This is more of a life question than a technical one. I hear conflicting opinions on this when it comes to switching fields late. Some say it's never too late, others say that chances are lower. My background is applied math, and I want to go into physics for a PhD. So I guess I will just have to fork over the cash for another bachelors degree. Shouldn't take me more than 2 years though since I have all math and GEs done. Though I have to finish a PhD afterwards, which is up to 6 years. By then, I'll be close to 40. I know that is a huge time and financial investment, but really in the grand scheme of things I will simply just have to retire late. I want to hear peoples opinions on this. What would you do in my shoes?