Theories of the Universe and Solar System

Study Notes

A gravitationally bound system centered around the Sun.
Includes objects that orbit the Sun directly or indirectly.
Formed approximately 4.6 billion years ago from a rotating cloud of gas and dust known as the solar nebula.

Hebrew Bible: God separated light from darkness, created the sky, land, sea, moon, stars, and all living creatures.
Hindu Text "Rig Veda": Universe is an oscillating entity, starting with a cosmic egg or Brahmanda containing the entire universe.
Primordial Universe (Greeks): The original state of the cosmos was a primordial mixture of all its ingredients, existing in infinitesimally small fragments.
Atomic Universe: Greek philosophers Leucippus and Democritus believed the universe is composed of tiny, inseparable, and indestructible atoms.

Steady State Theory: The Universe has always been the same and will remain that way forever.
Big Bang Theory: The earliest state of the universe was extremely hot and dense. It then expanded and cooled. It suggests that galaxies, stars, and planets retain the explosive motion from creation, moving away from each other at high speeds.
Oscillating Universe Theory (George Gamow): The expansion of the universe will stop, reverse, and return to its original state, leading to another Big Bang.
Cosmic Inflation Theory (Alan Guth, Andrei Linde, Paul Steinhardt, Andy Albrecht): After the Big Bang, the universe expanded very rapidly, much faster than the speed of light. This expansion slowed down but continues at a slower rate.
Multiverse: The universe is just one of many bubbles that grew as part of a multiverse, the concept of multiple worlds.

Geocentric Model: Earth-centered.
Ptolemy's Geocentric Model: Based on sky measurements, it placed Earth at the center with all planets and the Sun orbiting it.
Heliocentric Model: Sun-centered
Copernicus' Heliocentric Model: First proposed by Nicolaus Copernicus, a Polish astronomer.
De Revolutionibus Orbium Coelestium: Copernicus' book published in 1543, outlining the heliocentric system.

Terrestrial Planets: Mercury, Venus, Earth, and Mars. They have rocky surfaces.
Mercury: Smallest terrestrial planet with an iron core accounting for about 3/4 of its diameter. Difficult to see due to its proximity to the Sun.
Venus: Most similar to Earth, often called Earth's "sister" planet. Similar size and close in orbit to Earth. Most visible planet in the night sky. Young surface with fewer craters.
Earth: Only known planet with life. 2/3 covered in water, perfect conditions for breathable atmosphere. Largest terrestrial planet and fifth largest in the solar system. Estimated age: 4.5 billion years old.
Mars: Reddish color, easily visible in the night sky.

Jovian Planets: Jupiter, Saturn, Uranus, and Neptune. Large in size compared to terrestrial planets. Composed mainly of gases like hydrogen, helium, and ammonia. May have solid cores.
Jupiter: Largest planet in the solar system in terms of size and mass. Diameter is 11 times larger than Earth. Mass is 2.5 times greater than all the other planets combined.