History of Life
But 1st an Intro Video
Timeline• Big Bang: ~13.75 bya (billion yr ago)
– or 13.75 Ga Giga = Ga = 10^9– or 433.6 x 10^15 seconds (SI base unit)
•
• Milky Way Galaxy: ~13.2 bya
• Sun: ~4.57 bya
• Earth: ~4.54 bya
• Moon: ~4.53 bya, ~30–50 mya after the Solar System
Formation of Galaxies
~ 1 billion years after the Big Bang...
Some clumps of matter dispersed by their internal motions, others grew by attracting other nearby matter.
Surviving matter clumps became the beginnings of today's galaxies.
When a clump becomes massive enough, it starts to collapse under its own gravity & becomes a protogalaxy.
Galaxies & Within (intragalaxies)
large groupings of stars, dust, and gas held together by gravity
contain all the familiars: billions of stars, some with planets, moons, comets, asteroids.
& the less familiar: nebulae, neutron stars, black holes, and dark matter
The Milky Way: Our galaxy
1 ly = ~10 trillion km (10^16 m) = ~ 6 trillion miles
Within the early Milky Way:
Nebula: giant clouds of
gas,
dust,
&
the birthplace of stars
Crab Nebula in visual spectrum from Hubble telescope
Nebular Theory:
The theory that explains the formation of Earth and it’s solar system.
The Earth, like all the other planets, formed out of the disk of gas and rocks that orbited the sun.
If the Earth was made out of a bunch of chunks of rock that collided and stuck together... what would it be like inside?
4.54 bya, when Earth had reached it’s final size, it was a hot and lifeless planet.
Formation of Earth's Moon
continuous bombardment by meteorites, and intense volcanism
4.1 bya - 3.8 bya: Late Heavy Bombardment at the end of the Hadean Eon
Achaean EonEarth has significantly cooled, no stable atm, no O2, no O3
LIFE?
End of Part 1
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