What did Albert Einstein mainly study?

What is a pressure of 8.00 ATM equal to in mm Hg? How long does it take to sail 19 miles at 6 knots? A wave has a period of 0.2 seconds the frequency of the wave is? What is the perception in the change of a sound frequency as the source moves closer or farther from The listener? What are the appropriate unit measured in force mass acceleration weight and pressure? What are some advantage of goinright instead of left around an obstacle? What is the mass of an average car? Wave lenght is measured from the crest to the trough? Which fundamental force is the result of warped spacetime? What is the difference between fracture and dislocation? How can you put destructive force in a sentence? What choose the best description of a magnet? Would particles pass straight through gold foil? Why is Nuclear Power so expensive? What is oil intensity? How many unpaired electrons in Ti? How did people react initially to the light bulb? What kind of waves can be used in radar system? How do forces acting on an object? Can light reflect and absorb and transmit all at the same time?

What did Albert Einstein mainly study?