I believe you can use the "energy-momentum tensor" to express the conservation of both energy and momentum for fields ([tex]\partial_{\mu} T^{\mu \nu} = 0[/tex]). But I'm wondering: why's a

*tensor*needed, specifically, to describe this conservation of energy and momentum for fields? For particles, I believe a four-vector suffices (?). I'm not quite clear on this.

Thanks in advance for your wisdom. :-)