For physics the PhD program usually consist of 2 years of post graduate level courses on modern topics. They are covering similar things as your undergrad courses, just fill integrating calculus and differential equations as well as showing you less of the “classic” examples.
Then you take your qualifying exam to verify you really know that material.
After that you work under a faculty PhD on developing an independent thesis topic. This can take a year or two depending on the student and the field. Then it takes a year or two to do the experiment and write the thesis.
And a thesis is a different best than most research papers. It must explain *everything* involved in the experiment. It can’t leave our details other papers do that are “standard practice” or settled concepts. So instead of being a few pages long of just the important findings and methods, it’s a 100-200 page book.
The student must then defend thier ideas as faculty try to tear it apart or just plain stump the student. So you have to know it very well.
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