A
The Big Bang model involves astounding heat, where the universe initially consisted mostly of energy with a light dusting of matter.
Matter (starting with quarks) gradually congealed from energy as the universe cooled through expansion, confirming Einstein's equation ($E=mc^2$).
$\textbf{Observational evidence}$ supports the Big Bang:
The universe acted as a cooling thermonuclear reactor in its first second (temperature $\approx$ $10$ billion degrees).
Laboratory data on nuclear processes accurately predicts the observed ratio of light atomic elements (hydrogen and helium) formed in the first three to four minutes.
Heavier atomic elements (up to iron) were later forged in stars; the rest were created by supernovae explosions.
Persistent $\textbf{unanswered questions}$ about the Big Bang and the initial conditions include:
What "banged" and how did it become a universe?
How is the universe smooth on a large scale (uniform background radiation) but lumpy (stars, galaxies) on a local scale?
How was the expansion rate so finely tuned to prevent the universe from collapsing or flying apart too quickly?
What was the source of the enormous energy for the Big Bang itself?
The early universe following the Big Bang was primarily energy; as it cooled through expansion, matter (starting with quarks) gradually formed from energy, demonstrating Einstein's equation ($E=mc^2$).
$\textbf{Evidence for the Big Bang}$ comes from the early universe acting as a thermonuclear reactor:
The universe's temperature was about ten billion degrees at one second.
Predictions for the ratio of light elements (mostly hydrogen and helium) produced in the first $\textbf{three to four minutes}$ align with observations to high accuracy.
Heavier elements (up to iron) were later created in stellar furnaces, and the rest were formed by exploding stars ($\textbf{supernovae}$).
Persistent questions about the universe's initial state include:
The source of the Big Bang's enormous energy.
What caused the universe to be smooth on a large scale (uniform background radiation) yet clumped on a local scale (stars, galaxies).
How the expansion rate was finely tuned to prevent immediate collapse or flying apart.
No comments:
Post a Comment