On Wed, Apr 30, 2025 at 2:38 AM Alan Grayson <[email protected]> wrote:
*> The Casimir Effect can be predicted classically, as Van der Waals > forces. BTW,* > *No. They are different phenomena, for example the Casimir Effect is proportional to 1/d^4 where d is distance, but for the Van der Waals force it's proportional to 1/d^6. More importantly, the Van der Waals force exists because of quantum mechanical fluctuations in the distribution of electrons in atoms or molecules. The Casimir Effect requires Quantum Electrodynamics for a full description, while Van der Waals forces can be described using simpler quantum mechanical perturbation theory. * *It's true that Van der Waals first introduced his theory in the 1870s and that was decades before quantum mechanics, so his explanation had to be based just on classical physics. Van der Waals amended the ideal gas law by injecting not one but two new mathematical constants into it, but he gave no explanation as to why they had the particular values that they had, he obtained them by empirically fitting experimental data. The full explanation wouldn't come until 1930 using quantum mechanical perturbation theory. The Casimir Effect needed something more advanced, full Quantum Electrodynamics, so it wasn't derived until 1948. But neither could have been predicted by classical theory alone. * *John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis>* 3b0 -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/CAJPayv1pqrA24ucJ-rCL4%3DExfeQGBFRBougOmBaH9TkRRzkhvQ%40mail.gmail.com.
