Physics
rallain | April 7, 2010Check out this video demo:
So, that is just plain water. If I am careful, I can make that thin aluminum disk stay on the surface of the water. This is not the same as floating in Archimedes principle. It is different. This is staying on the surface because of surface tension.
Bouyancy
I think my best explanation of buoyancy was in the post about MythBusters floating a lead balloon. But, basically for buoyancy there is an upward force from the water on the thing that is floating. If I want to explain this in terms of the particle model of a gas or fluid, I could say that the particles in…
esiegel | April 5, 2010The most formidable weapon against errors of every kind is reason. I have never used any other, and I trust I never shall. -Thomas Paine
I've been telling you the history of the Universe over the past few months in serial. Parts 1 through 8 are currently up, and have taken us from Inflation up through the formation of neutral atoms, covering the first 380,000 years of the Universe. During this whole time, like a giant balloon, space has been expanding.
One thing I haven't paid much mind to is just how the Universe has been expanding during this time. The concept is relatively straightforward…
drorzel | April 5, 2010Not a full Obsessive Update (because not much happened over the weekend, when we took SteelyKid to my parents' place for Easter), but a quick reminder to folks in the Ithaca, NY area: I'll be giving the physics colloquium at Cornell this afternoon at 4pm. If you're in the area, and want to hear me talk about communicating science and the use of blogs, it's at 4pm in the Schwartz Auditorium in Rockefeller Hall.
It's going to be a long day-- I have a class at 9:15, then I'm driving to Ithaca. SteelyKid stayed with Grandma and Grandpa (day care is closed today and tomorrow), so I'll be going…
jdupuis | April 3, 2010OK, so Friday Fun a day late.
Anyways, April Fools day was a couple of days ago and I thought that the ScienceBlogs home page was the funniest science-related prank of the day.
So, for those of you that missed the headline and the little story that went with it, here goes:
CERN Scientists Awaken Balrog
When the Large Hadron Collider brought protons up to full speed on Tuesday,
smashing them together at 99 percent the speed of light, the world did not end
as some feared. But disturbing news emerged Thursday morning that CERN
scientists have desperately been trying to cover up a catastrophe of…
drorzel | April 2, 2010I forgot to schedule a blog post to remind people to tune in to my appearance on WAMC's "The Roundtable" yesterday morning, talking about How to Teach Physics to Your Dog. If you missed it, and have fourteen minutes to kill, they have the segment on their audio archive now.
It went well, and I had fun. I was really flattered when somebody at work asked if I'd gotten the questions in advance-- actually, I only got into the studio about three minutes before the interview started. Nice to see that a real radio studio looks pretty much like what you see on tv and in movies, only smaller, as is…
rallain | April 2, 2010In this part of the world, we have oak trees. Technically they are called live oaks - but I don't get it. Of course they are alive. I was at a soccer game and this is the tree I always look at.
Look how far those limbs extend horizontally. That branch is about 12 meters long. Why is this amazing? Have you ever tried to hold an 8 foot 2 x 4 board horizontally by holding one end? Pretty tough. How about I calculate the forces needed to hold that branch in place? I will do a simple model and then maybe later I can make it more complicated. Suppose I replace that limb with one straight…
esiegel | March 31, 2010The stakes are high, and win or lose, worth playing for. -Fred Hoyle
Yesterday was a record-setting day for humanity. Over at CERN, the Large Hadron Collider achieved a new record for the most energy ever created in a laboratory collision in the history of humanity: 7,000,000,000,000 electron Volts, or 7 TeV (Tera- or Trillion-electron-Volts) for short.
Sure, we get energies higher than this all the time from black holes, neutron stars, and other catastrophic processes in space. Occasionally, we even observe them, in the form of Cosmic Rays!
But there are two big differences between cosmic…
drorzel | March 31, 2010If you scroll way down the list of this year's Goldwater Scholarship winners, you'll find:
Peter John Bonventre
Institution: Union College
Major(s): Physics/Mathematics
Career Goal: Ph.D. in Mathematics or Physics. Conduct research and teach at the university level.
Pete's one of our junior physics majors. He's done summer work on both nuclear physics and condensed matter physics, and is a work-study student in the department. So, we're obviously thrilled to see him win. Congratulations, Pete!
There's a Goldwater Foundation press release here, with more information and statistics about the…
drorzel | March 31, 2010Physics Central is having a contest:
Do you love lasers? Ever wanted to unravel the mystery of the stimulated emission? Then the LaserFest video contest is for you. Take any laser you want and use it to somehow express a physics concept. Shine, lase, bounce and wave your way into physics history.
The winner will receive a trophy lovingly made by APS staff from some of our favorite laser toys as well as $1,000 cash. All entries must be received by May 16th at midnight.
If you know how to make videos for YouTube, and know something about physics, here's your chance at (Internet) fame and (…
rallain | March 29, 2010Here is a quick Apolo Ohno quiz. Which one of these pictures is fake?
If you picked picture B - you are probably correct. That is a picture of "Apolo" being catapulted into a pool of slime at the Nickelodeon awards show (click on the link to see the video - I don't think I can embed it). Ok - time to crank out an analysis.
