### FOUR FUNDAMENTAL FORCES

Gravity: very weak force. Only force that in relativity. It equals the heavens and earth.

Electromagnetism: much stronger, apart of quantum mechanics.

Strong Nuclear: Keeps nucleus together, apart of quantum mechanics.

Weak Nuclear: Radioactive decay, apart of quantum mechanics.

Relativity ≠ Quantum Mechanics

### Einstein's General Relativity

Einstein explained this gravity as making an indent in space and time. Taking the earth and sun for example, they both lie on an axis. Thinking of a checkerboard type plane, the sun makes a very large indent into it while the earth makes less of an indent. The sun's indent is what cause the earth to always orbit the sun in the same position.

### QUANTUM MECHANICS

Quantum mechanics is the three forces of electromagnetism, strong nuclear, and weak nuclear. In terms of math, quantum mechanics is on the micro scale while relativity is on a much larger scale. Relativity differs from quantum mechanics because the forces in quantum mechanics are much smaller. Gravity deals with much bigger objects while electromagnetism, strong nuclear, and weak nuclear deal with atoms and subatomic particles.

### Unification

The leading theory for complete unification is the String Theory. Scientists are still trying to figure out a way to make Relativity = Quantum Mechanics. String Theory is very hard to prove with experimental evidence because the strings are way too small to be seen. These strings are said to vibrate at different frequencies to make up everything around us. Unification is so difficult because of how different relativity and quantum mechanics are. It is said that there are many other dimensions which also makes it much harder to prove the string theory.

### String Theory

The String Theory is what scientists believe is how the universe works. They say that little tiny strings, not visible by any modern technology, is what makes up everything we see. These little strings vibrate at different frequencies making up different things. Scientists have been trying to prove this theory is true in order to understand everything about the universe. For a long time they had faith that this had to be true until they discovered these strings can stretch into a membrane type object. There had been 5 different theory equations until Edward Witten came along and got rid of 4 of them. He basically said that each theory is the same as all of the others. This was a huge success for scientists because it helped show they were on the right track. Now, they are testing to find little atoms called gravitons. If they can prove that these gravitons are real, they might be able to confirm that relativity = quantum mechanics.