The discussion revolves around the concept of the velocity of a photon in four dimensions, specifically addressing its velocity in three spatial dimensions and the fourth dimension. Participants explore the definitions and implications of motion in four-dimensional spacetime and raise questions about the nature of photons and gravitational waves.
Participants do not reach a consensus on the definitions and implications of a photon's velocity in four dimensions. Multiple competing views and uncertainties remain regarding the nature of motion in four-dimensional spacetime and the physicality of photons and gravitational waves.
The discussion highlights limitations in definitions and assumptions regarding the nature of dimensions and motion, as well as the challenges in interpreting questions about four-dimensional physics.
Either ##c## or more or less anything you want depending on exactly how you define this.Epic Mythology said:What is the velocity of a photon through the three spatial dimensions x1, x2, x3?
I don't think this has a sensible definition.Epic Mythology said:What is the velocity of a photon through the fourth dimension x4?
I agree, it is undefined since proper time is not defined for a pulse of light.Ibix said:I don't think this has a sensible definition.
If you are talking about four dimensions, nothing moves in four dimensions. "Motion" is looking at different three dimensional slices of 4d objects and noting that those different slices aren't the same.Epic Mythology said:Interesting. Do physicists agree that a photon is a physical object? Do physicists agree that x4 is a physical dimension?
If so, what is the physical photon doing relative to the physical dimension x4? How is the physical photon moving relative to the physical dimension x4?
Do gravity waves propagate through four dimensions, or only three dimensions? Do objects move through spacetime or only space? Do objects move only through space, but never through time? Are you saying all objects are stationary in time?Ibix said:If you are talking about four dimensions, nothing moves in four dimensions. "Motion" is looking at different three dimensional slices of 4d objects and noting that those different slices aren't the same.
Gravitational waves. Gravity waves are a kind of deep water wave, the naming and study of which predate relativity by centuries.Epic Mythology said:Do gravity waves
In a relativistic model everything is a 4d structure. Whether you use the word "propagating" to describe them and how you interpret that is really up to you, but generally if you are thinking of anything as changing over time then you are thinking in three dimensional terms. Which is fine, but will severely hamper your understanding of answers about four dimensions.Epic Mythology said:Do gravity waves propagate through four dimensions, or only three dimensions?
If you are thinking of spacetime then you are (or should be) thinking of 4d structures whose "change over time" is encoded in their structure. To have a notion of motion you need to split spacetime up into space and time, and then you can talk about rate of change of place in space, which is motion.Epic Mythology said:Do objects move through spacetime or only space?
What would you mean by "moving in time"?Epic Mythology said:Are you saying all objects are stationary in time?
Ibix said:Gravitational waves. Gravity waves are a kind of deep water wave, the naming and study of which predate relativity by centuries.
In a relativistic model everything is a 4d structure. Whether you use the word "propagating" to describe them and how you interpret that is really up to you, but generally if you are thinking of anything as changing over time then you are thinking in three dimensional terms. Which is fine, but will severely hamper your understanding of answers about four dimensions.
If you are thinking of spacetime then you are (or should be) thinking of 4d structures whose "change over time" is encoded in their structure. To have a notion of motion you need to split spacetime up into space and time, and then you can talk about rate of change of place in space, which is motion.
What would you mean by "moving in time"?
3 questionsEpic Mythology said:What is the velocity of a photon through the four dimensions?
What is the velocity of a photon through the three spatial dimensions x1, x2, x3?
What is the velocity of a photon through the fourth dimension x4?
4 questions.Epic Mythology said:Interesting. Do physicists agree that a photon is a physical object? Do physicists agree that x4 is a physical dimension?
If so, what is the physical photon doing relative to the physical dimension x4? How is the physical photon moving relative to the physical dimension x4?
4 questionsEpic Mythology said:Do gravity waves propagate through four dimensions, or only three dimensions? Do objects move through spacetime or only space? Do objects move only through space, but never through time? Are you saying all objects are stationary in time?
3 questionsEpic Mythology said:Do you agree that mass curves both space and time? As a mass moves through spacetime, do you agree that the mass curves both space and time? Do you agree that as the mass passes a point, the space and time will curve in the vicinity of the point, and then, as the mass leaves the area, the space and time will return to being flat or uncurved?