<p>Could someone give the rough estimates of speeds of our travel through space?</p>

<p>I can easily find the two nearby ones:</p>

<ul>
<li>Earth's own rotation - depending on latitude, up to 40,075 km/24h = 463 m/s</li>
<li>Earth's orbital speed around the Sun - 940 000 000 km/year = 29,786 m/s</li>
</ul>

<p>Now how do these fare?</p>

<ul>
<li>Motion of Sun within the arm of the galaxy, around the center of the galaxy?</li>
<li>Motion of the galaxy within the local supercluster?</li>
<li>(if possible to measure at all) movement of the supercluster within the universe?</li>
</ul>

CC BY-SA 4.0
2019-02-15T22:39:48.357Z
@Manishearth: Pseudo-special frame of reference bound to CMB (one where red shift of CMB in all directions the same) is good enough. And you can measure the average in reference to any reasonably isolated body (a star outside a supercluster) then establish the "rest frame" as moving at that velocity relative to the one the measurement was made in and find velocities of superclusters in that frame.
SF.
CC BY-SA 3.0
2013-09-27T11:25:47.300Z
The last item is, I think, meaningless as the expansion of space is just that - an expansion, so the galaxy isn't "moving" in the traditional sense of the word.
ChrisF
CC BY-SA 3.0
2013-09-27T11:28:50.357Z
@ChrisF: Are you sure *on top of space expansion* there is no plain, old-fashioned *movement* happening, completely independently?
SF.
CC BY-SA 3.0
2013-09-27T11:30:00.790Z
No, I'm not 100% sure. Which is why I used the term "I think".
ChrisF
CC BY-SA 3.0
2013-09-27T19:28:06.677Z
The last item is meaningless because "within the universe" is not a reference frame. We can only talk about velocity when we have something to measure velocity relative to. The "universe" doesn't fit the bill for this.
Manishearth
CC BY-SA 3.0
2013-09-28T22:26:05.310Z
@Manishearth: We can create some virtual reference frame by averaging motions of all objects within universe relative to each other. Take three randomly moving objects: their reference frame will be one relative to which the sum of their vectors of speed is smallest. While it doesn't say anything about speed "relative to the universe" ("ether"), it's still a good clue "how fast given object is moving" (comparing to all the rest).
SF.
CC BY-SA 3.0
2013-09-29T06:05:59.820Z
@SF. Nope. "averaging the motions of all objects within the universe" is _another_ meaningless term, because you need to measure _that_ with respect to some reference frame. And given that most celestial reference frames are noninertial, linearity goes out the window and your answer changes on the basis of that.
Manishearth
<galaxy><movement>
How fast do we travel through space?
SF.
# How fast do we travel through space?

(Asked by: username_0 on 2013-09-27)

Could someone give the rough estimates of speeds of our travel through space?

I can easily find the two nearby ones:

* Earth's own rotation - depending on latitude, up to 40,075 km/24h = 463 m/s
* Earth's orbital speed around the Sun - 940 000 000 km/year = 29,786 m/s

Now how do these fare?

* Motion of Sun within the arm of the galaxy, around the center of the galaxy?
* Motion of the galaxy within the local supercluster?
* (if possible to measure at all) movement of the supercluster within the universe?

**Tags:** galaxy, movement

> **Comments:**
> **username_1**: The last item is, I think, meaningless as the expansion of space is just that - an expansion, so the galaxy isn't "moving" in the traditional sense of the word.  
> **username_0**: @username_1: Are you sure *on top of space expansion* there is no plain, old-fashioned *movement* happening, completely independently?  
> **username_1**: No, I'm not 100% sure. Which is why I used the term "I think".  
> **username_2**: The last item is meaningless because "within the universe" is not a reference frame. We can only talk about velocity when we have something to measure velocity relative to. The "universe" doesn't fit the bill for this.  
> **username_0**: @username_2: We can create some virtual reference frame by averaging motions of all objects within universe relative to each other. Take three randomly moving objects: their reference frame will be one relative to which the sum of their vectors of speed is smallest. While it doesn't say anything about speed "relative to the universe" ("ether"), it's still a good clue "how fast given object is moving" (comparing to all the rest).  
> **username_2**: @username_0 Nope. "averaging the motions of all objects within the universe" is _another_ meaningless term, because you need to measure _that_ with respect to some reference frame. And given that most celestial reference frames are noninertial, linearity goes out the window and your answer changes on the basis of that.  
> **username_0**: @username_2: Pseudo-special frame of reference bound to CMB (one where red shift of CMB in all directions the same) is good enough. And you can measure the average in reference to any reasonably isolated body (a star outside a supercluster) then establish the "rest frame" as moving at that velocity relative to the one the measurement was made in and find velocities of superclusters in that frame.  

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