Why Does Comet Fluctuate in Size but Sun Doesn't?

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Discussion Overview

The discussion centers around the phenomenon of size fluctuation observed in comets compared to the apparent stability of the sun's size. Participants explore the visual effects and perceptual differences that might explain these observations, touching on concepts related to color perception and optical illusions.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that the fluctuation in perceived size of the comet may be related to color perception and the way our eyes adapt to different stimuli.
  • One participant questions what fluctuations are being referred to, indicating a lack of clarity on the phenomenon being discussed.
  • A reference to chromostereopsis is provided, which may explain the visual effects experienced by some individuals.
  • Another participant describes experiencing a receding effect with the comet image, attributing it to the color blue and its impact on perception.
  • Some participants report that they do not perceive any fluctuations in the images, suggesting variability in individual experiences.
  • Discussion includes considerations of color blindness and its potential influence on the perception of these visual effects, noting demographic differences in color perception.

Areas of Agreement / Disagreement

Participants express differing views on whether fluctuations are perceived in the images, with some experiencing the effect and others not. There is no consensus on the cause of these perceptions, and the discussion remains unresolved regarding the nature of the fluctuations.

Contextual Notes

Participants mention the influence of color perception and individual differences, including color blindness, which may affect the interpretation of visual stimuli. The discussion references external sources for further exploration of these concepts.

Johninch
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The following picture has been posted in the Astronomy section (by Dave C426913).

https://www.physicsforums.com/file:///C:/Users/John/AppData/Local/Temp/msohtml1/01/clip_image001.jpg
Source: http://www.space.com/4643-incredible-comet-bigger-sun.html

Why does the comet fluctuate in size but the sun does not? Why does it appear to get smaller but not bigger?

P.S. I was not able to post the image, but you can see it via the link. If you copy the picture to another document you will see the same effect i.e. the image fluctuation is not embedded.
 
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I don't know. Perhaps the color or our eyes being accustomed to the sun and nothing much bigger? I don't know.
 
Johninch said:
Why does the comet fluctuate in size but the sun does not? Why does it appear to get smaller but not bigger?

I'm not sure what you're talking about. What fluctuations?
 
Drakkith said:
I'm not sure what you're talking about. What fluctuations?
The orange disk remains stable, while the blue disk repeatedly (at about 1 to 2 second intervals) "tries" to recede. The article referenced by Vanadium 50 explains it. I haven't finished studying the article yet, but it says that some people do not see the receding effect. So as I understand it, I am experiencing a receding effect because of the blue color, which my brain translates into a repeated reduction of disk size.

I am going to do some experiments with Excel using different colors and shapes.
 
Interesting. Both images appear stable to me.
 
I used to see that effect at times, and I thought it was due to tired eyes playing a trick.
Tthe effect I notice with the sun/comet image.
But not on any image from the Wiki article.
 
Hmm. I wonder if the folks who have issues seeing the effects know their Ishihara color test scores for color blindness. Color blindness comes in two flavors, and varying levels of color perceptual ability. So it is possible to have a less than perfect Ishihara number and still be able to see colors - most of the time.

The reason I posted this is obvious - color plays a part in some of the wiki examples.

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0024265/

Eight percent of white males are color blind, females less than ~1 percent. Color perception alleles live on the X chromosome, females have 2, males one. Color blindness is most common among European males.
 

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