Writing Code Isn't Rocket Science (It's Worse Than That)

Today, an old joke:

Q: What do rocket scientists say when they want to describe a portion of their work as easy?
A: "This bit isn't exactly brain surgery."

I think that pretty much everyone would agree that rocket science and brain surgery are both intellectually demanding pursuits. But it seems to me that there's a fundamental qualitative difference between them. 

Rockets are devices constructed by humans for specific purposes. Though there may be considerable systemic interactions between all the parts of a rocket which must work harmoniously together, those interactions are the result of careful design. The rocket as a whole can be decomposed into its original parts, and those parts can be independently tested to see if they meet their design criteria.

Furthermore, the aim of rocket science is usually to deliver a specific payload to a specific place at a specific time.  Though it is no mean feat to get to the moon, we can least for all practical purposes calculate the future position of the moon at any time you care to name to any degree of precision.

And yes, it's hard, and yes, mistakes are made, sometimes with tragic consequences.  But fundamentally, rocket science is about shaping raw matter into precise forms to achieve precise tasks.

Brain surgery isn't nearly so much like that.  We're presented with a lump of thinking, dreaming meat that we barely understand how it works and is presently being used to solve all manner of problems that evolution did not design it for. Our understanding of brains is strongest at the very low level – the neurochemical level – and at the very high level – the gross divisions of the brain into the centers that control particular muscles, responses, etc. But we have practically no understanding whatsoever of any level between those – we are no where close to understanding what algorithms the brain uses to recognize faces or write music.  And a working, living brain has trillions of interacting parts which were not designed with orthogonality or functional decomposition in mind. 

I've been thinking about the difference between brain surgery and rocket science lately in the context of my coworker Peter Hallam's essay on the difference between writing new code and modifying old code.

Naively, one would think that adding new features to code would be like rocket science.  You understand all the parts, you figure out how to redesign the parts to admit the new desired behaviour, you implement it, test it, and you're done.  It's an intellectual challenge, but it's fundamentally amenable to analysis because every part has a clear, well-designed function that can be tested independently.

But as Peter points out, anyone who has actually tried to add major new functionality to existing code knows that most of the time its more like brain surgery.  We know what the code does on a gross level.  (Say, tokenize source, parse, create symbol tables, bind type annotations, check reachability, generate code.)  We know what any part of it does on the microscopic level. (Say, move the contents of this register to that memory location.)  The hard part is understanding what the algorithms are that make up the large-scale behaviour, and understanding how to tweak them to admit the new desired behaviour without breaking anything.  (How does tweaking early nullable realization during binding affect rewriting lambdas into expression trees?  Who knows?  Not me, that's for sure!)  Understanding all that stuff is the incredibly hard part; actually putting the code under the knife is comparatively trivial.

A big part of good implementation of software-in-the-large is making sure that the program is more like a rocket than a brain.  Coming up with tools to enable that admirable goal is the hard part.

Comments

• Anonymous
  April 10, 2006
  The comment has been removed

• Anonymous
  April 10, 2006
  No, apparently I cannot.  When I try to, the blog software automatically corrects it to a relative link.  Complain to the people who wrote the blog software -- I have no control over it.
  

• Anonymous
  April 10, 2006
  Just FYI, my version of RSSPopper (0.35c on Outlook 2003) seems to handle relative links fine.

• Anonymous
  April 10, 2006
  The engineering-vs-brain-surgery distinction you're making <a href="http://en.wikipedia.org/wiki/Synthetic_proposition">sounds semi-familiar</a>, doesn't it?

• Anonymous
  April 10, 2006
  P.S. <a href="http://www.google.com/reader">Google Reader</a> turns the relative path to absolute. Correctly, I mean.
  
  

• Anonymous
  April 10, 2006
  http://en.wikipedia.org/wiki/Synthetic_proposition
  
  &^$*%@!!1!
  
  Comment preview would be a nice feature.

• Anonymous
  April 10, 2006
  As I said above, I do not control the blog software.  Take it up with the people who wrote the software if you want new features.
  
  I am aware of what the differences are between synthetic and analytic propositions, but I have no idea how you're relating them to the difference between brain surgery and rocket science.  

• Anonymous
  April 10, 2006
  The comment has been removed

• Anonymous
  April 11, 2006
  Actually Rocket Science is like brain surgery because of rocket engine. Basically a rocket engine is a chamber attached to a nozzle. Attach to the chamber are pumps and fuel lines that mix the fuel in an attempt to get nice even combustion.
  
  The biggest problem of rocket science is getting that nice even combustion. Combustion instability is a big problem to solve for new engines and why rocket engineering is so hard. :ike software development it is more art than scinece. It is also the reason that you have to test your rocket before committing to regular operation.
  
  Sorry to puncture your analogy and I understand what you were getting at.
  
  
  

• Anonymous
  April 17, 2006
  The comment has been removed

• Anonymous
  April 20, 2006
  PingBack from http://www.navarik.com/home/blog/?p=273

• Anonymous
  April 20, 2006
  And of course there's the software archaeology aspect of understanding old code: http://blogs.msdn.com/larryosterman/archive/2004/05/20/135952.aspx
  
  There are code bases out there that have been worked and tweaked so often that it is often impossible to actually fully understand them, no matter how long you've been working on them.
  

• Anonymous
  April 21, 2006
  PingBack from http://hans.gerwitz.com/2006/04/21/programming-is-brain-surgery.html

• Anonymous
  April 21, 2006
  Perhaps a more apt distinction can be drawn between, say, brain surgery and designing a mechanical watch?

• Anonymous
  April 23, 2006
  PingBack from http://amygdala.wordpress.com/2006/04/24/links-for-2006-04-23/

• Anonymous
  April 27, 2006
  Last Post today: Three good reads!
  1) Peter Hallam from Microsoft, pointing out the important thing of a good IDE. He starts with the experience that developers spend 2-5% of their time in writing new Code, 20-25% in modifying existing Code and the rest

• Anonymous
  December 05, 2007
  Brain surgery is just highly advanced plumbing.  It's neuro-modeling you're talking about with regards to the way a lump of thinking meat writes music.

• Anonymous
  December 11, 2008
  PingBack from http://hans.gerwitz.com/2006/04/11/programming-is-brain-surgery-2.html

• Anonymous
  April 06, 2009
  So you are saying rocket science isn't exactly brain surgery?

• Anonymous
  January 10, 2010
  Nhlanhla Mlitwa Obviously the complexity suits the proprietorship and the protectionist aspect. I make business out of it I ould not complain. From the open source perspective, can we not make deliberate efforts to to make code modifications more simpler? Is this a worthwhile route?, what are implications for hacking?.

• Anonymous
  January 10, 2010
  Obviously the complexity suits the proprietorship and the protectionist aspect. I make business out of it I ould not complain. From the open source perspective, can we not make deliberate efforts to to make code modifications more simpler? Is this a worthwhile route?, what are implications for hacking?.