Old space information, relevant conclusions?

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SUMMARY

The discussion centers on the implications of observing ancient light from space and its relation to the universe's expansion. Participants emphasize that while the universe's expansion is inferred from the Hubble constant, which has shown consistent scaling over time, there is no definitive proof that this expansion has not halted at some point in the recent past. The analogy of gravity is used to illustrate the uncertainty in predicting cosmic behavior, yet the consensus is that the long-term trend of expansion is unlikely to reverse suddenly.

PREREQUISITES
  • Understanding of the Hubble constant and its significance in cosmology
  • Familiarity with concepts of cosmic expansion and redshift
  • Basic knowledge of gravitational theory and its implications
  • Awareness of astronomical observation techniques and their limitations
NEXT STEPS
  • Research the implications of the Hubble constant on cosmic expansion
  • Explore the concept of redshift and its role in measuring distance in space
  • Investigate theories regarding the potential for changes in gravitational forces
  • Study the historical observations of cosmic background radiation and their significance
USEFUL FOR

Astronomers, astrophysicists, and students of cosmology who are interested in the dynamics of the universe and the implications of observational data on cosmic theories.

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If the information we see in space is very old, and the universe "seems" to be expanding, how can we know that it is still expanding?
 
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If it had stopped anytime in the recent past we probably wouldn't know about it. We just have no reason to believe it would suddenly stop doing what it's been doing for 13 billion years. Kind of like gravity. We don't know if gravity is going to turn off tomorrow, but we have absolutely no reason to even consider that it might.
 
Yes, but, the information becomes less ancient as distance decreases. The expansion rate of the universe is deduced as a function of time. The Hubble constant scales smoothly across the history of the universe. That does not prove expansion did not suddenly halt a handful of millions of years ago, but, is viewed as highly unlikely.
 

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