What problems did Einstein try to solve?

Answer 1

1. When Maxwell's Equations predict an electro-magnetic wave travelling at a certain speed, what frame is that speed measured from?

2. How to explain the photo-electric effect.

3. How to explain Brownian Motion.

4. Can gravity be added to special relativity?

If he had solved any one of the above issues, Einstein would have been regarded as one of the great minds of the 1900s. He solved all of them!

However, he was unable to solve either of these:

1) Can the electric field be added to general relativity?

2) Is there a general paradigm for our Universe in which quantum mechanics is only a useful subset of reality?

They both remain unsolved today.