Saturday, January 31, 2009

Discussing Religion

  • Slashdot recently discussed free, open source software for experimental physics.

  • A pretty breezy piece in the NYT about the physics of tackling (in American football).

  • Cocktail Party Physics is literally discussing physics, or rather astrology, at parties, or rather social gatherings. This reminded me of a dinner party from last month. We were talking about what to tell children when they directly ask if God/Santa/ToothFairy/etc exist. I said I tell them I don't believe in God, but I avoid answering the other questions (mostly because I don't want them "spoiling it" for other kids). Anyway, so a friend asked if I was an atheist or an agnostic. Knowing she's somewhat spiritual and not wanting to offend, I gave a response I thought fairly polite (as well as accurate):

    I'm an atheist because I don't think God exists.

    But this person persisted, questioning my use of the word "think." So I continued:

    Well, I don't know that God doesn't exist, but similarly, I don't know that you exist. However, I live my life accepting in pragmatic terms that others probably exist since it's easier than not and there is evidence for your existence (although not conclusive). However, there's no evidence of God's existence, so to the extent that you want to consider me agnostic, I'd have to say I'm just as agnostic regarding the existence of ferries, ghosts, etc.

  • This discussion reminds me of something I read on Facebook recently. This woman from high school I barely know was posting a combination of religious and political stuff. Mostly just enough to merit a smile, like how she joined a group celebrating Sean Hannity. Or a status update about how dare Obama disrespect Bush in his inaugural speech. But then she posted the oft-told parable about a religious Marine knocking out a liberal professor (among many hits on Google, you can read the story at this blog). I'm amazed at the behavior of some people who make themselves out to be very moral and God-fearing. It probably didn't occur to her that she was advocating for violence against anyone. In any case, I avoided commenting, but took the preventative measure (to forestall her getting me upset) of "de-friending" her. Apparently, the de-listed friend isn't notified, which has its advantages and disadvantages.

Wednesday, January 21, 2009

Assymmetry in an Outlet (Part I)

I had mentioned the question posed to me by a layperson (nonscientist) recently:

In a normal electrical outlet, the current oscillates between positive and negative, and hence left and right between the two prongs of some device. So then, why are some plugs polarized? Shouldn't things be symmetric?

There are some helpful comments there, but I think they're perhaps not sufficient for someone with little understanding of electricity. So I figured I'd give it my best shot. This is perhaps my first posting trying to explain physics. There's so much good stuff on the web, but I couldn't quite find what I wanted for this person, so I'll write it myself.

So I'll start with an analogy and restrict myself to the case of DC first. There'll be a quiz at the end so pay attention.

You know the "log ride" at an amusement park (as always, there's a wiki when you need one)? It's an artificial "canal"-type conduit in which you float on an artificial "dug-out" log. Basically a mild roller coaster on water.

So imagine such a ride that is never go up or down. Assuming there's nothing pushing on the water, your log would just sit there. So forget the log, and we'll just consider the water. The water seeks its own level. Here level is the potential energy of the water and it's all at the same potential.

To make the ride interesting, the ride is instead constructed with a high starting point and the water is pumped up to that point. This high water is now at a different potential and it falls because of gravity.

The analogy is that the water is similar to charges and the water's height is analogous to electric potential (measured in the familiar units of volts). The water pump is like a power supply, or, for the case of an outlet in your home, the power company. In either case, you get a potential difference. With the ride, the water is higher than the rest of the ride. With the outlet, one prong is at a higher potential than the other and therefore charges want to make it to the other prong.

Quiz time:

  • If you plug in a simple light bulb to an outlet, you're putting a load across the prongs. To what property of the ride does this correspond?
  • Electrical resistance is essentially a measure of the difficulty the charges face in going to lower potential. What property of the ride is analogous to resistance?

Next time I'll discuss grounding and AC circuits within this analogy.

Sunday, January 18, 2009

The Importance of Being Grades

I read Julianne's discussion of what a graduate admissions committee does not want to see. I thought a couple of the entries a bit funny:

  • Transcripts with three times the number of courses (and substantially better grades) in music than in physics.
  • "Stu Dent has excellent physical intuition and will undoubtedly succeed in graduate school". Except, Stu has mostly B's and C's in their physics courses and a 15th percentile on the physics GRE.

because, with some simple modifications, both probably apply to me (I took a bunch of music classes, but not "three times" as many, I got mostly Bs in physics and no Cs, and I did much better than 15th percentile). Perhaps needless to say, but I don't think undergraduate grades are particularly indicative of much.

So I was happy to see Arjendu discuss the issue from a different perspective.

As for my story, in high school I somehow felt than the only challenge was to get straight As without doing any work. Having succeeded at that, I somehow never recovered in college. I didn't work very hard but of course didn't get all As. So my graduate application was just good enough to get into a good school.

I should note also that I am probably the only physics major of my class who applied to graduate schools in physics who remains in any type of physics career.

Sunday, January 11, 2009

How many columnists for the NYT with 4-letter names can you identify?

  • A pretty convincing two part (Part I and Part II) posting in favor of variable toll roads. I've mostly been against toll roads seeing them as part of a slippery slope in which the basics are up for sale (how far off until only the rich get to breath safe air?). But this isn't a case of funding the construction of a road with a toll. Instead it's a payment meant to optimize flow physics terms, I suppose it would be stabilizing a critical point of the system. (Coincidentally, Cocktail Party Physics is also discussing traffic.)
  • Cool picture of millions of dollars cash was airdropped via parachute onto a huge oil tanker.
  • You might check out Frank Rich's column today in the NYT if you want to get angry.

Friday, January 09, 2009

Me Eat Burger

  • Another sign I'm getting old: the average number of pills I take each day, which used to be close to zero, has gone up quite a bit.
  • I don't have much of an opinion on this upcoming or delayed transition to digital, but I can say that HDTV is a bit of a scam. Sure it looks great, but for many network broadcasts, the standard definition shows are just the middle section of the video. So what this means is that when you watch a show in high def, all you gain is some extra field of view on the sides. You know those annoying station identifiers and advertisements for news shows that appear in the corners of the screen? In high def shows, they don't appear in the corners because then the simple video processing to get a standard definition feed would cut them off. So they get even more annoying! And then the cable companies compress the signal, especially apparent during fast motion...
  • I'm more pedantic than the next guy, but this whole "fewer/less" thing is getting out of hand. I was watching TNT or TBS or some channel which kept advertising how it has "less commercials" thanks to the sponsorship of some company. And now there's a TV show by the title 10 Items or Less.
  • Lots o' physics bloggers actually take the time to explain things and answer actual questions. I much prefer asking questions but my readers are the absolute worst in terms of answering. So I guess I'll pose a question recently asked of me, and, when no one else provides an answer, I suppose I'll answer it. So the question is:

    In a normal electrical outlet, the current oscillates between positive and negative, and hence left and right between the two prongs of some device. So then, why are some plugs polarized? Shouldn't things be symmetric?

  • What does an Angry Physicist eat? Perhaps an angry whopper?