Conceptual Physics (12th Edition)

Published by Addison-Wesley
ISBN 10: 0321909100
ISBN 13: 978-0-32190-910-7

Chapter 35 - Think and Explain: 54

Answer

It meets the telescopes at the speed c.

Work Step by Step

Einstein's second postulate is that the speed of light in vacuum (free space), c, is the same for all observers. Ignoring the small slowing effect of air, the light arrives moving at c, not 0.9c.
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