Friday, April 28, 2017


Kelley and I were talking about space last night, partly because the Cassini probe completed a dive between Saturn and its rings, and partly because Jace has been been learning about planets. We watched this excellent video, which starts out comparing the sizes of various planets and stars, then zooms out to compare the scale of galaxies and more.

Such mind-boggling vastness can make one feel very small, so naturally we tried to counter that by thinking of the tiniest things in the universe. Here is the chart we came up with. Unfortunately, I got some things wrong, so please refer instead to the revised chart below it.

Here we have the revision with text labels and more accurate spacing. The axis is a log scale, so each step of 3 brings you to something a thousand times bigger or smaller.

A few of our observations:

  • It takes approximately the same step in size (~9 orders of magnitude=a billion* times bigger in diameter) to get from an electron to an atom, from an atom to us, and from us to the sun.
  • Two more of those steps take you from sun to observable universe, but the galaxy is well past the first of those. (This was the main error in my napkin version--the galaxy is approximately one billion solar systems across, not one billion suns.) Note: That is linear distance; our galaxy contains 100 billion stars. 
  • Two big steps in the other direction take you from an electron down to the Planck length (below which "distance" ceases to mean anything).
  • Once you contemplate the vastness of something a billion-billion-billion** times bigger than you, it is not helpful to say "Well, yes, but that's just the observable universe. The whole thing could not only be far vaster, it could truly be infinite."
For a great illustration of the bigger-than-us half of the chart, check out this xkcd image. If you want to look at an interactive zoomable chart with a lot more objects than mine, this is a good one.

*I use the American billion here. If you are feeling European today, feel free to translate to milliard.
**Octillion for Americans, or quadrilliard for the traditionalists.

Monday, April 24, 2017

Useful Tools: Books and Movies

This is the second in a series of posts recommending useful resources in various areas. These are apps or tools I use regularly. Today's topic is: Books and Entertainment.
All apps are for Android, and links will take you to the Google Play store. (website and app) is the standard portal for borrowing digital content from public libraries. I have checked out tons of ebooks this way. Reading them in the Overdrive app works fine, but when possible I get my books in kindle format, as I prefer the reading experience and features of the kindle app. I've also enjoyed many audiobooks from my library via Overdrive. (website and app) is another library content portal, with a different licensing system. If your library subscribes, this would be well worth trying out. Their book selection is much more limited, but most items are recent releases or other titles that Overdrive doesn't have. In addition, Hoopla has a broad selection of music, TV shows, and graphic novels. (It's how I listened to the Hamilton soundtrack and watched The Librarians). 

In contrast to Overdrive's model, in which a library buys a certain number of copies to lend (which results in waitlists for popular titles, and different collections available from different libraries), Hoopla's content is always available, with a limit on the number of items a patron can check out each month. So if Hoopla stocks something you want, you can get it right away!

My only complaint is that Hoopla's app does not deal well with orientation changes of your device. If you turn your phone, it will spend time loading the book again and probably lose your location. Make sure you lock your phone display into portrait if you plan to read something in the app. is the best book tracking website I've seen. I love it: for logging and reviewing books I've read, for finding and keeping track of books I want to read, and for seeing what my friends recommend. In most respects I find the app inferior to the web version, but it does have the incredibly convenient feature of adding books by scanning them. This used to be ISBN barcode-only, but a recent update added the ability to identify books from the cover. Strangely, that messed up the reliability of ISBN-scanning, but the cover-scanning feature works so well that I usually don't miss it. Adding a dozen library books at a time is fast and simple, which is great since I try to keep up with all of the picture books we check out. aspires to be Goodreads for movies. (At least, that's how I use it. I'm sure the creators have a somewhat different vision for their product, to judge from the number of features I don't use.) I use it to log and rate movies I see, but that's about it. I tried several similar websites, and this was the best one for my purposes.


Friday, April 21, 2017

Useful Tools: Commuting in Boston

This is the first in a series of posts recommending useful resources in various areas. These are apps or tools I use regularly. Today's topic is: Commuting in Boston.
Apps referenced are for Android, and links will take you to the Google Play store.
  • First, the item not specific to Boston: Shuttles operated by many universities and hospitals across the country are tracked by the TransLoc Rider app. I used this one both in Atlanta (Emory) and here in Boston (LMA/Harvard), and the real-time location data was helpful with knowing when to leave to catch the bus I needed. To find out if they have a system near you, check out their map or agency list.
  • For commuter rail in Boston, the website is the best of several tools I tried. The only feature that is missing there is upcoming departures of inbound trains. If that is something you need, this rail tracker app is the best alternative. I should also note that trains with missing location feeds appear in the app, but are absent on the website (with a notification at the bottom that the data is missing). Even so, the website's map makes it much more useful than the app. And, unless you have a monthly pass, you probably want to use the official mTicket app to buy commuter rail tickets.
  • For the city buses, I recommend BostonBusMap. This app is the best of several that I tried. There is a bit of a learning curve to figure out how to navigate the many options and views, but after that it is intuitive and full-featured. I tend to use "stops and predictions on all routes" as my default view and select the stop near me--especially since multiple routes serve my usual stops.
  • I haven't had much occasion to use any of the subway lines, so no recommendations on that front at the moment. Sorry.