Exploring the Mystery of Light Speed: Nearest Star vs. Farthest Galaxy

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SUMMARY

The discussion clarifies the concept of light speed as defined by the theory of Special Relativity, emphasizing that while the speed of light remains constant at approximately 299,792 kilometers per second (c), the time it takes for light to travel varies based on distance. Light from the nearest star reaches Earth before light from the farthest galaxy due to the difference in distance, despite both traveling at the same speed. The conversation highlights the importance of understanding the distinction between speed and time in the context of light propagation.

PREREQUISITES
  • Understanding of Special Relativity principles
  • Familiarity with the concept of light speed (c)
  • Basic knowledge of frames of reference in physics
  • Awareness of astronomical distances (e.g., light-years)
NEXT STEPS
  • Research the implications of Special Relativity on time dilation
  • Explore the concept of light-years and astronomical measurements
  • Study the effects of gravitational fields on light propagation
  • Learn about the frame of reference and its impact on perception of time and distance
USEFUL FOR

Astronomy enthusiasts, physics students, educators, and anyone interested in the fundamental principles of light and its behavior in the universe.

Jim Beam
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So, if the speed of light appears to reach the observer at the same time no matter the observers velocity, then does that mean that light from the nearest star reaches us just as quickly as light from the farthest galaxy?
 
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Jim Beam said:
So, if the speed of light appears to reach the observer at the same time no matter the observers velocity, then does that mean that light from the nearest star reaches us just as quickly as light from the farthest galaxy?

I think you may have misread or misunderstood something. Light doesn't take the same amount of TIME regardless of the source. It has the same SPEED, regardless of the source. The constancy of the speed of light is one of the fundamental postulate of Special Relativity, NOT the constancy of the TIME that light travels.

This correction should answer your question above.

Zz.
 
ZapperZ is right, light is emmited from a source, no matter what its inetrial frame is, at c. But if one source if further from the other, the closer sources light will reach us first. Now if you were in the frame of reference of the light, then it would all reach us at the same time, since at the speed of light, d becomes 0, and time becomes 0, so you can say that light is everywhere in the universe at the same time. But we do not live or can see the frame of reference of light, so using this explanation is rather useless.
 

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