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Well, I'm in a way, not qualified to ask this question as I've just started physics and presently learning Newtonian mechanics. Still I'm asking this out of curiosity, but quite serious as I am greatly wondered on how is it possible that there can be no speeds greater than light and all that stuff. So pardon me if my question is to naive or something like that.

Now consider this set up. We are in empty space and in a way isolated from all other interactions other than the interactions between the two masses which are present here. One of them is very, very massive and the other relatively light (may be the massive one is a very massive star or hypothetical object with a very, very high mass). Also suppose that they are very,very far, so that they don't collide soon enough (I've not numerically analysed the situation as I don't have enough knowledge for that )

Now both would attract each other due to gravitational force between them and they would accelerate them as they approach each other ( there would be also other forces acting like EM forces, but I'm neglecting them and assuming that there is no overall charge to cause significant force ).

Now what I think is that the lighter mass(as it will have a large acceleration owing to a tremendous force between them) can exceed the speed of light if they are far enough and the other one is massive enough, can't it?

In this situation I've ignored the time as I don't think it would matter if the time scale of this to take place is extremely large because it is a hypothetical experiment.

I just want to ask you that is my opinion wrong (that definitely is!)and how it is wrong. I'm not expecting you to tell the very precise reasoning behind your reply because I may not be able to digest it now or understand it completely (still it would be kind of you if you could explain me all that intuitively in simple words).

I'm looking forward for your replies.

EDIT

The questions you mentioned doesn't takes into account exactly what I've asked. Also at this stage I don't want and mathematical treatment of relativity as I'm not in a position to understand it and asked this question out of curiosity . I'm quite satisfied with the answer by BowlOfRed and would brush up the concepts like escape velocity and things like that as now I feel I don't have the desired understanding of these concepts. Thanks for providing me links as they might be useful later. Thank You.

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    $\begingroup$ Possible duplicate of Why can't anything travel faster than light? $\endgroup$ Nov 30, 2017 at 10:14
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    $\begingroup$ Possible duplicate of What is so special about speed of light in vacuum? $\endgroup$
    – Kyle Kanos
    Nov 30, 2017 at 11:04
  • $\begingroup$ @sammygerbil and Kyle Kanos The questions you mentioned doesn't takes into account exactly what I've asked. Also at this stage I don't want and mathematical treatment of relativity as I'm not in a position to understand it and asked this question out of curiosity . I'm quite satisfied with the answer by BowlOfRed and would brush up the concepts like escape velocity and things like that as now I feel I don't have the desired understanding of these concepts. Thanks for providing me links as they might be useful later. $\endgroup$ Nov 30, 2017 at 11:34
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    $\begingroup$ Your question does not explain what is special about two masses attracting. Why do you think they would exceed the speed of light? Why is this different from two rockets thrusting towards each other, starting from a sufficient distance apart? It is not the mechanism of acceleration which limits relative velocity, it is space and time itself. $\endgroup$ Nov 30, 2017 at 12:25
  • $\begingroup$ See aslso (Almost) double light speed $\endgroup$ Nov 30, 2017 at 12:32

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If you allow a mass to free fall onto an object starting with zero speed from "far enough" away, it will strike the surface with a speed equal to the escape velocity.

Therefore any object with an escape velocity less than the speed of light (not a black hole) cannot accelerate some other mass to a speed greater than that before a collision happens.

See also Will free-fall object into black hole exceed speed of light $c$ before hitting black hole surface?

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  • $\begingroup$ Thanks for your answer. I didn't took it in that way and was unable to make out that it is related to escape velocity. Will read more on this. $\endgroup$ Nov 30, 2017 at 10:07

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