Hi, I am currently doing a major in mechanical engineering. Im starting my 3rd year now. After i finish my major I'm thinking of getting my masters in aerospace engineering. I think that is going to take me like 5 or 6 years till i finish both things. Afters my masters, I what to do a major, a masters and a PhD in physics. How long will it take me to finish a phD in physics having the engineering background?