What are those colors you see when you rub your eyes? - Paul CJ Taylor
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In the 1600s, Isaac Newton conducted a series of experiments to better understand the lights and colors that sometimes appear when your eyes are closed. If you’ve ever sat around an evening campfire or unintentionally glanced at the Sun, you may have noticed illuminated patterns briefly dance along your vision. So how do these visual illusions form? Paul Taylor explores the science of afterimages.
Additional Resources for you to Explore
Afterimages can be generated by staring at anything under normal lighting conditions and then closing your eyes or looking at a blank wall. Afterimages are particularly easy to see after staring (under normal lighting) for up to 30 seconds. Check out this demonstration where negative afterimages can make a black and white photo seem colored. Build your own negative afterimage apparatus and explore the effect of distance.
Isaac Newton was an extraordinary physicist and mathematician. He is famous for his theory of gravity, his three laws of motion, and for his work developing calculus - mathematical tools for studying change. In addition to this theoretical work he also performed experiments and worked in the field of optics, the science of light. For example he showed with prisms that sunlight is really made up of light of different colors. In addition to possessing a brilliant mind he also did some things that come across today as less-than-intelligent, such as staring at the sun’s reflection or putting a needle (“a bodkin”) under his own eyeball. Do not try this at home! Newton wrote about his experiments staring at the sun in a letter, mentioning that afterwards “I began in three or four days to have some use of my eyes again.” You can see his original lab notebooks written in his own hand at the Newton Project.
“Phosphene” is a term often used to refer to a visual percept in the absence of any real light. Pressure phosphenes (also called “deformation phosphenes”) are also easy to see, just by gently rubbing your eye when your eyes are closed - and the first reports of this go back at least to Alcmaeon of Croton in Ancient Greece. There are other phenomena that can also give rise to visual percepts without light. Many people see floaters, for example: learn more about them in this TED-Ed lesson.
On the one hand, such visual phenomena lend themselves easily to experimentation. Because they can be generated so easily, people have been experimenting with them and writing about them for hundreds, if not thousands of years. Results from these experiments have long guided our understanding of how we see - any theory of vision needs to be able to explain how afterimages and phosphenes arise. On the other hand, studying perception can require extreme ingenuity and developing new neuroscientific methods. Today we can safely and non-invasively stimulate the brain to generate phosphenes, for example, using a method called transcranial magnetic stimulation (TMS). TMS can also generate simple movements, as in this lecture from the Royal Institution.
Isaac Newton was an extraordinary physicist and mathematician. He is famous for his theory of gravity, his three laws of motion, and for his work developing calculus - mathematical tools for studying change. In addition to this theoretical work he also performed experiments and worked in the field of optics, the science of light. For example he showed with prisms that sunlight is really made up of light of different colors. In addition to possessing a brilliant mind he also did some things that come across today as less-than-intelligent, such as staring at the sun’s reflection or putting a needle (“a bodkin”) under his own eyeball. Do not try this at home! Newton wrote about his experiments staring at the sun in a letter, mentioning that afterwards “I began in three or four days to have some use of my eyes again.” You can see his original lab notebooks written in his own hand at the Newton Project.
“Phosphene” is a term often used to refer to a visual percept in the absence of any real light. Pressure phosphenes (also called “deformation phosphenes”) are also easy to see, just by gently rubbing your eye when your eyes are closed - and the first reports of this go back at least to Alcmaeon of Croton in Ancient Greece. There are other phenomena that can also give rise to visual percepts without light. Many people see floaters, for example: learn more about them in this TED-Ed lesson.
On the one hand, such visual phenomena lend themselves easily to experimentation. Because they can be generated so easily, people have been experimenting with them and writing about them for hundreds, if not thousands of years. Results from these experiments have long guided our understanding of how we see - any theory of vision needs to be able to explain how afterimages and phosphenes arise. On the other hand, studying perception can require extreme ingenuity and developing new neuroscientific methods. Today we can safely and non-invasively stimulate the brain to generate phosphenes, for example, using a method called transcranial magnetic stimulation (TMS). TMS can also generate simple movements, as in this lecture from the Royal Institution.
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Meet The Creators
- Director Sofia Pashaei
- Educator Paul CJ Taylor
- Narrator Alexandra Panzer
- Composer Cem Misirlioglu, Work Play Work
- Sound Designer Cem Misirlioglu, Work Play Work
- Director of Production Gerta Xhelo
- Produced by Abdallah Ewis
- Editorial Director Alex Rosenthal
- Editorial Producer Shannon Odell
- Script Editor Max G. Levy
- Fact-Checker Charles Wallace
