Chapter 10 - A Brief History of the Universe

Question 1

Challenges & limits of cosmology

Answer 1

Much of what we know relies on theory
Radiation takes time to reach us even at speed of light, so we can’t see anything that happened further away than distance light has traveled since birth of cosmos
Expansion of space
Conceptual horizons

Question 2

The moment of creation

Answer 2

Most popular theory is that vacuum field existed in potential before big bang, pulsing gently with quantum fluctuations, from these emerged tiny ephemeral “bubbles” of spacetime appearing and disappearing, then one fluctuation triggered self-organizing process
Energy in universe balances energy to blow it apart against gravit, so total energy of vacumm field is same as before big bang, thus the sum of matter and energy is zero and in balance

Question 3

Evolution of the cosmos

Answer 3

Bubble expanded > energy released as radiation and particles
4D space > time
Big bang created space, which is emerging
Energy > subatomic particles > protons & neutrons (helium nuclei)
One force > gravity & electromagnetism > weak & strong nuclear forces
Nuclei & electrons > atoms
Matter = anti-matter, but anti-matter decays slightly faster
Gravity + matter + variations in density > planets, stars, galaxies, etc.
Dust + gas > earth
Electromagnetism prevented matter from disappearing into black holes

Question 4

Cosmic microwave background radiation

Answer 4

Afterglow of big bang

Question 5

Dark matter

Answer 5

More matter than previously estimated in order for gravity to create structures (otherwise would have been torn apart by centrifugal forces due to their rotation)
Nobody knows what it is, maybe black holes or brown dwarfs, or new particles which only interact with matter through gravity

Question 6

Dark energy

Answer 6

Draws matter apart in opposite to gravity, perhaps vacuum field of space, unknown form of matter, or something else