Moozy

@ Strange : Question: Why cosmoslogists have come to the conclusion that the universe is expanding ? Answer: The redshift (i.e. the Doppler effect) of galaxies.

Very often for copyright considerations, they publish artist's view, or 3D images instead of received real images.

Thank you Janus for this detailed answer. I am reading a book on the "run away" of galaxies (in french, "la fuite des galaxies") and I wanted this point to be clarified (a Doppler effect can be detected on a stationary object provided the receiver is moving). By the way, Happy New Year 2015 to all the distinguished members of this forum

Thanx robittybob1, but I was expecting more elaborate answers... The question is not as 'shallow' as it may seem

About the Doppler effect: We know that when a vehicle passes at high speed in front of a stationary observer, the sound of the horn is high frequency when the vehicle approaches, then low frequency when the vehicle moves away. My question: what happens when, on the contrary, a moving observer passes at high speed a stationary vehicle honking? Do we get the same Doppler effect? My guess: the effect is the same ...