting when that will happen exactly. If I had to guess we might have some economic struggles in the short term, but over all keep with the exponential growth for a couple more decades.

If there are limits on growth, how do they work? Economic value depends on perception of value, but it is not clear to me how perception is related to physical quantities. How is energy related to economic transactions? How is knowledge, economic value, and information related?

 

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I didn’t know how RSS worked for a long time. It’s too bad because RSS is a great way to follow websites that you like. It stands for Real Simple Syndication (see wiki article for more info) and is a way for websites to create feeds of their content that users can subscribe to. This is one of those cases where a little barrier can be enough to block adoption. I wanted to share with you how RSS works in case you also are wondering how those little broadcast symbols work.

Following a website or blog on social media is pretty straightforward; you just click on the button for Facebook/Twitter/Instagram/etc. You can achieve the same thing with RSS, but you need to know a couple things first. If you just click on the button you might be asked to open a text file with a bunch of code in it.

rssText

That’s what I did, which is wrong. That code is actually a computer readable version of the latest posts from the website. Instead, you copy the link (right click and press “Copy link location”), and then you subscribe to that link in your RSS reader. But wait, I also had no idea what an RSS reader was. It turns out an RSS reader is just an app that automatically reads a website’s RSS feed and pulls the latest posts and updates from the websites that you follow. I’m using Inoreader right now which allows me to follow several blogs all in one place. Here’s a screenshot from my phone:

Screenshot_20190811-162619_Inoreader

If you want to start following websites outside of social media (and without spamming your email inbox) then sign up for a RSS reader. There are a bunch of options with readers, Feedly is a popular one. Many are free and you always can switch later if you realize that another has features that you like.

I’ll end by noting that you may already be using RSS without knowing it. iTunes or Spotify (or wherever you get your podcasts) are essentially readers for podcasts that are broadcasted using RSS! So if you want to create a podcast you just need to create an RSS feed and connect it to iTunes (see this tutorial for example).

I’m planning on looking into how I can use RSS more on this site. I hope you enjoy RSS too. May it help you break free of the social media silos and find the content you like.

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Diarrhea is definitely unpleasant, but how does it work physiologically?

What causes food and drink to pass through the system more quickly? Is the motion caused by mechanical action of the intestines, or could it be that the intestines somehow stop absorbing fluid? If they can turn absorption on and off, how does that happen?

The BRAT diet (Bananas, Rice, Applesauce, and Toast) is often recommended as a home remedy to diarrhea. The idea is that these bland foods are “easier” to digest than foods with a lot of fat, protein, or fiber. Why are some foods easier to digest than others? Is it related to the size of the food molecules, with small molecules more easily diffusing into the bloodstream?

Is diarrhea a response to fight against infection? Is it effective? How does it work?

Does diarrhea cause damage to the intestines? I could imagine that if stomach acid goes down into the intestines that it could damage all the little intestinal villi that are important in absorbing nutrients. I wonder if diarrhea could upset the microbiome as well.

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My colleague, Jarek Blusewicz, recently told me about autonomous RC cars and how they can be a fun project for playing around with AI and robotics. I didn’t know that autonomous RC cars were a thing, but it turns out that lots of individuals and teams are playing around with them, and doing awesome work. I found a video of a RC car autonomously drifting around in controlled circles. It is amazing to watch, especially when the camera zooms in on the front wheels steering back and forth to maintain the drift as the car slides over the surface. It looks like a professional driver, but the car is completely controlled by a computer.

Researchers at Georgia Tech created an autonomous rally RC car for “aggressive off-road driving”. They really mean aggressive! The car hits a turn at almost full speed and then power slides through it while kicking up clouds of dirt. Here’s a picture of their AutoRally car in action.

autorally_platform_header
Credit: AutoRally: An Open Platform for Aggressive Autonomous Driving. Brian Goldfain, Paul Drews, Changxi You, Matthew Barulic, Orlin Velev, Panagiotis Tsiotras, James M. Rehg. Control Systems Magazine (CSM), 2019.

The best part about the Georgia Tech work is that it is all open source, with a site on Github including detailed instructions about how to build the car (it wouldn’t be cheap, but could be great for a group or organization).

The AutoRally car is controlled with a reinforcement learning algorithm, which I have been finding to be widespread for controlling robots in general. It’s something that I would like to learn more about and play with.

 

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Recently, I read the article “Wired Bacteria Form Nature’s Power Grid: ‘We Have an Electric Planet’” in the New York Times, and was super impressed. I vaguely knew that reactions with electron transfer are widespread in nature (for example in photosynthesis), but I had no idea that bacteria could transport electric charge. This breaks down mental barriers in my mind. Previously, I put electronics like computer chips and solar cells in a different category than biological stuff. But if bacteria can get energy from minerals like a battery and transport charge along their cells, maybe bacteria don’t rely on technology that is fundamentally different than what we use in our cellphones.

If you want to dig into this research, which seems to have really taken off recently, here is a review article.

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I’m hearing more and more that good posture is important for health and wellness. Doing a quick search I found several articles including one from Harvard Health touting the benefits of good posture. This article suggests exercises that are supposed to help with improving posture.

How realistic is the expectation that people can change their posture on their own? I see some people with excellent posture, and lots of others with their head hunched forward. Do some people just naturally have good posture? Are their people who have gone from terrible posture to good posture? How did they do it? What is their stories?

I am a believer that it is possible to improve posture through exercise and stretching. I think about people who do ballet, and they all seem to have extraordinary posture. Their training and exercises must play a role.

I also think about posture in terms of the structure of our bodies. There are ligaments holding the spine together and these ligaments actually support the loads on the back (the spine is a tensegrity structure). If the length of those ligaments changes then the curve of the spine will change. I think that exercises could slowly change the lengths of these ligaments and strengthen them so that the spine has the optimal curvature.

Still even if it is possible theoretically to improve your posture, how difficult will it be? Should we leave good posture to the dancers and figure skaters, or can we take on the task of aligning our bodies?

 

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I looked up the growth charts from the WHO which show how kids (boys in the figure below) grow from birth to 19 years of age. The curves are nice and smooth so it seems like you might be able to predict adult height based on the height as a 1 year old. But the charts only show the averages. How often do children change height percentiles? How common is it for kids to grow early and end up short? Or vice versa how common is it for kids to grow late but to end up on the tall end?

cht_lhfa_boys_z_0_5

Source: https://www.who.int/childgrowth/standards/cht_lhfa_boys_z_0_5.pdf?ua=1

cht_hfa_boys_z_5_19years

Source: https://www.who.int/growthref/cht_hfa_boys_z_5_19years.pdf?ua=1