Astronomy. the angular motion of a star relative to a suitably defined frame of reference, expressed in seconds of arc per year.
A Look At American Sign LanguageWhat is ASL or American Sign Language? American Sign Language, or ASL, is the visual signing language used by the Deaf community in the United States. English speakers in Canada and in a handful of other counties use ASL, too. Interestingly, those countries include the Philippines, Singapore, Jamaica, China, Chad, the Democratic Republic of the Congo, Cambodia, and Bolivia—a varied group. There are other sign languages …
Inertia vs. Momentum: Which Keeps You Moving?Science is real. Science is cool. Science uses a lot of terms that we all think we know. But, do we really know what we are talking about? In the spirit of scientific community and understanding, let's clear up one big scientific misconception that we all get wrong ...
- proper adjective,
- proper fasciculus,
- proper fraction,
- proper function,
- proper noun,
- proper palmar digital nerve,
- proper plantar digital nerve,
- proper substance of cornea,
- proper substance of sclera
Compare tangential motion.
Origin of proper motion
First recorded in 1595–1605
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
the very small continuous change in the direction of motion of a star relative to the sun. It is determined from its radial and tangential motion
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Movement of a celestial object in the sky that is the result of the object's own motion in space rather than of how it is observed from Earth. All celestial objects are in motion with regard to each other, but because objects outside the solar system are so distant from Earth most of them seem fixed in the sky. Over long periods of time, however, their proper motions result in gradual changes in their relative positions as viewed from Earth. Measurements of these motions by modern instruments can be extrapolated forward or backward in time to produce a celestial sphere on which the stars have somewhat different positions than they have today. In general, objects nearest the Earth have the greatest proper motions and will move the farthest on the celestial sphere in such extrapolations. Extremely distant objects, although they may be moving through space at equal or higher speeds than nearby objects, will appear to move little in the sky even over thousands of years.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.