Newsgroups: comp.robotics
Path: brunix!news.Brown.EDU!noc.near.net!howland.reston.ans.net!math.ohio-state.edu!cs.utexas.edu!csc.ti.com!tilde.csc.ti.com!mksol!strohm
From: strohm@mksol.dseg.ti.com (john r strohm)
Subject: Re: Distance to Mars
Message-ID: <1993Jun17.141154.29062@mksol.dseg.ti.com>
Organization: Texas Instruments, Inc
References: <1993Jun10.145007.12268@mksol.dseg.ti.com> <1993Jun16.203416.13079@isrc.sandia.gov>
Date: Thu, 17 Jun 1993 14:11:54 GMT
Lines: 30

In article <1993Jun16.203416.13079@isrc.sandia.gov> loucks@isrc.sandia.gov (Cliff Loucks) writes:
>john r strohm (amoung others) writes:
>> 
>>At closest approach to Earth, Mars is roughly 30 million miles away,
>>which works out to about 160 light-seconds.  At farthest, Mars is some
>>200 million miles away, or about 1100 light-seconds, or about 20
>>light-minutes away.
>
>Just a little nit...
>
>A light-year is a unit of distance; the distance light travels in a
>year.  A light-second would then be a distance of 186,000 miles.
>
>Light would take about 160 seconds to travel 30 million miles, while
>160 light-seconds is a distance of 30 million miles.
>
>Cliff
>-- 
>
>Cliff Loucks  <=>  loucks@isrc.sandia.gov
>Sandia National Labs, Albuquerque, New Mexico

Cliff, I must be extraordinarily dense today, but I don't understand what
nit you are picking.  I admit that I didn't explicitly say that "radio waves
from Earth would therefore take between 160 seconds and 20 minutes to get to
Mars, depending on where Earth and Mars were at the time."  I assumed that
anyone who was on here would know that radio waves travel at the speed of
light, and not instantaneously, and would do the rate*time=distance in their
heads.  (Rate*time=distance is rather simple if distance is expressed in
light-time units and rate is known to be "speed of light".)
