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| The Earth |
1. The diameter of the Earth is 12,700 km. Traveling at 5 km/sec will take 2540 seconds or 42 minutes. The S-waves will never arrive from an earthquake directly on the opposite side of Earth: they cannot penetrate the outer liquid core.
3. The volume of a sphere is proportional to the cube of the radius. The radius of the metallic core is 3500 km and the radius of Earth is 6350 km. So the percentage occupied by the core volume is
The crust is (on average) about 30 km thick, so the inner radius of the mantle is 3500 km and its outer radius is 6320 km. Thus the fraction of the volume occupied by the mantle is
(63203 - 35003) / 63503 = 0.82
The core and mantle together occupy 82% plus 17% or 99% of Earth's volume, leaving 1% for the crust.
5. A magnetosphere implies a magnetic field strong enough to dominate the electrical and magnetic environment within the magnetosphere; practically, this means the ability to deflect the solar wind of charged particles. If the magnetic field were too weak to deflect the solar wind there would be no significant magnetosphere.