Velocity and recessive velocity

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Discussion Overview

The discussion centers on the concepts of velocity and recessive velocity, particularly in the context of relativity and the expansion of the universe. Participants explore the implications of these terms and their relationship to the speed of light.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the difference between velocity and recessive velocity, suggesting that recessive velocity may allow for speeds exceeding that of light.
  • Another participant argues that recessive velocity refers to the velocity of an object moving away from an observer and emphasizes that the speed of light is a limit for all objects, regardless of their direction.
  • A participant expresses confusion about the implications of relativity, particularly regarding the speed of light being constant for all reference points and questions how two light particles would interact from a light's perspective.
  • Another participant clarifies that one cannot adopt the perspective of a particle of light and suggests considering the scenario from the viewpoint of a person traveling at near-light speed instead.
  • A later reply reiterates that all velocity is relative according to relativity, emphasizing that recession velocity is defined by an object's movement away from a specific point in space.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of recessive velocity and its relationship to the speed of light. While some clarify and refine the definitions, no consensus is reached regarding the implications of these concepts.

Contextual Notes

There are unresolved assumptions about the definitions of velocity and recessive velocity, as well as the implications of relativity on the perception of speed from different reference frames.

dracobook
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What is the difference between velocity and recessive velocity. I read that with velocity, an object may not past the speed of light; but with recessive velocity, an object may past the speed of light.
 
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There's no difference. "Recessive velocity" or "velocity of recession" just refers to the velocity of some object moving away from the observer. The opposite would be "approaching velocity" or "velocity of approach", for example.

The speed of light is a limit on the speed of an object in space, whether an object is coming towards you or going away. However, maybe you are thinking of the expansion of the universe, in which space itself expands, carrying objects such as galaxies along with it. The expansion of space, as opposed to the movement of objects in space, is not limited by the speed of light.
 
thanks James R. Yeah I was thinking of the expansion. I also have another problem. Well, according to relativity (I think) the speed of light is the same for all reference points. So, imagine if you willl, that you are a particle of light. You are traveling in a straight line from point A to B and another particle of light is traveling parallel and in the same direction as you. According to relativity, wouldn't the second particle of light be traveling ~3*10^8 meters per second relative to you? Wouldn't this happen if the object was traveling parallel yet in the opposite direction as well? ..:( I don't think I understand relativity very well..
 
You can't really look at things from the point of view of a particle of light. From that particle's perspective, the size of the universe would be zero, for a start.

If you consider your scenario from the point of view of a person traveling at 99.9999% the speed of light, then you would indeed see the light particle traveling the same direction as you as going at 3*10^8 metres per second, as usual.
 
At this point might I clarify that the crux of this is that all velocity is relative. There is no such thing as absolute velocity according to Relativity and every situation must be considered by the relative velocities of objects with reference to one another. In this sense, recession velocity would be the velocity with which an object moves away from the observer's specific point in space. Recession in this context just means 'moving away from'.

Hope that helps.
 

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