Physics
rallain | October 4, 2008Magic tricks are cool. Especially when the trick is really physics. In this trick, I can make one of the four balls move more than the others. (When you watch the video, you will see why I am not a professional magician). You could set this up in a variety of ways. I state that if we (me and people around me) all work together with our mind and focus on the same ball, our brain waves can resonate with that ball and make it move. I let the people around me pick. In this video, I make the smallest two move.
So, what is the trick? The trick is not a trick. It is not resonance with brain…
drorzel | October 4, 2008Over the past several weeks, I've written up ResearchBlogging posts on each of the papers I helped write in graduate school. Each paper write-up was accompanied by a "Making of" article, giving a bit more detail about how the experiments came to be, what my role in them was, and whatever funny anecdotes I can think of about the experiment.
If you haven't been following the series, or would just like a convenient index of the posts, here's the complete set:
Introduction and explanation of metastable xenon.
Experiment 1: Optical Control of Ultracold Collisions and the making thereof.…
rallain | October 4, 2008I think it is time for me to talk about energy. My ultimate goal is to give some insight into the many stories about perpetual motion. To do this, I will first talk about the fundamentals of energy.
**What is Energy**
I started thinking about this, and at first I realized that I did not have a good, short explanation of energy. The most commonly used definition in science text books is:
*Energy: the ability to do work (or something dreadfully vague like this).*
But what is work? It may be no surprise to find that many college level physics texts avoid defining energy. After some serious…
rallain | October 2, 2008Gas prices may be trending down, but they are still quite high. How can we save gas? One of my colleagues suggested we can save gas by getting rid of all drive throughs. This means it is my job to estimate how much could be saved.
**Starting Assumptions (estimations)**
How many drive-throughs are there in the U.S.A.? When I think of drive-throughs, I think of McDonalds. [Wikipedia](http://en.wikipedia.org/wiki/Mcdonalds) says there are 31,000 restaurants world wide. I am going to say there are around 20,000 in the U.S. that have drive-throughs. So then, how many total drive-throughs?…
drorzel | October 2, 2008As mentioned in the previous post, the cold plasma experiment was the last of the metastable xenon papers that I'm an author on. My role in these experiments was pretty limited, as I was wrapping things up and writing my thesis when the experiments were going on.
The main authors on this were Tom Killian, now running his own cold plasma lab at Rice and Scott Bergeson, now running his own cold plasma lab at BYU. Scott was a pulsed-laser expert with a remarkably cavalier attitude toward things like anti-reflection coatings on vacuum windows, and Tom came from Dan Kleppner's hydrogen BEC project…
drorzel | October 2, 2008This is the last of the papers I was an author on while I was in grad school, and in some ways, it's the coolest. It's rare that you get to be one of the first people to do an entirely new class of experiment, but that's what this was. It kicked off a new sub-field (or sub-sub-field...), the history and status of which was written up in Physics a little while back.
The ultracold plasma experiment may be the ultimate version of what we jokingly called the "NIST Paradigm" of cold-atoms physics research, which could be summarized as "I wonder what will happen if we stick this other laser in?" It…
rallain | October 2, 2008I was recently re-watching a MythBusters episode and I found something I had wanted to explore previously (but accidentally deleted the episode). Here is a short clip from the "shooting fish in a barrel" episode:
Did you see what I found interesting? That big barrel of water left the floor from being hit by a bullet.
The question here is: Does a bullet have enough energy to increase the gravitational potential energy of the barrel to that height?
First, let me gather some data. From the episode, the Mythbusters were firing a 9mm pistol round into the barrel. I don't know much about…
pontiff | October 1, 2008DonorChoose, an organization which matches teachers requests for funds with donors, is running their annual blogger challenge. Already Cosmic Variance is trying to harness their vast resources of physicists, The Optimizer is appealing to the base nerd in everyone, He of Uncertain Principles is offering up his dog's services for donations (does the dog know?), and the moral Mathematician is offering solutions to math homework problems (err I mean blog posts on a chosen topic.) But I think you shouldn't fall in this trap and support those blogs....
Because, of course instead you should…
rallain | October 1, 2008I actually have some important things to do. However, I thought I would make another scratch program. Yes, this will all lead to something useful (that is what I told my wife). Anyway, in this program, I made a spaceship with 4 thrusters. The great thing about this is it show what forces do to the motion of an object. I already had a suggestion to make it into a game with a score.
Learn more about this project
Use the arrow keys to turn on the 4 thrusters.
rallain | October 1, 2008I can't remember how I found this, but [Scratch](http://scratch.mit.edu) is a graphical programming language developed at MIT. My kids love this. In order to make sure they don't know more than I do, I created my own scratch program. I am sure someone from the scratch community will attack it for some reason, but I am ok with that.
The program shows a numerical calculation of the motion of a box with a constant force on it. You change the mass and the force. It "sort of" plots the position as a function of time. Don't worry python, I still think you are the best.
