Q: What are “actual pictures” of atoms actually pictures of?

Something IBM made with some very flat, very clean, very cold copper and a few hundred carbon monoxide molecules.

Something IBM made with some very flat, very clean, very cold copper and a few hundred carbon monoxide molecules.

Physicist: Actual pictures of atoms aren’t actually pictures at all.

There are a few good rules of thumb in physics.  Among the best is: light acts like you’d expect on scales well above its wavelength and acts weird on scales below.  In order to take a picture of a thing you need light to bounce off of it in a reasonable way and travel in straight lines (basically: behave like you’d expect).  But the wavelength of visible light is about half a micrometer (a two-millionth of a meter) and atoms are around one ångström (a ten-billionth of a meter) across.  On the scale of atoms, visible light acts too wonky to be used for photographs.

Atoms are literally too small to see.

An actual photograph of a billiard ball (#3) and what we have in lieu of a photograph of an atom.

(Left) A photograph of a 3 ball.  (Right) What we have in lieu of a photograph of an atom.

You could try using light with a shorter wavelength, but there are issues with that as well.  When light has a wavelength much shorter than an atom is wide, it takes the form of gamma rays and each photon packs enough energy to send atoms flying and/or strip them of their electrons (it is this characteristic that makes gamma rays dangerous).  Using light to image atoms is like trying to get a good look at a bird’s nest by bouncing cannonballs off it.

There are “cheats” that allow us to use light to see the tiny.  When the scales are so small that light behaves more like a wave than a particle, then we just use its wave properties (what else can you do?).  If you get a heck of a lot of identical copies of a thing and arrange them into some kind of repeating structure, then the structure as a whole will have a very particular way of interacting with waves.  Carefully prepared light waves that pass through these regular structures create predictable interference patterns that can be projected onto a screen.  Using this technique we learned a lot about DNA and crystals and all kinds of stuff.  This is the closest thing to a photograph of an atom that is possible using light and, it’s fair to say, it’s not really what anyone means by “photograph”.  It’s less what-the-thing-looks-like and more blurry-rorschach-that-is-useful-to-scientists.  Even worse, it’s not really a picture of actual individual atoms, it’s information about a repeating structure of atoms that happens to take the form of an image.

(Left)

By passing light (left) or even electron streams (right) through a regular, crystalline structure we create an interference pattern that gives us information about the structure of the crystal (but never pictures of individual atoms).  The picture on the left (left) is a pattern created by DNA (species unimportant).  Notice how not obvious the helical structure is.  The picture on the right is created by an electron beam passing through some simple mineral or salt.

These techniques are still in use today (are relatively cheap), but since 1981 we’ve also had access to the Scanning Tunneling Electron Microscope (STM).  However, despite the images it creates, the STM isn’t taking a photograph either.  The STM sees the world the way a blind person on the end of a tiny robotic arm sees the world.

The essential philosophy behind the Scanning Tunneling Electron Microscope is what allows this dude to know more about the bottom of this chili cauldron than you do.

The STM is basically a needle with a point that is a single atom (literally, it is the pointiest thing possible) which it uses to measure subtle electrical variations (such as a stray atom sitting on what was otherwise a very flat, clean surface).  The “Tunneling Electron” bit of the name refers to the nature of the electrical interaction being used to detect the presence of atoms; when the tip is brought close to an atom electrons will quantum tunnel between them and the exchange of electrons is a detectable as a current.  The “Scanning” bit of the name refers to how this is used to generate a picture: by scanning back and forth across a surface over and over until you’ve bumped every atom with your needle several times.  The pictures so generated aren’t photographs, they’re maps of what the STM’s needle experienced as it was moved over the surface.  The STM “sees” atoms using this needle in the same way you can “see” the bottom of a muddy river with a pokin’ stick.

An STM and some of the pictures it "paints".

An STM and some of the pictures it pokes into being.

This technology has been around for decades and, like the advent of the synth, has given rise to all manner of jackassery.

This entry was posted in -- By the Physicist, Physics, Quantum Theory. Bookmark the permalink.

58 Responses to Q: What are “actual pictures” of atoms actually pictures of?

  1. Anonymusman says:

    “Here is a really bad explanation: “The particle goes from the source to the screen, passing through both slits at the same time. Its motion is described by a probability amplitude wave which interferes with itself. The position the particle is detected is governed by the squared amplitude of the wave which is the probability of finding the particle there.” This explanation is full of gobbledigook words and mystery, and is typical of the “No one can understand quantum mechanics” popular school of thought.

