Why do photons naturally travel at c?

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Discussion Overview

The discussion centers on the nature of photons and the reasons they travel at the speed of light (c). Participants explore various theories, properties of photons, and the implications of their speed in the context of physics, touching on concepts from relativity and quantum field theory.

Discussion Character

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

Main Points Raised

  • Some participants suggest that photons travel at c because they are massless and have infinite range in space.
  • Others propose the anthropic principle, stating that light travels at the speed of light because it is light, viewing this as axiomatic.
  • A participant questions the terminology of "speed of light," arguing that c is a more general invariant speed applicable to other massless entities, not just light.
  • There is a discussion about the implications of space-time geometry on the speed of light, with references to Einstein's work and the metric of flat space-time.
  • Some participants mention electric permittivity and magnetic permeability as properties that determine the speed of light.
  • One participant speculates that photons may allow "space" to "freely" enter them, suggesting a unique property that contributes to their massless nature.
  • Another participant references Einstein's own uncertainty about the nature of photons, indicating that even established figures in physics have struggled with these concepts.
  • There is mention of causality and the necessity of an invariant speed of light for the concept of time to hold, along with a suggestion to explore the mathematics of transformations related to this topic.
  • A later reply discusses quantum field theory, asserting that photons have no rest mass because they do not interact with the Higgs field.

Areas of Agreement / Disagreement

Participants express a range of views on why photons travel at c, with no clear consensus reached. Multiple competing explanations and models are presented, indicating ongoing debate and exploration of the topic.

Contextual Notes

Some statements rely on specific definitions and assumptions about mass, space-time, and the properties of light. The discussion includes unresolved mathematical steps and varying interpretations of theoretical concepts.

  • #31
Andrew Mason said:
Compared to whatever neighbourhood of c you can suggest. What is the right word, if not collapse?

AM

Collapse implie ssome sort of catastrohic/irrevrsible process, thoguh I suppose you use it in the sense of fold-up, to convey the fact taht most of the stars you would see would appear in a very narrow area.
 
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  • #32
I apologize in advance for making an assumption --- but in another thread the writer seemed to be understandably confused by the famous balloon model where the galaxies are spots on the expanding balloon. You can get the impression that the universe IS the balloon and the center is the center of the balloon. But as jcsd points out, you have to consider the universe as the SURFACE of the balloon. If the center of the balloon exists, it is in hyperspace or some such; and, just like there is no "center" of the surface of the world, obviously there is no center to such a universe ... unless you take the trivial case that the "center" is where ever I am now. If you add to that the fact that the universe does not seem to have the curvature of a sphere (I can't rremember if that is positive or negative) and you get even more complications.
 
  • #33
donjennix said:
You can get the impression that the universe IS the balloon and the center is the center of the balloon. But as jcsd points out, you have to consider the universe as the SURFACE of the balloon. If the center of the balloon exists, it is in hyperspace or some such; and, just like there is no "center" of the surface of the world, obviously there is no center to such a universe ... unless you take the trivial case that the "center" is where ever I am now. If you add to that the fact that the universe does not seem to have the curvature of a sphere (I can't rremember if that is positive or negative) and you get even more complications.
I am talking about the 3 dimensional 'slice' that exists for each frame of reference and which we see (as would all other observers sharing our reference frame) as our spatial universe. That universe has a centre. I am not saying it is an absolute centre because other observers in other reference frames would disagree. But all observers in our reference frame would agree where the centre is located (assuming that we could do all the necessary measurements).

AM
 
  • #34
Andrew Mason said:
I am talking about the 3 dimensional 'slice' that exists for each frame of reference and which we see (as would all other observers sharing our reference frame) as our spatial universe. That universe has a centre.
:confused: :confused:

The standard cosmological models are unbounded, so the universe we observe has no centre, except that of the observer herself (Copernicus eat you heart out!).

Garth
 
  • #35
Andrew Mason said:
I am talking about the 3 dimensional 'slice' that exists for each frame of reference and which we see (as would all other observers sharing our reference frame) as our spatial universe. That universe has a centre. I am not saying it is an absolute centre because other observers in other reference frames would disagree. But all observers in our reference frame would agree where the centre is located (assuming that we could do all the necessary measurements).

AM

Yes we are talking about spatial slices, infact the discussion of the sphere fits in well with the spatial slice of the case of the RW metric which describes a finite universe which is essentially a 3-sphere (i.e. the surface of a four-dimensional sphere).

As Garth says the Copernican cosmological principle is a pretty fundamantal assumpion in neraly all areas of cosmology and a geometric cnetre is a total violation of this principal.
 
  • #36
Tuning in top the couple of posts only, I would point out the democracy of homogeneous and isotropic spaces. Every point can be taken as the centre of the space. The homogeneity and isotropy destroy any uniqueness that "the centre of the universe" might otherwise have.
 
  • #37
hmm,

No one mentioned that the frequency and wavelength values of light are produced by the natural harmonic numbers of simple oscillation. There is always symmetry between values whose product is c.

TRoc
 

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