Please explain this light speed question.

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Discussion Overview

The discussion revolves around the relativistic effects of traveling at significant fractions of the speed of light, specifically addressing why two observers moving away from a common point at 0.6C do not have a relative speed of 1.2C. It explores concepts of velocity addition, mass increase, and time dilation within the framework of special relativity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions why two objects traveling at 0.6C in opposite directions do not result in a combined speed of 1.2C.
  • Another participant references a previous thread that addressed the same question, suggesting that the addition of velocities does not follow classical rules.
  • A participant proposes a scenario where they accelerate to 0.6C repeatedly and questions if this could lead to exceeding the speed of light, speculating that time dilation might be a factor.
  • One response explains that energy imparted during acceleration contributes to an increase in apparent mass rather than speed, referencing high-energy physics experiments.
  • Another participant suggests using the Velocity Addition formula to calculate the effects of repeated acceleration bursts.
  • One participant asserts that instead of increasing speed, mass increases and leads to gravitational effects, speculating about becoming a black hole as they approach the speed of light.
  • A later reply disputes the idea of becoming a black hole, stating that while speed increases, no observer would see them reach the speed of light.
  • Another participant emphasizes the importance of understanding transformations between coordinate systems in the context of relativistic speeds.

Areas of Agreement / Disagreement

Participants express differing views on the implications of relativistic speeds, particularly regarding the addition of velocities and the consequences of mass increase. There is no consensus on the interpretations of these concepts, and the discussion remains unresolved.

Contextual Notes

Participants reference earlier discussions and mathematical definitions, indicating that assumptions about velocity addition and transformations between frames of reference are critical to the conversation. Some mathematical steps and definitions may not be fully clarified.

Who May Find This Useful

This discussion may be of interest to individuals exploring concepts in special relativity, particularly those curious about the implications of high-speed travel and the nature of mass and energy in relativistic contexts.

ollybygolly
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If you are traveling .6C away from your point of origin and your friend is traveling .6C away from the same point of origin but in the opposite direction, why are you not traveling 1.2C away from your friend?
 
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Same question was asked and answered in another thread just a few hours ago... Look here
 
I want to ask a couple more here that may have been covered in that other thread, but In an effort to keep things clear and not to hijack that other thread I am going to post them here.

in my original question that was ansered in the other thread it shows that .6c+.6c is not 1.2c.

However, let's go a step further. Let's say the two objects start coasting once they hit .6c. So I'm in my spaceship and I no longer feel any acceleration. I'm floating around in the cabin. My frame of refference is that I am not moving at all. I'm just sitting there floating.

Now I hit my thruster again and I accelerate to .6c again from my original frame of refference.

Why can't I do this over and over until I am going faster than light as measured from my original starting point? Is it that every time I make a speed jump time dialates in response?
 
In your original frame, the energy you impart would mostly go into apparent mass. This is how the LHC and other devices work. Energy is imparted to the protons, but as they get close to the speed of light, it shows up as mass rather than speed increase.
 
Just try it and see what the Velocity Addition formula gives you for each additional burst of acceleration.
 
So instead of going faster, my mass increases. As my mass increases, I exert more gravity on the space around me. And as my gravity grows time dialates. So in essence I would turn myself into a black hole about the same time I reached the speed of light, if I could get that fast.

Any good free on line physics courses out there? Ones that expain how a particular mathamatician came up with their equations and the proofs they used?

I have a lot of probably stupid questions that I'm sure would be answered by taking some classes.
 
ollybygolly said:
So instead of going faster, my mass increases. As my mass increases, I exert more gravity on the space around me. And as my gravity grows time dialates. So in essence I would turn myself into a black hole about the same time I reached the speed of light, if I could get that fast.
No, that's not what happens. You will go faster. But no observer watching you will see you reach c. You definitely won't become a BH.

Any good free on line physics courses out there? Ones that expain how a particular mathamatician came up with their equations and the proofs they used?

I have a lot of probably stupid questions that I'm sure would be answered by taking some classes.
I recommend classes, but I can't name any specifics wothout knowing your level of mathematics.
 
ollybygolly said:
[..] in my original question that was ansered in the other thread it shows that .6c+.6c is not 1.2c. [...]
That would conflict with the basics of mathematics: .6c+.6c=1.2c by mathematical definition of addition. What was perhaps not made clear is that you asked about a transformation between coordinate systems.

See for an elaboration some earlier threads, for example:
https://www.physicsforums.com/showthread.php?p=3992825#post3992825
 

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