Our world is full of beautiful colors, so it’s easy to forget that the spectrum of light visible to humans is a teeny sliver of what’s out there in the universe. But wouldn’t it be fantastic to see in the dark? Scientists have done that, with mice!
Visible light is a small part of the electromagnetic spectrum.
Most of us are born with the capability to see what scientists define as visible light. It’s a matter of how our eyes function. Other animals see far more.
Snakes which hunt for warm blooded prey can detect infrared light (given off by body heat) with special sensors.
Pit organs enable snakes to see in infrared, or heat vision. A python (top right) and rattlesnake (bottom right) Arrows pointing to the pit organs are red; black arrow points to the nostril.
Blind snakes can still hunt and successfully find prey because of their pit organs.
Other animals are adapted to the opposite end of the the light spectrum.
Bees actually have five eyes! Two compound and three simple.
Bees find flowers with the ultraviolet capabilities they have in two of their five eyes.
Each of the two huge compound eyes is made up 150 tiny structures called ommatidia.
The number of ommatidia in the bee’s eyes allows it to find different types of flowers and hone in on the nectar location by their ultraviolet patterns.
The three simple eyes are called ocelli. Their job is to discern light intensity.
So it makes sense that many flowers have ultraviolet patterns on their petals. And that bees can see the patterns!
Butterflies and many other insects can see UV light, too!
Flower photographed in visible light (left) and ultraviolet light (right). The flower on the right is what a bee sees.
Human vision of a Black-Eyed Susan (top right.) What a bee sees in UV. (bottom right)
image ((C) Dr Schmitt, Weinheim, Germany, uvir.eu
Humans can’t perceive UV light directly because the lens of the eye blocks most light in wave length range of 300nm~400nm. If a lens is removed, such as with cataract surgery, then the human eye can detect UV light.
Interestingly, Monet could see UV iight! In 1923, Monet needed cataract surgery. This ability to see UV light is reflected in his later works. He painted white water lilies blue.
Humans with no lenses may have a more colorful world, but that is not true for bees. Bees can’t see red – closer to the longer wavelength end of the spectrum – while humans can. To a bee, red looks black. Bees see in shorter, UV wavelengths.
Let’s get back to those longer wavelengths, or red side of the spectrum. Seeing in infrared would enable us to see in the dark!
We’ve already mastered the ability to capture images of our world in infrared. Notice the red coloration closer to the equator, where it’s hotter. (image courtesy NASA)
Why not our eyes?
To break this limitation, researchers at the University of Science and Technology of China developed ocular injectable photoreceptor-binding nanoparticles. That’s a mouthful!
With the nanoparticles, mice were clearly able to perceive near-infrared light. They tested the mice using patterns projected in IR, indicating a reward. The patterns were repeatedly sought by the mice, indicating this was not just a general awareness but detailed perception in the wavelength. And the mice have suffered no ill effects!
The type of vision the researchers are trying to achieve wouldn’t be like the cool images infrared goggles produce. It would be more like seeing an object that was giving off heat with a brighter and greener intensity.
Does this mean we can throw away our heat vision goggles?
Don’t get too excited just yet. The FDA hasn’t approved this to date. And don’t forget, you need to have a needle put into your eyes…
But injected nanoparticles that glue themselves to photoreceptors could possibly be used to treat people with vision problems or to deliver drugs inside our eyes.
Vision augmented with near-infrared capabilities wouldn’t let us stalk prey through the woods, but it could potentially open up our world in other ways. Seeing new wavelengths of light might add nuance to common vistas, for example, or it might reveal things that previously cloaked themselves in invisible wavelengths.
Stargazing would never be the same! Infrared photons from stars constantly stream into our atmosphere. The NASA image below was taken in infrared.
Which would you rather have? Infrared vision or ultraviolet? Someday, you may be able to choose!