Physics
drorzel | September 10, 2010When Kate and I were walking Emmy last night, we were talking about the historical development of relativity. As one does, when walking the dog. I mentioned a couple of the pre-1905 attempts to explain things like the Michelson-Morley experiment, and how people like Lorentz and FitzGerald and Poincare were on the right track, but didn't quite get it all together.
Kate asked about what it would've been like to be a physicist working at that time, when both relativity and quantum mechanics were being born, trying out new approaches and not really knowing whether a given approach would turn out…
rallain | September 10, 2010Here is the next item.
There is a threaded plug on the top. I took it off so you could see inside. The whole thing is pretty heavy.
Good luck, and let's be careful out there.
rallain | September 9, 2010Through random surfing, I found this clip from The Amazing Race (which is apparently some type of reality show). Don't really know the set up except that it appears some girl is trying to launch watermelons with a slingshot. This looks bad, but she seems to not be seriously injured.
Watermelon smashed on face. Wow. What can I we calculate here? Bring in the video analysis.
How fast was the watermelon going?
First, this is not a very good quality video. The frame rate sucks and there is a very slight panning and zooming (which I will ignore) Second, I really don't have anything to scale…
drorzel | September 9, 2010Over at Tor.com, Jo Walton is surprised that people skim over boring bits of novels. While she explicitly excludes non-fiction from her discussion, this immediately made me think of Timothy Burke's How to Read in College, which offers tips to prospective humanities and social science majors on how to most effectively skim through huge reading assignments for the information that's really important.
I've mentioned this before, but I don't think I've done a science version. I've been doing more reading of journal articles lately than I have in a while, though, and it occurs to me that similar…
esiegel | September 8, 2010"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return." -Unknown
Someone showed me a picture yesterday, and my initial reaction was simply, "WOW!" See for yourself:
But, as a physicist, I look at something like this and I immediately need to figure out what's going on here.
First off, you notice that this is clearly some type of fighter jet, being photographed from below with the Sun illuminating it from above. A little google-fu reveals that the silhouette matches that of an F-22…
rallain | September 8, 2010Actually, it should be called Happy "Magnitude of the local Earth gravitational field" day. You know, 9.8 N/kg on September 8 (9/8). Get it? Well, the idea was for the physics students and faculty to build some stuff to do outside - projectile motion type stuff. Well, we had the idea a while ago and then kind of forgot about it.
In order to just get something done, I set up the "shoot the falling target" demo. (previously known as shoot the monkey). Here is a quick video demo (seriously - first take too).
What is going on here and what does this have to do with g? Well, it doesn't…
drorzel | September 8, 2010The theory of relativity takes its name from a very simple and appealing idea: that the laws of physics should look the same to moving observers as to stationary ones. "Laws of physics" here includes Maxwell's equations for electricity and magnetism, which necessarily means that moving observers must see the same speed of light as stationary observers (Einstein included the constancy of the speed of light as a second postulate in his original relativity paper, but it's redundant-- the constancy of the speed of light is a direct consequence of the principle of relativity). This leads directly…
rallain | September 7, 2010Congratulations Fran. Not only did she answer the "What the heck is this?" correctly, she was the first commenter.
Here is the original item:
It is of course a gas discharge tube. You put these tubes in there (as shown above) with helium or neon or whatever in there and it excites the gas to give off light.
Honestly, we have like 10 of these things laying around. Some of them are newer and say "Danger 5000 volts"), but these older ones say nothing. Here is an example of one of the first ones I saw.
I didn't figure out what it was for a while because most of the ones we have don't have those…
rallain | September 7, 2010You can call it football if it makes you happy. Anyway, this is a popular story going around. The physics of the magic curving soccer kick. Here are two ends of the spectrum.
First, there is the lower, easier to consume version from io9.com
Physics forced to come up with whole new equation to explain "impossible" soccer kick
I will summarize this article for you:
"Have you seen these crazy soccer kicks where the ball curves? It happens because the ball spins and physics. Here is a video"
Oh, and they have a diagram - which doesn't seem to come from the original paper and they also have…
drorzel | September 7, 2010In chapter 2 of How to Teach Physics to Your Dog, there's a footnote about the ubiquity of uncertainty principle analogies in the mass media:
To give you an idea of the breadth of subjects in which this shows up, in June 2008, Google turned up citations of the Heisenberg Uncertainty Principle in (among others) an article from the Vermont Free Press about traffic cameras, a Toronto Star article citing the influence of YouTube on underground artists, and a blog article about the Phoenix Suns of the NBA. Incidentally, all of these articles also use the Uncertainty Principle incorrectly--by the…
esiegel | September 3, 2010"We have been forced to admit for the first time in history not only the possibility but the fact of the growth and decay of the elements of matter. With radium and with uranium we do not see anything but the decay. And yet, somewhere, somehow, it is almost certain that these elements must be continuously forming. They are probably being put together now in the laboratory of the stars. ... Can we ever learn to control the process. Why not? Only research can tell." -Robert Millikan
Ah, energy, if only you were free, limitless, and easily accessible. If you were, we could do anything we wanted…
drorzel | September 3, 2010Over at Confused at a Higher Level, Melissa offers an alphabetical list of essential supplies for a condensed matter experimentalist at a small college. This is a fun idea for back-to-school time, so I'll steal it, and offer the following alphabetical list of essentials for Atomic, Molecular, and Optical physics at a small college, kind of a condensed version of the three part series I did a few weeks ago.
