Allan Rubin said yesterday his mother died of natural causes Sunday. He says the Philadelphia native had been living in the Princeton, New Jersey, area.
Rubin found that galaxies don't quite rotate the way they were predicted, and that lent support to the theory that some other force is at work, namely dark matter.
Dark matter, which hasn't been directly observed, makes up 27 per cent of universe as opposed to 5 per cent of the universe being normal matter. Scientists better understand what dark matter isn't rather than what it is.