Cosmology Primer: The Evolving Universe
| time = 10 -43 sec |
size = 10 -30 today |
temp = 10 32 Kelvin |
The Planck era. Quantum gravity is important; current
theories are inadequate. We can't get any closer to the Big Bang
at
t=0 and say anything with confidence (or even with informed
speculation).
| time = 10 -35 sec |
size = 10 -26 today |
temp = 10 28 Kelvin |
Inflation. A temporary period of domination by
a form of dark energy at an ultra-high energy scale. A speculative theory,
but one that has so far been consistent with observations.
| time = 10 -12 sec |
size = 10 -15 today |
temp = 10 15 Kelvin |
Electroweak phase transition. At high temperatures,
electromagnetism is unified with the weak interactions. This is the
temperature at which they become distinct.
| time = 10 -6 sec |
size = 10 -12 today |
temp = 10 12 Kelvin |
Quark-gluon phase transition. Quarks and gluons
become bound into the protons and neutrons we see today.
| time = 10 sec |
size = 10 -9 today |
temp = 10 9 Kelvin |
Primordial nucleosynthesis. The universe cools
to a point where protons and neutrons can combine to form light atomic
nuclei, primarily Helium, Deuterium, and Lithium.
| time = 3.7×10 5 years |
size = 10 -3 today |
temp = 3×10 3 Kelvin |
Recombination. The universe cools to a point where
electrons can combine with nuclei to form atoms, and becomes
transparent. Radiation in the Cosmic Microwave Background is a
snapshot of this era.
| time = 10 8 years |
size = 10 -1 today |
temp = 30 Kelvin |
The dark ages. Small ripples in the density
of matter gradually assemble into stars and galaxies.
| time = 9×10 9 years |
size = 5×10 -1 today |
temp = 6 Kelvin |
Sun and Earth form. From the existence of heavy
elements in the Solar System, we know that the Sun is a
second-generation star, formed about five billion years ago.
| time = 13.7×10 9 years |
size = 10 0 today |
temp = 2.74 Kelvin |
Today.
Next: The Luminous Universe