Universe
Universe is everything. It includes all the space, and all the matter and energy that space contains. It even includes time itself.
- Smallest atom to the largest galaxy is part of it
- It is measured using Light Year(ly)
- The observable universe is 93 billion light-years (about meters)
🚀 Voyager 1: Earth's Farthest Emissary
Launched by NASA on September 5, 1977, Voyager 1 is the most distant human-made object in existence. In 2012, it made history by becoming the first spacecraft to enter interstellar space (the space between stars).
- Primary Mission: Explored Jupiter and Saturn, revealing active volcanoes on Io and the thick atmosphere of Titan.
- The Golden Record: Carries a copper phonograph record filled with Earth’s sounds, images, and greetings for potential alien life.
- Pale Blue Dot: Captured the iconic photograph of Earth from 6 billion kilometres away in 1990.
- Status: Still transmitting data back to Earth from over 24 billion kilometres away, using its aging nuclear power source.
Different Branches of Science for the Study of Universe
- Cosmology: Whole universe (origin & future)
- Astronomy: Starts, Planets, Galaxies
- Astrophysics: Physics of Celestial bodies
- Astro-biology: Life in the universe
- Planetary Science: Planets and Stars
- Exoplanetology: Worlds beyond the Solar system.
Important Terms for understanding Universe
- @ 🔗Various units for Measuring Astronomical Distances (ly, AU, PC)
- Aphelion: The point when a celestial body is farthest from Sun. For earth it’s 152.5 million km.
- Perihelion: The point when a celestial body is closest to Sun. For earth it’s 147.5 million km.
Philosophical Hypotheses regarding the Creation of the Universe
Monistic
- Core Concept: The universe originated from a single, unified substance, energy, or ultimate reality.
- Scientific Parallel: The Big Bang Singularity, where all matter, energy, space, and time existed as a single point.
- Philosophical Example: Spinoza’s Pantheism, which views God and the physical universe as one identical substance.
Dualistic
- Core Concept: The universe was created through the interaction or conflict of two independent, co-eternal forces.
- Scientific Parallel: Matter and Antimatter, or the fundamental interaction between space-time geometry and mass-energy.
- Philosophical Example: Zoroastrianism, which attributes creation to the opposing forces of supreme light and absolute darkness.
🪐 The Big Bang Theory (BBT)
Core Concepts & Timeline
- Origin: The universe originated from an unthinkably hot, dense singularity approximately 13.8 billion years ago. This means near-infinite temperature, density, and energy were condensed into a single point.
- The Singularity: At the very beginning, all matter and energy in the observable universe were concentrated at a single, zero-volume point.
- Expansion Dynamics: The physical fabric of space itself expanded and continues to expand to this day.
- Rate of Expansion: The expansion rate initially slowed down due to gravitational attraction, but transitioned into an accelerated expansion rate roughly 6 billion years ago driven by Dark Energy.
- First Atoms: Light atomic nuclei (mainly Hydrogen and Helium) formed through Big Bang Nucleosynthesis within the first 3 minutes of initial expansion.
- Atomic Matter: Within roughly 380,000 years, the temperature dropped to approximately 3,000 K, enabling neutral atomic matter to form (Recombination Era).
- Macro Structure: Subsequent gravitational condensation took place over millions of years, collapsing gas clouds to trigger the formation of the first stars, planets, and galaxies.
Historical Context
- Georges Lemaître: First propounded the “primeval atom” theory in 1927; it gained widespread recognition and acceptance around 1931.
- Edwin Hubble: Provided the critical empirical evidence supporting cosmic expansion in 1929 by demonstrating galaxy redshift proportional to distance (Hubble’s Law).
Thermodynamic Principles
- Temperature-Volume Relation: Governed by the thermodynamic principle where temperature is inversely proportional to volume:
- Cosmic Cooling: As the universe expands, its volume increases, causing the wavelengths of moving photons to stretch (cosmological redshift), which reduces the overall temperature.