Study finds that, contrary to long-held assumptions, we humans can detect infrared light with the help of just our eyes

Dec 2, 2014 12:02 GMT  ·  By

As it turns out, there is no need whatsoever for us mere mortals to be jealous of world-acclaimed hero Superman and his insanely cool X-ray vision. Not when we have a superpower of our own that's even cooler because it's real, that is.

Thus, scientists with the Washington University in St. Louis, US, say that, contrary to long-held assumptions, it is possible for us mere mortals to detect supposedly invisible infrared light with the help of just our eyes.

How and when people can see infrared light

Like X-rays, ultraviolet light and radio waves, infrared light is considered to be outside our visual spectrum. What this means is that we cannot see it with the naked eye and instead need high-tech equipment to detect its presence.

The thing is that, as shown by an investigation recently carried out by brainiacs with the Washington University, infrared light is not exactly invisible to the naked eye. On the contrary, the human retina can sometimes sense it.

In a paper in the journal Proceedings of the National Academy of Science, the researchers explain that, in order for this to happen, pairs of infrared photons must hit the same pigment protein in the human eye at nearly the same time.

In laboratory conditions, this phenomenon was recreated by firing pulses of infrared light emitted by lasers at retina cells. Interestingly enough, these experiments were carried out after several people reported seeing flashes of green light while toying with an infrared laser.

What exactly happens in the eye?

In their paper in the journal Proceedings of the National Academy of Science, the specialists behind this research project explain that, in standard vision, just one light particle, i.e. a photon, serves to create a molecule dubbed a photopigment and thus jump-starts the process of turning light into vision.

However, evidence at hand indicates that the combined energy of two infrared light particles can too activate a photopigment and thus make it possible for the human eye to see outside the so-called visible spectrum, which includes light waves 400 to 720 nanometers long.

“If a pigment molecule in the retina is hit in rapid succession by a pair of photons that are 1,000 nanometers long, those light particles will deliver the same amount of energy as a single hit from a 500-nanometer photon, which is well within the visible spectrum,” says researcher Vladimir J. Kefalov.

Not just a cool science experiment

Specialist Vladimir J. Kefalov and fellow researchers explain that, as cool as the find that people can sometimes see infrared light might be, the fact of the matter is that there is more to this series of experiments than just documenting a previously unknown human superpower.

Thus, the scientists argue that their find could pave the way for the development of better tools that fire a pulsing, infrared laser into the eye and that can help study the human retina and stimulate it, were it to cease functioning properly for various reasons.

“We hope that ultimately this discovery will have some very practical applications,” explains researcher Vladimir J. Kefalov.

Study finds the human eye can detect infrared light (5 Images)

Study finds the human eye can detect infrared light
The idea is to have two infrared photons act on the same pigment protein in rapid successionInfrared light usually falls outside the visible spectrum
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