This is probably just a coincidence, but

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    coincidence
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Discussion Overview

The discussion revolves around the interpretation of time dilation and its relationship to kinetic energy and the equation E=mc^2. Participants explore the implications of a hypothetical "sum velocity" of c for all objects and how this relates to classical and relativistic physics.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that if all objects have a "permanent space-time velocity" of c, then their kinetic energy could be expressed as EK = mc^2.
  • Others argue that the equation E=mc^2 only applies when velocity v=0, and the general equation for energy should include momentum.
  • Several participants challenge the initial claim that kinetic energy is equal to mv^2, pointing out the missing factor of 1/2 in the classical kinetic energy formula.
  • Questions are raised about the meaning of "velocity in space" and "velocity in time," as well as the concept of "space-time velocity."
  • One participant expresses skepticism about whether the original poster understood the implications of their statements regarding time dilation and velocity.
  • Another participant suggests that the original idea may have been influenced by popular science literature, though doubts are cast on the original poster's understanding of the concepts.
  • A later reply acknowledges a misunderstanding of Newtonian physics and apologizes for the confusion caused by the initial post.

Areas of Agreement / Disagreement

Participants generally disagree on the interpretation of kinetic energy and the implications of time dilation. Multiple competing views remain regarding the relationship between velocity, energy, and the nature of time.

Contextual Notes

There are unresolved mathematical steps regarding the application of kinetic energy formulas and the definitions of velocity in different contexts. The discussion also reflects a mix of classical and relativistic perspectives without a clear consensus.

Trepidation
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[tex]EK = mv^2[/tex]
energy kinetic = mass times velocity squared

So... Isn't one way to interpret time dilation that everything moves through time and space with a sum velocity of c (somehow), and that as velocity in space increases velocity in time therefore decreases? I've read this in several places, anyway.

If this is the case, then the permanent space-time velocity of all objects is c... Which means that their kinetic energy would be:

[tex]EK = mv^2[/tex]

[tex]EK = mc^2[/tex]

So er... [tex]E=mc^2[/tex]
 
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Trepidation said:
[tex]EK = mv^2[/tex]
energy kinetic = mass times velocity squared
So... Isn't one way to interpret time dilation that everything moves through time and space with a sum velocity of c (somehow), and that as velocity in space increases velocity in time therefore decreases? I've read this in several places, anyway.
If this is the case, then the permanent space-time velocity of all objects is c... Which means that their kinetic energy would be:
[tex]EK = mv^2[/tex]
[tex]EK = mc^2[/tex]
So er... [tex]E=mc^2[/tex]
The equation [itex]E=mc^2[/itex] only applies when [itex]v=0[/itex]. The general equation for any [itex]v[/itex] is
[tex]E=\sqrt{(mc^2)^2+c^2p^2}[/tex]
where [itex]p[/itex] is momentum.
So indeed just a coincidence.
 
Trepidation said:
[tex]EK = mv^2[/tex]
energy kinetic = mass times velocity squared
So... Isn't one way to interpret time dilation that everything moves through time and space with a sum velocity of c (somehow), and that as velocity in space increases velocity in time therefore decreases? I've read this in several places, anyway.
If this is the case, then the permanent space-time velocity of all objects is c... Which means that their kinetic energy would be:
[tex]EK = mv^2[/tex]
[tex]EK = mc^2[/tex]
So er... [tex]E=mc^2[/tex]

1. Since when is kinetic energy equal to mv^2? What happened to the 1/2?

2. What exactly are "velocity in space" and "velocity in time"?

3. What is "space-time velocity"?

4. This statement is puzzling: "... Isn't one way to interpret time dilation that everything moves through time and space with a sum velocity of c (somehow),... " Everything does NOT move with a "sum velocity of c (somehow)".

Zz.
 
ZapperZ said:
1. Since when is kinetic energy equal to mv^2? What happened to the 1/2?
Of course. I completeley overlooked this most obvious argument!
 
Trepidation said:
[tex]EK = mv^2[/tex]
energy kinetic = mass times velocity squared

No, its [tex]E_K = \frac{1}{2} m v^2[/tex]


If this is the case, then the permanent space-time velocity of all objects is c... Which means that their kinetic energy would be:
[tex]EK = mv^2[/tex]
[tex]EK = mc^2[/tex]
So er... [tex]E=mc^2[/tex]

[tex]E=mc^2[/tex] only applies to a an object when [tex]v= 0[/tex] as another pointed out. It has nothing to do with kinetic energy.
 
ZapperZ said:
Everything does NOT move with a "sum velocity of c (somehow)".

The length of the velocity four-vector of any particle is 1 in geometric units, which corresponds to c in SI units. A particle in it's rest frame is moving through time at a second a second. To compare lengths with times, we multiply by c, to find that it is moving c metres a second.
 
masudr said:
The length of the velocity four-vector of any particle is 1 in geometric units, which corresponds to c in SI units. A particle in it's rest frame is moving through time at a second a second. To compare lengths with times, we multiply by c, to find that it is moving c metres a second.

But really, do you honestly think the OP knew about this and that this is what he/she is describing by making that erroneous statement? I highly doubt it.

Zz.
 
ZapperZ said:
But really, do you honestly think the OP knew about this and that this is what he/she is describing by making that erroneous statement? I highly doubt it.
Zz.

I believe one of Greene's recent popular science texts (with some grandiose title) expresses this idea (and I assume this is where the OP got the idea from); whether or not the OP fully understood it or not is, of course, another matter.
 
masudr said:
I believe one of Greene's recent popular science texts (with some grandiose title) expresses this idea (and I assume this is where the OP got the idea from); whether or not the OP fully understood it or not is, of course, another matter.

I'm not so sure... Greene cannot make a silly mistake of equating KE with mv^2 and missing out that 1/2, which is the OP starting premise.

Zz.
 
  • #10
I comprehend the idea, but the important thing is that I apparently don't comprehend simple Newtonian physics. Forgive me for the incorrect formula and the idiotic post... I just saw something that sort-of corresponded and then decided to post it, and consequently wound up with a bunch of gibberish.

Again, sorry. I don't know what I thought when I was writing EK=mv^2. Thanks for replying to this, anyway.
 
  • #11
ZapperZ said:
I'm not so sure... Greene cannot make a silly mistake of equating KE with mv^2 and missing out that 1/2, which is the OP starting premise.
Zz.

Sorry, I meant the notion of having a velocity of c at all times, as opposed to the definition of non-relativistic classical kinetic energy.
 

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