Ripples in the very fabric of space and time called "gravitational waves" may have provided the first tantalizing evidence of tiny black holes born during the Big Bang. These primordial black holes could, in turn, account for most if not all of the universe's most mysterious stuff, known as dark matter.
Unlike stellar mass black holes, primordial black holes weren't born when massive stars died, but instead from fluctuations in density that occurred immediately after the birth of the cosmos. That means they can be much smaller than stellar mass black holes, which have at least the same mass as several suns. These Big-Bang-born "non-astrophysical" black holes can have masses as small as that of an average asteroid or as large as a massive planet.
