The Standard Cosmological Model has introduced in physics two new concepts that didn't exist before:
- Dark
matter: It seems
to be five times more abundant than ordinary matter, but we don't know
what it is, what it's made of. We only know that it appears to be affected
by gravity, and so far, its existence has been concluded in two different
ways: a) By analyzing the rotational motion of galaxies, which seems to
require that there is more mass in them than what we can see. b) By
studying the cosmic microwave background radiation, which has served as
the basis for adjusting the standard cosmological model.
- Dark energy: We have no idea what it is. Some speak of a fifth fundamental interaction (or force), the quintessence, which would join the four we know: gravitational, electromagnetic, strong, and weak. Others offer different explanations, none of which have received experimental confirmation. The hypothesis of its existence is supported by two observations: a) Analyzing the expansion rate of the universe, after the 1998 discovery that this rate is accelerating. b) By studying the cosmic microwave background radiation, which has served as the basis for adjusting the standard cosmological model.