Accounting for Cosmological Expansion in Distance Measurements

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SUMMARY

This discussion focuses on accounting for cosmological expansion when measuring distances to distant astronomical objects, particularly Quasars with high redshifts. It emphasizes the importance of understanding co-moving coordinates, co-moving distance, luminosity distance, diameter distance, and proper distance in the context of an expanding universe. The conversation highlights that the expansion rate can vary based on different cosmological models, such as radiation-dominated and matter-dominated eras. A recommended resource for further study is "Introduction to Cosmology" by A. Liddle.

PREREQUISITES
  • Understanding of co-moving coordinates
  • Familiarity with luminosity distance and proper distance concepts
  • Knowledge of cosmological models and their implications
  • Basic grasp of redshift and its significance in astronomy
NEXT STEPS
  • Research the mathematical formulation of co-moving distance
  • Study the differences between luminosity distance and proper distance
  • Explore the implications of radiation-dominated and matter-dominated eras on cosmic expansion
  • Read "Introduction to Cosmology" by A. Liddle for a comprehensive overview
USEFUL FOR

Astronomers, astrophysicists, and cosmologists interested in understanding the effects of cosmic expansion on distance measurements and the evolution of the universe.

Brantoc
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Some objects, Quasars for example have extremely high redshifts, and come from a time long past, and place far away. When determining distance on such large scales, how do you also factor in the cosmological expansion of the universe, meaning 10 billion years ago the universe was much smaller than today, the light would be stretched over time as the universe expands.

In some respects, if we see an object that is very old, were we really this far away when the light was emitted, and how far are we away today? do you assume consistent expansion, or did it once expand faster and today is it slowing?

Does someone have an example equation/result from a distant object?
 
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Things you could read about:

co-moving coordinates
co-moving distance
luminosity distance
diameter distance
proper distance

The expansion is different in each cosmological model
and it can also vary with time within the model itself.
For example you can distinguish between radiation
dominated era and matter dominated era and then
obtain different functions for the expansion.

The book that I would suggest would be
"Introduction to Cosmology" by A. Liddle.

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