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B Solar System Moving Speed

  1. Aug 8, 2018 #1
    Hello Dear Ones.

    1. How Scientists exactly calculated movement speed of solar system ?

    thank you very much.
     
  2. jcsd
  3. Aug 8, 2018 #2

    berkeman

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    Movement with respect to what?
     
  4. Aug 8, 2018 #3

    berkeman

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  5. Aug 8, 2018 #4
    -Speed of Sun Around Milky Way 230km/s. - This One.
     
  6. Aug 8, 2018 #5
    or better - sun default movment speed.
     
  7. Aug 8, 2018 #6

    phinds

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    That does not appear to be a meaningful phrase. What do you have in mind? Do you understand that all motion is relative and that it is meaningless to say speed unless you say relative to what?
     
  8. Aug 8, 2018 #7
    The speed of the Sun around the Milky Way is around 250 kilometers per second. See Bland-Hawthorn and Gerhard (2016). Most of this speed is due to the Milky Way's rotation velocity, which is around 238 kilometers per second in the solar neighborhood. However, the Sun's orbit is slightly elliptical and we are currently closer to the Galactic center than usual, so we are moving about 12 kilometers per second faster than the Galaxy's orbital speed. 238 + 12 = 250.

    This speed is much less than the speed of the Local Group of galaxies through the universe. As discussed in the October 2018 issue of Sky & Telescope, that is about 630 kilometers per second. It arises from galaxy clusters that try to pull us their way as well as voids that try to push us away.
     
  9. Aug 8, 2018 #8

    Bandersnatch

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    There are various methods, but usually it involves measuring radial velocity to some object or objects using a spectrometer. The Doppler shift of some reference spectral lines in the light of the observed object reveals its relative velocity along the line of sight.
    The problem with using single-object radial velocities as a proxy for solar orbital velocity is that one has to find something that can be reasonably treated as at rest w/r to the centre of the Milky Way, which is difficult.
    But one can instead measure velocities of a large ensemble of objects, and use clever statistics to disentangle orbital velocity from the data.
    Below is one such clever paper, published recently:
    DETECTION OF A DEARTH OF STARS WITH ZERO ANGULAR MOMENTUM IN THE SOLAR NEIGHBORHOOD, Hunt et al.
    It uses both radial and tangential velocities (provided by spectrometry and parallaxes respectively) to look at the distribution of velocities of neighbouring stars. There's a dip in the expected distribution, which can be attributed to scattering of low angular velocity stars by gravitational interactions in the galactic nucleus. The interactions fling some of these stars away to the galactic halo, removing them from the distribution. This dip provides a reference frame for being at rest w/r to the galactic centre. The relative velocity of such stars w/r to the Sun is then the negative of orbital velocity.

    One can follow the references discussed in the introduction section of the linked publication to find other papers, using different methods, which all converge around the same value for orbital velocity.
     
  10. Aug 8, 2018 #9

    phinds

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    RELATIVE TO THE CMB ! You really should state that since this thread is at a beginner level.
     
  11. Aug 8, 2018 #10

    Chronos

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    Technically speaking, that would be 'relative to the CMB rest frame', would it not?
     
  12. Aug 8, 2018 #11
    I think this measurement is absolutetly wrong, due lack of understading of simplicity of human mind. What is default speed ? Lets be simple in thoughts. sun is moving, no doubt. we can reduce this movement to the simple movement of object trough infinite space, imagine as dot moving trough black space. so if its moving it has its own energy, and ITS OWN SPEED , it doesnt matter how is relative with other cosmical objects are, it moves, it has is OWN speed. We looking for is true speed, not relative speed. So if you imagine this movement as dot in black infinite space and you will put other immovable object in front of movement trajectory, after collosion sun as dot to for example to wall, will transform kinetical energy to another kind of energy and there`s no doubt that WILL HAVE precisely measurment of units, of speed, energy. etc. This measurment is wrong , because is relative. not true. We dont measure what speed of object is relation to other object, because it will give wrong result, we looking for speed of object in subject, as sun in space, its own.
     
  13. Aug 8, 2018 #12

    phinds

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    Yes, you are correct.
     
  14. Aug 8, 2018 #13

    phinds

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    This is complete and total nonsense. You really need to come to grips with the fact that all motion is relative. There IS no absolute speed as you think there is. You are arguing against science that was established LONG ago.
     
  15. Aug 8, 2018 #14
    Please read my statments very carefuly. I SAID THAT we dont look for relative speed, we looking for its true speed. relative speed is just comparison of two movement speed of objects. WE measure object speed in SPACE. You can transform movement speed to termodynamical energy, and it gonna gave its own units. if you cannot feel space, its your own psychological problem
     
  16. Aug 8, 2018 #15

    phinds

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    Again. Total nonsense. There IS NO "true speed". ALL speed is relative. Space is just geometry. There is nothing to "feel"

    @shimun a standard law is this: when you find yourself in a hole, stop digging. I suggest you do some reading in the basics of physics/cosmology before you go any further.

    This forum is here to help people overcome misconceptions such as exactly the one that you have but we don't have infinite patience and if you persist in your incorrect statement that there is an absolute speed, this thread will likely be shut down since it is pointless to argue with such statements. You would be much better off accepting that you are wrong and trying to figure out why.
     
  17. Aug 8, 2018 #16

    jim mcnamara

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    @shimun - We are here to help. But it requires that you get the concept that you are misinformed, and your original question was flat wrong by accepted standards.
    You need to understand the concept of a frame of reference:
    https://en.wikipedia.org/wiki/Frame_of_reference

    Several very nice graphics in that article.
     
  18. Aug 8, 2018 #17

    russ_watters

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    Since you won't listen to @phinds, I'll repeat: there is no such thing as "true speed".
     
  19. Aug 8, 2018 #18

    Dale

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    As others said, there is no absolute speed. If you transform movement speed to heat then all you have done is measure the original speed relative to the frame where the object came to rest. The math works out the same regardless of which frame that is. So it does not provide any additional information.
     
  20. Aug 9, 2018 #19
    @shimun maybe you can start here, in order to get correct understanding of what is relative motion, and why there is nothing like "true" (or absolute) speed
     
  21. Aug 9, 2018 #20

    Chronos

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    All speed is coordinate dependent, like every fraction has a denominator. Without a coordinate system [reference frame] the very concept of speed lacks any meaning.
     
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