It&#x27;s a perfectly fine limiting case of G + Λg = 8πT.<p>A minor point: it&#x27;s &quot;the Newton equation&quot; or &quot;Newton&#x27;s equation&quot;, but not &quot;the Newton&#x27;s equation&quot; (in the same way that one could write &quot;the Eisenhower presidency&quot; or &quot;Eisenhower&#x27;s presidency&quot;, but not &quot;the Eisenhower&#x27;s presidency&quot;).