I can recall from what I learned about ordinals yesterday that $\varepsilon_{0}$ is the answer to $\omega\uparrow\uparrow\omega$, but what is $\varepsilon_{1}$? I assume $\varepsilon_{1}$ is equivalent to $\varepsilon_{0}\uparrow\uparrow\omega$, but this question is to clarify $\varepsilon_{a}=\varepsilon_{a-1}\uparrow\uparrow\omega$ for $a>0$.
Springing from this question, if this is true, how could you get to $\varepsilon_{\omega}$? $\omega$ is a limit, so you cannot simply say $\varepsilon_{\omega}=\varepsilon_{\omega-1}\uparrow\uparrow\omega$.