Any science enthusiast, and probably any science fiction fan, has heard of dark matter.  80% to 90% of the matter in our universe is invisible.

You may be wondering, as I did, how we know about it if it’s invisible.  The answer is that we’ve observed it by its effects.

As Earth orbits the sun, its motion is controlled by two forces: the sun’s gravity and the Earth’s momentum (velocity).  These forces are perfectly balanced, and if Earth’s momentum were a bit higher it would escape the sun’s gravity and fly off alone into space.

In the same way, stars orbit the center of the galaxy, their momentum balanced to the center’s gravity.  Except the balance is wrong, and the stars are moving too fast.  They should fly off, yet they don’t; thus, some invisible stuff must be increasing the gravitational force of our galaxy.

There could be a simpler explanation.  Perhaps our laws of gravity are incorrect.  We’ve only studied how gravity affects falling objects, planetary orbits, and the interactions of stars.  Maybe there’s more to gravity than we can see on such small scales, and we require a galactic perspective to see our error.

As far as I know, most scientists are not ready to rewrite gravity.  Not without more evidence.  Personally, I think the existence of dark matter is easier to believe, but science fiction writers should be aware of crazy new ideas in science.  They may become the basis for a great story.


  • Observations of the Bullet Cluster, a group of galaxies colliding with each other, may prove that dark matter exists.  Click here.
  • Other scientists say a Modified Gravity Theory can explain the Bullet Cluster.  Click here.
  • The theory of dark fluid combines dark matter with dark energy, another big, invisible part of our universe.  Click here.

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