Caption: Pole Vault.

Does this pole vaulter feel his FitzGerald contraction during his approach?

Explanation of the FitzGerald contraction:

1. What we mean by length---a spatial separation measured at once instant in time---means that length is reference frame dependent if simultaneity is---which it is by the time dilation effect (time flow rate variation effect) of special relativity.

2. The length dependence on reference frame is called the FitzGerald contraction after its sort-of discoverer Irish physicist George Francis FitzGerald (1851--1901). FitzGerald is only a sort-of discoverer because though he had the idea of a contraction in the direction of motion and the FitzGerald contraction formula, he did NOT have a consistent theory of all related effects---the consistent theory is, of course, special relativity itself (see Wikipedia: George Francis FitzGerald: Length contraction).

3. The length of an object in its own rest frame is its proper length.

   Proper length is an intrinsic property of an object unlike length in general that depends both on proper length and reference frame of length measurement.

4. The formula for the FitzGerald contraction is

   L = L_0*sqrt[1 - (v/c)**2] ,

   where L is measured length along the direction of motion, L_0 is proper length, and v is the velocity of motion.

   If v = 0, L = L_0. If v = c, L = 0.

5. To illustrate the FitzGerald contraction, say a pole vaulter runs along with his/her pole level and passes through a shed open at both ends.

   The pole's proper length is greater than the length of the shed.

   But the pole vaulter runs very fast and in a ground-frame observer's observation the pole is contracted to be less than the shed proper length and the whole pole is inside the shed for some time interval.

   The pole vaulter's frame perspective is that the shed was contracted.

   Yes, the ends of the pole were inside the shed, but NOT at the same time in his/her reference frame.

6. Yours truly does NOT think that FitzGerald contraction has ever been verified for a macroscopic-scale object in the lab. No one ever mentions such a verification. It seems a very hard thing to do.

   However, many results depend on the FitzGerald contraction, and so it has been indirectly verified endlessly.

   Also it's a basic result of special relativity, and so all of special relativity depends on it.