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Relativity confusion

  1. Nov 15, 2009 #1
    If Big Bang is the begining of the relevant time. What would it be like to be observing the universe on the surface of a planet that has a relativistic speed close to c in reference to earth.

    - How would that person observe the universe and the events taking place in it?

    -Is space-time a whole in the universe? Would reaching relativistic c in reference to the earth cause a relativistic mass going towards infinity. Will this cause a universal space-time curve, or a relative one?

    If space-time curves can be relative, what does this mean?

    I am quite confused already asking too many questions. :)
  2. jcsd
  3. Nov 16, 2009 #2
    A person on the planet moving close to c would see the events the same as the person on earth. They would simply disagree on when the events took place
  4. Nov 16, 2009 #3
    Thank you.

    I think your first sentence contradicts the later. In that knowledge i have asked my questions :)

    They would disagree on the amount of speed the universe is expanding too. Also they would disagree on every galaxy's position and every galaxy's distance between each other. Those people need to find something they can agree on really..
    Last edited: Nov 16, 2009
  5. Nov 16, 2009 #4
    It's the only question I kinda understood.

    And whey I said 'see' I literally meant 'see'. For example, the would both see an apple fall, but they would disagree on when the apple fell.
  6. Nov 16, 2009 #5
    Oh, i see.

    But how are they both going to identify a reference apple? a reference planet? a reference galaxy?

    And in your example i am not questioning these people's ability to communicate or see the said apple, etc.. They can hear each other loud and clear! But still i can't see how they can identify same object and agree on it that it is the same object :)

    See i am not even putting in the fact that you don't know earth's vectoral speed in the universe, and another planet at c in reference to earth. Practically can not remain at that speed all the time it will keep experiencing vectoral slowing down and accelerating through the process making the time dilation and length contraction differences changing at random intervals. And i am talking about big differences.

    So such objects in the universe will give you a redshift. But the amount of the redshifting will change randomly.

    Well, ok, not randomly it can be calculated. Good luck with that though ;)
  7. Nov 17, 2009 #6


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    The visual appearance of the universe from a relativistically moving ship is discussed at :


    there's a link to a peer-reviewed paper at the URL above (the paper is written by the website author).

    As far as the gravitational field of a rapidly moving object goes, it gets complicated. The closest analogy is to the electric field of a rapidly moving charge, where the electric field gets crushed into a plane wave. Imagining that the gravity gets crushed in a similar manner is oversimplified, but I've found it's not too helpful to point out in this circumstance that there's really no such thing as a gravitational field. And the solution has been discussed in the literature, and it is a plane gravitational wave...

    For the gory details, look up the Aichelburg-Sexl solution.

    or on arxiv

  8. Nov 17, 2009 #7
    Well the picture clearly shows me that, if i accelerate enough i will see the collective universe in front of me. Which is what i was talking about with that twin paradox on the other topic.

    From that point on, saying i am not affected by their collective gravitational force would be absurd. Anyway i won't go into there.

    The same also tells me that, if i reached "c" the universe in front of me would become a singularity point. And say i am magically slowing down slowly. Then i would see a singularity expanding, picture it in your mind. Expanding singularity, forming galaxies slowly and moving towards you or away from you. The faster you slow down, the faster the singularity in front of you will expand.

    Does this mean if i do the opposite will the universe in front of me and behind me would stop redshifting or blueshifting at the relative speed of x when i take the reference frame as the spaceship that is going with c? How awesome would that be :)

    Really breathtaking how they are all actually already there. Its just an optical illusion or? :)

    I don't want to go into the gory parts. I like simple and i like razors.
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