Measuring the size of the observable universe

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SUMMARY

The observable universe is commonly estimated to be 93 trillion light years in diameter, although some physicists argue that it may be infinite. This estimation is based on Hubble's constant and the assumption that the universe was finite at the first Planck time, approximately 10^-35 meters. The debate centers around whether the universe's finiteness is an assumption or can be derived from specific equations. Current experimental models cannot definitively distinguish between a "really large" universe and an infinite one.

PREREQUISITES
  • Understanding of Hubble's constant and its implications on cosmic expansion
  • Familiarity with the concept of Planck time and its significance in cosmology
  • Knowledge of inflation theory and its role in the early universe
  • Basic grasp of the differences between observable and total universe
NEXT STEPS
  • Research the implications of Hubble's constant on cosmic measurements
  • Study the concept of Planck time and its relevance in cosmology
  • Explore inflation theory and its impact on the size of the universe
  • Investigate current models that differentiate between finite and infinite universes
USEFUL FOR

Astronomers, cosmologists, physics students, and anyone interested in the fundamental nature of the universe and its size.

g.lemaitre
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The size of the observable universe usually gets put at 93 trillion light years, though some people believe it is infinite, though I'm not sure which camp is in the majority. Those who believe it is 93 trillion light years across are they just assuming that the size of the universe at the first Planck time was finite, I'm guessing 10^-35 m? And they are just using Hubble's constant, along the evidence of the extent to which Hubble's constant has sped up and slowed down over time, to calculate the size of the universe? I've read quite a few times that some physicists believe the universe was a centimeter across after inflation, hence finite. Again, let me state my question more succinctly, is the idea that the universe is finite just an assumption or is there some equation which requires it?
 
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The size of the observable universe usually gets put at 93 trillion light years, though some people believe it is infinite
I would expect this "infinite" refers to the total universe, not just the observable part. Otherwise, can you provide a source for this claim?
The same is true for the size of the observable universe (which is not the size of the total universe) after inflation.

The universe can be finite or infinite - if it is small enough, it can be possible to measure its size, but we cannot distinguish between "really large" and "infinite" with current experiments and models.
 

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