abdul rehman said:
is it possible to do a bachelors in eng and then do masters and phd in theoretical physics. any eng?
Ed Witten got his bachelor's in history and he is now a highly acclaimed theoretical physicist. However, unless you're the next Ed Witten, you might want to consider majoring in physics.
As others have suggested, you could major in engineering and take some physics courses on the side. I would recommend the following in addition to the standard physics 1&2 courses.
Contemporary physics
Electrodynamics (beyond what is covered in physics 2)
Statistical Mechanics
QM
Condensed Matter physics
Optics, lasers, and microscopy
Analytical Mechanics
You should also take a circuits and electronics course if you are not required to take such a course in your aerospace curriculum.
I am double majoring in EE and physics, but I am taking an extra year to do it (most single major engineering students I know finish in 5 years anyways). I know the way engineers approach solving problems is vastly different than the way physicists approach problems in the typical curriculum. For instance, EEs rely heavily on Laplace transforms and s-domain analysis to do circuits problems whereas physicists tend to be turned off by such methods. Perhaps this is because you lose a bit of physical insight if you work in the s-domain. Also, engineers (particularly in control systems) will even attempt to do some mechanics problems solely in the s-domain. In addition, a physicist will be exposed to Lagrangian and Hamiltonian mechanics, whereas I don't think any engineers learn about, unless they take a specialized graduate course or something (correct me if I am wrong).
There will certainly be things you will learn in aerospace engineering that you will never cover in physics, and vice versa. Most physicists have a very superficial knowledge of fluid mechanics and aerodynamics, for instance, whereas an AE will have very thorough knowledge of such subjects. However, a physicist will have some knowledge in QM, stat mech, condensed matter, etc whereas an AE will have no knowledge here. An AE will learn thermodynamics (and probably fairly thoroughly) from an engineering standpoint, but this is very different from the way a physicist will learn it. One point of view is not harder or superior than the other though...the two viewpoints are just geared toward different goals.