This means that Eratosthenes estimated the circumference of the Earth to be about 40,000 km. He also knew that the circumference of a circle was equal to 2 times Ï (3.1415...) times the radius of the circle. (C = 2Ïr) With this information, Eratosthenes inferred that the Earth's radius was 6366 km.
Ankylosing spondylitis is a form of chronic inflammation of the spine and the sacroiliac joints. The sacroiliac joints are located at the base of the low back where the sacrum (the bone directly above the tailbone) meets the iliac bones (bones on either side of the upper buttocks) of the pelvis.
Ankylosing spondylitis is often abbreviated to AS and is also known as seronegative spondyloarthropathy, and simply spondylitis. 2. The condition is grouped into a set of overlapping arthritis disorders that doctors call the spondyloarthritides or spondylarthritis.ere are some key points about ankylosing spondylitis. More detail and supporting information is in the body of this article. 1  Ankylosing spondylitis is a type of arthritis. 2  It mostly affects the lower part of the spine, and where it joins to the hip.