on 4/29/2002 6:36 PM, Brian J White at [EMAIL PROTECTED] wrote: > why do people > have a problem with the term and loose measurement "light-year"?
On this metric discussion list, the main reason not to like the light-year is that it's not SI. An argument I've read on this list (but don't think is as important) as the "not SI" one) is that the year used to determine the light year is not clearly defined. That argument is countered by the fact that none of the measurements that are typically reported in light-years is very accurate anyway; therefore, it doesn't matter which one of the several kinds of "year" is used. As long as light years are used as a loose measurement, there are not very many good arguments against it, except for one: It's not SI, therefore we lose all the good things we can do with such values when they and all other values are expressed in a coherent, rational system like SI. There are also those who don't like the light-year because they do not like to have a length unit (the light-year) that is dependant on a unit of something else (like year of time). However, the current definition of the metre is the distance light travels in a certain fraction of a second. So why is that so bad when it comes to the light-year? (Those who don't like the light-year tend also not to like the current official definition of the metre, either.) There are others who DO LIKE the light-year and give arguments about how easy it is to visualize large distances in light-years instead of terametres and exametres and other SI units* . I just don't believe anyone can visualize such enormous distances (or the enormously fast speed of light for that matter) in any unit at all. We can do things with those values (especially in SI) intellectually, like making comparisons, calculating relationships, etc., but we cannot visualize or really comprehend them (IMHO). Regards, Bill Hooper physics professor (retired), Florida, USA *There are those who will say that I should have referred to terametres and exametres as "other multiples of the SI unit, metre" instead of "other SI units". ======================== Keep It Simple - Make It Metric! ========================
