Light Years: Subjectivity and Distance Measurement

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Discussion Overview

The discussion revolves around the concept of light years as a measurement of distance, particularly questioning the role of visibility in this measurement. Participants explore the implications of subjective perception in distance measurement and the methods used to determine distances in astronomy.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant expresses confusion about the use of visibility in measuring distances, suggesting that if other species had different visual capabilities, their perception of distances to stars might differ.
  • Several participants clarify that a light year is defined as the distance light travels in one year, asserting that this definition is independent of visibility.
  • One participant questions whether visibility plays a role in measuring distances, prompting others to emphasize that visibility is not a factor in the definition of a light year.
  • Another participant mentions that brightness is just one method among many for determining distance, referencing external resources for further techniques.
  • One participant provides an example of measuring the speed of light using a laser, arguing that the measurement of a light year does not depend on visibility and can be determined through known distances and the speed of light.

Areas of Agreement / Disagreement

Participants generally agree that a light year is a fixed distance based on the speed of light and is not related to visibility. However, there remains disagreement regarding the implications of visibility in distance measurement, with some participants questioning its relevance.

Contextual Notes

There are unresolved aspects regarding the methods of measuring distances in space, and the discussion highlights a lack of clarity on how visibility might influence these measurements.

neugie92
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Light years-I just don't understand how something as subjective as visibilty, is used as a major indicator of distance. Isnt that subjective. What if some species had a million times the eye power than us humans, wouldn't they view the distance of let's say stars very differently because it wouldn't be as many 'light years' away from them.

Maybe I'm confused about how light years are actually measured, it just seems like using somethings visiblity to us, is a poor way to try to figure out actual distance.

Thoughts?
 
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A light year is the distance that light travels in a year. It has nothing to do with visibility.
 


mathman said:
A light year is the distance that light travels in a year. It has nothing to do with visibility.

but to meaure the distance traveled we base it on an increase or decrease in visibility? am I wrong?
 


There is no relation to visibility.

A light year is the distance light travels in one year. As the speed of light in vacuum is constant, this length is constant, too. It does not matter how good some eyes are.Edit: Looks like two topics got merged, as I posted the other replys were not in the thread.
 
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neugie92 said:
but to meaure the distance traveled we base it on an increase or decrease in visibility? am I wrong?

Yes, you are wrong. I can turn on a laser beam and bounce it off of a mirror at a known distance from me to measure the speed of light. Then, knowing this speed, I just multiply it out and the resulting distance is 1 light-year. It has nothing to do with visibility. The laser could be a bazillion watts or 1 microwatt, it does not matter as that does not affect the speed of the beam.

Maybe you are confused over how we measure the distance to objects in space. There are a variety of methods, and Jimmy's links go over some of them.
 

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