The question might sound a lil funny, but it popped up when I was preparing some work on the influence of electrostatic force & gravity... Though electrostatic force can be repulsive or attractive, gravity is always attractive.... Then it occurred to me, that its because there are two types of charges but theres only one kind of mass..(is it right? or theres something more to it?) But every things looks to be in equilibrium, so there must be something that neutralises gravity (and thats the dark energy??)... But universe is expanding!!....Gravity is attractive force, dark energy is weak force, and electrosatic force isnt applicable here...Then why is the universe still expanding? Shouldnt it contract??