Daily Archives: February 9, 2010

Snowmageddapocalypse II: The Wrath of Khan

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The federal government has been shut down for the last two days, which is probably a good thing — it alleviates stress on the transportation system, which is nowhere near full capacity at the moment, and I imagine there are a lot of people who would have great difficulty getting to work, especially so as you look north. Even here in northern Virginia, I can see side streets that have significant snow and ice, and where I would not choose to drive for fear of getting stuck.

So what’s next? More snow!

We are anticipating up to a foot where I am, and even more as you move into Maryland. The official warning starts at noon today, and snowfall has already been reported ~50 miles away, an hour prior to that. I just got back from the store; I had to refill my pantry, and pickings of perishables were scant (Yes, we have no bananas). I chatted with a nice lady while in the very long line; she also works for the federal government, and we agreed that it will probably be closed down tomorrow too — there’s no way the roads are going to be in better condition than they are now.

At least they are doing a better job of snow removal at my apartment complex. I surrendered my parking spot (no friction-related trouble getting out), and noticed that the snow removal crew was attacking vacated areas with their little Bobcat tractor/loader. I was able to find a cleared spot when I got back, so I’m good for now. Just fighting some cabin fever, because daytime TV sucks.

We Love xkcd

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Last fall, someone animated the xkcd cartoon that celebrated the boom-de-yada song

Now, in a bit of life imitates art – imitates life-imitates art-imitates life, (does surreal come in layers,or are they orthogonal dimensions?) we have a collection of people of varying degrees of celebrity in the science and tech world (I recognized Bruce Schneier and Phil Plait, despite being a bit bleary-eyed) singing it, mostly off-key.

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The Real Skeptics

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We might err, but science is self-correcting

An Oxford colleague, one of the world’s top climate scientists, made the same point last week when he said to me: “It’s odd that people talk about ‘climate sceptics’ as though they are a special category. All of us in the climate science community are climate sceptics. It’s our job to question and challenge everything.” Any scientist will tell you that when you turn up at a conference the audience will do its best to tear your findings to pieces: no one takes anything for granted.

I can vouch for this being true, as I’ve seen it firsthand. There are some very frank exchanges that go on at conferences, either in the Q&A session or after a talk is done. Putting those coffee breaks in the schedule isn’t just for caffeination opportunities — they are also a chance to track someone down and hash out claims made in talks (or pump them for more information, depending on your motivation). I recall a conference a few years back where someone came up to a colleague who had just given a talk and said, “You do realize what you said about X was bullshit, right?” We proceeded to have a spirited conversation on the subject and eventually agreed that what had been said was true under the conditions that had been implied, but was not generally true. And you can be sure we clarified that when it came time to write it up for the conference proceedings.

To the Good People of the DC Area, a Driving Tip

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And even to the bad ones.

People in this area generally don’t know how to drive in the snow. The generally slow clearing of snowy conditions definitely does not help, but folks just aren’t helping things by sucking at driving. Between the time I was excavating my car and the recent trudge over to a local fast-food restaurant (I won’t blatantly advertise the chain — for free — but according to Concrete Blonde, their iconic spokesperson is going to die tomorrow), I have seen and heard dozens of people slip and slide their tires over the snow and ice.

Today’s public service lesson is Friction.

The details of friction on the microscopic level are quite complicated, but the general idea is this: the frictional force is proportional to the normal force (N) on an object. The normal force is that force the surface exerts on it, so for an object which is not accelerating vertically, the normal force and weight (W) cancel (the net force being zero). The proportionality constant for the frictional force (f) is the greek letter mu; I’ll just use u since I don’t want to muck around with LaTex. f = uN (Who said physics isn’t fun? It says it is, right there!)

It turns out that there are two categories of friction: static friction, for when an object is moving, and kinetic, or sliding friction, for when two surfaces are moving over one another. Generally speaking, the coefficient of kinetic friction is smaller than that of static friction, and the implication of this is that (all things being equal) once two surfaces start to slide over each other, they will continue to slide. They won’t suddenly “catch,” unless there is a change in the surface conditions.

So when your tire starts to slide on the snow or ice, or any other surface for that matter, it is going to continue to slide. This is the concept behind pumping your brakes when you start to skid, and the reason that anti-lock brakes are a popular safety feature. Once you start to slide, continuing that action is the wrong thing to do, much less gunning your engine to make the wheels spin really fast (coefficients of friction can decrease with speed, and melting the snow makes for a slipperier surface). Your best bet is easing up off the gas and starting over. Rock back and forth a little so there’s some momentum, and you don’t need quite as much force to get going faster. Once you start to skid, you’ve lost.