Stars don’t twinkle. When light travels through thousands of kilometres, the turbulence of the atmosphere scatters it. As a result, it appears to change in brightness and position. In other words, inferior vision of human eyes make them twinkle. My motive here is not to denigrate the 209 year old nursery rhyme by Jane Taylor; but to analyze the second line.
“How I wonder what you are”.
Indeed, for a long time astronomers wondered why stars appear to twinkle and how to make it stop so that they could study them well. A solution was finally found by William Harper who devised the theory of adaptive optics. In simple terms, if you shoot a laser to a bright star, comparatively non-twinkling, and measure the wavefront scattering; you have a reference to compare and correct the twinkling of the star you are interested in.
Some of you might be wondering why I am talking about astronomy in a neuroscience blog. The reason is today I met a neuroscientist who specializes in adaptive optics. Over lunch, Prof. Joseph Carroll from medical College of Wisconsin explained how adaptive optics is used today as a imaging and correcting tool of retina. I was sitting there thinking about the beauty of science. A seemingly innocuous theory can spread like a forest fire that end up engulfing 2-3 disparate disciplines.
Why do we need adaptive optics when we can just get contact lenses or glasses? Lenses can only correct for the aberrations that remain fairly constant over lifetime. However, certain distortions change considerably from one area to another. Adaptive optics can correct for this kind of errors, one microscopic area at a time through the same principles as the twinkling stars.
When applied in a slightly different manner, this technique has made it possible to capture images of photoreceptors of the retina. Photoreceptors are the cells that gives us the ability to see. Unlike most of the retina, which is transparent and refracts light, photoreceptors have the ability to reflect them. A deformable mirror placed on the path of this reflected light adapts to the different wavefronts and can be recorded through a ophthamoscope or microscope.
So the major thing to take away from this post is dig deeper into nursery rhymes and fairytales. They are always the gateways of fame. If you feel my claim is baseless, think about The Tale of Three Brothers (If you don’t know what that is, you are a muggle).