I'll admit it: I *love* code. Computers are magic, and since my first taste as a 5 year old, I've been pretty well hooked on them. When I started with them, they weren't like the toaster appliances they are now, and learning to become the wizard beh...
If you put something containing molecules with magnetic asymmetry (such as H2O), like, maybe, a human body part, into a big magnetic field, a lot of those molecules will align with the field. Not very useful - "wellness" believers aside - but if you then use a strong radio antenna to create magnetic field pulses in a different orientation than the big field, the molecules will alter their spin according to the radio waves. Still not that cool. When you turn off the antenna, the molecules flip back and when they do that, they alter the magnetic field, and you can pick up that signal with a sensitive antenna. Lots of crazy biophysics here, but if you then take that time-series data, and some wonderful math by a guy named Fourier, and a lot of powerful computers, you can turn that data into an image showing a map of the charged molecules. Wave the magic wand, and you've got this:
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Brain MRI By Novaksean - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44348140
I spent several years working on ways to describe normal brain development in children, and then working on ways to detect Alzheimer's, based on all that magic, and doing something that can have an impact on people's lives like that feels AMAZING. Maybe I'll write some more about that stuff later.
You can also do a lot of "evil" marketing stuff, like take the location data in people's phones and use it to learn people's travel and shopping patterns. How long did people spend in a shopping mall? Which tourist attractions did they visit, in which order? If they went to a Disney property, are they more or less likely to also go to a Universal property, when visiting Orlando? A little less heart-warming, but there're some really interesting challenges in that area of work - and a lot of really fun geometry and statistics in there. Not to mention what feels like a LOT of data which can make doing any analysis that much harder.
Computational fluid dynamics can let you predict a crowd's egress route during an emergency evacuation of a large area. Turns out an extra inch or two in the width of a doorway is the difference between thousands of people getting out of a stadium safely instead of getting trapped inside and trampling each other. (Full disclosure: I didn't work on any stadium design, but I did spend a few months working on this kind of software, and it was both terrifying and exciting.)
Turns out there are also much less complicated things which are still amazingly useful: A simple flashcard-like app can help kids learn a new language. An app that highlights words while you read can help a learning disabled child read more comfortably.
And there are engineering challenges which are worthy of a whole different set of stories: An app that unites storytellers with an audience can democratize writing, bring content to areas of the world without libraries, and generally change people's lives, while running out of int64 space for IDs (that means using more than 2^63 records in a database table), servicing over 30,000 hits per second, and the list goes on.
Why belabour all of this? Look back a sec - how many areas of human endeavour did you count? Healthcare, tourism, architecture, education, entertainment: Computer science and engineering apply to all of them, and virtually every other you can think of, in a deeply meaningful way.
