Is the Light Cone a Valid Representation of Light's Behavior?

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SUMMARY

The discussion centers on the validity of the light cone as a representation of light's behavior in space-time diagrams. Participants clarify that while light rays spread isotropically, the hypotenuse of the cone does not represent the path of any particle or signal, as it exceeds the speed of light (c). The space-time interval remains zero for events connected by light-speed paths, emphasizing that the slant edge of the cone does not correspond to actual motion. The distinction between light cones and world lines is crucial for understanding relativistic effects.

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  • Understanding of space-time diagrams
  • Familiarity with the concept of light cones in relativity
  • Knowledge of the speed of light (c) and its implications
  • Basic grasp of the spacetime interval and null trajectories
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zarmewa
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As smatter in the subject therefore I have the following confused questions about the light-cone.

As we all know that when a flash of light is released from source, light-rays spread out isotropically in space, tracing out a cone on a space-time diagram. As "light-cone" is expanded at the speed of light, and light emitted at the apex and moves on the surface of the cone, therefore, at any instant “t” say one light second, the radius, edge and the vertical axis of cone represent a right angle triangle in which

Vertical axis is the perpendicular of triangle; x = time

Radius of cone is the base of triangle; y = speed of light in one second

Edge of the cone is the hypotenuse of triangle; z = space-time diagram of a pulse in one second

Thus x2 + y2 = z2, where z > c, so is this possible?

The space-time interval is always zero between two events connected by a light speed path BUT the slant edge of cone which is GREATER than the speed of light "c" represents the true motion of a pulse [world line] in both space and time, therefore, isn’t time dilating even in a stationary light clock due to extra distance covered by a pulse in its world-line?
 
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I don't think the Light Cone in a spacetime diagram is the same as a light cone from an object emitting light.
 
zarmewa said:
Vertical axis is the perpendicular of triangle; x = time

Radius of cone is the base of triangle; y = speed of light in one second

Edge of the cone is the hypotenuse of triangle; z = space-time diagram of a pulse in one second

Thus x2 + y2 = z2, where z > c, so is this possible?
The hypotenuse you're describing doesn't represent the path of any particle or signal---its just some line that you're drawing. The length of that line is 'z', which is not a velocity (like the speed of light 'c').

zarmewa said:
The space-time interval is always zero between two events connected by a light speed path BUT the slant edge of cone which is GREATER than the speed of light "c" represents the true motion of a pulse [world line] in both space and time
The spacetime interval (ds) is zero along a null-like trajectory (i.e. light path); a 'pulse' would follow the same time of (45deg) null-trajectory----not a world-line (horizontal or vertical depending on how you're drawing your diagram).
 

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