## Thursday, May 28, 2015

### astro pictures for the day

Image credit: ESA/Herschel/PACS/SPIRE/Ke Wang et al. 2015

interstellar clouds are known to be light years in length, but I can't help sharing some of this interstellar gas clouds stats - contains 80,000 solar mass worth of material, 280 light years in length . . . it's diameter is only five light years! This particular gas cloud is 18,000 light years away.

Image Credit: ESO

Credit:
ESA/Hubble & NASA

Image Credit: Nasa/ Dawn spacecraft of Ceres

- May 28 latest of Ceres,

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

- some thought for the day extra,

How did the Cartesian plane come about?  Not until the end of section 1 of Descartes "The Geometry"(which is actually an appendix to Descartes "Discourse on the Method", hence it's the only reason to by Descartes 'Discourse'!) does he hint at a Cartesian plane. The majority of what he presents just uses two lines.  When he considers possibly doing his algebraic geometry(not to be confused with modern mathematicians meaning of 'algebraic geometry') to three dimensions, he points out making normals at every dimensional extention from a point of a curve. A normal is a perpendicular line.  He uses normals often to set up his equations, which are quite a bit more than what even today's 'college algebra' students or even Calculus 1 and maybe even two ever see!

It's just interesting how the full general idea didn't come into view till he considered the three dimensional case!