... bounded by a wall of nothing, but space can expand into the nothingness as needed to accommodate expanding matter?

What if I am on a planet of a star that is at the edge of space and fire a rocket into that nothing wall?

I have a real problem with two aspects of current theory:

1. The "nothing"
2. String theory.

We go to all the trouble to discover and define chemical compounds, a periodic table of elements, isotopes, atoms, protons, neutrons, electrons, 6 "flavors" of quarks, gluons, leptons, photons, neutrinos, positrons, muons, hadrons, pions, mesons and baryons ... and they are all just tiny, one-dimensional vibrating filaments of energy called "strings".

Give me a break. Brian Greene is just "stringing us along".