Dear Dr. Stern: I wish to know what is the angle between the ecliptic and the axis of the Milky Way?
Thankyou! Reply I do not know offhand, but one can calculate. The angle G between two planes is the angle between the two vectors perpendicular to them. Let the vector (X1, Y1, Z1) be of length 1 (“unit vector”) and perpendicular to the ecliptic. Let (X2, Y2, Z2) be similarly a unit vector perpendicular to the plane of the galaxy. Then with dots denoting multiplication, the “scalar product” of the two vectors (“scalar” is a number without a direction, not a vector) is X1.X2 + Y1.Y2 + Z1.Z2 This can be shown to equal cos(G), where G is the angle between the two vectors. That is: X1.X2 + Y1.Y2 + Z1.Z2 = cos (G) The system of coordinates has z pointing to the north pole, and (x, y) in the equatorial plane of Earth. The x axis is the intersection between the ecliptic and the equator, and the x direction points to the position of the Sun at the spring (“vernal equinox”). The axis of the Earth is inclined by an angle A = 23.5 degrees (approx) to the equator. It points perpendicular to the in
