Explaining the Aperture Illusion
Looking through a peephole can change the direction an object appears to move—a tilted rod going left to right seems to move downward at an angle when viewed through a hole (see video clip below). Dale Purves and his colleagues at Duke University think they know why. They asked volunteers to describe how they perceived the motion of moving lines seen through apertures. They also developed computer simulations of a virtual rod moving in three-dimensional space in which information regarding its direction was stripped out (via projection onto a two-dimensional surface). How the volunteers saw the movement nearly perfectly matched those generated by the flattened-out simulation, suggesting that images formed on our basically two-dimensional retinas do not convey aspects of three-dimensional motion. Hence, our perceptions of the directions of moving objects are mental constructs based on past experience. Scrutinize the analysis in the January 6 Proceedings of the National Academy of Sciences USA.
—Charles Q. Choi
Protein For Sight
A protein called histone deacetylase 4 (HDAC4), which regulates bone and muscle development, also promotes healthy vision, according to Harvard Medical School researchers. Reducing levels of this protein in the eyes of lab mice led to the death of retinal cells—specifically, rod photoreceptors and bipolar cells, which relay signals from photoreceptors to the optic nerve. Boosting its levels decreased naturally occurring death among the bipolar cells and prolonged the lives of photoreceptors in mice with diseased eyes. See more in the January 9 Science.
—Charles Q. Choi
Silkworms: What the Astronauts Eat?
Interplanetary travel probably means that astronauts will need to carry ecosystems along to supply food and oxygen. Past studies of potential space food have considered poultry, fish and even snails, newts and sea urchin larvae, but they all have downsides. Chickens, for instance, require a lot of food and space, and aquatic life is sensitive to water conditions that may be hard to maintain.
Scientists at Beihang University in Beijing suggest recruiting silkworms, which are already eaten in parts of China. These insects breed quickly, require little space, food or water, and produce only minute amounts of excrement, which could serve as fertilizer for onboard plants. Silkworm pupae, which are mostly edible protein, contain twice as much essential amino acids as pork and four times as much as eggs and milk. The scientists, whose conclusions were published online December 24, 2008, by Advances in Space Research, also point out that chemical processes could even make the silk digestible. Move over, Tang. —Charles Q. Choi
This article was originally published with the title Explaining the Aperture Illusion.
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3 Comments
Add CommentExplaining the Aperture Illusion
Reply | Report Abuse | Link to this.....when viewed through a hole (see video clip below).
What video clip? I can't find the clip!
The illusion is created by the the eye watching the directional reduction of the black space.
Reply | Report Abuse | Link to thisIs it just me, or does this not seem like a true illusion? If the information is so constrained as to make either visual explanation equally plausible and rational, that's not an illusion. For example, one could program the output to show a partial line getting smaller and moving down and to the right, and it would be indistinguishable from the "partial" view of a diagonal line moving horizontally to the right. That is, one is not "mistaken" in the interpretation as one is with a true illusion.
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