Four Forces and "Gravitons" Hello. Well, we were watching an old video, presumably from the 80s or so in physics class, and it stated: There are 4 basic forces in the universe: ElectroMagnetic, Gravity, Weak and Strong. Now, EM and Gravity make sense to me that they exist, but weak and strong seem iffy. I'm not really even sure what they are. Later in the video, something else deeply disturbed me - they said gravity was caused by particles called gravitons. Of course, it's theoretical, but it jsut seems whack. First of all, it doesn't seem logical that something that directly affects particles would be caused by particles. I dunno, I guess that seems circular to me. Seeing as the video was pretty old, what are some more modern and accepted theories on all this?