Cloudflare; software never fails; Newton; compasses
We find a flaw in Cloudflare's initial assessment of their problems, we learn what it means for us that software never fails, and poke amateurishly at physics.
You have arrived at the mid-week hump. Have a $container of $beverage and enjoy some reading before you speed along with the rest of your life.
New articles
Questions for Cloudflare
Accident analysis is where we learn about as many things as possible that go wrong in our systems. To do it well, we need techniques that cast a broad net early in the analysis – otherwise we tend to get sucked into the details. Cloudflare has published an initial assessment that unfortunately makes it seem like they are not casting a broad net early on.
Full article (5–12 minute read): Questions for Cloudflare
Software Never Fails
One of the most confusing ideas of system-theoretic analysis is that software never fails. The article goes into what this means, but it has consequences for how to design robust software systems, so it's well worth knowing.
Full article (14–28 minute read): Software Never Fails
Flashcard of the week
I keep confusing numbered laws in physics for each other, so I have flashcards for some of them. One of them asks
Which is Newton's second law?
and the answer is
F = ma
The reason I highlight this flashcard is there are so many fun ways to use Newton's second law as a crowbar to pry open other parts of physics. One thing that lit a bulb in my head was when someone pointed out to me that
ma = mv' = (mv)' = p'
i.e. force is the time derivative of momentum. Each unit of force applied for a second increases momentum by one unit. When we add up a bunch of such changes, the total change in momentum is called impulse. Thus force can also be thought of as the average impulse over a longer period of time.
This is connected to the thing space people do when they discuss delta-v instead of acceleration. They don't care about the momentaneous forces involved, but they care very much about what the total effect of the maneuver is.
There's a parallel between momentum and kinetic energy, too. Force is the time deriviative of momentum, and power is the time derivative of kinetic energy. The impulse of kinetic energy is a quantity called work.
But then these two are connected in another fun way:
- Force applied over time is an impulse, which changes momentum.
- Force applied over a distance is work, and changes kinetic energy.
An intuition for momentum is "how long time would I need to apply a unit force for to stop the thing" whereas kinetic energy is about "what distance would I need to apply a unit force over to stop the thing?"
There's also a way to translate between them through power, which is equal to the product of force and velocity (I think?), but this is where I get lost and have to do more reading/thinking.
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