I get that humans have never done anything that approaches even a hundredth of a percent of the speed of light. And I can believe that general relativity never causes strong enough effects to care, except obviously for probes specifically intended to study relativity.<p>But when it comes to GPS, I guess I just have a hard time taking your word for it. If there were no info either way on the internet, I would probably believe you, but why is there no source that can back you up? It&#x27;s &quot;tens of thousands of regurgitations&quot; vs one guy saying &quot;trust me, I&#x27;ve talked to some engineers&quot;. I have to believe the regurgitations, especially when their explanations and math makes sense.<p>&gt;It was certainly included. The question of necessity, however, is another matter.<p>So you&#x27;re saying GPS satellites do take relativity into account, but the engineers you&#x27;ve talked to said &quot;I guess we could take it out and it would still probably work&quot;? That sounds a little tenuous.