- #1
acesuv
- 63
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I've heard two hypothesis:
Which one is it?
1. The air causes the image of the moon to literally appear larger
2. The increased size of the moon comes purely from illusion of perspectiveWhich one is it?
ModusPwnd said:2
Try it by comparing it to an object for reference. (a ruler perhaps)
That's why it's called the moon illusion. It is an incredibly compelling illusion, even for those who know that it's all in our heads.acesuv said:So #1 is definitely wrong? :uhh:
Pick a camera, make one picture at the horizon and one when the moon is high in the sky (with the same camera settings of course), and compare.acesuv said:So #1 is definitely wrong? :uhh:
No. 3. The increased size of the moon is real. Right now the moon appears largest because it is at its closest distance from to the earth. It is 14% larger and 30% brighter than at the apogee.acesuv said:I've heard two hypothesis:
1. The air causes the image of the moon to literally appear larger
2. The increased size of the moon comes purely from illusion of perspective
Which one is it?
I had just been out for a walk and remarked to my wife how much larger the full moon on the horizon appeared tonight than on previous occasions. So I just assumed the question as asking why the full moon appears larger at the horizon now as opposed to on other full moon occasions.mfb said:Well, that is not related to its apparent position in the sky.
That is precisely the premise, Andrew. It's called the moon illusion. It's a very compelling illusion to a significant majority of viewers. I myself am susceptible even though I am fully aware that it's all in my head. A full moon on the horizon looks huge compared to the tiny circle the moon makes when it is high in the sky. There have been a number of competing hypotheses put forth to explain why this illusion is so compelling.Andrew Mason said:If the question is why does it look bigger on the horizon than higher in the sky I am not sure I agree with the premise.
phinds said:acesuv, just FYI, had you typed the subject line of this thread into Google you would have gotten the same information as give here. Try to remember that Google is your friend.
Your measurements were not precise enough. The moon should be about 1.5 percent larger when directly overhead than when it is seen on the horizon.cabraham said:A long time ago I observed the moon high in the sky and at the horizon comparing its image to a coin. I held the coin at arm's length and observed the relative size and coverage. To my surprise and in accordance with what I read about this subject, the size of the moon was unchanged. Blocking it with the same coin held at arm's length affirmed that the size of the moon's image is the same high in the sky and at the horizon.
Nothing at all to debate here. The image appearing larger at the horizon has already been correctly explained. We perceive the sky as a canopy with a low height, but the horizon seems far away. At the horizon the size is the same as high in the sky. But because we think the horizon is further away than the sky canopy, our mind falsely concludes that the horizon image is larger.
The coin affirms positively that the images are both the same size. Trust measurements more than your senses.
Claude
Andrew Mason said:Your measurements were not precise enough. The moon should be about 1.5 percent larger when directly overhead than when it is seen on the horizon.
Andrew Mason said:Your measurements were not precise enough. The moon should be about 1.5 percent larger when directly overhead than when it is seen on the horizon.
I was just pointing out that the moon is not the same size high in the sky as it is at the horizon. And I don't know what "near enough for jazz" means but it doesn't sound like science.sophiecentaur said:Also, the length of your arm could effectively change as you raise it and lower it. That experiment is certainly near enough for jazz and you shouldn't really be dissin' it.
sophiecentaur said:Also, the length of your arm could effectively change as you raise it and lower it. That experiment is certainly near enough for jazz and you shouldn't really be dissin' it.
gerben said:Moreover, the distance from (each of) your eye(s) to the tip of your finger is not the same for every orientation of your stretched arm.
Many people have noticed that the moon appears larger when it is closer to the horizon, compared to when it is high in the sky. This phenomenon is known as the moon illusion, and it is an optical illusion that is caused by our brain's perception.
No, the size of the moon does not physically change when it is at the horizon. It remains the same size throughout its orbit around the Earth.
The moon illusion is caused by a combination of factors, including the moon's position in the sky, our brain's perception, and the objects around us that provide a sense of scale.
Yes, the moon illusion can also occur with other celestial objects, such as the sun and stars. However, it is most noticeable with the moon due to its large size and brightness.
Yes, the moon illusion has been studied by scientists for centuries, and there are several theories that attempt to explain it. Some suggest that it is a result of the brain's perception and depth cues, while others propose that it is influenced by atmospheric conditions and the curvature of the Earth.