curvature on the earth?????????? caused by the presence of a nearby massive object (like the Earth). but how does gravity act upon us? i got the idea of how it does in space. but earth? if it's a curvature, then what's keeping us on the ground. surely, there's no curvature on earth! can you explain this? have a look at http://curious.astro.cornell.edu/relativity.php#links" [Broken]. can you explain the truck part in this? i got confused.