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2

As an alternative to Anna's nice historical discourse a heuristic that covers modern uses of the phrase would be that energies are "high" when the QCD can be treated as perturbative. That regime sets in considerably above the nucleon mass scale, say 10s of GeV. So LHC physics is in, JLAB physics is out (even with the 12 GeV upgrade).


3

Elementary particle physics is an outgrowth of what was high energy physics, historically at the time. X-rays were high energy physics when first discovered, they are part of the tools of solid state physics now. Alpha particles and gamma rays were high energy physics at their time, they are nuclear physics now. Mesons discovered in cosmic rays started ...


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It is possible to test whether two mathematical formalisms are equivalent No, it is not possible. Mathematics allows you to talk about things about which you can't determine if they are equivalent. The word problem is a small example and most mathematical systems themselves suffer the same problem. So now consider the set of all possible ...


0

In general, it is possible to derive "minor" concepts from a more general theoretical framework. This is the very definition of deductive reasoning, and it is in fact at the foundation of the scientific method. However, there are cases where the hierarchy of concepts is not so clear, in the sense that it is not always straightforward to decide which is the ...


0

You have read that the basic physics equations would fit on a t-shirt. This is true in a very broad sense, but you need to be very careful here: First of all, let us distinguish a mathematically phrased theory about physics from the world around us. Whether or not the universe "has" a mathematical structure is an ontological question which physics can't ...


2

First, can the numerous equations in our physics books (the advanced placement physics equations: classical mechanics; fluid and thermal physics; waves and optics; modern physics; and electricity and magnetism) be calculated from these “fundamental equations? No. They're derived from postulates and observation and experiment, not from five magic beans. ...


0

Here's an answer from a slightly different, more philosophical perspective. Physical laws are not "laws" that describe and embody some absolute truth. The entire endeavor of physics is to find mathematical descriptions that match our observation of how reality behaves, and allow us to make predictions about future observations. A "law" is just the best ...


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If we somehow manage to come up with the TOE that even explains dark matter and dark energy, can we know if the TOE is all there is? Take the current favorite candidate for a theory of everything, a string theory to be decided in some future while we are still alive. It will model all of particle physics, quantize gravity all in one mathematical ...


7

can we know if the TOE is all there is? One of the main principles of science is falsifiability. All scientific theories are falsifiable. A theory may explain all we currently know but we always have the hope and expectation that our knowledge may expand. We must not know if things we don't yet know will also conform to current theories. That is an ...


15

Thermodynamics, electromagnetism, and classical mechanics were the "TOE" of physics at the time of Lord Kelvin. They remained a "TOE" until new phenomena were discovered, which could not be explained by their theories, such as the photoelectric effect, the energy quantization of photons, the atomic spectra, and many others. In the same way, a TOE which ...



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