Life doesn&#x27;t use full rotation much because life has no way to connect up the rotating part to the circulatory and nervous systems.<p>But that&#x27;s not the point of the article. He&#x27;s talking about &quot;em cities&quot;. What he means are really big, perhaps planet sized, data centers running brain simulations, at hardware densities near the limits of what physics permits. This fantasy runs into cooling problems, so he&#x27;s discussing that.