In space-time I like to think of objects going through a "stream" of movements that remain concrete in the 4 dimensions of space-time, all movements being inter-related with one another with respect to the frame of reference. But let's compress this stream so only what remains is the overall average of the movements made by the object in space-time. I envision a sort of spherical shape. The less an object tends to move it's parts the more it will appear to be spherical in form. Imagine a tree, to help look at this image http://www.sustland.umn.edu/implement/images/planting_fig1a.gif Gives you an idea as to how an object can appear to look like a sphere. A tree doesn't move very quickly relative to the earth year, or the ground for that matter, so it doesn't really change its form much from that of a sphere. Now imagine a human being, in the form illustrated by Leonardo Da Vinci http://www.enchantedlearning.com/artists/davinci/gifs/proportions.GIF As you can see, the human doesn't look like that much of a sphere. Overtime, on average however, the human will tend to look like a sphere. Waving your limbs around in the 3 dimensions of space will allow you to see that you can indeed look more like a sphere, but this is only averaged overtime. The connection to the tree and the human is this: The tree moves a lot slower relative to the human being. The human being moves a lot faster relative to the tree. The tree will tend to look more like a sphere because of it's relative speed to that of the ground of Earth or it's inertness, if I am using that right. The Earth looks quite like a sphere, though it's moving fast. But we're talking relativity. Am I making sense here or is this ridiculous?