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Total velocity of resting object on earth from universal frame of refe

  1. Apr 2, 2013 #1
    I'm interested in calculating the total velocity of an object on earth from the farthest frame of reference (the observable universe). I apologize that I am not a physics or science major so please bare with me.

    I've posted on another google forum and was told a few different ideas.

    Initially I used normal vector addition to add the velocities of the rotation of the earth, the orbit around the sun, the movement of the sun in the galaxy, and then the movement of the galaxy in the universe. When I do that with the numbers I have I get:

    3 000 900 km/hr.

    I've tried adding the velocities using the formula linked to for special relativity
    u + v
    w = ---------
    1 + uv/c2

    and I got this:

    3000895.06594378 km/hr

    which is -4.93405622430146 km/hr difference than the normal vector addition I performed before to get: 3 000 900 km/hr.

    Does that sound right?

    Basically If a ball was rolling on a table at a certain velocity on earth, I would like to know the total velocity it is moving taking into account ALL of the cosmological motion it exists within (also taking into account SR). Does this question have a quantifiable value?

    Thanks for your time.

  2. jcsd
  3. Apr 2, 2013 #2


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    If you simply add together a bunch of speeds, you will get a greater sum than when you use the relativistic velocity formula, so yes, that sounds right.
    Not really. Certainly you can calculate a value based on your assumptions of how fast each thing is moving relative to the next thing but finally you will run out of things with a measurable speed difference.
    You're welcome, and welcome to the Physics Forums.
  4. Apr 2, 2013 #3
    Thanks for your reply. So for the values that do exist (those which I was able to google), the value is accurate as far as they are?

    And since I was able to find a value for the movement of our galaxy (which I assume is approximate) within the universe; the farthest frame of reference that is quantifiable would be floating outside our galaxy (assuming no other motion or forces are acting on that frame)?

    Therefore, at rest an object on earth is roughly moving at 3 million km/hr (according to my data) from that "intergalactic" frame?

    Thanks for your time!

  5. Apr 2, 2013 #4


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    I'm only saying the calculation is accurate. I'm not saying it is a significant calculation to be interested in making. Why does it interest you?
    As long as you realize that the "intergalactic" frame is no more significant than the "solar system" frame or the "earth" frame or the "Jupiter" frame or any other frame moving with any speed short of light speed in any direction with respect to any of those other frames.
  6. Apr 2, 2013 #5
    I have a friend out there. Hehe, j/j. I'm interested in calculating this value simply because it represents the farthest calculable frame of reference for earth based motion. I'm an artist and programmer and I find the visualization and math intriguing.

    Absolutely, I'm not favoring or singling out the "intergalactic" frame as special. I'm interested in that frame since it is so far. We don't know the motion of our universe in whatever it is that exists outside of it, or whether it is at motion at all. So as I understand it the "intergalactic" frame is farthest measurable frame with actual velocities to add. Is this mode of thinking flawed?

    Thanks for your time George.

    Last edited: Apr 2, 2013
  7. Apr 2, 2013 #6


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    It's flawed in the sense that you are using a Special Relativity application (relativistic velocity addition) to "solve" a problem that also involves gravity and an expanding universe where SR no longer applies. But if it is for artistic purposes, you are allowed license, right?.
  8. Apr 2, 2013 #7
    Is this problem too complex for someone like myself to calculate? What sort of calculations are needed to get an accurate number?

    Do the values that exist say for the velocity of our solar system within the galaxy not take into account red-shift / expansion? I would of assumed they needed the doppler CBR stuff to even come up with that number no?

    It seems to me the velocites can be added with SR accurately to the point of our galaxy frame. It is when we try to jump outside that frame into the frame of the universe where it becomes meaningless to use SR. Is this correct? or is SR meaningless in all frames?

    I of course am allowed to show whatever I like. But for the sake of my own interest and the project I would like to get the numbers as accurate as possible. I need not understand all the math or physics but I would like to perform those calculations. Is this not possible to any degree? I don't mind stepping back a frame and only calculating within the Milky Way frame of reference.

    The time article here states all the relevant velocities: (they may be a bit different than my previous data) and speaks of new data showing the velocity of the Solar system is actually less than previously thought. Are these values not taking into account the other forces you speak of?


    Thanks again for your continued feedback.

    Last edited: Apr 2, 2013
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