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Comment by ainiriand | Hacker News Reader

Technically, it is not the picture of an atom. The wavelength of light is way too big for atoms. The picture is about the photons emitted by the atom after photo-stimulation. But anyway , one of the coolest pictures I've ever seen.

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Technically, pictures always represent the light emitted or reflected off objects, not the objects themselves (hence photo-graphy, "drawing with light").

However I agree that "Picture of light emitted just by a single trapped atom" would be a more accurate title and yet still incredibly cool.

First, reflection and emission are not the same. But more importantly, the only sensible definition of "seeing an object" is that the angular distribution of the light entering your eyeball carries some information about the geometric shape of the object. Otherwise, we could just as correctly say that when we look at dog we are seeing the sun or the overhead florescent bulbs; that's where the photons came from. Likewise, if I put a piece of strongly frosted glass between me and the dog, it would be misleading to say I can "see the dog" even if the photons that come from the dog reach my eye. The key reason this is wrong is that strongly frosted glass scrambles the information.

>Otherwise, we could just as correctly say that when we look at dog we are seeing the sun or the overhead florescent bulbs; that's where the photons came from

No, they didn't. The energy came from the sun, however the photons which are collected in your retina to form the image of a dog were emitted from the dog itself. "Reflection" is just the stimulation of photon emission via radiation.

https://en.wikipedia.org/wiki/Photoelectric_effect

You're gesturing at an unconvincing objection: that there is no difference between reflection and emission because there is a sense in which light passing through matter is continuously being absorbed and re-emitted. (I say "gesturing" because you don't actually know the physics; it is completely different than either stimulated emission or the photoelectric effect, which you could tell by reading the Wikipedia articles.) Explaining why this objection is boring and unconvincing would ultimately be a long discussion in the philosophy of science ("how can we keep using folk terminology that presumes a sharp devision between two concepts when a theory of physics suggests they are actually just part of a continuum?"), but you can get a sense of that by noticing that emission generally involves a change in the frequency of light while reflection does not.

> Technically (...) The picture is about the photons

Technically, all pictures are about photons.

For the images to human interface, sure. But you can use pretty much anything small and fast enough to take pictures - neutrons, neutrinos, various ions, phonons...

Now, taking photos is inherently photon/E&M based.

It's as much a picture of an atom as a picture of an energized light bulb filament is a picture of a light bulb filament. I don't think anyone would say the latter is "technically" not what it is.

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