What is the fastest speed which anything can move? What is the fastest speed which anything can move? In a vacuum nothing travels faster than the speed of light. Does the speed of light change for observers depending on their position or motion? Does the speed of light change for observers depending on their position or motion? The speed of light is the same for all observers no matter how they or the light source are moving. The Strong Nuclear Force The Electromagnetic Force The Weak Nuclear Force Gravity The strongest of the four forces. Acts inside the nucleus. Attractive force between protons and neutrons that holds the nuclei of atoms together. Very short range force. > Acts over a distance of 10-15 m which is the diameter of a medium size nucleus. 2nd strongest force. Strong force is 137 times stronger. The electromagnetic force holds atoms and molecules together. Responsible for all forces experienced with the exception of gravity. (All contact forces are electromagnetic in nature). Range is infinite (strength obeys inverse square law.) 3rd strongest force. Strong force is 1,000,000 times stronger. Responsible for radioactive decay and neutrino interactions. VERY short range force. > Acts over a distance of 10-18 m which is 0.1 % of the diameter of a proton. Weakest of the four forces. Strong force is1.67 x 1038 times stronger. Responsible for the structure of the universe on the larger scale. Range is infinite (strength obeys inverse square law.) STRONG :Glues protons together, protons must be very close, strongest of all forces, limited range WEAK : responsible for radioactive decay; neutron decay ELECTROMAGNETIC : electrons kept in orbit. Opposites attract; holds atom together GRAVITY :the weakest of the forces four fundamental forces, yet it, all objects are influenced by it, at an infinite distance