What is the Planck epoch?

The period when the first atoms of hydrogen formed, about 380,000 years after the Big Bang The earliest period of the universe (before 10^-43 seconds), when quantum gravity effects dominated and our current physics cannot describe what happened The era when the universe reached its maximum temperature and began cooling The moment when matter and antimatter annihilated, leaving only matter behind

What happened during cosmic inflation?

The universe contracted briefly before beginning its long expansion The temperature of the universe reached its maximum value during inflation The universe expanded exponentially, roughly doubling in size about 100 times in an incredibly short time between about 10^-36 and 10^-32 seconds All matter in the universe was created during inflation from pure energy

What is the horizon problem, and how does inflation solve it?

The universe has no horizon — inflation proved that we can see to infinite distances The CMB is extremely uniform, but regions on opposite sides of the sky were too far apart to ever exchange heat — inflation stretched a tiny, uniform region to cosmic size, explaining the uniformity Inflation created the cosmological horizon by preventing light from traveling farther than 46 billion light-years The problem that we cannot see beyond the edge of the universe — inflation solved this by making the universe transparent

What is the flatness problem, and how does inflation solve it?

The universe is completely flat, with no three-dimensional structure — inflation created the illusion of depth The universe's geometry is extremely close to flat (Euclidean), which requires the initial density to be fine-tuned to extraordinary precision — inflation naturally drives any geometry toward flatness by expanding away curvature The problem that the universe appears flat because our telescopes cannot detect its curvature Inflation created the flat disk shape of the Milky Way and other spiral galaxies

How did quantum fluctuations during inflation become the seeds of all cosmic structure?

Quantum fluctuations had no effect during inflation — structure formed later from random thermal motions Quantum uncertainty created tiny density variations, which inflation stretched to cosmic scales — these became the overdense regions that later collapsed into galaxies Quantum fluctuations created the first protons and neutrons, which then arranged into galaxies During inflation, quantum effects created dark matter, which seeded galaxy formation

What is baryogenesis, and why is it one of the great unsolved problems in physics?

The process that created the first baryons (protons and neutrons) from quarks — this is well understood The process that created a slight excess of matter over antimatter (about 1 in 1 billion) in the early universe — the origin of this asymmetry is not yet fully understood The production of all heavy elements like gold and uranium in the early universe The creation of dark matter from ordinary matter in the first second after the Big Bang

What is the quark-gluon plasma, and when did it exist?

A plasma created during inflation that filled the universe with charged particles The hot gas of ionized hydrogen and helium that existed before recombination at 380,000 years A hot, dense state of matter from before about 1 microsecond after the Big Bang, when quarks and gluons were free rather than confined inside protons and neutrons The plasma currently found inside stars where nuclear fusion occurs

What happened during the hadron epoch?

From about 380,000 years to 1 billion years, when protons captured electrons to form neutral atoms From about 1 microsecond to 1 second after the Big Bang, quarks combined into protons and neutrons as the universe cooled below the quark confinement temperature The era of nucleosynthesis, from 1 second to 20 minutes, when protons fused into helium nuclei The period of inflation from 10^-36 to 10^-32 seconds when the universe expanded exponentially

What is reheating in the context of cosmic inflation?

The process by which the Sun heated the early solar system after forming The warming of the universe by dark energy after it cooled below the CMB temperature The process after inflation ended when the energy of the inflaton field was converted into a hot plasma of particles, filling the universe with matter and radiation The re-ionization of the universe by the first stars about 200-400 million years after the Big Bang

What is the monopole problem, and how does inflation solve it?

The problem that early stars had no planetary systems — inflation created the angular momentum needed for planet formation Grand unified theories predict magnetic monopoles formed in the early universe, but none are observed — inflation diluted their density to virtually zero by expanding the universe enormously The monopole is the name for the singularity at t=0 — inflation smoothed it out to create flat space The problem that the universe has only one observable pole — inflation explains why the other pole is beyond our horizon