Is Object 2 Traveling at Double the Speed of Light Relative to Object 1?

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Discussion Overview

The discussion revolves around the concept of the speed of light in relation to objects with mass and the implications of relative motion between two objects traveling close to the speed of light. Participants explore the principles of special relativity and the characteristics of particles with different rest masses.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that no material object with non-zero rest mass can exceed the speed of light.
  • One participant proposes that if two objects are moving at 0.99c in opposite directions, their relative speed would not be double the speed of light, but rather calculated using the relativistic velocity addition formula.
  • Another participant provides the formula for relativistic velocity addition, indicating its relevance to the discussion.
  • There is a claim that all particles with a rest mass greater than zero travel below the speed of light, while particles with zero rest mass, like photons, travel at the speed of light.
  • Some participants question and confirm the relationship between rest mass and the speed of light, particularly regarding photons.
  • One participant raises a question about the concept of causality in relation to mass and the speed of light, suggesting a connection between the two.

Areas of Agreement / Disagreement

Participants generally agree on the principle that no material object with mass can exceed the speed of light. However, there are differing views on the implications of relative speeds and the nature of particles with zero or negative rest mass, leaving some aspects of the discussion unresolved.

Contextual Notes

The discussion includes various assumptions about the definitions of rest mass and the implications of special relativity, which may not be fully articulated by all participants.

expscv
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i was curious ,


is it ture that nothing can exceeds the speed of light, such all object (except photon) max speed is "speed of light" ?


2. if both object travel close to light of speed, but in oppsite direction

so realvtive to object 1, is object 2 travel at double of "speed of light"??
 
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Yes, it is true that no material object (with non-zero rest mass) can travel at (or faster than) the speed of light.

If two objects are moving with, say, 0.99c (99% of the speed of light) relative to some third object (every speed has to be relative to something) going in opposite directions then the speed of each one, relative to the other, is (0.99c+ 0.99c)/(1+ (.99c)(.99c)/c2)= 1.98c/(1.9801)= 0.9999c.
 
The formula HallsofIvy used is from Einstein's Special Relativity, which is the theory we must use to deal with such speeds.
 
Here is the full formula in case you wanted to know:

[tex]u' = \frac {v+u}{1 + \frac{vu}{c^2}}[/tex]
 
All particles with a rest mass greater than 0 travel at below the speed of light.
Particles with 0 rest mass only travel at light speed.
Particles with less than 0 rest mass should, if they exist, travel at only greater than light speed.
 
whydoyouwanttoknow said:
All particles with a rest mass greater than 0 travel at below the speed of light.
Particles with 0 rest mass only travel at light speed.
Particles with less than 0 rest mass should, if they exist, travel at only greater than light speed.


oh? so photon is equal to 0 rest mass?

becasue it can travel exactly at speed of light?
 
expscv said:
oh? so photon is equal to 0 rest mass?

becasue it can travel exactly at speed of light?

Yeah, photons have no mass.
 
expscv said:
oh? so photon is equal to 0 rest mass?

becasue it can travel exactly at speed of light?

not exactly, *ahem*

A photon can travel at the speed of light because it has zero rest mass
 
Are you sure there is "causality" here? c speed and 0 mass are pretty much hand in hand IMO. I would say either way to say it is good.
 

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