odd facts 8.18.2005

Well, last week I was in Washington D.C., in part to visit my wife's parents. Nice folks, though I think one's in-laws are always a little odd--because they represent a style of parenting which one is not used to.

For part of that trip I brought along my laptop and I spent my time burried in astronomical texts, writing some Java code to compute planetary ephemeris data--because I can. (I used to work for JPL, and I figure it's always good every now and then to blow the dust off of one's old knowledge.)

While investigating a dumb comment I put into my Yahoo IM, I came across the following article on Wikipedia: Terrestrial Time:
Terrestrial Time (TT) is the modern time scale that is used instead of ephemeris time, which is obsolete. TT was introduced by the International Astronomical Union (IAU) in 1991 as the coordinate time scale consistent with the theory of relativity for an observer on the surface of the Earth. TT is a new name for, and is equivalent to, Terrestrial Dynamical Time (TDT).

Okay, here's what's going on. The Earth moves around the Sun at around 35,000 miles per hour, and objects on the surface of the Earth also move as the Earth rotates. Now according to the theory of relativity, objects in motion exist in their own relativistic coordinate frame--and time for an object in motion moves more slowly than time for objects at rest. The shift in time frames occur due to the change of the coordinate frame during acceleration or deceleration: specifically, d(Velocity)/d(Time) causes changes in the Einsteinian space/time coordinate system.

Or something like that; it's been a few years since I studied such things.

The long and the short of it is that if you hang a clock outside of our solar system, and hang a clock on the surface of the Earth, you get a very imperceptable drift in time. And that drift, in the 4,000+ years since the theoretical 'zero' of the Julian Date time system (which astronomers use to calculate time as a day--and fraction of a day--count since some theoretical time in the past), the theoretical clock outside our Solar System and the clock on the Earth has drifted approximately 32.1 seconds apart.

Meaning a year on Earth is approximately 0.008 seconds faster than a year outside our Solar System.

Okay, so I'm a bit of a geek...

posted by William Woody at 12:27 PM

Post a Comment Home

A moderate conservative living in the left coast, surrounded by the sureal, wonders if there is a sane life living amongst those who have lost touch with reality.

View Profile
Recent Items:

compare and contrast
education and "extremism"
economics and immigration policy
everything but culture
wilson lied, thousands died!
newsflash: animals exhale carbon dioxide!
quote of the day
astounding hypocrisy of the left
spinning science

Powered by Blogger