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earth-sci-Chapter-1.pdf
- 2. • Provide thescientific explanation for the origin of the Universe and the elements in it • describe how the Earth formed according to the nebular theory • create a model of the basic internal layers of the earth
- 3. any massive self-luminous celestialbody of gas that shines by radiation derived from its internal energy sources
- 4. either of twogeneral types of stellar assemblages held together by the mutual gravitational attraction of its members
- 6. • also knownas galactic clusters, do not have a distinct shape; • their stars are loosely clustered together in an amorphous gravitationally bound group.
- 7. • globular clusterslook like faint smudges of light against the darkness of space. • But a telescope reveals their true form: thousands to millions of stars form a spherical shape with a bright, dense core.
- 8. Galaxies are vastcosmic islands of stars, gas, dust, and dark matter held together by gravity.
- 9. • ELLIPTICAL • SPIRAL •IRREGULAR
- 10. ELLIPTICALS account for about one-thirdof all galaxies, vary from nearly circular to very elongated possess comparatively little gas and dust, contain older stars and are not actively forming stars anymore
- 11. SPIRALS appear as flat,blue- white disks of stars, gas and dust with yellowish bulges in their centers divided into two groups: normal spirals and barred spirals
- 12. IRREGULARS have very littledust, are neither disk-like nor elliptical These galaxies are abundant in the early universe, before spirals and ellipticals developed
- 13. • A planetis a celestial body that: ⚬ (a) is in orbit around the Sun, ⚬ (b) has sufficient mass for its self-gravity to overcom rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and ⚬ (c) has cleared the neighborhood around its orbit.
- 14. • A "dwarfplanet" is a celestial body that ⚬ (a) is in orbit around the Sun, ⚬ (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, ⚬ (c) has not cleared the neighborhood around its orbit, ⚬ (d) is not a satellite.
- 15. • All otherobjects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
- 16. Our planetary systemis located in an outer spiral arm of the Milky Way galaxy.
- 17. There are manyplanetary systems like ours in the universe, with planets orbiting a host star. Our planetary system is called “the solar system” because we use the word “solar” to describe things related to our star, after the Latin word for Sun, "solis."
- 19. • speculates thatthe Universe goes through repeated cycles of the big bang and subsequent expansions • ‘big bang’ was not the beginning of the Universe but rather a transition phase
- 20. • A studyconducted by a group of researchers in 2013 speculated that our Universe might have originated from the debris spewed out of a collapsed four-dimensional star or a black hole.
- 21. • The plasmacosmology (or plasma universe theory) speculates that electromagnetic forces and plasma play a much more important role in the Universe instead of gravity.
- 22. • the basicidea is that the Universe has no beginning and no future. Instead of a hot Big Bang, the theory advocates for a cold and slowly evolving Universe.
- 23. • the Universefollows an infinite cyclic model. It means that our current Universe will be replaced by an endless number of universes. • Each iteration of the Universe is divided into two phases, ‘Kalpa’ (or the day of Brahma) and ‘pralaya’ (the night of Brahma), and each is 4.32 billion years long.
- 24. • asserts thatthe observable Universe remains the same at any place and time. In the Universe, which is forever expanding, matter is continuously created to fill the space.
- 25. • the universeas we know it started with an infinitely hot and dense single point that inflated and stretched — first at unimaginable speeds, and then at a more measurable rate — over the next 13.8 billion years to the still- expanding cosmos that we know today
- 29. According to thistheory, the Sun and all the planets of our Solar System began as a giant cloud of molecular gas and dust. Then, about 4.57 billion years ago, something happened that caused the cloud to collapse.
- 30. From this collapse,pockets of dust and gas began to collect into denser regions. as the denser regions pulled in more and more matter, conservation of momentum caused it to begin rotating, while increasing pressure caused it to heat up
- 31. Most of thematerial ended up in a ball at the center while the rest of the matter flattened out into disk that circled around it. While the ball at the center formed the Sun, the rest of the material would form into the protoplanetary disc.
- 33. Due to theirhigher boiling points, only metals and silicates could exist in solid form closer to the Sun, and these would eventually form the terrestrial planets of Mercury, Venus, Earth, and Mars. The planets formed by accretion from this disc, in which dust and gas gravitated together and coalesced to form ever larger bodies.
- 34. Because metallic elementsonly comprised a very small fraction of the solar nebula, the terrestrial planets could not grow very large.
- 35. The giant planets(Jupiter, Saturn, Uranus, and Neptune) formed beyond the point between the orbits of Mars and Jupiter where material is cool enough for volatile icy compounds to remain solid (i.e. the Frost Line)
- 36. The ices thatformed these planets were more plentiful than the metals and silicates that formed the terrestrial inner planets, allowing them to grow massive enough to capture large atmospheres of hydrogen and helium.
- 37. Leftover debris thatnever became planets congregated in regions such as the Asteroid Belt, Kuiper Belt, and Oort Cloud