As the particles grew in mass gravity began to aid

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As the particles grew in mass, gravity began to aid the process of their sticking together, accelerating their growth into boulders large enough to count as planetesimals, which means “pieces of planets”. With different orbits crossing each other, collisions between planetesimals tended to occur at higher speeds and hence become more destructive. (produce more fragmentation than accretion) Meteorites appear to be surviving fragments from the early period of condensation The leading model for Jovian planet formation holds that these planets formed as gravity drew gas around ice-rich planetesimals much more massive than Earth. Moons that accreted from ice rich planetesimals within these disks ended up with nearly circular orbits going in the same direction as their planet's rotation and lying close to their planet's equatorial plane. Solar wind is a stream of charged particles (protons/electrons) continually blown outward in all directions from the Sun. The high energy radiation from the young Sun ionized gas in the solar nebula, creating many charged particles. Nearly all stars, including the Sun, have their original rapid rotations slowed by transferring angular momentum to charged particles in their disks (particles that are later swept away). Asteroids are the rocky leftover planetesimals of the inner solar system, comets are the ice rich leftover planetesimals of the outer solar system. Heavy Bombardment – the period of planetesimal collisions in the first few hundred million years of the solar system Capturing Moons – the planetesimals would have been slowed by friction with the gas, just as artificial satellites are slowed by drag in encounters with Earth's atmosphere. If friction reduced a passing planetesimal's orbital enough, it could have become an orbiting moon. Radiometric dating – the method by which we measure the age of a rock Radioactive isotope has a nucleus that can undergo spontaneous change, radioactive decay is breaking apart of having one of its protons turn into a neutron. Chapter 9 For Earth, most of our detailed information comes from seismic waves, vibrations that travel through the interior and along the surface after an earthquake. Three Layers divided by density: Core – highest density material, consisting primarily of metals such as nickel/iron, in the central core Mantle – Rocky material of moderate density, mostly minerals that contain silicon, oxygen, and other elements, forms the thick mantle that surrounds the core. Crust – lowest density rock, like granite/basalt, forms the thin crust, essentially representing the world's outer skin. Earth's core consists of a solid inner core and a molten (liquid) outer core .
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Christopher Reinemann
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