Being an amateur astronomer, I find the AU (Astronomical Unit) quite useful. It is a unit-independent distance marker that allows for quick comparisons of the distances of solar system objects. It allows people (even lay people, where astronomy is concerned) to instantly visualize the distances of planets, asteroids, and comets from the Sun or Earth.
Earth Mass Units or "e" (comparisons of planetary masses to the Earth's mass where e = 1) are also used in astronomy. E are used on the Voyager Interstellar Record that is affixed to each of the two Voyager spacecraft that are leaving the solar system. The masses of the nine planets in terms of e are included. An explanation of the magnitude of e (they used universal constants, but I forget which one or ones) is included in the binary-language coding on the record. If the spacecraft are found by intelligent alien civilizations in the distant future, they will be able to compare the masses of the Earth and our other eight planets to the masses of their worlds. -- Jason ----- Original Message ----- From: David Shatto <[EMAIL PROTECTED]> To: U.S. Metric Association <[EMAIL PROTECTED]> Sent: Wednesday, September 10, 2003 10:03 AM Subject: [USMA:26932] NASA NEO report > I thought some of you might be interested in this... > > "NASA Releases Near-Earth Object Search Report > NASA has released a technical report on potential future search efforts > for near-Earth objects after a year of analysis by scientists working on > this issue. This Science Definition Team was chartered to study what > should be done to find near-Earth objects less than 1 kilometer in size." > > Here's the link to this report: > http://neo.jpl.nasa.gov/neo/report.html > > This is a 166 page report written mostly using metric; in fact, the words > "miles" or "feet" do not appear at all. You might not have ever seen so > many m and km in a NASA report before! > > The main exception is that they use the non-SI unit AU quite a bit. > Maybe you'd brand me a heretic, but I think this is a useful unit for > discussing distances of objects in relation to Earth - it beats "so many > million km from Earth." 1 AU is the distance from Earth to our sun (at a > certain point in our elliptical orbit). > > David Shatto > Los Angeles >
