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I know humans can feel sunlight - even blindfolded, it's easy to tell if one is in the noon sun or indoors. However, I don't know about artificial light. Can humans feel sufficiently harsh artificial light?

I suspect that very very intense light will exert enough radiation pressure to be felt, but it would likely be lethal too. If that's the case, then I'd guess that we can feel sunlight because it contains ultraviolet radiation, which would make artificial light (i.e. light from lamps, bulbs and such) "invisible" to the skin.

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    $\begingroup$ You can certainly feel a heat lamp or an LED flashlight’s light. $\endgroup$
    – Ed V
    Commented Jun 28, 2022 at 13:58
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    $\begingroup$ Anybody who's ever performed under bright theater/tv/movie lights knows the answer to that one. $\endgroup$
    – Solomon Slow
    Commented Jun 28, 2022 at 14:06
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    $\begingroup$ @BioPhysicist yeah, I imagine we feel something else from the Sun. $\endgroup$
    – Allure
    Commented Jun 28, 2022 at 14:32
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    $\begingroup$ I used a variety of lasers in my career and you can definitely feel some of them! When the field service engineer installed our pulsed Nd-YAG laser with frequency doubler, tripler and quadrupler, he ran his fingers quickly through the tripled beam. The light pulses hitting his fingers made snapping sounds and little puffs of “smoke” were seen. I tried it myself and the laser pulses felt like sharp little snaps on my fingers. No damage, cool demo. $\endgroup$
    – Ed V
    Commented Jun 28, 2022 at 14:59
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    $\begingroup$ I reckon you've felt the heat from your stove. $\endgroup$
    – alemi
    Commented Jun 28, 2022 at 15:11

2 Answers 2

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I'd guess that we can feel sunlight because it contains ultraviolet radiation...

We feel sunlight because it's electromagnetic radiation (EMR), and whenever EMR of any wavelength is absorbed by some material, it's energy is converted to heat in the material. In other words, sunlight warms your skin and your clothing, and all of its wavelengths contribute to that warmth.

...which would make artificial light (i.e. light from lamps, bulbs and such) "invisible" to the skin.

Sunlight is bright! Normal indoor lighting is several orders of magnitude less bright (less powerful) than sunlight. At noon in the tropics, Every square meter of the Earth's surface receives about 1000 Watts of sunlight. Compare that to the roughly 100 30 Watts of LED lighting that I use to light up all of the walls, ceiling, and floor (tens of square meters) at night time in the office where I am typing this right now. And, that's 100 W of electricity: Only a fraction of that power actually gets converted into light.

Edit: Revised my estimate of the electrical power used by LED lights in my office.

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  • $\begingroup$ I'd guess that you're using about 11W of electricity and producing about 9W of visible light with modern LED bulbs. Of course, every light bulb is 100% efficient if you include infrared. The big wattage number on the packaging is the visible light equivalent of traditional incandescent bulbs. $\endgroup$
    – g s
    Commented Jun 28, 2022 at 17:56
  • $\begingroup$ @gs, Hmm,.. I don't think they're that efficient, but you're right about one thing. I added up the actual wattage of all of the lights in my office and it's more like 30W. $\endgroup$
    – Solomon Slow
    Commented Jun 28, 2022 at 18:47
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We don't 'feel' the force exerted by light on our skin but its presence in that it is converted to heat. So we can 'feel' the presence of light. There is no essential distinction between artifical or natural light, they are both electromagnetic radiation. Thus we can feel the presence of artifical light through warmth too. Generally, artifical light sources are too weak to detect by people by their warmth but if you hold your hands close to an incandescent bulb you can easily feel the warmth.

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  • $\begingroup$ FWIW, answering a question while also voting to close it gives the impression of "I think I deserve to answer this, but no one else should be able to." The purpose of closing a question is so that it does not receive any (more) answers until the OP fixed the problems of the post. $\endgroup$
    – BioPhysicist
    Commented Jul 6, 2022 at 16:44

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