Einsteins light beam Lets go for a ride again

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Discussion Overview

The discussion revolves around the conceptual implications of light propagation, particularly in relation to Einstein's thought experiments about riding a beam of light. Participants explore the nature of light, its attenuation over distance, and the concept of light-years as a measurement of distance rather than time.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant ponders whether a beam of light stops as it fades with distance, questioning the nature of light's propagation.
  • Another participant clarifies that the beam of light does not stop but rather spreads out and becomes weaker as distance increases, likening it to the diminishing flow of water from a hose.
  • A different participant challenges the idea that light cannot travel beyond a certain point, explaining that gravity and electromagnetic waves extend to infinity, although their strength diminishes with distance.
  • There is a correction regarding the definition of a light-year, with one participant stating that it is a measure of distance, not time.

Areas of Agreement / Disagreement

Participants express differing views on the nature of light's propagation and its implications, indicating that multiple competing perspectives remain without a consensus.

Contextual Notes

Some assumptions about the nature of light and its interaction with the universe are not fully explored, and the discussion includes unresolved questions about the implications of light's behavior at vast distances.

tiger51
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Einsteins light beam...Lets go for a ride...again

I am not directly in the physics field, but I use physics at work and have always been enamored by it. If I did not post this question in the right place forgive me.

So here is my ponder if you will. I read Walter Isaacson's book when it came out a few years ago, and kept thinking and imaging riding that beam of light that Einstein rode many times in his head. Than I thought about the power of light. If you have a flat plane (imagine our world is indeed flat) and turned on a light and you start backing up while always looking at the light. Soon the light to you the observer has faded with the distance. Does this mean the beam of light has stopped? if riding at the tip of the beam does that mean that you would stop to? Then increase that size to the sun and start backing about from the sun at some point the light can not go any further I imagine, so where is the absolute light? I think about this because we use light to calculate time in light years. right?
 
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Does this mean the beam of light has stopped?

no, it just means the beam is spreading out with distance and hence becoming attenuated...weaker...the beam dims as the surface area of a square increases from the source...

like a hose you spray...the water flow weakens with distance from the nozzle..but don't take that analogy to far...
 


Then increase that size to the sun and start backing about from the sun at some point the light can not go any further I imagine,

Not really true, gravity and electromagnetic waves (light) extend to infinity but of course approach zero strength at infinite distance. On the other hand, if you get far enough away from a light source, the universe may be expanding fast enough that the light will never reach your location...yet tomorrow there will be some cosmic background radiation visible to us that was not visible yeterday...
 


tiger51 said:
I think about this because we use light to calculate time in light years. right?
No, a light-year is the distance traveled by light in one year.
 

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