Learn more about…
drorzel | October 1, 2008I signed up for the Adopt-a-Physicist program run by the APS, and I've been "adopted" by three high school classes. The program pairs professional physicists with high school classes, and provides a web forum both groups can access. The students ask questions, and I answer them.
I'd love to be able to link directly to the forums, but they're password-protected, so you can't get in. The questions so far have been really good, though, and I'm enjoying providing answers.
Some of my answers have included pointers to the blog, so I thought I'd give a shout-out here to the classes that have "…
rallain | September 30, 2008Which wastes more fuel? (and thus produces more carbon dioxide). This is a difficult to question to answer for a variety of reasons. The main reason is that a speed change from 71 mph to 70 mph is different than a reduction from 56 to 55 mph.
First, let me be clear that the question of how much fuel is wasted using daytime running lights (or DRL as they are called) has already been addressed. The first source I found was howstuffworks.com
**Assumptions**
The daytime running lights on a car run at about 100 watts (for the pair)
The energy density of gasoline is 1.21 x 108 Joules/gallon.
A car…
rallain | September 30, 2008**Pre Reqs:** [Intro to Forces](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php), [Vectors](http://scienceblogs.com/dotphysics/2008/09/basics-vectors-and-vector-ad…)
Hopefully now you have an idea of what a force is and what it isn't. What do you do with them? The useful thing to do with forces is to determine the total force acting on an object. At the beginning of the introductory physics course, you will likely look at cases where the total force is the zero vector. This is called equilibrium. Even if you are looking at cases where the forces don't add up to the…
drorzel | September 30, 2008Via FriendFeed, I came across an article by Deepak Singh on attention and science, which spins off a long rant by Kevin Kelly on the idea that Where ever attention flows, money will follow. Deepak writes:
Attention can be driven by many mechanisms, marketing being the most effective one. The key is gaining sufficient mindshare, which is often accompanies by a flow of capital. In science, the money follows topics of research that have mindshare. Similarly people fund companies in areas that generate mindshare for whatever reason.
The question I often ask myself, both from my time as a marketer…
rallain | September 28, 2008When mowing the lawn, I like to listen to podcasts. One of my favorites is [Buzz Out Loud](http://bol.cnet.com). This weekend, I was listening to episode 817 and one of the topics of discussion was MySpace and their DRM free music stuff. [Wired](http://blog.wired.com/music/2008/09/myspace-launche.html) had a description of what they were going to do. That is not my point. The point is the claim that you could make an infinite number of playlists. How about I calculate (or estimate) the number of different playlists one could make.
First, the idea behind the idea. Calculating the number…
drorzel | September 28, 2008There's an interesting exchange over at the Reality-Based Community around the topic of "earmarks" for science, like the grizzly bear DNA study McCain keeps mocking. Michael O'Hare argues that science should not be funded by earmarks:
Almost any piece of scientific research, especially in biology, that isn't called "Cure cancer!" is liable to the kind of ignorant ridicule lobbed at these. Sure, some research is deeply silly and some is not worth doing. But that non-specialists can make fun of something from its title means nothing, and these japes indicate only the smug ignorance of the…
rallain | September 26, 2008On a previous episode of The MythBusters, Adam and Jamie made a lead balloon float. I was impressed. Anyway, I decided to give a more detailed explanation on how this happens. Using the thickness of foil they had, what is the smallest balloon that would float? If the one they created were filled all the way, how much could it lift?
First, how does stuff float at all? There are many levels that this question could be answered. I could start with the nature of pressure, but maybe I will save that for another day. So, let me start with pressure. The reason a balloon floats is because the air…
rallain | September 26, 2008**Pre-reqs:** None.
I intend to talk about forces and force diagrams, but there is a more fundamental question to address first. What is a force? Most texts define it as a push or a pull. That really isn't a bad definition. Maybe a better (or maybe worse) definition would be "forces are things that change the motion of an object" (change being the key word). If I had to choose one definition of force, it would be something like this:
**Force:** *A force is an interaction between two objects. There are 4 known forces:*
Gravitational force: An attractive long range force between objects…
rallain | September 25, 2008In a [previous post](/dotphysics/2008/09/basics-making-graphs-with-kinematics-stuff-part-ii/), I talked about how to plot kinematics data with a spread sheet and how to fit a quadratic function to the data. In the back of my head I remember "Don't trust Excel". I seem to recall someone claiming that Excel did not do a proper fit. To test this, I collected some data and used several methods to fit the data:
MS Excel's built in function fitting
Using the spread sheet (Excel) to manually calculate the best fit parameters
Vernier's Logger Pro (version 3.6.1)
Plot 0.997 - http://plot.micw.eu…
pontiff | September 24, 2008Major news from the quantum information front. Today I see posted on the arXiv a paper by M.B. Hastings: arXiv:0809.3972 "A Counterexample to Additivity of Minimum Output Entropy." If correct this resolves one of the most famous open problems in quantum information theory, and, even more interestingly says that in a quantum world, transmitting classical information down quantum channel defies your classical intuition. Blessed be our quantum world, which just continues and continues to amaze.
Previously I explained the idea channel capacity. You're sending (classical) information from one…