How Do Photons from Very Old Galaxies Reach the Hubble Telescope?

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SUMMARY

The discussion centers on the ability of the Hubble Space Telescope (HST) to observe light from galaxies that existed up to 10 billion years ago. Participants explain that photons emitted from these ancient galaxies began their journey when the universe was significantly smaller, approximately 4.5 billion years ago. Due to the expansion of the universe, the path of these photons has been extended, allowing them to reach the HST despite the initial distance being much shorter. This phenomenon is likened to running on a down escalator, illustrating the complexities of cosmic distances and light travel.

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  • Understanding of cosmic expansion and the Big Bang theory
  • Familiarity with the principles of light travel and photon behavior
  • Knowledge of the Hubble Space Telescope's capabilities and observational history
  • Basic grasp of astronomical distances and time scales in billions of years
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  • Research the concept of cosmic inflation and its impact on light travel
  • Explore the mechanics of the Hubble Space Telescope and its observational techniques
  • Learn about the implications of redshift in understanding the universe's expansion
  • Investigate the history of light travel from ancient galaxies to modern telescopes
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Astronomers, astrophysicists, students of cosmology, and anyone interested in the mechanics of light travel and the capabilities of the Hubble Space Telescope.

bkilkerr
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With the Hubble telescope now able to see back in time by as much as 10 billion years, can anyone explain the path of the photons from very old galaxies entering the HST during the last 10 billion years and particulary where they were around 4,500 million years ago?
 
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I'm guessing you're wondering how they could be traveling for 10Gy if, 4.5Gy ago the universe was a mere 4.5Gly wide.

Think about running up a 'down' escalator. If you do it right, you can run for a half mile on an escalator that is only 100 yards long.

While light from a galaxy 4.5Gy ago may have started out only a few Mly away, the universe has expanded greatly in the time it traveled here, so its jounrey was vastly extended.
 

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