Like the rest, I also think these last few pages have been great.
I've been listening an astronomy podcast for a while and curiously these last months they are especially interested in matter and dark energy.
In any case, I have a question.
I have heard in this podcast, on YouTube and here on Red Café:
@Invictus , in another thread "or all we know, this universe could be a lab experiment in a wider cosmos which is why we have such
elegant physical laws".
what exactly means the term elegant?. To the precision of the laws? How do they fit together? or rather refers to how they are fair to promote life?
I don't know what Invictus meant or the context, so just a few general remarks. I'll use terms like elegance or beauty interchangeable unless stated.
Theories in math or physics can be elegant just like fashion can be. Its ultimately hard to define, but depends on simplicity (making few assumptions), rigidity (theory is difficult to change), surprising consequences and in (high-energy) physics additionally naturalness (~no fine tuning of certain parameters necessary).
A theory that manages to unify forces would be almost always be considered elegant. Theories, that use supersymetry (SUSY) are extremely popular for the same reasons. General relativity is usually seen as a beautiful theory even so its not really natural. The standard model of particle physics is usually on the opposite end of the spectrum: not elegant/beautiful.
Naturalness means roughly how much one need to specify/"fine-tune" initial conditions and/or parameters to explain macro-states. Its a statistical assumption about probability distributions of phase spaces and/or parameter spaces. Its particularly important because at least some physicists, who research on fundamental physics, are adhering to it. In this context two parameters (mass of the Higgs and the cosmological constant) are very unnatural. Quantum Field Theories (QFTs) strongly suggest(ed) that the LHC should have found *something* new at the probed energy scales, if naturalness applies.
One of many reasons (and certainly a less important one) why string theory is popular is, because it at least could turn out to be beautiful in the sense, that it gets rid of/explains unnatural parameters. It also opens up the possibility of a very large cosmological multiverse, but thats a different topic.
In this sense, the best established theories are not as elegant as physicists would like them to be. It could be, that all of this get resolved once we understand physics better at higher energy and smaller scales. Most popular theories, that try to do that are certainly more beautiful. Yet at the same time that might not be the case. Its at least possible, that theories get refined and better measurements "just" find natural constants, that are inexplicable and fairly random in value.
to steal a quote from Feynman from wiki
There is a most profound and beautiful question associated with the observed coupling constant, e – the amplitude for a real electron to emit or absorb a real photon. It is a simple number that has been experimentally determined to be close to 0.08542455. (My physicist friends won't recognize this number, because they like to remember it as the inverse of its square: about 137.03597 with about an uncertainty of about 2 in the last decimal place. It has been a mystery ever since it was discovered more than fifty years ago, and all good theoretical physicists put this number up on their wall and worry about it.) Immediately you would like to know where this number for a coupling comes from: is it related to pi or perhaps to the base of natural logarithms? Nobody knows. It's one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man. You might say the "hand of God" wrote that number, and "we don't know how He pushed his pencil." We know what kind of a dance to do experimentally to measure this number very accurately, but we don't know what kind of dance to do on the computer to make this number come out, without putting it in secretly!
