Is the Universe's center of mass truly at rest?

[channeled intuition]

Proposition: at any given time, zero velocity for an object is attained by unknown acceleration in a universal unknown direction. Gravitational effects on that trajectory must be canceled out. As a generalist, my physics are basic at best, but where is the error in this idea?

 

[berkeman]

Proposition: at any given time, zero velocity for an object is attained by unknown acceleration in a universal unknown direction. Gravitational effects on that trajectory must be canceled out. As a generalist, my physics are basic at best, but where is the error in this idea?

Welcome to the PF.

What's a "universal unknown direction"? And what's a universal direction...?

 

[Dale]

at any given time, zero velocity for an object is attained by unknown acceleration in a universal unknown direction

At any given time, zero velocity for an object is attained by using its rest frame.

 

[channeled intuition]

universal direction=a direction pointing to the same location for every object in the universe.

 

[berkeman]

universal direction=a direction pointing to the same location for every object in the universe.

No such thing. There are lots of threads here on the PF about reference frames (there are no absolute frames of reference). I'll see if we have a FAQ that covers this for you...

 

[berkeman]

Here is a Google search of the PF website about absolute frames of reference. Happy reading! Let us know if you have any specific questions about your reading at the links:

https://www.google.com/search?q=absolute+frames+of+reference+site:physicsforums.com&oq=absolute+frames+of+reference+site:physicsforums.com&gs_l=psy-ab.3...23165.31971.0.32111.31.25.1.0.0.0.622.4239.2-2j3j5j1.11.0...0...1.1.64.psy-ab..20.3.1049...0i22i30k1j33i160k1.0.zxB213HZ50I

 

[channeled intuition]

50,388 / 2,450
Staff: Mentor No such thing. There are lots of threads here on the PF about reference frames (there are no absolute frames of reference).
New

so every telescope, in a conjectured universe telescopes on every galaxy, couldn't all point to the same quasar?

 

[russ_watters]

so every telescope, in a conjectured universe telescopes on every galaxy, couldn't all point to the same quasar?

Sure, but they wouldn't be pointing in the same direction nor would there be anything "universal" about that. I'm not really sure what you are trying to say with your "proposition". It doesn't make a lot of sense but implies something known to be false (the existence of a universal rest frame).

 

[Dale]

so every telescope, in a conjectured universe telescopes on every galaxy, couldn't all point to the same quasar?

Suppose two distant telescopes are pointed at the same quasar. If you take a gyroscope, align it's axis with the quasar at one telescope, and transport the gyroscope to the other telescope, then you will find that it does not align with the quasar.

Furthermore, there is no detectable anisotropy in the laws of physics.

 

[kuruman]

Here is a Google search of the PF website about absolute frames of reference. Happy reading!

The last time I discussed absolute frames of reference was many years ago with a couple of fellow physics graduate students. We came up with the brilliant idea that the center of mass of the Universe must be at absolute rest. Proof: If it moved, where would it go? Needless to say we were under the influence.