Maggie's Farm

A quote from an important essay which needs to get around: The Necessity of Mathematics:

Once, we had a troll at Pharyngula who, insisting that only "Theism" could solve the problem of dark matter, displayed some rather confused ideas about "energy" and "gravity." Using the actual physics, energy is interchangeable with mass — that's the content of Einstein's famous equation — and we've known since Newton that mass is the source of gravitational attraction. Of course, we've updated the Newtonian force law to the Einsteinian description of curved spacetime, but still, more energy means more mass which means a stronger gravitational pull. A sealed box of hot helium gas will actually pull very slightly harder on nearby objects than a box of the same size containing the same number of helium atoms at a lower temperature. Yet to our persistent Pharyngula commenter, "energy" and "gravity" were diametrically opposed concepts — because, I think, when you have "lots of energy" you're not "weighed down" but instead "bouncing around the room."

In short, inconsistencies which appear at the verbal level turn out to be illusory when you progress to the actual science.