Person: Gan De
Gan De was one of the earliest of the Chinese astronomers.
Mathematical Profile (Excerpt):
- He was one of the earliest of Chinese astronomers and made observations which he recorded giving dates and coordinates.
- We have included Gan De this archive for one reason only.
- That is that a quotation from his book Suixing Jing (Treatise on Jupiter) was recorded by later writers.
- Apparently, there was a small reddish star appended to its side.
- Of course the intriguing question is what was the small reddish star which Gan De saw?
- If he did see one of the Galilean satellites, then it would have been Ganymede which is the brightest of the four.
- Ganymede can have a magnitude of 4.6 which means that it is within the range which anyone might expect to see.
- However the reason that Ganymede is not readily visible is that Jupiter, being so much brighter and so close to Ganymede when viewed from earth, obscures the faint satellite.
- Gan De might have possessed exceptional eyesight and been able to separate the faint Ganymede and the bright Jupiter.
- The only thing in the description which would have one doubt this is the fact that Gan De records the small star on the side of Jupiter to be reddish.
- However, we must remember that he observed under conditions of absolutely no light pollution, something impossible today.
- Evidence on the positive side suggesting that he did indeed observe Ganymede comes from the accuracy of his observations in general.
- and also gave accurately observed details of the planet's movements throughout its 12 year cycle.
- We also know that Gan De produced star catalogues.
Born about 400 BC, China. Died about 340 BC, China.
View full biography at MacTutor
Tags relevant for this person:
Astronomy, Origin China
Adapted from other CC BY-SA 4.0 Sources:
- O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive