Re: Spaceship Question

Henri Wilson wrote:
On Tue, 14 Feb 2006 21:25:24 +0100, "Paul B. Andersen"
<paul.b.andersen@xxxxxxxxxxxxxxxx> wrote:


Henri Wilson wrote:

On Mon, 13 Feb 2006 23:17:49 +0100, "Paul B. Andersen"
<paul.b.andersen@xxxxxxxxxxxxxxxx> wrote:



Henri Wilson wrote:


On Sat, 11 Feb 2006 16:19:02 +0100, "Paul B. Andersen"
<paul.b.andersen@xxxxxxxxxxxxxxxx> wrote:



Yes Paul. You are slowly getting the idea.

Neither the rod nor the tape physically changes with movement. You assured me
that SR agrees with this.




So how do you propose to measure the length of a _moving_ rod, Henri?

Care to try again?
Think practical, Henri.
If you should measure the length of a train passing
by you at 200 km/h (but you don't know the exact speed),
how would you do it?


The easiest way would be to hop on board and pull out your tape again.

A more difficult way would be to place a line of detectors and W-synched clocks
along the track at known spacing and monitor the passage of the train's front
and back ends.

Sorry.
I read too fast and didn't notice this last statement.
Yes, Henri.
That's the way do do it. So you do know.
Now the question is:
Will this yield the same result as the tape method?
How do you know?


You know it should because you and all SRians agree that nothing actually
happens to the train's length when it moves.

In October 2003, I wrote:
| Henry is unable to grasp the distinction between
| the following two statements:
| 1. The observer's state of motion cannot affect the observed
| object in any way.
| 2. The observer's state of motion can affect the observer's
| measurements of the object.
|
| So when someone say that a frame dependent entity
| is frame dependent, Henry insists that the someone has said
| that an intrinsic property of the object is frame dependent.
|
| This is a claim he has repeated over and over in
| different versions for years.
|
| And will continue to claim.

QED
Again.

If the experiments DO happen to yield different answers, you will obviously
have to refine your techniques, particularly that of the latter one.

So the measurement made with my stationary instruments
must be wrong?
Why do you claim that?
Do you claim that something happened to my instruments because
the rod is moving?

Paul
.

Relevant Pages

  • Re: Spaceship Question
    ... Henri Wilson wrote: ... I can obviously not run after it with my tape. ... If you change reference frames so that the rod is now at rest ... NO.....light path of length of a rod is frame-dependent. ...
    (sci.physics.relativity)
  • Re: Spaceship Question
    ... Henri Wilson wrote: ... I can obviously not run after it with my tape. ... If you change reference frames so that the rod is now at rest ... in your rest frame, we do not call that a "moving rod". ...
    (sci.physics.relativity)
  • Re: Spaceship Question
    ... Henri Wilson wrote: ... You can be quite confident that your tape hasn't changed in any way. ... If I am to measure the length of a _moving_ rod, ... you hook one end of your tape onto one end of hte rod then ...
    (sci.physics.relativity)
  • Re: Spaceship Question
    ... Henri Wilson wrote: ... You can be quite confident that your tape hasn't changed in any way. ... If I am to measure the length of a _moving_ rod, ... you hook one end of your tape onto one end of hte rod then ...
    (sci.physics.relativity)
  • Re: Spaceship Question
    ... I can obviously not run after it with my tape. ... If you change reference frames so that the rod is now at rest ... in your rest frame, we do not call that a "moving rod". ...
    (sci.physics.relativity)