Proof of the existence of atoms

In summary, there was skepticism among some physicists about the existence of atoms until Einstein's work on Brownian motion in the early 1900s. This skepticism was mainly held by thermodynamicists who believed that the theory of bulk matter could stand on its own without the idea of atoms. However, other physicists, such as Max Planck, were skeptical of atomic theory until the late 1890s and early 1900s. Ultimately, Einstein's work on Brownian motion and other studies on the size and properties of atoms helped to solidify their existence in the scientific community.
  • #36
bhobba said:
Some arguments suggest it is just the most straightforward generalised probability theory after ordinary probability theory:
There's a lovely undergrad level derivation of this in Jochen Rau's new textbook "Quantum Theory: An Information Processing Approach".
He shows only quantum and classical prob are compatible with basic statistical principles like "operationalism", i.e. the ability of another party to confirm the claimed prepared state.
 
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  • #37
Son Goku said:
There's a lovely undergrad level derivation of this in Jochen Rau's new textbook "Quantum Theory: An Information Processing Approach".
He shows only quantum and classical prob are compatible with basic statistical principles like "operationalism", i.e. the ability of another party to confirm the claimed prepared state.

Thanks for the heads up. Just purchased the book and can report my 'reaction'. Could be 'the' undergrad book on the why of QM. Not what it means - that is much much harder - but why it is the theory we have.

Thanks
Bill
 
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  • #38
sophiecentaur said:
Lavoisier more or less introduced the idea of atoms before he had his head removed by those nasty French Revolutionaries in 1794.
Lavoisier was the head tax collector of Paris. He had the city surrounded by a wall in order to facilitate tax collection at the gates. Imagine having to go through customs in order to reenter your own city. Parisians had made short trips to the country to get out of the oudure and mud, now these took long detours and waits for inspection. What a pain in the @@$@$! In my opinion Lavoisier's wall was a significant motive for the revolution. The proportion of the upper class who were executed is smaller than generally supposed but Lavoisier might have been number one on the blacklist.
 
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  • #39
Son Goku said:
He shows only quantum and classical prob are compatible with basic statistical principles like "operationalism", i.e. the ability of another party to confirm the claimed prepared state.
This sounds more like philosophy than physics.
 
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  • #40
bob012345 said:
This sounds more like philosophy than physics.
The distinction is very blurred when you get down to it. It’s like love and marriage “…………”.
 
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  • #41
sophiecentaur said:
The distinction is very blurred when you get down to it. It’s like love and marriage “…………”.

As Feynman said philosophy (or what some consider philosophy anyway) was once used to make progress eg positivism and relativity. These days symmetry arguments are more in favour. They too may fail to work just as many marriages do. But that does stop people from trying.

Thanks
Bill
 
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  • #42
bhobba said:
As Feynman said philosophy (or what some consider philosophy anyway) was once used to make progress eg positivism and relativity. There days symmetry arguments are more in favour. They too may fail to work just as many marriages do. But that does stop people from trying.

Thanks
Bill
Nature does not seem to always obey every symmetry physicists conceive of.

https://www.nobelprize.org/prizes/physics/1957/summary/

https://www.nist.gov/pml/fall-parity
 
  • #44
sophiecentaur said:
The distinction is very blurred when you get down to it. It’s like love and marriage “…………”.
That's a good metaphor: Love=Physics; Marriage=Philosophy. As soon as you get into philosophy it's becoming more likely the physics is gone soon...
 
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  • #45
vanhees71 said:
That's a good metaphor: Love=Physics; Marriage=Philosophy. As soon as you get into philosophy it's becoming more likely the physics is gone soon...
I would think physics is more like marriage because there is always someone telling you what you cannot do.
 
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  • #46
rutherford experiment on scattering of alpha particles?
 
  • #47
gmax137 said:
I remember being told the same thing in a physics class, late 1970s. I was surprised to hear this, especially that Planck was among the sceptics. How could the father of quantum theory not believe atoms exist??This is a very interesting addition to the "story." Especially when combined with
Thanks too to @anorlunda for "promoting" this thread.
My understanding was that Planck quite hated his own "quantum hypothesis" that got him across the black body radiation finish line. He was convinced it was some form of trickery, but was just more or less desperate for the win.
 
  • #48
KipIngram said:
My understanding was that Planck quite hated his own "quantum hypothesis" that got him across the black body radiation finish line. He was convinced it was some form of trickery, but was just more or less desperate for the win.
Reference links please.
 
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  • #49
It's well known that Planck didn't like his own discovery, and during the long rest of his long life he was looking for an explanation within classical physics. You can read this in almost all books on the history of quantum theory or biography about Planck.
 
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  • #50
vanhees71 said:
You can read this in almost all books on the history of quantum theory

E.g. in "Constructing quantum mechanics, volume I" by Duncan and Jenssen. Great book.
 
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  • #51
hagopbul said:
rutherford experiment on scattering of alpha particles?
that was the unforeseeable finding that the positively charged matter of the atom is concentrated in a tiny volume of it.

The atoms themselves (and electron) accepted before that.
 
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  • #52
berkeman said:
Reference links please.
I'll try - it's been a long long time since I encountered that.

Edit:
Ok, I found this - it's not the same thing I read years ago, but it gets at it:

https://physicsworld.com/a/max-planck-the-reluctant-revolutionary/

A quote from there:
As to the quantum discontinuity – the crucial feature that the energy does not vary continuously, but in “jumps” – he believed for a long time that it was a kind of mathematical hypothesis, an artefact that did not refer to real energy exchanges between matter and radiation.

There is also another thread here:

https://www.physicsforums.com/threads/plancks-radiation-law-act-of-desperation.686243/
 
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  • #53
vanhees71 said:
It's well known that Planck didn't like his own discovery, and during the long rest of his long life he was looking for an explanation within classical physics. You can read this in almost all books on the history of quantum theory or biography about Planck.
We might say then that Planck wasn't very discreet about nature being discrete...
 
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  • #54
bob012345 said:
We might say then that Planck wasn't very discreet about nature being discrete...
We have all been 'helped' into that paradigm and it's easy too take it for granted. It must have been a real struggle at the time and with a lot of great brains opposing the idea very competently.
 
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