On 2008-02-22, Unruh <[EMAIL PROTECTED]> wrote: >>High precision orbital dynamics, such as the JPL's DE405, are done in >>Barycentric Dynamic Time, which runs at a different rate than TAI, but >>is "TAI like" in that it has no leap seconds. > > It does? The second was defined to make the speed of light a consant. Are > you saying they use a system in which the speed of light changes from time > to time? That sounds horrible.
I am saying that high precision orbital dynamics are done from the reference frame of the solar system, which we call the barycentric frame. The barycentric time rate is different from that of TAI by a factor of about 1e-15 if I remember correctly. > While it may be slowing on average, it is noise and it could well speed up > as well. Noise implies that the changes are both positive and negative, in which case a leap second won't be needed. If it is systematic, i.e. the changes are more in one direction than another, a leap second will be needed. _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