A is for Acousto-optic modulator This is a device that uses sound waves in a crystal to deflect light and shift its frequency. It's essential for rapid control of laser properties.
B is for…
drorzel | September 3, 2010Earlier this summer, I talked about the blog and the book on the phone with somebody from the APS, providing material for a profile of me that was posted yesterday on Physics Central. It's pretty good, but it's still a little strange to see my name and picture on their profile index with some of the other names there-- I don't really think of myself as being in the same category as Margaret Murnane or Mildred Dresselhaus, who are really amazing scientists.
So, it's very flattering to see this up there. It would also probably be a useful reference for anybody who would like to update my stub…
rallain | September 3, 2010Please note the official change of the title of this game, it is no longer "what is this".
Here is the item:
I suspect someone will know what this is. Honestly, I didn't figure it out right away. However, I have found that the readers as a group generally are more knowledgeable than me by myself.
Oh, I don't think there is really much description to add here. I included a meter stick for scale.
P.S. How come a device for measuring temperature is a thermometer and a device for measuring electric potential is a voltmeter? Shouldn't the meterstick be called either a length-meter or a meter…
rallain | September 2, 2010Yes, I love python. However, I am no expert. Most of the stuff I write in python is dirty and ugly code. Sometimes I figure out new things (things that programmers already know) and sometimes I forget these things. So, here are a few tips and tricks that I use from time to time. Really, I am writing this for future Rhett when he does a google search for "how do you save data to a file in python".
Saving data to a file
Suppose I am modeling a basketball falling through the air. I want to plot this data, so I save position and time data in lists. For example: Here is the info from scipy…
rallain | September 2, 2010A while ago, we had a ton of lightning. As a bonus, it always happened in the middle of the night. I love sleeping where it sounds like I am on the front line in WWI - no, I don't. But, while lying awake waiting for the next BOOM I thought of something. Instead of just counting the time between flash and boom, maybe I could make a lightning detector.
For mere mortals, the first step might be to google "lightning detector". I don't want to do that. What fun would that be? I did look up something. The current in a typical lightning strike is on the order of 30,000 amps. How could I…
drorzel | September 2, 2010"Hey, dude, whatcha doin'?"
"Signing these contracts. I'm not sure why they need four copies, but they do."
"Contracts for what?"
"The new book. Remmeber, the one we've been talking about these last few weeks? Sequel-of-sorts to How to Teach Physics to Your Dog? About relativity?"
"Oh, yeah, that's right! We're doing another book! Where do I sign?"
"What do you mean, 'Where do I sign?' You're a dog."
"I could, you know, put a paw print on the line, or something."
"I suppose you could, but it wouldn't be legally binding. Dogs aren't allowed to sign contracts."
"You know that's horribly…
drorzel | September 1, 2010I doubt that this will actually work, but then the Web has brought me some improbable successes before, so it's worth a shot:
I have a sealed glass cell (Pyrex, I think, if it matters) that I would like to get re-filled with a mix of rare gases-- partial pressures of 100mT Ne, 30mT Ar, 30 mT Kr. This will contain an RF plasma discharge to serve as a spectroscopic reference for my experiments, and thus needs to be very clean-- I can't have impurities coming out of the walls and quenching the metastable atoms I'm producing in the discharge.
The company that initially made the cell has not…
drorzel | August 31, 2010A lot of people have been blogging and Twittering about this subway map of science, which puts various branches of science in the place of the lines on the London Underground map, showing connections between them. It's a huge graphic, but a kind of cool image.
I do, however, have a problem with it, which is illustrated by the key to the lines shown at right. The category of physics is presented as "Theoretical Physics and Quantum Mechanics." I have no problem with the quantum part, as quantum mechanics is one of the greatest intellectual achievements in human history. I do have a problem…
drorzel | August 31, 2010Back in July, I did a post looking at how the fountain in our ornamental backyard pond shoots higher when the level of the pond drops. I set up a simple model of the process, which worked surprisingly well, but I said at the time that I really needed more data to say whether that agreement was real or accidental. Well, yesterday, I got some extreme data:
The leak in the pond has gotten worse, I think, and the water was barely covering the top of the pump box at all. A very rough calibration of this image, using the fact that the brick is 2in high, gives a height of the spray of about 62in,…