Do our eyes digest light?
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Ltryptophan (
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March 6th, 2017
from iPhone
Where do you light particles that enter the I end up? Are we eating them with our eyes?
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13 Answers
Particles in the visible range of the spectrum are absorbed (or reflected) by rods & cones in our retinas, setting off neurochemical reactions in our nervous system (or causing red eye in photos of us).
It means that the particle is not reflected or refracted, and the energy transmitted by the particle is transformed from light into some other form, in this case chemical energy sufficient to set off a chain reaction in the nerves leading from the retina to the brain.
edit: change “chemical” to “electro-chemical”
Everything that blocks light absorbs it. Eyes, skin, rocks – the light that doesn’t reflect away tends to mostly convert to heat energy. I wouldn’t say digest, since it’s not the usual term used, though it seems just like an imaginative analogous way to think of it.
Photons that strike a photoreceptor cell in the eye have their electromagnetic energy converted into signals. Photons have no mass and once their energy is converted they no longer exist.
@flutherother photons must have mass as if they did not then they wouldn’t have any energy.
Photons are weird. They have energy because they are waves. They have a type of mass but not the sort you hold in your hand or eat.
When biologists Reger to ‘digestion ’ they are taking about a metabolic system. Our eyes don’t eat.
They do have the sort of you can hold in your hand. It’s just so small that you would never notice it. Energy and mass are two different states of the same thing. You can turn mass into energy and energy into mass.
Photons do not have mass, otherwise they could not travel at the speed of light. They do, however, carry momentum: https://en.wikipedia.org/wiki/Photon The momentum transfer of photons from the Sun onto satellite solar panels is enough to rotate the whole satellite!
To me, digestion is the breakdown of “food” into its constituent chemicals. When a photon enters the eye, it is absorbed and disappears into electro-chemical energy (as described by @Zissou ). There are no traces of the photons left, so it is not really digestion to me.
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