Ultraviolet rays are part of sunlight, just above the spectrum of colours the human eye can detect. Much the same as infrared sits below red, just outside the visible rainbow. As you go from radio waves all the way up to gamma rays, energy increases. As a result, so does the danger posed.

So, if this light is harmful, why is the leader of the free world touting it as a potential cure for the coronavirus?

Info-graphic of the Electromagnetic Spectrum. Image courtesy of Jonathan S Urie It’s just high-energy light?


Nuclear fusion inside the Sun’s core produces waves across the entire electromagnetic spectrum. Gamma rays are converted to lower energies before reaching the surface, but the rest are emitted into space, hurtling towards Earth at, funnily enough, the speed of light. The most dangerous of these are absorbed by the atmosphere.

The Sun’s output peaks in the visible part of the spectrum, meaning this is the main type of radiation given off. Before thinking “Isn’t that lucky? What a coincidence!”, ditching your current beliefs and converting to cosmic creationist creeds, stop. Remember, the Sun was here long before humans. The science of the matter is that our eyes are adapted to the radiation our star most abundantly produces. If we inhabited a planet orbiting a star which peaked in infrared, we would likely see that instead.

Graph showing the distribution of the EM radiation emitted by the Sun. Image courtesy of the COMET program

Can it cure coronavirus?


It can kill airborne airborne virus particles and disinfect surfaces. This use has been common for well over fifty years. While helpful for cleaning, “UV light has not been shown to prevent covid-19 infection in humans or to kill the virus in infected patients.” This is according to the University of Pennsylvania, widely regarded as a more trustworthy scientific institution than Donald Trump.

Penn Medicine guidelines also point out how “The safety and efficacy of many UV light devices sold to the public are not routinely reviewed,” so, it might not yet be the time to try putting such radiation “inside the body, either through the skin or in some other way”. As far as I’m aware, a UV enema is not yet in development in any intellectual circles.

The risks

Even outside the body, overexposure to ultraviolet rays is a major risk factor for skin cancer. For these reasons, suncream is a must on exposed skin. Pasty complexions and turns of phrase like “Got to go red to go brown” probably constitute to Britain having relatively high skin cancer rates, especially considering we have four of the five cloudiest cities in Europe.

So, enjoy the summer weather as it really is a rare treat. But beware: don’t lie in the midday Sun hoping high-energy UV radiation will give you immunity when pubs reopen next week.

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