TAMU Physics Festival and Rotating Discs in Special Relativity

The Texas A&M Physics Department Physics Festival is today[5]!!! If you're in town, you should wonder over to the Mitchell Physics building, (see the picture), on University Drive. Nobel laureates will speak, there will be three showings of a physics circus, and there will be tens and possible over a hundred hands on demos to take a look at. Lately, the chemistry, mathematics, and engineering departments have gotten in on the fun, so things could get crazy! Oh, and there's almost certainly going to be exploding bottles of liquid nitrogen used to erupt water out of barrels, a perennial crowd pleaser.

On the theory side of things this week, I'm working on re-calculating the line element of the Takeno transform. The transform was derived by Takeno in 1952 in an attempt to explain what happens to a rotating disc when it rotates at special relativistic speeds. There's been a conundrum here almost since the inception of special relativity in 1905. It was pointed out that if length contracts in the direction tangential to travel, (along the circumference of the disc in this case), and it doesn't contract in directions at right angles to travel, then the circumference of the disc would grow smaller while the radius of the disc would be unchanged and the formula for the circumference, C=2*Pi*r would no longer hold. The issue has never been resolved to everyone's satisfaction nd there's still a lively debate in the journals[2][3][4].

References:
1. Takeno H. “On Relativistic Theory of Rotating Disk”, Prog. Theor. Phys. 7, (1952), 367

2. Spatial geometry of the rotating disk and its non-rotating counterpart

http://arxiv.org/pdf/1109.2488.pdf

3. On rotation and rotating frames: Franklin transformation and its modiﬁcation

http://arxiv.org/pdf/1208.1913.pdf

4. New Perspectives on the Relativistically Rotating Disk and Non-time-orthogonal Reference Frames

http://arxiv.org/pdf/gr-qc/0103076v1.pdf

5. Physics Festival

http://physicsfestival.tamu.edu/

Comments

The Valentine's Day Magnetic Monopole

There's an assymetry to the form of the two Maxwell's equations shown in picture 1. While the divergence of the electric field is proportional to the electric charge density at a given point, the divergence of the magnetic field is equal to zero. This is typically explained in the following way. While we know that electrons, the fundamental electric charge carriers exist, evidence seems to indicate that magnetic monopoles, the particles that would carry magnetic 'charge', either don't exist, or, the energies required to create them are so high that they are exceedingly rare. That doesn't stop us from looking for them though! Keeping with the theme of Fairbank[1] and his academic progeny over the semester break, today's post is about the discovery of a magnetic monopole candidate event by one of the Fairbank's graduate students, Blas Cabrera[2]. Cabrera was utilizing a loop type of magnetic monopole detector. Its operation is in...

Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

Now available as a Kindle ebook for 99 cents ! Get a spiffy ebook, and fund more physics The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems , there seem to be fewer explanations of the procedure for deriving the conversion, so here goes! What do we actually want? To convert the Cartesian nabla to the nabla for another coordinate system, say… cylindrical coordinates. What we’ll need: 1. The Cartesian Nabla: 2. A set of equations relating the Cartesian coordinates to cylindrical coordinates: 3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system: How to do it: Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables. The chain ...

More Cowbell! Record Production using Google Forms and Charts

First, the what : This article shows how to embed a new Google Form into any web page. To demonstrate ths, a chart and form that allow blog readers to control the recording levels of each instrument in Blue Oyster Cult's "(Don't Fear) The Reaper" is used. HTML code from the Google version of the form included on this page is shown and the parts that need to be modified are highlighted. Next, the why : Google recently released an e-mail form feature that allows users of Google Documents to create an e-mail a form that automatically places each user's input into an associated spreadsheet. As it turns out, with a little bit of work, the forms that are created by Google Docs can be embedded into any web page. Now, The Goods: Click on the instrument you want turned up, click the submit button and then refresh the page. Through the magic of Google Forms as soon as you click on submit and refresh this web page, the data chart will update immediately. Turn up the:...

Copasetic Flow

Search This Blog