1. The document discusses several theories on the origin of the universe and the solar system. It describes the leading theories for the formation of the universe as the Big Bang theory and inflationary theory, which propose that the universe began in an extremely hot and dense state around 13.8 billion years ago and rapidly expanded. 2. For the origin of the solar system, the most widely accepted is the nebular hypothesis, which suggests that the solar system formed from a rotating cloud of gas and dust around 4.6 billion years ago that flattened into a disk and planets formed from accretion of planetesimals within the disk. 3. Alternative theories proposed include the encounter hypothesis of a close star passing and stripping material,

1. Topic: Theories of the Origin of the Universe and the Solar System
Name: Lester John G. Francisco
Chapter 1
Facts About the Universe
- Cosmos- term that refers to the Universe
- The universe is approximately 13.8 Billion Years / 14 billion years
- Believed to be 93 billion light years in diameter
Theories about the Formation ofthe Universe
1. Divine Creation Theory
o Narrative of Genesis, described how God separated light from darkness, created the sky, land, sea,moon, stars,
and every living creature in a span of six days.
2. Brahmanda Theory
o “cosmic egg” or Brahmanda, containing the whole universe—including the sun, moon, planets, and space
expands out of a single concentrated point called Bindu, and will eventually collapse again.
3. Anaxagoras’ Theory
o Believed in a primordial universe and explained that the original state of the cosmos was a primordial mixture
of all its ingredients which existed to infinitesimally small fragments of themselves. At some point in time, the
mixture was set in motion by the action of the “nous” or mind. A whirling motion was produced which sifted
and separated the ingredients, ultimately producing the cosmos of separate material objects with different
properties that can be seen today.
4. Atomic Universe Theory
o Greek Philosophers Leucippus and Democritus believed that the universe was composed of very small,
indivisible and indestructible atoms.
o The universe is like a giant living body, with the sun and the stars as the most important parts to which
everything else was interconnected. What happens in one place affects the events that occur elsewhere.
5. Static Universe Theory
o Sir Isaac Newton described the universe as static, steady-state, infinite universe. In his description of the
universe, matter on the large scale is uniformly distributed, and the universe is gravitationally balanced but
essentially unstable.
6. Cartesian Vortex Model Theory
o French philosopher Rene Descartes outline this theory
o the vacuum of space was not empty at all but was filled with matter that swirled around in large and small
vortices. His model involved a system of huge swirling whirlpools of fine matter, producing what would later
be called gravitational effects.
7. Einstein’s Static Theory
o He believed that the universe was a static, dynamically stable universe, which was neither expanding nor
contracting.
8. Big Bang Theory
o The most known and acceptable theory of the origin of the universe. It is the current accepted model of the
formation of the universe.
o Formulated by Alexander Friedman and Edouard Lemaitre
o Describesthat the universe as expanding, and originated in an infinitely tiny dense point around 14 billion years
ago (gigayears ago or Gya) 13.8 billion years ago to be exact.
o According to the theory, matter wasnot presentat the beginning of time, there wasonly pure energy compressed
in a single point called singularity.
o Due to random fluctuation in an empty void, there wasa greatexplosion or expansion. The explosion sent space,
time, matter, and energy in all directions.
9. Oscillating Universe
o Proposed by Albert Einstein
o Follows the general theory of relativity equation of the universe with positive curvature. This curvature results
in the expansion of the universe for a time, and then to its contraction due to the pull of its gravity in a perpetual
cycle of big bang and big crunch.
10. Steady State Theory
o Proposed by Sir James Jeans in 1920 and then popularized by Fred Hoyle, Hermann Bondi, ND Thomas Gold
in 1948
o This theory predicted a universe that expanded but did not change its density – matter was inserted into the
universe as it expanded in order to maintain a constant density
o Universe is expanding in a constant average density. Matter is continuously created to form cosmic or celestial
bodies such as stars and galaxies

2. 11. Cosmic Inflation Theory
o Based on the big bang theory wherein a short early period of exponential cosmic inflation is incorporated in
order to solve the uncertainties of the standard big bang model such as horizon and flatness problems.
o Proposed by the American physicist Alan Guth and Andrei Linde in the 1980’s.
o Early universe was a rapidly increasing bubble of pure vacuum energy; no matter or radiation.
o After expansion and cooling arising from this inflation, the potential energy converted into kinetic energy of
matter and radiation then a big bang occurs because of extremely hot, dense condition of matter.
