Physics
esiegel | May 20, 2011"We all need to look into the dark side of our nature - that's where the energy is, the passion. People are afraid of that because it holds pieces of us we're busy denying." -Sue Grafton
No, not the dark side of our nature, just the dark side of nature! Because if all our Universe were made out of were atoms and photons, we wouldn't get a Universe that looks like ours.
What do I mean? Let's take a look.
Image credit: MPA Garching and Volker Springel.
The Universe starts off as a very smooth place, where regions that are denser or less dense than average are only something like 0.003% away…
milhayser | May 20, 2011
The moon entrances us—it is near yet far away, familiar, yet unremittingly mysterious. In synchronous rotation, it has a face it never shows. It pulls the oceans; it stirs the blood. It beckons into the unknown. On Universe, Claire L. Evans says that in 1969, six artists snuck "a minuscule enamel wafer inscribed with six tiny drawings" onto Apollo 12's landing module. Claire writes, "the artistry of this 'museum' is as much about the gesture of sneaking it, illicitly, onto the leg of the lunar lander, as it is about the drawings themselves." On Starts With a Bang!, Ethan Siegel…
drorzel | May 19, 2011Via Twitter, Daniel Lemire has a mini-manifesto advocating "social media" alternatives for academic publishing, citing "disastrous consequences" of the "filter-then-publish" model in use by traditional journals. The problem is, as with most such things, I'm not convinced that social media style publication really fixes all these problems. For example, one of his points is:
The conventional system is legible: you can count and measure a scientist's production. The incentive is to produce more of what the elite wants. In a publish-then-filter system nobody cares about quantity: only the impact…
esiegel | May 18, 2011"There is also an amplitude for light to go faster (or slower) than the conventional speed of light. You found out... that light doesn't go only in straight lines; now, you find out that it doesn't go only at the speed of light! It may surprise you that there is an amplitude for a photon to go at speeds faster or slower than the conventional speed, c." -Richard Feynman
You've been around the block a few times, and you know how it goes when you try to go faster and faster. Everything works just like you expect, until you start getting close to the speed of light, c. And then, all sorts of…
drorzel | May 18, 2011Today's lecture topic was position-space and momentum-space representations of state vectors in quantum mechanics, which once again brought up one of the eternal questions in physics:
Why do we use the symbol p to represent momentum?
I did Google this, but none of the answers looked all that authoritative. And, anyway, I'm sure that the readers of this blog can come up with fanciful speculations that would be far more interesting than the real answer. So, have at it.
(I'm too overextended and exhausted to post anything more substantive right now; maybe later this afternoon.)
drorzel | May 17, 2011Well, on video over the web, anyway... If you look at the Featured Videos on the National Geographic Channel web page, or, hopefully, in the embedded video below:
You'll see a short video clip of a program about quantum physics, that includes me and Emmy among the experts on camera. I'm pretty psyched, though I'm not sure what Alan Guth and Lawrence Krauss will think about sharing the bill with my dog...
This is from a show, tentatively titled "Parallel Universes," which is why I went to Buffalo back in October. Most of the scenes in that clip were shot in the abandoned railway station in…
esiegel | May 16, 2011Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice. -Robert Frost
Sure, if all we're talking about is the Earth, that one's a no-brainer. It's fire.
Our Sun, very slowly, is burning up its Hydrogen fuel into Helium, through the process of nuclear fusion. But over the course of billions of years, it starts to burn its remaining fuel at an ever increasing rate. Over the next billion or two years, the…
drorzel | May 16, 2011Several years ago, now, a group at Penn State announced a weird finding in helium at extremely low temperatures and high pressures (which is what you need to make helium solidify): when they made a pendulum out of a cylindrical container with a thin shell of solid He toward the outside edge, twisting about its axis, they saw a small but dramatic change in the oscillation frequency as they cooled the system below a particular temperature. They interpreted this as a "supersolid" phase of helium, with a quantum phase transition taking place that caused the "supersolid" to stop rotating with the…
drorzel | May 16, 2011Physics is a notoriously difficult and unpopular subject, which is probably why there is a large and active Physics Education Research community within physics departments in the US. This normally generates a lot of material in the Physical Review Special Topics journal, but last week, a PER paper appeared in Science, which is unusual enough to deserve the ResearchBlogging treatment.
OK, what's this paper about? Well, with the exceptional originality that physicists bring to all things, the title pretty much says it all. They demonstrated that a different style of teaching applied to a large…
drorzel | May 13, 2011Back when I was an undergrad, we did a lab in the junior-level quantum class that involved making a dye laser. We had a small pulsed nitrogen laser in the lab, and were given a glass cell of dye and some optics and asked to make it lase in the visible range of the spectrum.
