Tag Archives: math

On The Downhill

Ross and I don’t tend to talk that much on the uphill when we’re hiking, largely due to the fact that I’m nearly always moving at a pace that makes me even less chatty than usual. But we often have wonderful, relaxed, surprising conversations on the downhill, after we’ve both had a chance to wring out the week’s preoccupations along with our sweat. Frequently these talks are about his science, my science, or some mathematical or statistical concept or other—I think because sore feet lead to a refreshed mind, and we’re both willing to take on sweeping or difficult ideas without much of a sense of expectation that we’ll get anywhere in particular.

Anyway, today I told Ross about a neat probability puzzle that Carl Bergstrom, an evolutionary and theoretical biologist at UW, tweeted last night. While we were hurtling back down to the trailhead we talked about possible approaches to the puzzle; we talked about why certain seemingly important and seemingly missing pieces of information didn’t matter; and we talked about the answer, which is beautifully simple and elegant. (Carl called it “easy”, but I certainly didn’t arrive at it on my own—although I have the good fortune of being able to pretend that that’s because the tweet containing the solution was the first one I saw…)

In case you are interested, here is the puzzle, and here is the solution. You can have fun thinking through it now, or save it for the downhill on your next hike!

Today’s climb was notable for another reason. We had been promised a terrible weather weekend, with rain predicted in all directions. As it turned out, and as you know if you live in Seattle, today was an absolutely beautiful day—partly cloudy, but definitely partly sunny, and very warm. But since we didn’t know that beforehand, instead of venturing particularly far afield we decided to sleep in and settle for yet another hike of our old, slightly boring, and extremely crowded friend Mt. Si. To make things at least little more interesting we did it with full packs (this just means all the gear you’d need for a multi-day climbing trip, and for me personally ranges from about 35 to about 43 lbs, depending on the trip and what group gear I’m carrying. Today I packed something like 36 lbs, approximately a third of my body weight). Anyway, it had been nearly eight months since I’d hiked with a full pack, so while I thought I’d probably do fine I didn’t have especially high hopes for my pace heading up the mountain, which involves 3,200 feet of gain in 3.9 miles.

Notably, though, I wound up topping out at 1 hour and 53 minutes. I don’t usually like to get hung up about finishing times, since that tends to be (emotionally speaking) a poor way to judge success if you’re someone who is never the speediest in your group. But I’ll acknowledge that personal records can be worth a high-five, and today’s time was both a decisive 13 minutes faster than my previous best for getting to the top of Si with weight, and the first occasion on which I made it up carrying a full pack in under 2 hours. So that was nice…except probably for all the other innocent hikers on the trail who had the unfortunate experience of hearing what must have sounded like a gasping bulldog behind them as I came up. (I breathe hard on the uphill. I told you.)

Okay, folks. That’s me. Take it easy like Carl’s probability puzzle.

Si view

The unexpectedly good view from today.

Me

So sweaty.