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
-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