Saturday, March 22, 2014

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

3.  On rotation and rotating frames: Franklin transformation and its modiļ¬cation

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

5.  Physics Festival

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