Cosmology: Origin of the Universe

Origin of the Universe

• Cosmology investigates the universe's origin, development, structure, history, and future.
• Different theories have emerged over time to explain how everything came into being.

Historical Development of Theories

• Religious Cosmology:

  • Genesis: Describes God's creation of light, darkness, earth, and living creatures in six days.
  • Rigveda: Presents the universe as brahmanda or "cosmic egg," originating from Bindu and undergoing cyclical expansion and contraction.

• Philosophical Views:

  • Anaxagoras: Proposed a primordial universe created by "nous" or mind.
  • Leucippus and Democritus: Introduced the atomic universe, consisting of atoms and void.
  • Pythagorean Model: Suggested that celestial bodies orbited an "invisible fire," not the sun.
  • Aristotle's Theory: Advocated for the four elements and a geocentric model with Earth at the center, supported by Eudoxus.

Models of the Universe

• Geocentric Model: Proposed by Aristotle and Ptolemy; Earth is motionless at the universe's center with celestial objects revolving around it.
• Heliocentric Model:
  • Copernicus (1543): Rejected geocentrism, placing the Sun at the center.
  • Giordano Bruno (1584): Extended the idea to consider many star systems.

Scientific Developments

• Sir Isaac Newton: Formulated laws of motion; described a static, infinite universe that was gravitationally balanced yet unstable.
• René Descartes: Proposed a static universe filled with swirling matter, influencing concepts of gravitational effects.
• Albert Einstein: Developed the Theory of General Relativity, initially considering a static universe.
• Edwin Hubble: Demonstrated in 1929 that the universe is expanding via observations of galactic redshift.

Modern Theories of the Universe

• Big Bang Theory:

  • Proposed by Georges Lemaître in 1927; explains that the universe expanded from a singularity approximately 14 billion years ago.
  • Supported by Edwin Hubble’s findings of an expanding universe.

• Steady State Universe:

  • Introduced by Fred Hoyle, Thomas Gold, and Hermann Bondi; suggests that new matter is continuously added to maintain consistent density as the universe expands.

• Oscillating Universe:

  • Concept of expansion followed by contraction, leading to repeated cycles of Big Bang and Big Crunch.

• Inflationary Universe:

  • Alan Guth's model incorporates an early phase of exponential cosmic inflation to address gaps in the Big Bang theory.

• Multiverse Theory:

  • Developed by Andrei Linde; proposes the existence of multiple, potentially infinite, universes beyond our known cosmos.