1. 2011
    Nov
    21

    Yo Momma's so fat this counts as TWO blog posts

    I have a bunch of good posts lined up for later this month (and beyond), but since I’m busy packing for Thanksgiving travels today, I haven’t had time to polish them up properly. So have some marginally physics themed fat jokes instead. (It should go without saying that these are not to be taken seriously)

    • Yo Momma so fat, every time she turns around, the Earth skips a day

    • Yo Momma so fat, she really is a spherical cow

    • Yo Momma so fat, she has her own atmosphere

    • Yo Momma so fat, she’s hogging all the Higgs bosons (no wonder the LHC hasn’t found it)

  2. 2011
    Nov
    19

    OPERA neutrinos still faster than light

    Among this week’s big news in physics is that the OPERA experiment, which reported a detection of faster-than-light neutrinos back in September, has repeated their experiment and is still finding the same results. What they have changed this time is the width of the neutrino pulses, down to \(\SI{50}{ns}\).

    In the original measurement, neutrinos were generated in bunches more than \(\SI{3}{km}\) long, so that it took \(\SI{10.5}{\micro\second}\) for each bunch of neutrinos to pass through a detector. This spread is much larger than the \(\SI{60}{ns}\) or \(\SI{18}{m}\) discrepancy that the original OPERA paper reported. Some scientists were concerned that the neutrino bunches were getting distorted in flight, which could skew the apparent average time that it took for the neutrinos to travel the distance they did. I’m not sure how valid of a criticism this was, since if you look at the picture at the left, you can actually identify peaks and valleys of the experimentally detected shape of the neutrino bunch (the black dots, representing the rate at which neutrinos are detected as a function of time), which match up pretty well with corresponding features …

  3. 2011
    Nov
    18

    Switching car insurance

    You know how car insurance commercials always say “people saved an average of $XXX by switching to this company”? How is it that every insurance company can make the same claim? Simple: the people who wouldn’t be saving money don’t switch, and don’t get counted in the average.

  4. 2011
    Nov
    16

    Second derivative in polar coordinates

    Here’s an interesting, and perhaps occasionally useful, identity: suppose you have a function defined on a two-dimensional space, \(f(\vec{r})\). And suppose that this function is independent of the angle of \(\vec{r}\) but rather is only a function of the magnitude \(r = \norm{\vec{r}}\). Then

    $$\lapl f(r) = \frac{1}{r}\pd{}{r}r\pd{}{r}f(r) = \frac{1}{r^2} r\pd{}{r}r\pd{}{r} = \frac{1}{r^2}\pdd{}{(\ln r)}f(r)$$

    (where \(\ln r\) is shorthand for \(\ln\frac{r}{r_0}\) where \(r_0\) is some constant) In other words, the radial term of the polar Laplacian is equal to the second logarithmic derivative divided by \(r^2\) for rotationally invariant functions.

    At this point you might be wondering, why the heck is this interesting? Well, for me, it’s because my current research project happens to involve logarithmic derivatives of rotationally invariant functions in 2D space. But for (almost) everyone else, this is related to the way electric potential drops off with distance in 2D space.

    Consider, for example, a wire that carries a charge density \(\lambda\) (but no current). Since this system is translationally symmetric (nothing changes if you …

  5. 2011
    Nov
    15

    CP violation at the LHC

    Yesterday’s big news in the physics world: the LHCb experiment has observed a \(3.5\sigma\) asymmetry between the decays of \(D^0\) and \(\bar{D}^0\) mesons. This has already been described in detail elsewhere on the web: Sean Carroll has a nice explanation accessible to non-experts, or you can look at the presentation of the results from the HCP conference (which itself is reasonably clear and informative, if you have some experience looking at particle physics presentations).

    For those who are not inclined to click on links, here’s a quick summary of the story. CP symmetry violation is a difference between the behaviors of a particle and the mirror image of its antiparticle. The probability of a CP-violating process to occur is controlled by a complex phase parameter in the quark mixing matrix. There are two kinds of CP-violating processes that we can detect:

    • Some particles (kaons, D and B mesons) transform into their antiparticles and back as they propagate. CP violation means that the oscillation probability for going from the particle to the antiparticle is different from the probability to go from the antiparticle to the particle. Intuitively, you could imagine that the meson spends …
  6. 2011
    Nov
    14

    The Uncanny Valley

    Here’s an interesting piece from the BBC about robots, and why humans can find them a little creepy. It links to a paper about the “Uncanny Valley”, the hypothesis that in the spectrum of resemblance to humans, there is a certain region of “almost-humanness” which we actually find repulsive.

    While it’s interesting speculation, I have my doubts that it’s that simple. One thing that you learn from “physicist’s intuition” is that whenever you make a graph of something, it’s usually pretty smooth, unless there’s some specific reason for it not to be. In other words, to have a “dip” like the Uncanny Valley, there has to be something really special about whatever is at the bottom of that dip.

  7. 2011
    Nov
    11

    Would you do what JoePa would do?

    Ever since the story of the sex abuse scandal and coverup in Penn State’s football program broke last Saturday, there has been a lot of attention focused on Joe Paterno’s role in it, specifically regarding whether he deserved to be punished for failing to report the incident to the police.

    There have also been a lot of people saying that it’s wrong to be devoting so much attention to the coach when we should be focusing on the victims and using this as an opportunity to increase awareness of child abuse prevention. They are right, of course. To their credit, many Penn State students are doing just that, between holding a candlelight vigil tonight and encouraging everyone to wear blue at this weekend’s football game.

    But there is a sense in which I think it’s worth talking about Paterno’s role. Not because of his celebrity, but because he is the “everyman” in this incident. Many of us could imagine ourselves being in much the same situation that he was when Mike McQueary told him what he saw. The question of Paterno’s guilt is a question of ethics that, in the quest to stop …

  8. 2011
    Nov
    10

    A giant rock floating through space (technical term)

    Who says science can’t be fun sometimes?

    Asteroid 2005 YU55, a giant rock floating through space, looks like a giant rock floating through space, reports one astronomer, who observed the giant rock as it floated through space past the Earth on Tuesday.

    http://www.csmonitor.com/Science/2011/1109/Asteroid-2005-YU55-looks-like-a-giant-rock-floating-through-space-reports-astronomer

  9. 2011
    Nov
    10

    Facts and the Penn State scandal

    Many of this blog’s readers will know by now about the sex abuse allegations involving a former football coach at Penn State (where I’m a student). If you haven’t heard about it, take a look at this excellent summary of the allegations. You can also read the grand jury report, which first made this whole thing public, at that page, or via the New York Times.

    What I find most, um, “interesting” about this is how many of the reactions to the scandal don’t tell you to do just that.

    I don’t often talk about ethical issues because they’re messy business, and this story, in particular the role that Joe Paterno plays in it, is a perfect example of why. Paterno is the heart and soul of Penn State. He’s been working at the school for 61 years, helping it grow academically and athletically every step of the way. You can’t argue with the fact that he has done a tremendous amount of good for the university, and the students and alumni are definitely justified in loving him for it. Heck, even though I’m not a football fan in the slightest …