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This question, I suppose, applies to all kinds of 'new' observational equipment that allow us to observe parts of nature that we weren't able to observe before. This may include the electron microscope when it was first invented. Another example may be the fairly new 'quantum microscope' which can be used to receive images of electron orbitals in atoms (or, at least, something similar).

How do we check that these instruments, when they are first designed and built, are giving us 'accurate' images such that what we observe is really what is there.

For example, with a (low power) microscope, we can use it to observe things that we can already observe with our naked eye and therefore confirm its accuracy. The same with electron microscopes on some scales. You can observe an ant with the naked eye and when an ant is put under an electron microscope, although there are now more details, you can tell its an ant (the ant's structure i.e. legs, head, antenna etc... are still visible).

Is the same thing possible when using very powerful equipment like scanning tunnelling microscopes or is some other process used all together? It seems to me that if you're inventing some observational equipment that allows you to see parts of nature never observed before, you would need to be able to check in some way that the image corresponds to something "real".

Thanks.

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  • $\begingroup$ Any number of surface reconstructions were known before STM. These structures were known through ion, electron, and x-ray techniques, including precise measurements of their repeat spacings. Things like the 7x7 reconstruction of Si(111) come to mind. $\endgroup$
    – Jon Custer
    Aug 24, 2018 at 13:25
  • $\begingroup$ @JonCuster So is my general idea correct? That we compare images generated by new devices with those created by techniques we already know to be reliable? Also could you link me to examples of any of those images/techniques? $\endgroup$
    – Joe Lee-Doktor
    Aug 24, 2018 at 13:37
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    $\begingroup$ Something like nature.com/articles/351215a0 might get you started. $\endgroup$
    – Jon Custer
    Aug 24, 2018 at 13:42
  • $\begingroup$ @JonCuster So is this saying that 'high temperature surface-reconstruction' is a phenomena observable with both electron diffraction techniques and STM only that STM provides much higher resolution? $\endgroup$
    – Joe Lee-Doktor
    Aug 24, 2018 at 14:04
  • $\begingroup$ With LEED/RHEED one can determine through electron diffraction that there is a surface reconstruction and what the size of a cell is. Diffraction theory allowed people to determine what the atom positions were (or were likely to be). STM showed the atoms in their actual positions (which were well predicted), but furthermore allowed one to directly observe the terrace/step (3D) structure of the surface which provides key insight into how growth occurs. $\endgroup$
    – Jon Custer
    Aug 24, 2018 at 14:07

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I think that the method of finding that what you are probing is consistent is in numerical confirmation of the values obtained by theoretical studies.

Checking that something is real by means of human sensory experience comparisons stops right when our senses cannot reach that information (ex.: too small things). After that, you can only compare new data with mathematical results.

Sometimes you can bypass the problem trying to use a microscopic effect to produce a bigger, macroscopic effect, so you can transpose the subject to our sensory domain. For example you cannot see a microscopical particle of 1 nm, only a microscope can, but if you put 1 billion particles together in line, you can see a meter of particles of 1 nm with naked eye.

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  • $\begingroup$ It wouldn't necessarily have to be direct overlap between human sensory perception and the scanning techniques. Are there any objects/phenomena observable using both scanning tunnelling microscopes AND electron microscopes, for example? $\endgroup$
    – Joe Lee-Doktor
    Aug 24, 2018 at 14:21
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    $\begingroup$ Yes, in fact there is a microscope called STEM (Scanning and Tunneling Electron Microscopy) which uses the same particle - the electron - for both scanning or tunneling, adjusting the parameters for both utilizations. Common objects studied in STEM is something about which you want to know its surface but also its intern. $\endgroup$
    – Costantino
    Aug 24, 2018 at 18:55

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