The 4% Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality

by Richard Panek

MACHO

The light from a foreground object told astronomers how much mass appeared to be there. The gravitational-lensing effect on the background object told them how much foreground mass was there. The difference between the two amounts was the dark matter.

According to this “cosmopaleontology,” as the team called this approach, the dark matter collapsed upon itself first, and then those centers of collapse grew into galaxies and clusters of galaxies—again, an image consistent with the bottom-up, cold-dark-matter formulation.

It was as if dark-matter boxcars from both clusters had raced,

ghostlike, right through the cosmic train wreck.

In one generation astronomy had gone from the lone observer on a mountaintop taking photographs in visible light to dozens of collaborators around the globe pursuing a variety of specializations by looking at increasingly narrow bands along the electromagnetic spectrum.