Physics
drorzel | December 7, 2010Today is the official release date for the paperback edition of How to Teach Physics to Your Dog, so I wanted to write up something cool about quantum physics to mark the occasion. I looked around the house for inspiration, and most of what we have lying around the house is SteelyKid's toys. Thus, I will now explain the physics of quantum teleportation using SteelyKid's toys:
"Wait, wait, wait... You're not seriously planning to explain something quantum without me, are you?"
"I could hardly expect to get away with that, could I. No, I'm happy to have your contributions-- the book is about…
drorzel | December 6, 2010I'm going to be at a media training session for most of the day. I had hoped to have a long and silly post about physics to schedule today, but, well, that didn't happen. So here's a silly poll to pass the time.
The name of element number 13, chemical symbol Al, is pronounced with how many syllables?survey software
We normally deal in macroscopic quantities of this one, so quantum superpositions of answers are right out.
drorzel | December 2, 2010In reading a bunch about relativity and related subjects as research for the book-in-progress, I have run across a usage question that seems like a good basis for a poll. So:
The "Classical" in "Classical Physics" means:online survey
Please note that none of these options include quantum mechanics, so you are restricted to only one answer, not a superposition of multiple answers at the same time.
drorzel | December 1, 2010I hadn't heard anything about Dance of the Photons: From Einstein to Quantum Teleportation before it turned up in my mailbox, courtesy of some kind publicist at Farrar, Straus, and Giroux, otherwise I would've been eagerly anticipating it. Anton Zeilinger is a name to conjure with in quantum optics, having built an impressive career out of doing laboratory demonstrations of weird quantum phenomena. He shared the Wolf Prize earlier this year with John Clauser and Alain Aspect, and the three of them are in a small set of people who probably ought to get a Nobel at some point in the near future…
drorzel | November 30, 2010At least, that's the obvious conclusion from the Royal Society's Science Sees Further page. The introduction touts it as "a series of articles on some of the most exciting areas of science today," but what's striking to me is that none of the twelve topic listed (Ageing Process, Biological Diversity, Cognition and Computation, Cultural Evolution, Extra-Terrestrial Life, Geoengineering, Global Sustainability, Greenhouse Gases, New Vaccines, Stem Cell Biology, Uncertainty in Science, and Web Science) includes any of the most obvious exciting developments in physics. Many of them have some…
drorzel | November 30, 2010Somebody asked a question at the Physics Stack Exchange site about the speed of light and the definition of the meter that touches on an issue I think is interesting enough to expand on a little here.
The questioner notes that the speed of light is defined to be 299,792,458 m/s and the meter is defined to be the distance traveled by light in 1/299,792,458 seconds, and asks if that doesn't seem a little circular. There are actually three relevant quantities here, though, the third being the second, which is defined as 9,192,631,770 oscillations of the light associated with the transition…
drorzel | November 26, 2010Today is "Black Friday," the semi-ironic name given to the day after Thanksgiving when major retailers roll out Incredible! Deals! to draw shoppers in at an ungodly early hour. Personally, I don't plan to come within a mile of a mall today, but if that's what floats your boat...
Of course, if you're thinking of gifts for a person interested in science (and if you're reading this, you ought to be...), you could do a lot worse than to look at this list from GeekDad at Wired, which I'm sure you'll be shocked to notice includes How to Teach Physics to Your Dog. If your holiday shopping takes you…
drorzel | November 25, 2010It's Thanksgiving here in the US, so blogging will be light to nonexistent. For the sake of those looking for a quick escape from the chaos of a family gathering, or, you know, those poor benighted souls in other countries for whom this is just another Thursday, here's a thematically appropriate poll about science:
What are you most thankful for?online surveys
Have a great holiday/ Thursday.
drorzel | November 24, 2010Given that I'm currently working on a book about relativity, I'm spending a lot of time idly thinking about various relativistic effects. Many of these won't end up in the final book, but they're fun to think about.
One thing that occurred to be earlier, while thinking about something else entirely, is the Doppler shift. In particular, I was thinking about the detection of planets around other stars, which is often done using the Doppler shift due to the orbiting planet's tug on its star. If the orbit is more or less aligned with our line of sight to the star, then the star wobbles back and…
esiegel | November 22, 2010"Surely something is wanting in our conception of the universe. We know positive and negative electricity, north and south magnetism, and why not some extra terrestrial matter related to terrestrial matter, as the source is to the sink. ... Worlds may have formed of this stuff, with element and compounds possessing identical properties with out own, indistinguishable from them until they are brought into each other's vicinity. ... Astronomy, the oldest and most juvenile of the sciences, may still have some surprises in store. Many anti-matter be commended to its care! ... Do dreams ever come…
drorzel | November 19, 2010I keep forgetting to mention this here, but a while back I was contacted by a tv host in California about the Goodnight Moon post. Anyway, I will be appearing via Skype tomorrow morning at 9:20 my time on the Good Day Sacramento program, to talk about bedtime stories, dog physics, and such things. Internet fame continues weird.
