Big Bang Theory, Galaxies, and Earth’s Habitability
Evidence for the Big Bang Theory
Evidence confirming the Big Bang theory:
The Big Bang theory is supported by several key pieces of evidence:
- The universal expansion itself.
- The atomic composition of the Universe, which is consistent with this theory.
- The cosmic microwave background radiation. This is a relic radiation detected in all directions, representing the “glow” or “switch on” of the initial explosion. It appears as microwave radiation today due to the expansion of the Universe.
- The light from distant galaxies is shifted towards red, indicating they are moving away (Doppler effect). This suggests the universe originated from a single point.
Timeline of Big Bang Events
Schedule of the Big Bang events:
Before the Big Bang, scientists believe the observable universe, including all its matter and radiation, was compressed into a hot, dense mass. This point experienced a violent expansion, marking the origin of time, space, and all groupings of matter. This almost incomprehensible state is speculated to have existed just a fraction of the first second of time.
The massive blast allowed all known matter and energy of the universe, including space and time, to arise from some type of unknown energy.
The theory holds that, in an instant (one trillionth of a second) after the Big Bang, the universe expanded at an incomprehensible speed from its origin (inflation phase).
As the universe expands over time, its size (volume) increases, but its temperature and density decrease. Consequently, as time passed, the material cooled and began to form diverse types of atoms, which eventually condensed into stars and galaxies of our present universe.
Galaxies, Nebulae, and Stellar Relationships
Defining galaxies and nebulae and establishing the relationship between stars and nebulae:
A galaxy is a group of stars, celestial bodies, and cosmic matter concentrated in a particular region of space due to gravitational attraction, forming a unity in the universe. A nebula, on the other hand, is a cloud of gas and dust. The relationship between them is that a star can become a nebula when it dies and explodes, and sometimes, stars are formed in nebulae regions, which are areas with high density.
Why Life is Possible on Earth
Factors that make life possible on Earth:
Several factors contribute to the habitability of Earth:
Distance from the Sun:
Earth’s distance from the Sun results in an average temperature of 15°C, allowing water to exist in a liquid state. Water is essential for life, and its absence causes death.
Perfect Size and Atmosphere Composition:
If Earth were smaller, its mass would not be able to attract gravity to its protective atmosphere. If the atmosphere were too thick and dense, it would not let sunlight pass through. The atmosphere allows visible light to pass through, which is essential for plant processes (photosynthesis). The ozone layer traps high-energy radiation and plays a protective role. The atmosphere is rich in oxygen, which facilitates cellular respiration (common to all living animals and plants). Finally, the atmosphere contains greenhouse effect gases, which absorb and re-radiate the radiation reflected back to space.
The greenhouse effect is a natural process that warms the Earth’s surface, maintaining the Earth’s temperature at around 33 degrees Celsius warmer than it would otherwise be, allowing life on Earth to exist.
Planets of the Solar System
Planets of the solar system, ordered by position relative to the Sun:
The planets of the solar system, in order from the Sun, are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.