    There are different approaches to explaining things and many competent physicists use the term “particle” all the time. They think they know what they mean and that it makes things simpler for you. Sometimes it doesn’t and it would be better to be more realistic and detailed. IMO.”

    Ok up until now, this whole conversation was at least rational, but if you have a problem with the way we describe things, then you’re just proving to be promoting a humbug. Plus – the terms used in the description are middle school science. I don’t understand how this is “gobbledygook”. If you don’t understand the concept then don’t argue.

  2. Jefferson says:

    “Ok up until now, this whole conversation was at least rational, but if you have a problem with the way we describe things, then you’re just proving to be promoting a humbug. Plus – the terms used in the description are middle school science. I don’t understand how this is “gobbledygook”. If you don’t understand the concept then don’t argue.”

    I hagvbe problems with dscribing things, I was talking about you, people not me, this is what you need to change, again, not me you said it your progfessors teachers and etc, again not me, I’m just correcting what you messed up, that’s all.

    And if there is anyone irrational here it’s you, people, not me, spending too many hours in calculations you completely, lose your tocuh with reality and start to make things up and create humbugs, that’s all.

    You just don’t like the truth about yourselves, you cannot stand that someone tells you, ysou made up things, and misinterpret everything just to fit mathematics, this is not a big deal, and as well as the limitations of observations and measurements just like measurement illusions as well.

    You’ve been brainwashed by yourselves, much like drug addit cannot really see that drugs is messing with hi/her mind, and it’s the same effects, and no this is not irrational, it’s just purely rational conclusions created by studying you how you do your “science”, nothing else.

    You always want to be the smartest and the only ones capable of doing everything, while at the same time you get lost by what you created in the first place.

    And please don’t lie this is not the case, because your actions beat what you write.

    There is nothing to be said here by me anyway.

    Enjoy your delusional “science”, more like religion.

    Enjoy the fairy tales that you created.

  3. SOUMYADIP SINHABABU says:

    Yes, scientists yet don’t understand about the micro world according to physicist Richard Feynman.we are simply familiar with the equations and procedure of Quantum physics. By why it behaves like it still remains a mystery.

  4. Jefferson says:

    To SOUMYADIP SINHABABU:

    “Yes, scientists yet don’t understand about the micro world according to physicist Richard Feynman.we are simply familiar with the equations and procedure of Quantum physics. By why it behaves like it still remains a mystery.”

    Equations and models make all mthe stuff out of thin air, nothing real, again, and this is what Feynman ignored in the first place, he has too much reliance on something that doesn’t exist in the real-world-equations, instead he should rely on the real world and its limitations and our limitations to comprehend and make upo stuff out of thin air when we deal with mathematics.

    Not true at all, since all of the equations and interpretations and observations are made up by mathematics and its equations, i’ts not the real-world stuff we directyl observe and study so you can actually say this is it.

    The entire physics suffers from the same syndrome, not just QM and relativity, if you follow the equations, you don’t follow the real world, you only follow the equations and their “logic”, not the real-world logic, completely and entirely different issues here.

  5. Dylan Juhren says:

    Great article. I wonder how learned people can compete with the wikipedias, medias(television) and academics that are pumping out these 1984 prototypes. On the subject of scifi they would be like droids and stormtroopers. You can see this mis-thought in all of their destructions; space, politics, virus’. A respectable group would be in order to replace the unqualified authorities such as school boards etc.

    Again ty for sharing.

  6. One Morphy says:

    Know you know a shit. – Socrates
    Everything you guys know, it’s because has been told to you.
    No source can be verified 100% in 2022.
    Know what you know.
    Know what you don’t know.
    You actually don’t know what you really don’t know.
    It starts with exploring within, and kill that monkey ego.
    Life is Matrix. Open your eye/s.

  7. Jefferson says:

    One Morphy, this is just another solipisism BS…..

  8. LeesburgMichael says:

    I apologize for coming late to this party, and I do not know who wrote the explanation above about What are actual pictures of atoms actually pictures of, but this is a fantastic explanation and answer to that question. When I have the time, which unfortunately is not now, I will explore more of the articles in the column to the right. Whoever this article’s author is, Thank you very much.

Leave a Reply

Your email address will not be published.