mspringer | April 10, 2009Earlier this week I wrote up a brief outline of an experiment to measure the speed of sound using only your singing talent. I'd like to be able to do the same thing with the speed of light. But it's a lot harder because light is so friggin fast. As with sound, the speed of a traveling wave c is equal to the product of the wavelength and frequency. If you can find both of those you can find c. Or you could do something like directly measure the time it takes light to travel a specific distance. This is what the early experiments done by Galileo and others attempted without success.
Today…
mspringer | April 9, 2009I have a project for you, since I know practical physics is pretty popular around here. This one involves orbital dynamics, optics, and astronomy. The required experimental apparatus is just your eyes, a clock, and an internet connection.
There are these satellites orbiting overhead by the name of the Iridium constellation, working diligently to provide various communications services to its customers. We're not so interested in that. What we are interested in is the fact that these satellites have highly reflective mirror-like antennas which reflect sunlight down to the earth. With a…
mspringer | April 8, 2009So not only did I miss the Saturday and Sunday posts, but also the Monday and Tuesday ones as well. Gah! It's honestly quite a bit more difficult to keep to the one-per-day regimen this semester than I though. Nonetheless I'll try to stick to that schedule to the greatest extent possible. KBO.
Today I'd like to talk about singing in the shower. You will notice, if you're brave enough to try it, that certain notes resonate with a particular volume. It's probably why so many people like to sing in the shower - it turns the most humble voice into booming thunder. Or at least an…
mspringer | April 3, 2009I'm going to be out of pocket most of this weekend, though with any luck I'll still have the standard Saturday miscellany and Sunday Function posted. Today I'll be on the road, and leave you with a slightly useless bit of trivia:
The average density of books in my apartment is 1.83 per square meter.
Fortunately books are pretty compact and so in actuality there's a very small number of square meters with many books on them. Nonetheless, I was still a but surprised that the average was as high as it was. I keep a spreadsheet with all my books listed by title, author, and LoC call number, so…
mspringer | April 2, 2009I've wanted to do some writing about statistical mechanics, but it's difficult to do without it turning into deathly boring strings of equations. There's ways to make it interesting, I'm sure, and I think webcomic artist Randal Munroe has found one:
Full size at the link. "Hmm," thought I when I read it. "that sounds about right. Where's the factor of 2 from?" It's a reflection of the fact that it takes two to tango, as it were, and so you have to convert the population density into tango density.
But really for certain unorthodox folks that 2 may not be accurate. Maybe they enjoy those…
mspringer | April 1, 2009This is a pulley, pulled straight off Wikipedia:
On the test that my students had last week, there was a question involving pulleys connected in a sort of eclectic arrangement. The objective was to find the tension in certain ropes which were holding the pulleys up.
Imagine instead of being connected to the ceiling, the pulley in the picture is being held up by your hand. Hanging from the pulley is a heavy metal block, and the rope holding the block up is itself being temp taut by another person. So just like the picture, except for simplicity assume that the rope is not pulled at an…
mspringer | March 31, 2009I have a Fermi problem for you. By the very nature of a Fermi problem, a precise answer is impossible, we're merely looking for a justified order-of-magnitude estimate. Here goes:
During last week's Earth Hour event, what amount of CO2 was not released that otherwise would have been? What is that number in terms of percentage reduction compared to the total worldwide CO2 release during an equivalent time period not during Earth Hour?
Now I'm not knocking the idea. I like to see people avoid trashing the biosphere too badly. Doubly so when it's possible to shave some money off of the…
mspringer | March 30, 2009Before we figured out that the universe was a very large open space with lots of stuff scattered about, the ancients had some interesting ideas on how the sky worked. Roughly speaking, celestial phenomena came in three kinds. There are the stars, which remain a constant, fixed background. There are the planets, which move about the sky in complicated but predictable patterns. And finally there were other transient phenomena - nova, supernova, comets, meteors, and the rest. These last were often seen as particularly significant by virtue of their rarity.
If you go outside tonight and look…
mspringer | March 29, 2009The quadratic formula. With the exception of the Pythagorean Theorem, it's probably the single most common mathematical formula people carry from high school. It's not a function as such, it's something that solves a function. Let me give an example:
Pick a number x, square it, add twice x to that, subtract 3 from that. You might want to figure out what x makes the answer equal to zero. It's the kind of thing we have to do in physics all the time. In this case, the answers (and you can find them by several methods) happen to be -3 and 1. Plug them in and you'll see that you end up…
mspringer | March 28, 2009Saturdays I tend to use for soapboxing on things which may or may not be related to physics. Today I think it will be free speech. There's a Supreme Court case involving Hillary: The Movie in the context of McCain-Fiengold campaign finance law. Suffice it to say that free speech is non-negotiable in my opinion, political speech most of all. SCOTUS really screwed the pooch by not overturning the law with prejudice the first time it came up, and here's hoping they get it right this time.
"It's not a musical comedy", sniffed Souter and Breyer. No, it's not. It is obviously partisan…
mspringer | March 27, 2009Apologies for the light posting. Busy week, and it's going to be a busy weekend too in physics land. Well, that's what I signed up for.
