The Manga Guide to the Universe

What Wi Ultimately Become of the Universe? 227

during the 1980s and 1990s, observations of cosmic background radiation and Type Ia

supernovas in very distant galaxies (which also means the galaxies were formed relatively

shortly after the Big Bang) showed cosmologists that not only was the universe expanding,

but that the expansion was accelerating! This ran counter to the widely accepted belief that

the expansion was slowing down. Some kind of energy source was required to account for

this increasingly rapid expansion. As a result, it made sense to reincorporate the cosmologi-

cal constant into the relativistic equations of gravity.

If these ...