"Bill Hobba" wrote in message
...
| FrediFizzx wrote:
| I like the way Griffiths described an inertial frame in "Introduction to
| Electrodynamics".
|
| "To avoid this trap we define an inertial frame formally as one in which
| Newton's first law holds. If you want to know whether you're in an
| inertial
| frame, throw some rocks around---if they travel in straight lines at
| constant speed, you've got yourself an inertial frame, and any frame
| moving
| at constant velocity with respect to you will be another inertial
frame."
|
| I don't see that it has to be any more complicated than this.
|
|
| I like Landaus definition - it is a frame is which space and time are
| homogeneous and space is isotropic. It is equivalent to the one above via
| the POR (nice little exercise to show this). Problems come when you look
at
| it really closely. First you must specify a coordinate system.
Physically
| how do you do this - via rigid rods (SR later shows they do not exist) or
| exactly how? Secondly how do we synchronize clocks so we have a universal
| time? Using OWLS? Then the speed of light is constant by definition.
Take
| two clocks at the same point then sync them and slowly move them apart?
Are
| you sure they will then stay synced? Via two way light speed? Only if
your
| really sure of the isotropy property. Which then begs the question how do
| you show a frame of reference is homogeneous and isotropic? Although I am
| no expert he it just seems like a total mine field to me that I just hope
| someone has sorted out.
|
| My solution is you accept these things as extra axioms ie you can
construct
| from stationary rods that are rigid in the classical domain Cartesian
| coordinates (guaranteed by Euclidian geometry which you assume valid for
| stationary or slow moving lines and points). You also assume you
| conceptually have a synced set of stationary clocks at all points. But
| physically it still seems a problem.


OK, I get it. It is a physical measurement problem. How do we go out and
actually measure to see if the thrown rocks do go straight and at a uniform
velocity. Yes, it seems you need to start from Cartesian coordinates and
Euclidian geometry to validate it. Once you are in it, tough to validate.
Hmmm.

FrediFizzx

The answer comes to you shortly after you give up hope of finding it.