What crucial finding did Vera Rubin and Kent Ford report concerning the rotation curves of spiral galaxies?

Answer

The rotation curves did not drop off.

Rubin and Ford discovered that the rotational velocities of stars in the outer fringes of spiral galaxies were nearly as fast as those closer to the center, indicating the rotation curves remained flat.

What crucial finding did Vera Rubin and Kent Ford report concerning the rotation curves of spiral galaxies?

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