Mass Established by Relative Motion: Implications in GR?

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Discussion Overview

The discussion revolves around the concept of mass as established through relative motion and gravitational interactions, particularly in the context of General Relativity (GR). Participants explore whether mass can be considered absolute or if it is inherently relative, examining implications for both classical and modern physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that the determination of mass is circular, relying on gravitational interactions among celestial bodies, which raises questions about the absolute nature of mass.
  • Others argue that mass can only be discussed in relative terms, emphasizing that measurements depend on a defined standard, such as the platinum-iridium cylinder in France.
  • It is noted that gravitational and inertial mass are considered equivalent, with both being measurable through different methods, such as gravitational attraction and force application.
  • A participant points out that while the product of gravitational constant and mass can be observed precisely, the mass itself remains less certain due to the variability of the gravitational constant.
  • Some contributions clarify that "rest mass" is often viewed as an invariant quantity across reference frames, while "relativistic mass" varies with velocity.
  • There is a discussion about the connection between different mass standards, including human-scale and atomic-scale measurements, and the implications of upcoming changes to these standards.
  • Participants express differing views on the applicability of mass concepts in quantum mechanics, with some arguing that scale invariance is broken at atomic levels.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether mass is absolute or relative, and multiple competing views remain regarding the implications of these definitions in both classical and quantum contexts.

Contextual Notes

Limitations include the dependence on definitions of mass, the unresolved nature of the gravitational constant, and the implications of quantum mechanics on the concept of mass.

  • #31
jaketodd said:
The only question left in this thread is if having to use virtual particles to model interactions shows that we don't have the whole picture yet - I mean: Stuff that we haven't found to exist, and instead things acting as if those stuffs were there.

Thanks all,

Jake

To my limited knowledge on the subject, virtual particles are a result of doing the math a certain way. Whether this actually means anything or not is beyond me. It certainly works though.
 
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  • #32
Drakkith said:
To my limited knowledge on the subject, virtual particles are a result of doing the math a certain way. Whether this actually means anything or not is beyond me. It certainly works though.

Yes it works, but not being able to detect the particles leaves me wondering.
 
  • #33
jaketodd said:
Yes it works, but not being able to detect the particles leaves me wondering.

I look at it like one of the following:
1) There aren't actually an virtual particles, it's just a mathematical construct or whatever
2) They aren't detectable because if they were they would have to be real and thus not virtual. So kind of like trying to figure out the position and momentum of a particle down to any precision, it just isn't possible.
 
  • #34
Drakkith said:
I look at it like one of the following:
1) There aren't actually an virtual particles, it's just a mathematical construct or whatever
2) They aren't detectable because if they were they would have to be real and thus not virtual. So kind of like trying to figure out the position and momentum of a particle down to any precision, it just isn't possible.

So this takes a turn to the Uncertainty Principle. I forget, but aren't all quantities there; it's just not possible for us to measure the two pairs of information at the same time, which the UP lays out? If we broaden the UP to cover virtual particles, and there is a pair of information, one of which is detecting a virtual particle, then we should be able to detect them if we forget about the other piece of information. But a) is there even a pair of information for virtual particles, and b) is it possible to ignore the piece of information that would lead to detection of virtual particles, so they'd be particles, not virtual particles? Well wait a second, in the UP, there is the relation between energy and time. We can get the time of our virtual particles interacting if we ignore their energy? But we can't measure the energy of our virtual particles because they are traveling at the speed of light (virtual photons, for example) and thus time stands still for them, so they remain virtual?

Jake
 
  • #35
I tried answering again, but I can't explain it well enough. I suggest making a thread in the Quantum Physics forum for this jaketodd. Try the FAQ there as well along with searching for related threads. There should be plenty.
 
  • #36
A better way to say my last post is: We can't ignore the energy of virtual particles because that's what they are solely doing (transferring energy). So since we can't ignore their energy, we can't observe them in time. Anybody?

Thanks,

Jake
 
  • #37
jaketodd said:
A better way to say my last post is: We can't ignore the energy of virtual particles because that's what they are solely doing (transferring energy). So since we can't ignore their energy, we can't observe them in time. Anybody?

Thanks,

Jake

They are not transferring their own energy. They are mediating the force between 2 particles.
 
