Relativity Principle

[ajb]

It is the inability to derive consistent/accurate (physical laws) from an objective frame of reference, as no such state exists. Einsteinian Relativity is the precursor to the Uncertainty Principle (you get to UP via RP). Einstein jumped off the bus but wasn't able to refute Heisenberg....and he tried. The implications of Relativity, such as the Principle of Uncertainty, and consequently QED is hard to take in a single lifetime. We know it to be accurate due to our good fortune of being told so and having it demonstrated throughout our lifetimes.

 

Ok, as Sisyphus this is not usually what people mean when they speak of the uncertainty principle.

 

What special relativity says is that there are no preferred inertial frames of reference. In that sense they are all equivalent.

 

The trouble arises when we try to insist on the separation of space and time. Doing to means that many things you take for granted in classical mechanics that are invariant under Galilean transformations are not invariant under Lorentz transformations. By thinking "4-d" the troubles go away. For example, for any relativistic classical point particle the mass-shell condition holds "P² = m²" which is Lorentz invariant. All inertial observers agree on this, though they will in general disagree on the energy and momentum.

 

An other example is the space-time interval. The "twin paradox" comes from the simple fact that all inertial observers will agree on the length of a path in "4-d", though separately they will disagree on the time interval and spacial length.

 

So, I put it to you that all "paradoxes" and "inconsistencies" in special relativity are due to trying to hold onto "3-d" space + "1-d" time.

 

General relativity is a bit more confusing as we cannot apply our geometric understanding of flat space to interpret things in general.

[between3and26characterslon]

The relativity principle is Galelean not Einsteinian, it applies to Galelean frames of referrence. That is frames which have uniform rectilinear translation relative to each other, the frame you are in is stationary as far as you are concerned and all others are moving but this is true for all frames and that makes observations objective.