The expansion of the Universe is not constant ... Our Sun is on one of the spiral arms as shown in the diagram: The Sun's orbital speed is determined almost entirely by the gravitational pull ...

Astronomers see red-shift in virtually all galaxies. It is a result of the space between the Earth and the galaxies expanding. This expansion has the effect of increasing the wavelength of the ...

A diagram-type image representing stellar shells and tidal streams in haloes of ... It's all thanks to multi-object spectroscopy, which measures the redshift of these galaxies, and hence the distance ...