@syndicated - it is my understanding that _everything_ not only *has* energy, but on a basic level *is* energy. The electron, for example, as seen in the particle/wave-duality, is nothing but a lump of energy flowing around. Virtual particles pop in and out of existence in empty space, which creates what is known as "vacuum energy" - which again means there is no such thing as an empty void. Everything is built up of these miniscule particles, which means that everything is energy.
@dent - The more energy an object has, the more massive it is (e=mc2, right) - so mass has nothing to do with dimension, but with energy and velocity.
I am not sure that don Cristo has got it right. His assumption that time is a dimension is not necessarily correct. We do not currently have good enough definitions of time to state that time is a requirement for dimensions or energy to exist. Thus you could easily argue that mass is the fourth dimension, rather than the fifth. In string theory, you have 9 or 10 dimensions PLUS one of time. Only three of those are spatial.
Time is not a good way to measure the existence of matter, because since matter is just a manifestation of energy, it cannot completely go away. When an object is created, it's energy comes from somewhere, and when it is destroyed, the energy goes somewhere (remember - energy cannot disappear, only change form).
I think the fact that we have three spatial dimensions is what creates 3D objects. Their mass represents the energy they have in 3D space. There is no need to create a fourth dimension.
I have never heard anyone argue that X+Y+Z=M (it would obviously be quite silly). The X+Y+Z = Position is correct. In global position X+Y+Z is used, and you need at least three satellites to pinpoint your position on the surface of a globe. Yet this positioning can only measure your relative position and speed, not your mass.
Like don Cristo says, "Mass is not defined by 3 measurements in space-time." However, we can use several positions to calculate the shape of an object in 3D. We can *also* use additional data, like radius, to define size. Size and shape is pure geometry! All the objects we see exist in 3D. When you add the fact that all objects are energy what you get is a 3D model where matter and energy is one and the same.
This sounds like rambling, perhaps - that is not my intention. But all the dimensions and all the energy was created in the Big Bang. You need quite a lot of energy just to have the spatial dimensions around...
It is easy to confuse 3D space with 4D space-time. And the time dimension is a mysterious one...
Tormod