This caught my eye though. Via Swans on Tea though, I see a great demonstration of physics as art. There's a story of Feynman and several other physics lecturers who liked to attach a bowling ball to the high roof of their lecture halls and pull the ball out to an angle right by their faces and let it swing. Of course it comes almost back to hit them in the face,but not quite. The laws of nature just can't provide more energy than went in to the system…
mspringer | March 25, 2009Kal-El, native of the planet Krypton, came to Earth and was adopted by Jonathan and Martha Kent. Being a Kryptonian, he found that he had superhuman powers and used them for good as Superman[1].
We all know the story. But what do we know about Krypton? Any information would be a dramatic coup for astronomers of all varieties. Superman couldn't tell us, he was just an infant when he left[2]. We might have to do some deduction. I propose we start by trying to determine the orbital period of Krypton - in other words, how long a Kryptonian year was.
To do this, we need the equation for…
mspringer | March 24, 2009Cormac McCarthy is with good reason widely considered to be among the finest living American writers. The literary scene has appreciated his work for some time; the general public (including myself, though I do a lot of reading) was first exposed to his work in the uncommonly faithful film adaptation of No Country for Old Men.
Success breeds success in Hollywood, and McCarthy's most recent book The Road is being filmed.
It's an unforgivingly grim and brutal book. A father and son are trying to survive in post-apocalyptic America. It's an uglier post-apocalypse than most. More or less…
mspringer | March 23, 2009Missiles are a problem if you're fighting a modern war. You can get out of the way or you can hide behind something, but that's about it. Now anti-missile technology has had some success dealing with mid-range missiles. The Patriot system whose success was limited during the Gulf War has since been improved into a system that's quite effective in dealing with the large and somewhat lumbering tactical ballistic missiles fielded by a number of adversaries.
But smaller missiles and mortars remain an intractable menace. It takes mere seconds for something like a Qassam rocket to travel its…
mspringer | March 19, 2009Thursday and Friday of this week are the staff and faculty equivalent of spring break here at Texas A&M. I'm going to be spending them on the road, visiting family and friends. As such Built on Facts is going to be on break for a few days. We'll be back Monday - possibly sooner.
Until then, here's a video of a Tesla coil tuned to play the Imperial March while zapping somebody (safely clad in electricity-diverting chain mail). Enjoy, and I'll see you back here soon!
Oh, let me point something else out. The guy is standing on a box. The sparks flow down his body and over the box…
mspringer | March 18, 2009It's not all that often I agree with Mike Dunford politically, but in writing about the AIG bonuses he's right. The bonuses ought to stay with the executives who were paid them. Neither congress nor the president ought to try to tax these bonuses back.
Now obviously no executive at a failing bank deserves a bonus, even with the bank's money. Even more obviously it's repugnant to fund bonuses to failed executives with our tax dollars. But what's done is done, and there are three facts to be faced.
1. The executives' contracts require the bonuses, and the bailout bill specifically and…
mspringer | March 18, 2009Here is a question. It's a sort of subtle question, but one that can be answered with freshman-level physics. But it's an excellent test of understanding. I'm not promising that the question itself is not in some sense a "trick" question, but the trick is in how you might think about the physics, not the question itself. Which is to say, I'm not promising that what the question assumes happens can actually happen. But it might - it's up to you to tell me!
Ok. You have a perfectly efficient car, which transmits all of the energy in its fuel into kinetic energy of forward motion. Kinetic…
mspringer | March 17, 2009Sometimes I watch Survivorman on the Discovery Channel. It's a good show - much better than that other one - by virtue of the fact that the survival is real and he doesn't have a camera crew around to help him out. Sure he has a way to contact rescue should something go wrong, but it doesn't change the fact that he really is very good at wilderness survival.
One of the things he points out is that pretty much wherever on the planet you find yourself, you're going to find trash. This is especially true in island survival. Years of trash washing up can be useful when surviving, though he…
mspringer | March 16, 2009Driving in my car for five hours today, I had plenty of time to think about velocity. There's not much you can do about it, speeding doesn't take much time off the trip but it does add the risk of an expensive ticket. We single classical particles don't have a lot of options for getting from place to place very quickly.
The situation is a little more interesting with flows of current. If you want to fill a large bucket with water from a garden hose at one cubic foot per second, the hose is going to have to be turned on very high. Water will be flying out of the end of the hose at some…
mspringer | March 15, 2009Well, it's Gabriel, Gabriel playin'!
Gabriel, Gabriel sayin'
"Will you be ready to go
When I blow my horn?"
- Cole Porter, Anything Goes
The commenters in last week's Sunday Function proposed an excellent idea for this week. As we did then, we'll start simple and work up to it. Graph the curve f(x) = 1/x.
Now take the horizontal axis and think of it as an axle, one that can rotate smoothly. Hook a motor onto it and spin it up to a nice fast clip. The graph of the function will trace out a surface in three-dimensional space. In the business, we call it a surface of revolution. It looks…