Spherical Geometry #1 - Circles and Poles
In this series of posts I will be explaining the various terminology and methods involved in Spherical Geometry and Trigonometry and how it is used in Astronomy. So let's begin...
Consider a sphere as shown
A great circle is defined as the intersection of the sphere with a plane which contains the sphere's centre. Another way to think about this is that a great circle divides the sphere into two symmetric hemispheres. The radius of a great circle is same as that of the sphere itself. For example, the equator of the Earth and all the longitudes could be great circles of the Earth.
A small circle, on the other hand, is simply an intersection of any other plane with the sphere. In other words, circles on the sphere which aren't great circles are said to be small circles. It is obvious that small circles have smaller radii than the great circles, hence the name. For example, the latitudes of Earth other than the equator are small circles.
When the a line is drawn through the centre of the sphere perpendicular to a great circle, it intersects the sphere at two points. These two points are called the poles of that great circle. In the figure shown above, the points A and B are the poles.
Stay tuned for more astronomy....
Consider a sphere as shown
A great circle is defined as the intersection of the sphere with a plane which contains the sphere's centre. Another way to think about this is that a great circle divides the sphere into two symmetric hemispheres. The radius of a great circle is same as that of the sphere itself. For example, the equator of the Earth and all the longitudes could be great circles of the Earth.
A small circle, on the other hand, is simply an intersection of any other plane with the sphere. In other words, circles on the sphere which aren't great circles are said to be small circles. It is obvious that small circles have smaller radii than the great circles, hence the name. For example, the latitudes of Earth other than the equator are small circles.
When the a line is drawn through the centre of the sphere perpendicular to a great circle, it intersects the sphere at two points. These two points are called the poles of that great circle. In the figure shown above, the points A and B are the poles.
Stay tuned for more astronomy....
Comments
Post a Comment