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Everything scattering light has a characteristic spectrum. The spectrum is defined by the way wherein the particular thing interacts with light, and this is set by the (1) chemical makeup and (2) texture (at the wavelength-of-visible light scale). You cannot change the spectrum without changing one of these two things, either by e.g. (1) altering the ...


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The picture drawn by docscience is basically correct, but the math that goes along with it was wrong - as a result, the "height of 370000 km" part of the answer is completely off. The effect you describe is well known by navigators: when you measure the height of the sun or star with a sextant, you actually have to take into account the height of the eye ...


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The reason it may not happen in a plane is probably because you are tilted with respect to the horizon (even if it may not feel like it due to fictitious forces). "Touching the Earth", you are "forced" by gravity to be straight up, and thus the triangle described in the comment above works. Also, these kinds of strange properties usually come from an ...


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The construction and calculations below show that if the altitude is very small compared to Earth's radius, the line of sight as measured from local vertical is very near 90 degrees. The Earth's radius is about 6371 km. For the line of sight to fall 1 degree you would have to elevate your point of view by about 370000 km!


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Binocular vision has already been discussed, but it left out an important aspect. A single eye is sensitive to distance. The shape of the lens changes to focus on near/far objects. The reason this is needed is that our pupil has finite size and cannot be modeled as a pinhole. The same physics is going on here as in a lens of a camera focusing on an ...


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To have depth perception two eyes are needed. Our two eyes are some distance apart which causes the photons from an object to arrive at slightly different angles. The brain then reconstructs the depth field from these differences. Similarly, we can figure out how far nearby stars are by using images made by a telescope at two different times of the year, ...



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