Abstract
Over the past fifteen years, observations of some quasars with the techniques of very-long-baseline interferometry have shown that the angular separation between pairs of radio-emitting regions in their cores is increasing year after year. If the quasars are indeed as far away as implied by Hubble's law, then these angular motions translate into linear speeds several times the speed of light. Several theoretical scenarios have been proposed to show that the observed motions are illusory. The leading contender in this field—the relativistic beam model—and an alternative offered by the concept of a gravitational screen are described and compared in the light of recent observational data.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