12. Multiverse Theory
o Proposed by the Russian-American physicist Andrei Linde in 1983
o This theory sees the universe as just one of many “bubbles” that grew as a part of a multiverse.
o The concept of “many worlds” structure of the universe is initially developed and popularized by Hugh Everett
III and Bryce de Witt in 1960’s and 1970’s.
Theories about the Origin of the Solar System
1. Encounter Hypothesis
o About 5 Gya, a rogue star passed close to the sun and stripped materials (hot gases) from both the sun and the
rogue star. The hot gases continued to spin in the same direction as the sun, and coalesced into smaller lumps
which formed the planets.
2. Nebular Hypothesis
o Statesthat the entire solar systemstarts asa large cloud of gas that contracteddue to self - gravity. Conservation
of angular momentum requires that a rotating disk form with a large concentration at the center,which starts as
the protosun, while planets began forming within the disk.
o Rotating gas clouds or nebula of extreme hot gas. Due to rotation, central mass and shrinking, the rings
condensed into various densities of planets and satellites. Most mass formed the sun.
o Proposed by Immanuel Kant and Pierre Simon Laplace din the 18th
century.
3. Protoplanet Hypothesis
o The present working model for the formation of the Solar System. it is built on the main concepts of the nebular
hypothesis, with added concepts based on new knowledge on fluids and states of matter.
o Proposed by Thomas Chamberlin and Forest Moulton
o Also known as the Planetisimal Theory
o According to this hypothesis, the Solar system began with a fragment from an interstellar cloud composed
mainly of hydrogen, helium and trace amount of the light elements. The fragments of the interstellar cloud then
formed the dense central region of the central nebula, which collapsed more rapidly than its outlying parts. as
the solar nebula contracted,it rotated more rapidly, conserving its angular momentum. It also grew by accretion
as materials continued to fall inward from the surroundings. The solar nebula eventually formed into the sun.
o Gravitational instabilities ruptured the thin disk into eddies, each containing small particles which built up and
accreted. As the accretion continued, larger asteroid – sized aggregates called planetisimals are formed, which
orbited the center of the solar nebula.
o The planetisimals further grew in size due to the gravitational attraction they exert onto one another, forming
moon-sized bodies that would later become planets
4. String Theory
o Proposed by Albert Einstein.
o The theory states that there are strings attached to a certain void and these strings serves as the orbits of planets.
The strings are either closed or open and are mainly composed of electron, photon, and graviton.
5. M Theory
o Also known as the superstring theory. It states that one or both ends of the strings are attached to a sheet on
brace. Once an end of a certain string is detached, there sprouts a new system or galaxy. It states about 11 space
time dimensions.
o Proposed by Stephen Hawking and Leonard Mlodinow
6. Descartes’ Vortex Theory
o Proposed by Rene Descartes.
o the vacuum of space was not empty at all but was filled with matter that swirled around in large and small
vortices. His model involved a system of huge swirling whirlpools of fine matter, producing what would later
be called gravitational effects.
o Whirlpool like motion which soon started to accumulate and create the components of the solar system
7. Buffon’s Collision Theory
o States that there was a collision between the Sun and a giant comet. Due to the impact, the pieces’ scatter and
began to revolve around the sun.
o Proposed by George Louis Leclerc and Comte de Buffon
8. Jean-Jeffrey’s Tidal Theory
o Proposed by Jean Hopwood Jeans and Harold Jeffrey
o States that a star passed closed to the sun. the gravitational pull of the passing star raised tides found on surface
of the sun. The substances present on the surface of the sun was then torn out which formed the planets.