So, if you're an insomniac in central California, looking for something to do at 6:20 in the morning, tune in. I believe it's also available via live streaming, if you're not in the Sacramento area and want to see it live.
I have absolutely no idea what I'm going to…
drorzel | November 19, 2010Earlier this week, I talked about the technical requirements for taking a picture of an interference pattern from two independent lasers, and mentioned in passing that a 1967 experiment by Pfleegor and Mandel had already shown the interference effect. Their experiment was clever enough to deserve the ResearchBlogging Q&A treatment, though, so here we go:
OK, so why is this really old experiment worth talking about? What did they do? They demonstrated interference between two completely independent lasers, showing that when they overlapped the beams, the overlap region contained a pattern…
drorzel | November 18, 2010I'm grading a big backlog of homeworks today, so I don't have time to do any really lengthy posts this morning. Thus, a poll question inspired by going through these homeworks:
You are doing a physics homework problem. How many significant figures do you report?survey software
While the class in question uses some quantum ideas, the poll is strictly classical, so no superpositions of multiple answers are allowed.
(Honestly, at some point, I would expect laziness alone to compel people to round their answers off before their hands cramp up from copying all these digits...)
esiegel | November 17, 2010"I've been noticing gravity since I was very young." -Cameron Diaz
Yesterday, I told you about one of the simplest arguments for dark matter. We look out at the fluctuations in the microwave background on all the different angular scales we can measure -- from about 0.2 degrees all the way up to the whole sky -- and look at what the temperature fluctuations are doing.
We also look at the large-scale structure in the Universe, and try to correlate how mass clumps together.
We are only allowed -- by the laws of physics -- a few parameters to play with to try to fit this massive data set. We…
drorzel | November 17, 2010The big physics-y news story of the moment is the trapping of antihydrogen by the ALPHA collaboration at CERN. The article itself is paywalled, because this is Nature, but one of the press offices at one of the institutions involved was kind enough to send me an advance version of the article. This seems like something that deserves the ResearchBlogging Q&A treatment, so here we go:
OK, what's the deal with this paper? Well, the ALPHA collaboration is announcing that they have created antihydrogen atoms-- that is, a single antiproton orbited by a single positron-- at low temperatures, and…
esiegel | November 16, 2010"What makes the universe so hard to comprehend is that there's nothing to compare it with." -Anonymous
If I were brand new to theoretical cosmology, I might be skeptical of a whole bunch of "dark" things that I'd heard of. "Dark matter?" "Dark energy?" Come on; you've got to be kidding me! You're telling me that 95% of the Universe is not made of protons, neutrons, and electrons, like all the matter we know?
After all, I look out at the Universe, and this is what I see.
Stars, galaxies, gas and dust... normal matter, all of it. Yet all I need to do is start with two very well-supported…
drorzel | November 16, 2010Fall term classes ended yesterday, officially-- my last class was Friday-- so I'm shifting over to spend more time working on the sequel to How to Teach Physics to Your Dog, which involves talking to Emmy about relativity. Progress has been slower than last time, largely because the previous book was written while I was on sabbatical and before SteelyKid was born. But there's also a structural issue that's giving me some problems.
This is partly a matter of familiarity with the material-- I'm a low-energy physicist, so I've never needed to worry all that much about relativity. A bigger issue…
drorzel | November 15, 2010This is adapted from an answer to a question at the Physics Stack Exchange site. The questioner asked:
It seems that if the coherence length of a laser is big enough, it is possible to observe a (moving) interference picture by combining them. Is it true? How fast should photo-detectors be for observing of the interference of beams from two of the "best available" lasers?
This is a question about the itnerference of light waves, which is traditionally demonstrated via the famous "double slit" experiment, where a single laser is sent through a barrier with two narrow slits cut in it. The…
esiegel | November 12, 2010"A vacuum is a hell of a lot better than some of the stuff that nature replaces it with." -Tennessee Williams
Matter -- everything you know, love, hate, see, taste, and feel -- takes up space.
Even air must take up space. Not just wind, but still, stationary air takes up space. We've known this since Empedocles, in the 5th Century B.C., who had a clepsydra -- a hollow gourd with many holes in the bottom and a single hole at the top -- demonstrated it.
You plunge the gourd into a stream, lake or river, and it fills with water. If you lift the gourd up, the water leaks out of the bottom. But…
drorzel | November 12, 2010As mentioned in yesterday's post on ion trapping, a month or so back Dave Wineland's group at NIST published a paper in Science on using ultra-precise atomic clocks to measure relativistic effects. If you don't have a subscription to Science, you can get the paper for free from the Time and Frequency Division database, because you can't copyright work done for the US government.
This paper generated quite a bit of interest when it came out, because it demonstrates the time-slowing effects of relativity without any need for exotic objects like black holes or particle accelerators-- they deal…