Why Don't we Notice Dark Matter and Energy?

Baryonic matter and energy make up less than 5% of the universe. The rest is "dark matter" and "dark energy." This is known because galaxies don't follow the known rules of gravitational attraction; they don't fly apart and the equations show that much more (so far invisible) mass is necessary to keep them from doing so. My questions are: How is it that Einstein's (or even Newton's) equations work, even at a local level, if there is so much more hidden mass and energy? Shouldn't the calculations have shown that there was something missing right from the get-go?
- Bruce D (age 52)
Nice, France

Around here, the dark matter density is very low compared to the familiar matter density. Also, we believe that the dark matter is smoothly distributed, not lumped up in stars and planets. Much of it seems to bulge well outside the galactic plain. So the local effects don't amount to much- it's almost as if we were surrounded by a smooth niform distribution, not pulling in any direction. On a bigger, galactic, scale, you notice that there seems to be big lump toward the middle of the galaxy.

Mike W.

(published on 06/22/2016)