How accurate is the Standard Model at explaining everyday phenomena? How do we know the answer? I've read many times that "the Standard Model can explain all everyday phenomena (except gravity)." But I haven't been able to find out what exactly is meant by this. If I were to simulate (theoretically) some everyday object.. say myself over a long period of time, would the simulation make sense? Or would I explode into billions of little pieces or something other non-nonsensical would happen?
Also, whatever your answer, how do we know the answer?
 A: The Standard Model can not be used explain the weather, or the stock market, or why people can be loving or cruel, or many other everyday phenomena. It isn’t useful to chemists (well, maybe a little), or biologists, or sociologists, or meteorologists, or economists, or much of anybody other than physicists.
It can be used to explain how nature operates at the simplest level, where one asks the really basic questions that physicists like to ask, such as: Which particles are truly fundamental? What are all of their their properties? What truly fundamental forces act between them (leaving out gravity, which is not part of the Standard Model)? How, exactly, does each force work? What simple composite objects (such as nucleons, nuclei, and atoms) can form, and what are their properties? What is light, and how does it interact with matter?
The Standard Model will tell you why some particles have mass and others don’t. It will tell you that protons and neutrons have three quarks inside them, held together so strongly by gluons that you could never get them out. It will tell you why uranium is radioactive. It will tell you what makes the Sun shine. It will tell you why neutrinos can travel right through the Earth like it isn’t there. It will tell you why the light from a sodium streetlight is yellow, and why the sky is blue.
It, together with General Relativity, explains things at the basic level of physics. Other fields deal with the emergent phenomena that build on top of the low-level layer provided by physics. For example, in evolutionary biology, no one cares about quarks and gluons but everyone cares about natural selection. This is not even a concept in the Standard Model, because elementary particles are not living things that reproduce themselves like biological organisms do. But physics at least helps you understand how DNA can exist.
When you study reasonably simple systems, you find that you can sometimes actually calculate or simulate how they work. And then you can do an experiment to see if it agrees with what you predicted. The Standard Model is really, really successful at giving results in agreement with observation. But you have to be observing something sufficiently simple for the Standard Model to be applicable.