My partner and I worked on this for almost the entire lab period, and got nothing more than the occasional faint flicker of a green beam. We got the TA to help us, and he couldn't do any better. The TA went to get the professor teaching the class, but he was helping other students with one of the other experiments (this…
oracknows | May 12, 2011Recently, there have been grumblings in the ranks of Orac-philes. All is not entirely well. Or, at least, all is less well than usual. Even more unusual, I feel your pain. I really do. We've been enduring a stretch when the anti-vaccine movement has been unusually busy for an unusually long time, leading vaccines to take over and dominate as the main topic of this blog for more than the last week. This has led not only to my getting tired of the topic, but to some of you apparently becoming tired as well of the sheer burning stupid that only the anti-vaccine movement can lay down with such…
drorzel | May 11, 2011While Kenneth Ford's 101 Quantum Questions was generally good, there was one really regrettable bit, in Question 23: What is a "state of motion?" When giving examples of states, Ford defines the ground state as the lowest-energy state of a nucleus, then notes that its energy is not zero. He then writes:
An object brought to an absolute zero of temperature would have zero-point energy and nothing else. Because of zero-point energy, there is indeed such a thing as perpetual motion.
This is really the only objectionable content in the book, but he certainly made up in quality what it lacks in…
drorzel | May 10, 2011When I was looking over the Great Discoveries series titles for writing yesterday's Quantum Man review, I was struck again by how the Rutherford biography by Richard Reeves is an oddity. Not only is Rutherford a relatively happy fellow-- the book is really lacking in the salacious gossip that is usually a staple of biography, probably because Rutherford was happily married for umpteen years-- but he's an experimentalist, and you don't see that many high-profile biographies of experimental physicists.
When you run down the list of famous and relatively modern scientists who have books written…
esiegel | May 9, 2011John Oliver: So, roughly speaking, what are the chances that the world is going to be destroyed? One-in-a-million? One-in-a-billion?
Walter Wagner: Well, the best we can say right now is a one-in-two chance.
John: 50-50?
Walter: Yeah, 50-50... It's a chance, it's a 50-50 chance.
John: You come back to this 50-50 thing, what is it Walter?
Walter: Well, if you have something that can happen and something that won't necessarily happen, it's going to either happen or it's gonna not happen. And, so, it's kind of... best guess at this point.
John: I'm... not sure that's how probability works,…
drorzel | May 9, 2011While I've got a few more review copies backlogged around here, the next book review post is one that I actually paid for myself, Lawrence Krauss's Quantum Man: Richard Feynman's Life in Science, part of Norton's Great Discoveries series of scientific biographies. I'm a fan of the series-- past entries reviewed here include Richard Reeves's biography of Rutherford, Rebecca Goldstein's biography of Goedel, and David Foster Wallace on Cantor's work on infinity (which is less of a biography than the others). I'm not a huge reader of biographies, but I've liked all the books from this series that…
drorzel | May 8, 2011The folks at Harvard University Press were nice enough to send me an advance copy of Ken Ford's new book, 101 Quantum Questions: What You Need to Know About the World You Can't See a few months ago. I've been too busy working on my own book to read any other physics books, though, so the actual book made it into print before my review. Better late than never, though.
As the title promises, this is a book about modern physics written in Q&A format. It's presented as a list of questions about physics, such as "1: What is a quantum, anyway?" and "6: Why is solid matter solid if it is mostly…
esiegel | May 6, 2011"God does not play dice with the Universe." -Einstein
"Einstein, don't tell God what to do." -Neils Bohr (disputed, but awesome)
Einstein, the brilliant mind behind general relativity and the concept of "spacetime," is making the news again this week. As you all know, gravity isn't some mysterious invisible force traveling across space, it comes about because energy itself -- most commonly in the form of mass -- distorts the very fabric of space.
Image credit: GNU user Johnstone and NASA's Galileo spacecraft.
Of course, wrapping your head around this can prove quite difficult. Space, as we…
drorzel | May 6, 2011In comments to yesterday's post about precision measurements, Bjoern objected to the use of "quantum mechanics" as a term encompassing QED:
IMO, one should say "quantum theory" here instead of "quantum mechanics". After all, what is usually known as quantum mechanics (the stuff one learns in basic courses) is essentially the quantization of classical mechanics, whereas QED is the quantization of classical electrodynamics, and quantum field theories in general are quantizations of classical field theories. I think saying "quantum mechanics" when one talks about something which essentially has…
drorzel | May 5, 2011An academic email list that I'm on has started a discussion of lab writing, pointing out that students in some lab classes spend more time on writing lab reports in a quasi-journal-article format format than they do taking and analyzing data. This "feels " wrong in many ways, and the person who kicked off the discussion did so by asking for alternatives to the journal-article style lab report.
This is a recurring discussion in physics education, because everybody who teaches lab courses struggles with this issue (guess what I'm procrastinating from grading right now...). It's made much worse…
drorzel | May 5, 2011NASA held a big press conference yesterday to announce that the Gravity Probe B experiment had confirmed a prediction of General Relativity that spacetime near Earth should be "twisted" by the Earth's rotation. A lot of the coverage has focused on the troubled history of the mission (as did the press conference, apparently), but scientifically it's very impressive.
The shift measured is very, very small-- 0.04 arcseconds over the course of a year, or 0.000011 degrees-- but agrees nicely with the predictions of relativity. I'm not sure whether to try to work this into the book-in-progress as I…