- #1
JC2000
- 186
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While trying to understand parallax and its use in measuring distances here, I had a few questions.
(1) Parallax is defined as the apparent movement of an object with reference to another object in the background when one views it from different angles. As in the movement of a finger relative to the background when viewed through either eye. Also, the source states that the illusion of seeing two points of the background when focusing on the point closer to the observer. This is attributed to the crossing/uncrossing of the eyeballs.
(a) Is the second scenario also an instance of the parallax effect?
(b) If so, how? (The first scenario involves movement of the foreground with respect to a background when the observers vantage points change (distance between eyeballs). On the other hand, the second scenario involves 'duplication' of the point in the background simply due to crossing over of lines of vision of each eyeball. The only common aspect between the two is that the shift is greater when the distance is smaller.).
(c) Have I misunderstood something in the second scenario?
(2) On the following page, the parallax method is used to find the distance of the moon from the Earth using a star in the background and by changing vantage points between Athens and Selsey.
(d) Here it is assumed that the tree points (Athens, Selsey and the Moon) form an isosceles triangle. I am unclear about the justification behind this.
(e) How is the angle of apparent movement of the star calculated?
(f) Is the angle of apparent movement of the star the same as the angle of apparent movement of the Moon because both the scenarios that were described in (1) are the same?
(g) None of this seems to correspond to the given image with the moon as the vertex of the triangle.
Sorry for the huge wall of text and asinine questions, I seem to be having a tremendous mental lapse.
(1) Parallax is defined as the apparent movement of an object with reference to another object in the background when one views it from different angles. As in the movement of a finger relative to the background when viewed through either eye. Also, the source states that the illusion of seeing two points of the background when focusing on the point closer to the observer. This is attributed to the crossing/uncrossing of the eyeballs.
(a) Is the second scenario also an instance of the parallax effect?
(b) If so, how? (The first scenario involves movement of the foreground with respect to a background when the observers vantage points change (distance between eyeballs). On the other hand, the second scenario involves 'duplication' of the point in the background simply due to crossing over of lines of vision of each eyeball. The only common aspect between the two is that the shift is greater when the distance is smaller.).
(c) Have I misunderstood something in the second scenario?
(2) On the following page, the parallax method is used to find the distance of the moon from the Earth using a star in the background and by changing vantage points between Athens and Selsey.
(d) Here it is assumed that the tree points (Athens, Selsey and the Moon) form an isosceles triangle. I am unclear about the justification behind this.
(e) How is the angle of apparent movement of the star calculated?
(f) Is the angle of apparent movement of the star the same as the angle of apparent movement of the Moon because both the scenarios that were described in (1) are the same?
(g) None of this seems to correspond to the given image with the moon as the vertex of the triangle.
Sorry for the huge wall of text and asinine questions, I seem to be having a tremendous mental lapse.