4 ms·

So, pardon my ignorance, but can we finally say that atoms are particles with concrete dimensions? Last time I checked the whole field seemed measuring everythi

So, pardon my ignorance, but can we finally say that atoms are particles with concrete dimensions? Last time I checked the whole field seemed measuring everything into probabilistic and statistical terms.

nabla9 6y ago
We can meaningfully talk about concrete dimensions just like before. Atomic radius is mean distance from the nucleus to the boundary of the surrounding shells of electrons. Because the outer shell of electrons is fuzzy, there are multiple ways to define radius: covalent radius, Van der Waals radius and ionic radius. In molecules atoms overlap in different ways because they share electrons and electrons interact. There still exists fundamental uncertainty about the location of atoms and molecules. Electrons, atoms and molecules have de Broglie wavelength. For molecules with tens of atoms the wavelength is in the order of picometers.
fsloth 6y ago
Our understanding on the nature of atoms is not something someone suddenly "discovered". Rather, we've gathered evidence of various phenomena over the century. There are lots of models to explain the findings. This is a bit of a long winded list of discoveries. There is no simple sophism you can utilize and say "atoms are this or that" unless you actually understand something of the background. This Khan academy lecture is as good resource as any: https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/v/chem37-history-of-atomic-chemistry https://www.khanacademy.org/science/chemistry/electronic-str...
marcosdumay 6y ago
You can resolve atoms despite all the uncertainty just like you can resolve a tree at distance despite it not having a clear surface. The electron distribution falls with an exponential function on large distances, what is much cleaner than a tree surface anyway.
- AtHeartEngineer 6y ago
  This is a good analogy
potas 6y ago
Not an expert, but as far as I understand it, both, i.e. atoms are ("physical") manifestations of (probabilistic) quantum fluctuations. If I'm wrong, it would be great if someone could ELI5.
- criddell 6y ago
  I hope somebody weighs in because ever since I read that matter is just quantum field excitations I've lost all intuition about what reality is. Everything seems to be nothing.
  - ramijames 6y ago
    I'm going to lean towards everything being nothing, with everything together being a giant illusion. But, well, I'm having one of those days. :(
  - ckocagil 6y ago
    Learn about the quantum eraser experiments and your jaw will drop. https://youtu.be/8ORLN_KwAgs https://youtu.be/8ORLN_KwAgs
    - criddell 6y ago
      Oh wow. It's weirder than I thought.
  - procgen 6y ago
    This scene from The Sopranos addresses this idea beautifully: https://www.youtube.com/watch?v=QFDq985HvPk https://www.youtube.com/watch?v=QFDq985HvPk "Everything is everything."
analog31 6y ago
For better or worse, Cryo-EM doesn't settle this. The results are inherently statistical no matter what, and probably can't distinguish between one microscopic model of the atom and another. I haven't seen the equations, but both the amount of data, and the amount of processing, are profound. I work in a peripherally related area, and just one anecdotal note is that the people doing this work think nothing of a single measurement filling up a terabyte hard drive with data. There are naturally a lot of views about this topic, but one that resonated with me (perhaps recently discussed in HN) is that science can't necessarily make things intuitive, because it has this nasty habit of telling us when our intuition is wrong.
COGlory 6y ago
What you see with cryo-EM are essentially clouds of electron density. So unfortunately, it doesn't address this.
- natechols 6y ago
  Confirmed. I've worked with structures at close to sub-atomic resolution (0.8Å), where you can even see the "deformation" of hydrogen bonds and lone pairs in the electron density. But the actual information we have is simply a grid of electron density values averaged over an entire crystal.

nabla9 6y ago

We can meaningfully talk about concrete dimensions just like before. Atomic radius is mean distance from the nucleus to the boundary of the surrounding shells of electrons. Because the outer shell of electrons is fuzzy, there are multiple ways to define radius: covalent radius, Van der Waals radius and ionic radius. In molecules atoms overlap in different ways because they share electrons and electrons interact. There still exists fundamental uncertainty about the location of atoms and molecules. Electrons, atoms and molecules have de Broglie wavelength. For molecules with tens of atoms the wavelength is in the order of picometers.

fsloth 6y ago

Our understanding on the nature of atoms is not something someone suddenly "discovered". Rather, we've gathered evidence of various phenomena over the century. There are lots of models to explain the findings. This is a bit of a long winded list of discoveries. There is no simple sophism you can utilize and say "atoms are this or that" unless you actually understand something of the background. This Khan academy lecture is as good resource as any: https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/v/chem37-history-of-atomic-chemistry https://www.khanacademy.org/science/chemistry/electronic-str...

marcosdumay 6y ago

You can resolve atoms despite all the uncertainty just like you can resolve a tree at distance despite it not having a clear surface. The electron distribution falls with an exponential function on large distances, what is much cleaner than a tree surface anyway.

AtHeartEngineer 6y ago
This is a good analogy

potas 6y ago

Not an expert, but as far as I understand it, both, i.e. atoms are ("physical") manifestations of (probabilistic) quantum fluctuations. If I'm wrong, it would be great if someone could ELI5.

criddell 6y ago
I hope somebody weighs in because ever since I read that matter is just quantum field excitations I've lost all intuition about what reality is. Everything seems to be nothing.
- ramijames 6y ago
  I'm going to lean towards everything being nothing, with everything together being a giant illusion. But, well, I'm having one of those days. :(
- ckocagil 6y ago
  Learn about the quantum eraser experiments and your jaw will drop. https://youtu.be/8ORLN_KwAgs https://youtu.be/8ORLN_KwAgs
  - criddell 6y ago
    Oh wow. It's weirder than I thought.
- procgen 6y ago
  This scene from The Sopranos addresses this idea beautifully: https://www.youtube.com/watch?v=QFDq985HvPk https://www.youtube.com/watch?v=QFDq985HvPk "Everything is everything."

analog31 6y ago

For better or worse, Cryo-EM doesn't settle this. The results are inherently statistical no matter what, and probably can't distinguish between one microscopic model of the atom and another. I haven't seen the equations, but both the amount of data, and the amount of processing, are profound. I work in a peripherally related area, and just one anecdotal note is that the people doing this work think nothing of a single measurement filling up a terabyte hard drive with data. There are naturally a lot of views about this topic, but one that resonated with me (perhaps recently discussed in HN) is that science can't necessarily make things intuitive, because it has this nasty habit of telling us when our intuition is wrong.

COGlory 6y ago

What you see with cryo-EM are essentially clouds of electron density. So unfortunately, it doesn't address this.

natechols 6y ago
Confirmed. I've worked with structures at close to sub-atomic resolution (0.8Å), where you can even see the "deformation" of hydrogen bonds and lone pairs in the electron density. But the actual information we have is simply a grid of electron density values averaged over an entire crystal.