|关注一亩三分地公众号：ML will be a good area to focus on, if you have the modeling/math stats/some coding background. Since you are already interested in it, it's a good enough reason to learn it well (not just call a few packages, but really understand how it works).
for data science, I don't think phd is required (it's usually a "plus") and a grad degree in physics is usually quite appreciated. . From 1point 3acres bbs