It's easy to forget, but much of the world is not visible to us. I do not mean that things are really tiny or in any metaphorical way. No, most of the world is literally invisible.
This is because what we call visible light is actually a tiny part of the much larger electromagnetic spectrum. The rainbow we see is in the midst of a vast continuum of wavelengths, including high-energy gamma and ultraviolet radiation, to much lower levels of infrared and radio waves.
There is a lot out there that we miss. However, a group of researchers from the US and China has found a way to show the eyes of these otherwise invisible wavelengths in the near infrared, no goggles or bulky equipment necessary. Using nanoparticles injected into their eyes to turn infrared photons into visible ones, they say they have given mice the opportunity to look beyond the visible spectrum to which the rest of us are limited.
Beyond the Rainbow
The concept is fair simple. The scientists used nanoparticles that were designed to combine two photons of infrared light into a single photon that could accommodate mammalian eyes. The result is that incident infrared photons with wavelengths (read, energies) of 980 nanometers are translated into photons with wavelengths of 535 nanometers, which is in the green region of the visible spectrum. It effectively transformed infrared light into visible light in her eyes. Greening the planet indeed.
The nanoparticles were coated with a protein that helps them bind to photoreceptors and injected under the retina of mice, where they cling to the sticks and cones that turn photons into neuronal messages in our eyes. [1
Then they assembled them in a simple arrangement of two boxes connected by a point door opening. One box was dark, the other was illuminated by infrared light. As with a normal mouse, mice with the nanoparticles consistently prefer the dark box. But mice without nanoparticles did not care what box they were in – since only the available light was infrared, they both looked dark.
Further testing has shown that mice can not only see infrared light, their perception was good enough that they could distinguish infrared illuminated shapes from each other. To do this, the researchers relied on a simple water labyrinth test that challenged the mice to find a hidden platform to stand on. The position of the platform was indicated either by a circle or an infrared illuminated triangle, and the mice proved to be able to recognize certain shapes to find them.
They also confirmed that the nanoparticles did not impair the visibility of mice's normal light, and that they could see infrared in addition to normal lighting conditions. In addition, the researchers found no unpleasant side effects in the injections of nanoparticles. The mice's vision was undisturbed, the inflammation was negligible and the nanoparticles were flushed out of the eyes after a few weeks.
The researchers report their findings in the journal Cell Infrared-colored glasses
So, we probably all think exactly the same now. They made Predator mice!
The titular aliens have thermal imaging and thermal imaging is infrared, right? Something like that. Gang Han from the University of Massachusetts Medical School says the comparison is correct, but there is a functional problem. Actually, two of them. First, the nanoparticles injected by the researchers only received infrared photons of a specific wavelength in the near infrared. Thermal signatures release photons with much lower energies, far too low for the nanoparticles to pick them up. Han says nanoparticles that can absorb heat signatures are technically possible, but they have not developed them yet.
The other problem of heat-sight is that we are warm-blooded mammals. Even if we could take infrared photons at these wavelengths, our eyes would be flooded with photons from our own body heat. The resulting noise means we can not see anything at all due to the infrared static. I'm sorry, Bodyhacker.
Sci-fi dreams aside, there are actually some real applications for technology like these, says Han. Nanoparticles that adhere to our photoreceptors could one day be used to treat vision problems, as he says, as well as deliver drugs to our eyes. He believes that a similar technique could be applied to photons of higher energy than we could see, which also allows light to be seen in the ultraviolet spectrum.
The mouse and the human eye are also very similar, so the nanoparticles would do this. It probably works in humans without modification, he says. Of course, the procedure was not approved by the FDA, but the type of injection they use is already common, and the nanoparticles themselves do not seem to harm the mice. (Han himself says that he would do it, "if my spouse says yes …")
A vision enhanced with near-infrared features would not allow us to hunt prey through the forest, but could otherwise open our world , Seeing new wavelengths, for example, could add a nuance to the usual outlook, or reveal things that were previously concealed in invisible wavelengths.
Star observation would never be the same. Infrared photons are streaming down from the stars – astronomers often use infrared light to observe the universe.
Turning our eyes to the night sky would be a completely new experience. Stars and galaxies that were previously invisible would shine, and their electromagnetic transmissions became visible to our naked eyes. It would be a new perspective on the universe, no matter how small, beyond the limits of our biological senses.