I am in serious dilemma what to choose. I work as software profession till now for 5 yrs and I am already 30 yrs old.Lately I was thinking going back to school and apply for EE(signal procession or communication or RF) for phd. I got admission on them too but I am least interested onto it though I did my bachelor in electronics and telecom engineering.Here in US I did MS in CS some 5 yrs back.I really wanted to do phd before I become too old to do it.Now having family with 2 kids and me only source of income,it is tough but I am determine to do against all odds. Now my question is I am more interested in Physics(theoretical or mathematical) and I dream of having phd in physics in my belt but I don't have enough background on both physics and math except what they used to teach in engineering.So, should I go and complete my phd in EE where I will probably be around 35+ by then and latter part of my life just take physics as hobby? OR should I go for MS in mathematics and then latter phd in physics which will add more couple of year to it. I saw couple of resume floating in internet where they did Bachelor in EE and did MS and phd in Physics.So, I know this seems possible but at what cost? Somebody wrote do what you like and here I am in complete dilemma state as what to do?