The Basic Forces Physicists believe they can explain the universe using just four basic forces. The strong force functions only at the minute distances inside a nucleus and is responsible for holding particles in the atomic nuclei together. The weak force also functions at the nuclear level. It is far weaker than the strong force and is responsible for radioactive decay. Electromagnetism functions both at the atomic level and on a larger scale, and is responsible for interactions between charged particles resulting in electricity and magnetism.
Gravity is an attractive force that acts on large objects over large distances.
Gravity keeps our feet on Earth rather than letting us sail away. The gravity of a massive body like the sun acts on the Earth to keep it in orbit. Scientists started out with independent theories of how each of these four forces works. How Things Work Maldacena said he enjoys teaching because it is a learning experience for himself as well as for the students. He said he tries to keep in touch with his students during class by asking a lot of questions.