How do you define new and more recent?

My favorite headphone albums from the past two years were Moderat - MORE D4TA (2022) and Hans Zimmer - The Dune Sketchbook (2021).

My favorite headphone albums of all time, though I wouldn‘t call them new or recent, are Nine Inch Nails - The Fragile (1999), Burial - Untrue (2007), and Jon Hopkins - Immunity (2013).

The octet rule is a pretty old and simplified model for chemical bonding. It is only applicable for second- and third-row main-group elements in the first place and even there you‘ll find many exceptions (for example: borane clusters, pentacoordinate carbon atoms). Still, many small molecules and most organic compounds follow the rule, and since it is easier to learn than the modern, more accurate bonding concepts, it is still widely taught.

Current research on chemical bonding is done with either molecular-orbital theory or valence-bonding theory, which are both based on quantum mechanics and were introduced in the early 1930s. Both theories have no need for an octet rule, and they are much more complicated. Sometimes, researchers still study whether a molecule obeys or violates the octet rule, but since 1) the concept has become redundant, and 2) many exceptions have already been found, this is no longer an exciting field of research.

Most of the time: using computer programs based on quantum-mechanical equations to predict the outcome of chemical reactions. You can also predict the properties of molecules and materials.

That was very informative and probably what I was looking for. Thanks a lot!

Thanks for your reply!

There is exchange energy for bosons and it is attractive: https://en.m.wikipedia.org/wiki/Exchange_interaction

Exchange interaction exists for bosons and it is attractive: https://en.m.wikipedia.org/wiki/Exchange_interaction

Explains the superfluidity of helium-4, for example

This is unfortunately not what I mean, but thanks anyway. Technically speaking I am talking about the energy contribution in the Hamiltonian integral of a system of multiple identical particles that arises from the requirement that the total wave function must not change its sign upon exchange of particle labels (in the case of bosons). Does this exist for photons?

One thing I am wondering after reading your (really good) reply: Is there exchange interaction between photons?

I‘m a theoretical chemist and well familiar with exchange interactions between electrons, in magnetic materials, and in superfluid helium-4. Is there an equivalent attractive force between photons since they are bosons?

Now hold up with the sensationalism. They found an exoplanet with 1.0-1.2 Jupiter masses using microlensing, which is cool. But that‘s all the info they have on the planet. Calling this a near-identical twin of Jupiter is like saying “I weigh 80kg and I found out someone in another part of the world weighs 88kg - that must be my near-identical twin!“

It is a natural consequence of the wave-particle duality. If we go back to classical mechanics, angular momentum is present when something moves along a circular path. Very small particles are also waves, and the frequency (number of times the wave function goes up and down per length unit) is a measure for their (angular) momentum. The wave function must now "fit" the circumference - meaning that if you go around the circle the whole 360°, you must end up with the same value of the wave function and are not allowed to have a sudden step. This only works if the circumference is an integer multiple of the wavelength. As a consequence, only certain wavelenghts and frequencies are allowed, and the same is true for angular momentum.

This is a very simplified picture, of course, but I hope it gets the principle across.

First of all, there has been no evidence that magnetic monopoles exist. At least none so far. Everything we have observed in the universe can be explained without the existence of magnetic monopoles.

As to Dirac‘s statement about quantization: In a hypothetical system that contains an electric point charge (like an electron) and a magnetic point charge, the electromagnetic field generated by them has an angular momentum that is proportional to the product of the value of those two charges. Since quantum mechanics dictates that angular momentum must be quantized, this means that the electric and magnetic charges must also be quantized - if they weren‘t you could get a continuum of angular-momentum values.

To answer your questions: 1) If magnetic monopoles exist, their magnetic charges must be quantized. 2) There probably is no satisfying answer to the question why quantum mechanics describes our universe so well. It‘s just the way it is, at least the best description of it that we currently have.

If you have something black during a combustion process that‘s not ash but the remaining carbon. The carbon reacts with oxygen in the air to form carbon dioxide, a gas. Ash is the product of oxygen reacting with everything not containing carbon: calcium, magnesium, and a few other metals. The oxides of those metals (reaction products with oxygen from the air) are usually white in color and do not become gaseous at usual combustion temperatures. That is why this is what‘s left at the end of burning something and why it is white.