  • #38
Drakkith said:
They are not transferring their own energy. They are mediating the force between 2 particles.

Analogy: A messenger arrives with a message, not empty handed.

In other words, why can't a virtual particle be the carrier of force between two particles?

Jake
 
  • #39
jaketodd said:
Analogy: A messenger arrives with a message, not empty handed.

In other words, why can't a virtual particle be the carrier of force between two particles?

Jake

Virtual particles are considered to be. Did you mean real?
 
  • #40
Maybe this will help. Both real and virtual particles carry the force. When you turn on a laser, a light bulb, or your cell phone's antenna, you create real photons that stream out. These photons will eventually hit a mirror, the wall, or a receiving antenna and will exert a force on whatever it hits. You could say the light source exerted a force on the distant object and the force was carried by real photons. Real photons are created whenever an electromagnetic system radiates. But what if we have perfectly static electromagnetic fields (which is actually much rarer than you think)? Static fields don't radiate and therefore don't emit real photons, but we still observe experimentally that one object can exert a force on another object through a static fields. In the world of quantum field theory, everything is described by creation, destruction, and exchange of quanta (particles), so if there are no real photons to carry the force, the force must be carried by virtual photons. So virtual particles are more of a special limiting case where fields become static. But don't think of virtual particles as invisible balls being emitted and absorbed, but rather as just quantized pieces of a whole field.
 
  • #41
jaketodd said:
A better way to say my last post is: We can't ignore the energy of virtual particles because that's what they are solely doing (transferring energy). So since we can't ignore their energy, we can't observe them in time. Anybody?

I still think there could be something to this.
 
  • #42
jaketodd said:
A better way to say my last post is: We can't ignore the energy of virtual particles because that's what they are solely doing (transferring energy). So since we can't ignore their energy, we can't observe them in time. Anybody?


I still think there could be something to this.

I'm sorry I don't understand what that means.
 
  • #43
Drakkith said:
I'm sorry I don't understand what that means.

Well, according to the uncertainty principle, the more you know either time or energy, the less you know the other. If virtual particles exist as pure energy transmission (vs. for example, regular photons having momentum (virtual particles do not always result in momentum being transferred in the direction they hit another particle; only if it matches the direction of the force they are carrying to another particle)) then their energy can never be neglected to any extent, thus making only their energetic transmission observable, and never their existence in time observable. I know that's pretty complicated and hard to read, but I've thought through it several times, and it makes sense to me.
 
  • #44
then their energy can never be neglected to any extent

What? What does this mean? I don't understand what you mean by saying the virtual particles energy can never be neglected, it just doesn't make any sense to me. Am I misunderstanding something?
 
  • #45
Doesn't the relativistic relationship (E)^2-(pc)^2=(m0c^2)^2 give an absolute scale for mass?
 
  • #46
Drakkith said:
What? What does this mean? I don't understand what you mean by saying the virtual particles energy can never be neglected, it just doesn't make any sense to me. Am I misunderstanding something?

Maybe from this angle: You can't detect it as a real particle because it's purely a transmission of energy; no physical form. And the uncertainty principle comes in and says: Since you can only detect it by measuring it's energy, then it's hidden from existing in time. This is getting philosophical =)

If someone wants to shoot me down, please don't be too harsh, I'm trying here.
 
Last edited:
  • #47
I don't know jaketodd. Again, I recommend posting in the Quantum Physics forum about this if you really want to know.
 
  • #48
To understand how free or non-free fields mediate force or transport energy it is not important to refer to their quantum properties. So why speak of virtual or real particles?
 
  • #49
DrDu said:
To understand how free or non-free fields mediate force or transport energy it is not important to refer to their quantum properties. So why speak of virtual or real particles?

I'm bringing the uncertainty principle into it because it seems to appropriately have an interesting implication and explanation.
 
  • #50
One counter argument I've thought of is: Energy transfer can be timed. However, what is really being measured is the particle that the virtual particle is effecting, not the virtual particle itself.
 
  • #51
jaketodd said:
One counter argument I've thought of is: Energy transfer can be timed. However, what is really being measured is the particle that the virtual particle is effecting, not the virtual particle itself.

Counter argument to what?
 
  • #52
Drakkith said:
Counter argument to what?

It's a counter argument to virtual particles not being detectable in time.
 

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