1
$\begingroup$

Ok, so I read this question and it got me thinking about something. Is there anything genuinely stationary in our universe? What does it mean to be stationary or devoid of any motion? If there isn't anything stationary, can there be a time when a thing is stationary and devoid of any motion in the future? Is a reference point always needed to classify a particular thing as stationary? I may be sitting right now, not making the slightest movement, but that does not mean I am not in motion. I am in motion, in reference to the earth, the solar system and the milky way galaxy

Also, what would happen if, say, a "stationary" object was present in our universe? What would be the conditions required for this anomaly?

P.S. I have taken a look at this question too, but it doesn't completely answer the particular question I am asking, hence this question

$\endgroup$
6
  • 2
    $\begingroup$ If you think the answer that there is no absolute frame of reference doesn't answer your question, read it again :). $\endgroup$ Mar 1, 2023 at 4:18
  • $\begingroup$ @ConnorBehan Well, it doesn't answer the "whole" question... $\endgroup$ Mar 1, 2023 at 4:22
  • 1
    $\begingroup$ On this site , there should not be too many questions in one. They should be individually submitted. $\endgroup$
    – anna v
    Mar 1, 2023 at 5:18
  • 4
    $\begingroup$ If there was something you considered “stationary”, all you’d have to do is bicycle past it and it wouldn’t be stationary any longer, relative to you. $\endgroup$
    – Ghoster
    Mar 1, 2023 at 5:31
  • $\begingroup$ @Ghoster gotta love intergalactic cycling :) $\endgroup$
    – peek-a-boo
    Mar 1, 2023 at 10:04

4 Answers 4

2
$\begingroup$

The laws of physics do not allow us to distinguish who in a pair is moving and who is stationary. As such, the question of whether or not there is anything in our world that is truly stationary is meaningless, because we have no way at all of determining whether anything in our world is stationary to begin with.

$\endgroup$
2
$\begingroup$

Your question is like asking whether there is a particular point that is the centre of the surface of the Earth. The answer is that the surface of a sphere has no unique centre, so it is meaningless to speculate about where it might be. At any point on its surface, you can consider yourself to be centred on a sphere in the sense that the surface is spread around you equally in all directions. But all points on the surface are the same in that sense- none of them is the absolute centre. Likewise, there is no frame of reference in the universe that is absolutely stationary.

$\endgroup$
1
$\begingroup$

As far as is understood, there is not absolute sense of "stationary" so the question you link is not even really well defined. All that could be asked is "do the galaxies move relative to each other"? They do, and one day Andromeda and the Milky Way will merge into one galaxy. But the laws of physics allow any inertial reference frame to view itself as "stationary." This is, roughly, the principle of relativity.

For the second part then, there is no way to define a "stationary" object in any absolute sense. Nothing would "happen" as you could call one object stationary and someone else could disagree that another one was.

$\endgroup$
1
$\begingroup$

The word "stationary" in the modern (post-Newton) physics requires a reference frame: Object A is stationary relative to e.g. a non-rotating frame attached to the center of mass of the object B.

The laws of physics themselves don't distinguish between the reference frames, they are all made equal. Well, some frames are easier to deal with than other, but this is subjective.

On the other hand, one can build a hierarchy of frames by some criteria, e.g. the mass of the object the frame is attached to.

Using the mass of the object, one can go as high as "the majority of the mass of the (practically) observable universe".

While we can't simply calculate this frame of reference, there is a very good (until proven otherwise) proxy: the cosmic microwave background anisotropy.

And using the frame of the cosmic microwave background, we can derive that the Solar system moves with like 370km/s relative to it.

If we improve the accuracy of this number (by some advance in physics or astronomy) and then launch an object with exactly this speed in the opposite direction, chances are that the object (at least for a while) will be quite stationary in regard to the observable universe.

Not "completely devoid of motion", but still a very good start.

$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.