Does the Milky Way move through space?

  • Does our galaxy moves through space? Or does it stay in a single location? If it does move, what causes it to move?


    Check out the articles about Galaxy Clusters and the Great Attractor, they may be of interest to you.

    Only if you want to use something besides our galaxy's origin as your frame of reference. You could structure any maths to accurately describe our galaxy as the ONLY stationary one. It just isn't very modest to do so.

    "Through space" is not a thing. Space doesn't have locations. Motion is always relative to something else, like another galaxy, or the Cosmic Microwave Background, or whatever. You've already received some answers for the relative motion, see below.

    It's hard to think about something that has locations. Very interesting to think about. Thanks!

    I have a term that you might be interested in to Google: laniakea

    In Soviet Union, space moves through Milky Way!

    @el.pescado and in several other reference frames :-)

    @PlasmaHH - I looked up laniakea and came across an amazing Youtube video. Very very interesting, thank you mentioning it. You know, deep thinking about the universe, Milky Way, and other universes I wonder if we will be able to see the end or edge of space. I understand space most likely has no end, but crazy to think what things would look like if you could have an outside view of the over-all peak of what all this is.

    I think it's worth mentioning that not only does it "move", but it'll also collide with the Andromeda galaxy (our neighbor).

    I would advise a tall glass of skepticism when watching videos on YouTube. A good portion (though certainly not all) of them will be... inaccurate.

    It sounds like you have just embarked on your journey to understanding the cosmos. There is a lot of high quality, easily accessible material to help you learn, no matter how little you know. Three good things that jump to mind are Stephen Hawking's book "A Brief History of Time", Brian Greene's book/videos "The Fabric of the Cosmos" and Neil deGrasse Tyson's reboot of the "Cosmos" series (available on Netflix!). Really, that's just the tip. Plenty of videos have been made by Nova/PBS, BBC, National Geographic, Discovery, Science Channel, etc. Numerous books, suitable for laymen, also exist.

    the answer is "Very much so ...."


  • Does the Milky Way move through space?




    Yes it does.




    I'm very fascinated with space, although I don't have a degree or any formal education, I'm still very in love with everything about it and want to learn constantly.




    Good man Mike.




    One thing I ask myself is if our galaxy moves through space?




    It does. When we look at the Cosmic Microwave Background Radiation we see a "dipole anisotropy" due to the motion of the Earth relative to it:



    enter image description here



    Image courtesy of William H. Kinney's Cosmology, inflation, and the physics of nothing



    See Wikipedia for more:



    "From the CMB data it is seen that the Local Group (the galaxy group that includes the Milky Way galaxy) appears to be moving at 627±22 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 276°±3°, b = 30°±3°.[82][83] This motion results in an anisotropy of the data (CMB appearing slightly warmer in the direction of movement than in the opposite direction).[84]"



    627 km/s is quite fast. See this article, which says it's 1.3 million miles an hour. The speed of light is just under 300,000 km/s or 670 million miles per hour, so the Milky Way is moving through the Universe at circa 0.2% of the speed of light. Also see the CMBR physics answer by ghoppe which talks about the CMBR reference frame, which is in effect the reference frame of the universe.




    Or does it stay in a single location? If it does move, what causes it to move?




    I'm afraid I don't know why it's moving. Perhaps it's because the Universe is full of things moving in fairly random directions. Like a gas.




    Hopefully the question makes sense, if not I can elaborate.




    It certainly makes sense to me!



    Edit 13/09/2017 : as Dave points out in the comments, there are other motions, including the motion of the solar system around the galaxy, which is circa 514,000 mph. (See the Wikipedia Galactic Year article). And the motion of galaxies isn't neat and tidy either.


    Awesome response! There's a ton for me to look-up and read about. I really appreciate your time/explanation.

    My pleasure Mike. I try!

    "Why is it moving?" It would be an incredible coincidence if it were perfectly still. There are uncountable numbers of objects in the universe exerting gravitational attractions in different directions. They would have to exactly balance out the for the galaxy not to move.

    @Barmar : good point. Why didn't I think to say that? Duh!

    Well, at least everything *continues* to move (how it all started to is still up for debate I suppose ;) because stuff is still hot. When everything gets cold, absolutely nothing will move anymore.... supposedly: heat death of the universe. To put it simply as I understand it, eventually once all the atoms in the universe equalize in temperature, no work can be done anymore because there will be no potential energy left anywhere to do any work. Or something like that.

    "there exists the view that the mechanical movement of the universe will run down, as work is converted to heat, in time because of the second law [of thermodynamics]."

    @Barmar: From "A brief history of time" : `Newton realized that, according to his theory of gravity, the stars should attract each other, so it seemed they could not remain essentially motionless. Would they not all fall together at some point?` and `We now know it is impossible to have an infinite static model of the universe in which gravity is always attractive.`

    I think this answer is confusing, because the graphic shows motion of the solar system, rather than motion of the galaxy, and the solar system moves relative to the center of mass of the galaxy. Then the answer discusses the motion of the local group, but the Milky Way moves relative to the center of mass of the local group. See the article http://iopscience.iop.org/article/10.1086/527428/meta especially the caption of Fig. 3, for more information.

    @DavePfD : noted Dave. I've edited my answer to include something on that.

    _"627 km/s is quite fast. See this article, which says it's 1.3 million miles an hour."_ One might think that in Physics.SE, it would be sort of assumed that the reader knows how to convert km/s to miles/hour. Especially when 627 m/s is 1.4 mi/h, not 1.3, so the article probably uses other data.

    @Barmar Given the amount of advanced mathematics used in the study of physics, and the fact that the word "uncountable" has a specific mathematical meaning that almost certainly doesn't apply in this case, it might make sense to clarify whether you are asserting that the set of objects (planets, stars, motes of dust etc.) acting on the influence of gravity in the universe has equal cardinality with the set of real numbers or not.

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Content dated before 7/24/2021 11:53 AM