Transcript
Why can you gaze at a golden sunset without harm, and yet one fleeting glance at a solar eclipse could damage your vision forever? And in case you think those warnings are overblown, in the last two days since the solar eclipse, we've seen a jump in Google searches for things like eye pain, blurry vision, headache, and why is there a black dot? There are three key pieces to understanding the eclipse versus sunset puzzle. Light. You probably know that white light from the sun is made up of many colors. But as you go towards the blue end of the rainbow, each bit of light contains more energy. interacts differently with other molecules, in the air and in our eyes. 2. Light and our eyes. Chromaphores are molecules in our body that absorb certain colors of light and pass through or reflect others, like hemoglobin in our blood, which absorbs everything but the red. Our retina and the layer of cells behind it have a bunch of these that absorb blue light. At low levels it's fine, but when the light gets too bright, all that energy has to go somewhere. So it creates free radicals, which are sort of like microscopic, angry drunks bouncing around and messing up the place. But speaking of bright light, light and our light. atmosphere. When light hits the outer parts of our atmosphere, the reddish colors go right through, but the blues get scattered all around, only some making it down to the surface of the earth, which is why the sky is blue. At noon, the light travels through less atmosphere to hit the surface, so it's really bright and has all the colors. At sunset, it travels through more atmosphere, scattering more. Only around one-tenth of the total light makes it through, and almost none of the blue, hence that beautiful orange color, and no eye damage.
Additional notes
Replying to @mlehm1 ⚠️ WARNING: The sun has to be VERY low to the horizon for there to be almost no danger! A good quote from one of the below research papers is: “once the total irradianee falls below 3 mW/cm2 (corresponding to an elevation angle of less than 5° at sunset in relatively clear weather), most people find it reasonably comfortable to look at a sunset which Iasts for Iess than 10 minutes) 📚References DOI: 10.1016/j.survophthal.2006.06.009 DOI: 10.1038/eye.2010.149 PMID: 11157889 For a great video on the more technical aspects of Rayleigh Scattering, check out @ScienceAsylum on YT! #science #eclipse #solareclipse #edutok
References
- Solar retinopathy / eclipse eye-safety review. DOI: 10.1016/j.survophthal.2006.06.009.
- Solar retinopathy / eclipse eye-safety source. DOI: 10.1038/eye.2010.149.
- Solar/sunset eye-safety source. PMID: 11157889.