A sundial measures the angle between a point on the surface of the earth, the centre of rotation of the earth, and the sun. Because the earth rotates at a const

A sundial measures the angle between a point on the surface of the earth, the centre of rotation of the earth, and the sun. Because the earth rotates at a constant-ish speed, a sundial naturally shows equal hours. It is possible, but tricky, to make an unequal-hours sundial: https://www.cl.cam.ac.uk/~fhk1/Sundials/Newnham/write-up.pdf https://www.cl.cam.ac.uk/~fhk1/Sundials/Newnham/write-up.pdf https://www.cl.cam.ac.uk/~fhk1/Sundials/Newnham/article01.pdf https://www.cl.cam.ac.uk/~fhk1/Sundials/Newnham/article01.pd... https://www.cl.cam.ac.uk/~fhk1/Sundials/Newnham/article02.pdf https://www.cl.cam.ac.uk/~fhk1/Sundials/Newnham/article02.pd... https://www.cl.cam.ac.uk/~fhk1/Sundials/Selwyn/Selwyn.pdf https://www.cl.cam.ac.uk/~fhk1/Sundials/Selwyn/Selwyn.pdf