Kind of an arcane philosophical point, here, so I’ll be a little surprised if anybody responds, but this occurred to me while writing the previous post, and I thought I’d throw it out there. In the previous post, I quoted Feynman’s one sentence for the future:
Everything is made of atoms.
and suggested as an alternative:
Light is both a particle and a wave.
Part of the idea behind these is that the sentences would allow people who had received that bit of information as Revealed Truth to reconstruct much of modern physics. If you take seriously the idea that material objects are made of atoms, and set out to prove it, you can end up rediscovering most of modern physics.
But is this really true for both of these?
Obviously, we have reason to believe that the atomic hypothesis alone can lead to modern science because, in a sense, it did. The idea that matter is made of atoms dates back to the ancient Greeks, and investigations into the atomic structure of matter were crucial for the development of quantum theory in the early 20th century. (Though many people will say that the atomic hypothesis wasn’t really nailed until Einstein’s Brownian motion paper of 1905, if not later.)
It seems plausible to say that people who had been told that matter was made of atoms would be able to rediscover the rest of our modern theory of the world through experiments to look at the properties of atoms. What about the other way around, though? If you knew about the quantum nature of light, but not atoms, would you end up with modern physics?
The really arcane physics inspiration for this question is that there are well-known semi-classical theories of most of the experiments that are usually said to demonstrate the existence of photons. You can get nearly all of the classic results from considering atoms with quantized levels, but treating light as a classical electromagnetic wave. So, the ultra-nerdy version of this question is: Could you do the same thing in reverse? That is, could you construct a theory of the world in which you quantized the EM field, but treated atoms classically?
It would be really bizarre, sure, and I doubt it would be good for anything (other than making physicists’ heads hurt) but that’s not the question. The question is, could you do it?