Chapter 5: Earth and Its Moon We know the internal structure of the Earth and Moon by observing how Earthquake waves propagate through the interior. Compression and transverse waves can each travel through solids but only compression waves can travel through liquid. Therefore we know that at least part of the Earth’s core is liquid. Our information about the Moon is limited because there are few Moonquakes. We think the core is solid

Chapter 5: Earth and Its Moon Because the Earth has a liquid conducting core that rotates, electrical currents are set up which creates a strong magnetic field. Charged particles tend to spiral around magnetic field lines and get reflected when they become too strong. The Earth’s field is such that the solar wind particles are trapped in the Van Allen radiation belts Magnetosphere

Chapter 5: Earth and Its Moon Sometimes the reflection point occurs low in the atmosphere. As the charged particles slam into the atoms and molecules in the atmosphere they excite them and cause them to fluorescence. We call these events the Aurora. The Moon has no magnetic field.

Chapter 5: Earth and Its Moon Plate Tectonics The surface of the Earth consists of several plates which float on the molten interior. As these plates crash into each other they produce mountains. As they slide away from each other they produce trenches. The plates move about 2 cm/year

Chapter 5: Earth and Its Moon Origin of the Moon Video The giant impact theory best explains why the Moon is very much like the Earth’s mantel and contains very little nickel/iron. The creation and evolution of the Earth and Moon are closely related