# Can inertial reference frame ever have lenght contraction in all 3 space dimensions

1. Dec 19, 2012

### smm

can inertial reference frame ever have "lenght contractions" in 3d or in rest?

hi!
thank you for all answers in this topic in previous threatin same topic. i open this new
thread in same topic but here i try to keep the issue here very short and readable , with no speculation and concentrating to the question.

the question is about length contractions:

relativistic inertial reference frame in special relativity can have relative
properties like slower time and lorenz contraction. also particle in that reference
frame has more relative momentum and more relative energy than particle at rest.
these properties are always connected to the relative velocity of the reference frame
in special relativity, and once the frame or particle decelerate to relative rest, these
properties disappears and the particle becomes "normal".

but can such inertial reference frame or a object ever exist even in theory that has length contraction in all 3 space dimensions at the same time?

secondly can inertial reference frame have lenghth contractions when it is in rest

can there be length expansions?

i know a bit about relativity theories but i havent ever heard anyone talking about such things.

Last edited: Dec 19, 2012
2. Dec 19, 2012

### ghwellsjr

Re: can inertial reference frame ever have "lenght contraction" in all 3 space dimens

You shouldn't think of the Inertial Reference Frame (IRF) as having a slower time or length contraction. It's just an arbitrary coordinate system that allows you to specify locations of objects as a function of time. All the objects that you want to consider in any scenario are described in reference to that one IRF. None of them owns the IRF.
No, these properties are always connected to the speed of each object in the IRF. Once you define a scenario according to one IRF, you can transform the coordinates of all the significant events into another IRF moving with some speed relative to the first IRF and the objects can now have different speeds and different properties related to speed.
Whatever the instantaneous speed of a particle or object is, that determines its speed-related properties, so if its speed goes to zero in the IRF, then its speed-related properties become "normal". Or, like I said, you can convert all the coordinates of all the events in one IRF to another one such that a particle that was moving in the first IRF is stationary in the second IRF and its speed-related properties become "normal".
Certainly a particle or object can move in any direction so it can have a speed in any combination of the space dimensions and so be length contracted in all 3 dimensions. And there are ways to transform one IRF into another IRF moving in any combination of the space dimensions but the math is much more complicated than the standard configuration that only allows relative speed along the x axis.

Does this make sense to you?

3. Dec 19, 2012

### smm

are there more exotic forms of length contractions?

hi!
do you mean that you cant think that empty space already full of infinite or very high number of empty inertial reference frames that have zero energy or very little energy and that they are moving at any speed from zero to c to all directions and when particle accelerates, it kind a just selects another reference frame that was already there?
and that lorenz contraction and time dilation are properties of space, not properties
of particles?

i am here trying to open discussion of more exotic forms of length contractions than lorenz contraction if there are some hard facts or thoughts about them. i little widened the topic from previous thread. there must be, since relativity theory is over 100 years old.

what kinds of length contractions can exist?

(would the matter decay somehow if some exotic form of length contraction would suddenly pop up into existence and the matter is after that left alone under mercy of laws of nature?)

can there be for example length contraction in all 3 dimensions at the same time: for example a particle that has length contraction in all 3 dimensions such that its volume is L^3 times smaller?

4. Dec 19, 2012

### Vorde

Re: are there more exotic forms of length contractions?

I think the properties of space not particles is on track, but not quite there yet. Reference frames are just coordinates, like (x,y,z) Cartesian coordinates you learn about in algebra (although the coordinates in Relativity are more complicated). So an inertial reference frame (which all frames have to be in special relativity) is just a set of coordinates you pick where the origin is exactly where you are, and you aren't accelerating (so the coordinates are not accelerating).

The key here is that reference frames don't have energy, they are just coordinate systems used by observers who might have a lot of energy or velocity relative to something else. Your point about length contraction and time dilation being properties of space not of particles is very good though.

No. The reason is the following:

Length contraction only occurs in the direction of motion. And even though you can have an object zooming around in any shape in 3 dimensions (or any amount of dimensions in a hypothetical universe), the path the object is following will always be a curve.

I don't know how much math you know, but a curve is always one-dimensional. This means, that even though the direction which the length is being contracted in can change as the particle moves all over the place, it can only be contracted in one dimension at any one time.

5. Dec 19, 2012

### ghwellsjr

Re: can inertial reference frame ever have "lenght contractions" in 3d or in rest?

I took you at your word when you said:
But now I see that you aren't satisfied with the well-established Theory of Special Relativity and want to speculate on things that you know are deviations from it which means that you run a very high risk of getting yourself banned and so I don't want to devote any more of my time to an exercise that doesn't appear likely to be fruitful. Good luck.

6. Dec 20, 2012

### smm

Re: can inertial reference frame ever have "lenght contraction" in all 3 space dimens

hi! i am sorry about giving impression that i speculate over theories that are extremely well tested. everyone who is talking about science just have to be very humble to all scientific theories because they are extremely well tested in high precision in many kind of scientific experiments.

i thought the length contractions is meaningful topic - special relativitys length contraction is real physical phenomenon that is well tested and very well accepted phenomenon without any doubt.

it seems its shameful to me continue discussion before i learn more about this forum, because i have difficulties to write good threads and if i seem speculative and write carelessly its surely not good for the readers of forum and reputation of this forum. sorry

7. Dec 20, 2012

### Staff: Mentor

Re: can inertial reference frame ever have "lenght contractions" in 3d or in rest?

No. Length contraction is parallel to the boost, which only has one direction.

No.

Yes, but they would be non-inertial.