I think I could approach this analysis from a couple of directions. Since all I have is a crappy version of the video, I could just look at "could this be possible"? The other analysis I could do would be to measure his acceleration in free fall. Let me start with…
drorzel | March 29, 2010A flurry of things to kick off the new academic term. Reviews and news:
A nice write-up on Wired's GeekDad blog by Kathy Ceceri, about last week's homeschool event. Includes a picture of me giving a tour of my lab.
ZapperZ says that I'm not teaching physics, I'm teaching about physics. Which is probably fair, as he defines the terms. Of course, How to Teach Your Dog About Physics isn't as good a title.
And a bunch of upcoming events:
I'll be on WAMC's Roundtable this Thursday at 10am (well, after the news report that runs at the top of the hour).
I'm giving a Physics colloquium at Cornell…
rallain | March 26, 2010I am surprised at how many people (chemistry faculty included) have never seen this demo. (oh, technically it is called a cartesian diver demo) Basically, you put some floating object that has an air space in a closed bottle of water. When you squeeze it, the diver goes down.
For my setup, I used a glass eye-dropper. Put it in a cup to make sure it just barely floats and then put it in a completely full water bottle. If you don't have a eye-dropper, you can use anything that floats with an air space. I have done this with part of a straw before. Fold a small section of a straw in half…
rallain | March 26, 2010I am teaching physical science this semester. It appears that I will be teaching it again this summer. Ideally, I would like to switch to something like Physics and Everyday Thinking for large lecture courses. A course like this is being developed, but it isn't quite finished. Also, the current version includes chemistry and physics. I really need something different (we offer physical science 101 is physics and 102 is chemistry).
The current course is pretty traditional. Your basic physical science stuff. It has the following content.
Forces and Motion
Newton's Laws
Projectile motion…
rallain | March 26, 2010Time for another Fermi problem. There was a recent story in Science News that talked about the effects of the Chilean quakes on the Earth's rotation. The basic idea is that some ginmourmous amounts of rock moved closer to the Earth's center. Since the angular momentum of the Earth is conserved, the angular rotation rate would increase. The estimated change of the day was by about 1.26 microseconds.
Could all the cars in the USA be used to change the rotation of the Earth?
Well, I shouldn't have phrased the question that way. Of course 1 car technically is all you need to change the…
drorzel | March 25, 2010Been a little while since I've done an Obsessive Update, but a few noteworthy things have come up recently:
A very nice review at Pet Connection: "this brilliant and (relatively) simple book explains the basic premises of quantum physics in terms that dogs and most English majors can understand." Which is not to say that English majors are less likely to understand it than dogs-- English majors are a big part of our target audience, and it's nice to hear that it works for at least some of them.
Another blog review, this time at Synergy of One: "Throughout the book, the author's extremely…
drorzel | March 25, 2010I did one sketchy update from Portland last Tuesday, but never wrote up my impressions of the rest of the March Meeting-- when I got back, I was buried in grading, and then trying to put together Monday's presentation. And, for reasons that will become apparent, I was unable to write anything up before I left Portland
Anyway, for those who care, here are my impressions from the rest of the meeting:
Tuesday
In the 8am session, I went to the polymer physics prize talk by Michael Rubinstein, which was a sort of career retrospective, talking about how he wandered into the disreputable field of…
rallain | March 24, 2010How does a suction cup work? It is all about the atmosphere. Here is a demo. Take some type of "suction cup" device. In this case, I used a toy dart. Stick it to something smooth and lift it up. Like this:
What lifts up the metal block? The atmosphere. Diagram time:
But this isn't a very realistic diagram. Actually, the suction cup would be pushing down on the block because the force from the atmosphere would be too large to balance with the weight. Let me put some numbers in here. Suppose this is an aluminum block - I just going to pretend it is 4cm on a side (and a cube). In…
drorzel | March 24, 2010Several people have sent me links to news stories about last week's Nature paper, "Quantum ground state and single-phonon control of a mechanical resonator." (It was also presented at the March Meeting, but I didn't go to that session). This is billed as the first observation of quantum phenomena with a "macroscopic" or "naked eye visible" object.
Of course, there's a nice bit of irony in a story about quantum effects in a "naked eye visible" object that is accompanied by an image of the object in question taken with a scanning electron microscope. The longest dimension of the object in…
oracknows | March 24, 2010It has often been written on this blog and elsewhere that the mark of a true crank is hatred of the scientific consensus, be it consensus regarding the theory of evolution, the science that says homeopathy is impossible, anthropogenic global warming; various areas of science-based medicine; or the safety and efficacy of vaccines. Perhaps the most famous expression of distrust of a scientific consensus is the famous speech by Michael Crichton, in which he famously said:
Let's be clear: the work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science…
esiegel | March 23, 2010Note: I'm on vacation this week, so here's one from the vault. This article first appeared on my old website, back in February of 2009.
Some days the questions I get are easy, and some days I get questions from our longtime reader, Ben. This past week, there have been reports all over the news that our world may be a giant hologram. Let's take a look at what's going on.
In Hanover, Germany, there's an experiment called GEO600. These are two perpendicular lasers, and they shoot out for thousands of feet, get reflected, and come back to their original location to make an interference pattern…