String Theory:

• String theory has emerged as a proposal to unify gravity and quantum mechanics.
• Strings replace point particles and smooth out the geometry where gravity and quantum mechanics meet.

There are some challenges however.

• The strings are extremely small, on the order of one Planck length. Electrons and photons are made of one string with different vibrational characteristics, and these strings can interact by joining and splitting.
• Extra dimensions are needed in string theory. Questions naturally arise: Why don’t we see the extra dimensions? Of what importance are these extra dimensions? These dimensions are proposed to be microscopic dimensions that are complex in geometry.

Black Hole Thermodynamics:

• Bekenstein and Hawking assert that the entropy of a black hole is a function of the area conflicting with Einstein’s General Theory of Relativity.
• Andy Strominger and Cumrun Vafa came up with the idea that the microstates are hidden in the internal dimensions.