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This question already has an answer here:

According to Einstein and Brian Greene, does it logically follow that the photon remains stationary in the fourth dimension?

In An Elegant Universe, Brian Greene writes:

“Einstein found that precisely this idea—the sharing of motion between different dimensions—underlies all of the remarkable physics of special relativity, so long as we realize that not only can spatial dimensions share an object’s motion, but the time dimension can share this motion as well. In fact, in the majority of circumstances, most of an object’s motion is through time, not space. Let’s see what this means.” Space, Time, and the Eye of the Beholder, An Elegant Universe, Brian Greene, p. 49

Brian Greene and Albert Einstein also state that there is one and only one velocity for all entities through the four dimensions--the velocity of light or c.

A photon travels at c through the three spatial dimensions. All of its velocity is directed through the three spatial dimensions. Thus Brian and Einstein are stating that a photon must be stationary in the fourth dimension. For if the photon had any velocity component in the the fourth dimension, its velocity would be different from c, which is not the case.

On the other hand, if an object is stationary in the three spatial dimensions, it must be moving at c through the fourth dimension.

We can summarize this as:

Axiom: All entities have one velocity through the four dimensions--c. (Einstein & Brian Greene).

Axiom: The velocity of light (photons) is c through the three spatial dimensions. (Einstein)

Theorem: The photon remains stationary in the fourth dimension, as all of its velocity c is through the three spatial dimensions.

Does this logic make sense?

Also, do you prefer using the word "Axiom" or "Postulate"?

An Axiom or a Postulate is a Truth.

A Theorem is that which follows logically from Axioms.

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marked as duplicate by David Hammen, CuriousOne, AccidentalFourierTransform, John Rennie special-relativity May 23 '16 at 15:32

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Photon experience infinite time dilation and hence, time is stationary for it. Does photon experience time

 photon travels at c through the three spatial dimensions. All of its velocity is directed through the three spatial dimensions. Thus Brian and Einstein are stating that a photon must be stationary in the fourth dimension. For if the photon had any velocity component in the the fourth dimension, its velocity would be different from c, which is not the case.

All this is non sense because there is nothing like speed of time in actual world. It's just a minkowski space concept. You cannot compare speed of object in time axis and 3 dimensional world. Calculating speed in 4D

Axioms and postulate serve as a basis for deducing other truths. The ancient Greeks recognized the difference between these two concepts. Axioms are self-evident assumptions, which are common to all branches of science, whilepostulates are related to the particular science.

The two axioms are postulates and not axioms , since they are relevant to only one branch, physics.

Theorem seems to correct.

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