yun@eng.umd.edu (Dragon Taunter) (12/14/90)
Arnold G. Gill writes: >John Schultz writes: >> >>I have no trouble with the idea of light speed, light years, etc., but how >>can one telescope see back farther than another? Is it due to focusing power, >>or something similar? > > No -- it is due to the fact that the telescope has better light >collection abilities and/or better detectors. Either way, one can see fainter >objects, and for objects with the same intrinsic brightness, this means that >they can be seen further away. However, the real important quantity is the >magnitude limit (how bright an object is). The public finds things like 26th >magnitude difficult to understand, so they are told that one can see twice as >far. I would like to add that what is actually measured is the redshift. There is no way to measure directly the distance to object. One obtains a redshift and then choses a particular model of the universe to use for the calculation of distance. To within factors of two and pi the printed distance in the paper agrees with the values from the different models. Once again, the specifics have been diluted since news reporters do not expect the public to know what a z=4.5 reshift means. It does not help any for space sciences reporting that many science news reporters have backgrounds in biology. -- yun@wam.umd.edu zwy0c@scfvm.gsfc.nasa.gov (code 926) yun@eng.umd.edu zwy0c@charney.gsfc.nasa.gov 5 hrs 10' 39" W 39 deg 2' 9.7" N A milihelen is the amount of beauty required to launch one ship.