Gravity: Spinning Galaxies and Dark Matter
Measurements showed that the galaxies were spinning
faster than was predicted by how many stars they contemned.
In other words, the stars should be flying off the edges of the
galaxies -- the gravity law should not be working.
In order to explain the high rotation speed (and save the gravity law
in each galaxy) astronomers needed to add a huge amount of
''dark matter'' to each galaxy in their calculation so all the stars
Dark matter helps normal matter clump together.
Dark matter saves gravity law in each galaxy.
Without dark matter gravity law doesn't work in galaxy.
Question remains: what is dark matter made of ?
Short answer: we have no idea.