Why does ribosomes use rna instead of dna?

After some “pre-processing” inside the nucleus, the much shorter mRNA molecule (compared to the DNA chromosomes) is transferred from the nucleus to the cell cytosol, where a ribosome (aided by transfer RNA (tRNA)) performs the translation from mRNA to a protein (or, as the case may be, to another RNA) molecule.

bacterium is not correct

not: both offer magnification to the atomic level.