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University of South Carolina
ASTR 111

Astronomy Unit 12 -the age of the Earth and other planets is believed to be 4.6 billion years -the Coriolis effect causes moving objects to deviate to the right in the northern hemisphere and to the left in the southern hemisphere -the water on our planet was probably delivered by cometary impacts soon after the Moon formed -Radioactive atoms- are those that spontaneously break apart into other atoms and basic particles -isotopes, nuclei that have the same number of protons (determining the element) but a different number of neutrons -decay may involve losing one or more protons and/or neutrons from the nucleus. -protons are lost the atom is now a different element, if only neutrons are lost, the resulting atom is a different isotope, but the same element - parent isotope The original atom - daughter isotope-the resulting atom -Radioactive decay is random, so we cannot say when any individual nucleus will decay; - statistically the behavior is predictable -Half-life-large number of atoms, after a period of time half the nuclei will have decayed -radioisotopic dating-If we know the original ratios of parent and daughter isotopes when a rock formed and the current ratios, we can use these numbers to calculate the age of the rock -The electric currents in the Earth’s outer core are not aligned with the Earth’s rotation. -the Earth’s magnetic field poles are not the same as the Earth’s rotational poles. -The magnetic poles are about 1,330 km from the geographic poles. -magnetic north is not the same as astronomical north. -The isotopic ratio (neutrons to protons in the oxygen nucleus) for Earth’s water does not match the solar ratio -The Earth formed out of the solar nebula and differentiated with iron sinking to the core -large planetoid impacted with the Earth throwing debris into orbit. The Moon forms from this debris - a large number of meteoroids from beyond Neptune are came into the inner solar system as the outer gas giants form. -This rain of meteoroids provided most of the Earth water - first the Earth was so hot that most of this water evaporates and is lost as the Earth cools, the water remains to form the oceans -Theory is that the water in meteoroids formed beyond Neptune should have about t
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