Gemini Deep-Deep Survey Universe Time-Line
Credit: Gemini Observatory Illustration by Jon Lomberg
This timeline shows some pivotal events in the history of the Universe which is assumed to have begun with the Big Bang some 13.7 billion years ago. The "Redshift Desert" is a region where the light from galaxies has been redshifted (stretched by the expansion of the Universe) into a region of the spectrum where a natural glow in the Earth's atmosphere interferes with key spectroscopic features of many of these galaxies. This interference is especially problematic when trying to study dimmer galaxies in the early Universe. Using a sophisticated observing technique that overcomes this problem, the Gemini Deep Deep Survey revealed that a large number of galaxies from this period of cosmic history were fully formed and more massive than the widely accepted Hierarchical Model of galaxy formation predicts.
This timeline also illustrates the concept of "look-back time," which is what happens when astronomers look at more and more distant objects in space. Because light travels at a finite speed (about 300,000 km/s or 186,000 miles/s), it takes time for the light to reach our telescopes to be studied. This results in a cosmic "time-machine" because the light that we see from distant galaxies has traveled for billions of years. Thus, we see the galaxies as they were long ago when that light began its journey to our telescopes.
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