About two years ago I posted a question about a symmetrical twin paradox: Here.

Recently a new answer was posted and an intense discussion ensued: Here.

One of the points discussed concerns a preferred reference frame in this universe:

The asymmetry comes from the fact that the universe itself has a reference frame, and its size will lorentz contract. This is measurable by the people themselves--all that needs to happen is to send out a light ray and wait for the light ray to go around the world. The 'diameter of the universe' will be (light orbit time)/c. This time will be observed to be smaller the faster the observer is travelling. So all observers will agree that there is a global, absolute notion of motion, and this will pick out who ages when.

My questions

• Which (mathematical) characteristics determine whether there is a preferred reference frame in a universe?
• Does our universe have a preferred reference frame?
• If a universe has a preferred reference frame is this comparable with the old aether?
• If a universe has a preferred reference frame don't we get all the problems back that seemed to be solved by RT (e.g. the 'speed limit' for light because if there were a preferred frame you should be allowed to classically add velocities and therefore also get speeds bigger than c?

About two years ago I posted a question about a symmetrical twin paradox: Here.

Recently a new answer was posted and an intense discussion ensued: Here.

One of the points discussed concerns a preferred reference frame in this universe:

The asymmetry comes from the fact that the universe itself has a reference frame, and its size will lorentz contract. This is measurable by the people themselves--all that needs to happen is to send out a light ray and wait for the light ray to go around the world. The 'diameter of the universe' will be (light orbit time)/c. This time will be observed to be smaller the faster the observer is travelling. So all observers will agree that there is a global, absolute notion of motion, and this will pick out who ages when.

My questions

• Which (mathematical) characteristics determine whether there is a preferred reference frame in a universe?
• Does our universe have a preferred reference frame?
• If a universe has a preferred reference frame is this comparable with the old aether?
• If a universe has a preferred reference frame don't we get all the problems back that seemed to be solved by RT (e.g. the 'speed limit' for light because if there were a preferred frame you should be allowed to classically add velocities and therefore also get speeds bigger than c?

About two years ago I posted a question about a symmetrical twin paradox: Here.

Recently a new answer was posted and an intense discussion ensued: Here.

One of the points discussed concerns a preferred reference frame in this universe:

The asymmetry comes from the fact that the universe itself has a reference frame, and its size will lorentz contract. This is measurable by the people themselves--all that needs to happen is to send out a light ray and wait for the light ray to go around the world. The 'diameter of the universe' will be (light orbit time)/c. This time will be observed to be smaller the faster the observer is travelling. So all observers will agree that there is a global, absolute notion of motion, and this will pick out who ages when.

My questions

• Which (mathematical) characteristics determine whether there is a preferred reference frame in a universe?
• Does our universe have a preferred reference frame?
• If a universe has a preferred reference frame is this comparable with the old aether?
• If a universe has a preferred reference frame don't we get all the problems back that seemed to be solved by RT (e.g. the 'speed limit' for light because if there were a preferred frame you should be allowed to classically add velocities and therefore also get speeds bigger than c?

About two years ago I posted a question about a symmetrical twin paradox: Here.

Recently a new answer was posted and an intense discussion ensued: Here.

One of the points discussed concerns a preferred reference frame in this universe:

The asymmetry comes from the fact that the universe itself has a reference frame, and its size will lorentz contract. This is measurable by the people themselves--all that needs to happen is to send out a light ray and wait for the light ray to go around the world. The 'diameter of the universe' will be (light orbit time)/c. This time will be observed to be smaller the faster the observer is travelling. So all observers will agree that there is a global, absolute notion of motion, and this will pick out who ages when.

My questions

• Which (mathematical) characteristics determine whether there is a preferred reference frame in a universe?
• Does our universe have a preferred reference frame?
• If a universe has a preferred reference frame is this comparable with the old aether?
• If a universe has a preferred reference frame don't we get all the problems back that seemed to be solved by RT (e.g. the 'speed limit' for light because if there were a preferred frame you should be allowed to classically add velocities and therefore also get speeds bigger than c?