To clarify, I'm not confused as to how massless strings can add up to make massive objects, I understand why that happens. My question has more to do with the speed at which strings move. If strings are massless, they must travel at the speed of light, correct? If so, then first off, what is the difference between a string and a photon? Second, how do strings provide enough stability to construct all the massive objects in the universe? I am not moving at the speed of light, nor are the atoms in my body or the electrons and quarks that they are made of, but the strings that make up those quarks and electrons should be, according to relativity. I remember learning that neutrinos were once ruled out as a candidate for dark matter because they were too light and fast to provide the kind of foundation needed for the observed large scale structure of the universe. Why do strings not suffer a similar problem? Is my view of "strings" as tiny, vibrating little strands of energy inaccurate in some way? Any clarification on the subject would be much appreciated. Thank you!