Why Doesn't the Night Sky Shine as Bright as the Sun Despite Infinite Stars?

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SUMMARY

The discussion centers on Olbers' Paradox, which posits that in an infinite and eternal universe, every line of sight should end on a star, making the night sky as bright as the Sun. Participants clarify that the paradox does not imply infinite brightness but rather a brightness equivalent to that of an average star due to factors like star density, redshift, and the finite lifespan of stars. Key points include the inverse square law of brightness, the role of redshift in dimming distant stars, and the necessity of a homogeneous distribution of stars in space and time to uphold the paradox.

PREREQUISITES
  • Understanding of Olbers' Paradox
  • Familiarity with the inverse square law of brightness
  • Knowledge of redshift and its implications in cosmology
  • Concept of homogeneous distribution in spatial and temporal contexts
NEXT STEPS
  • Research the implications of redshift on distant celestial objects
  • Study the inverse square law in astrophysics
  • Explore the conditions required for Olbers' Paradox to hold
  • Investigate the de-Sitter model of cosmology and its relevance to eternal universes
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Astronomers, cosmologists, physics students, and anyone interested in the fundamental questions of the universe's structure and the nature of light from distant stars.

  • #31
On the subject of star lifetimes:

No, a star does not have to be infinitely long-lived. Suppose it exists for a long time then dies - what then?

Well, since your line of sight extends infinitely far in this model, the probability that there will be an active star somewhere behind the space the first star used to fill will tend towards 1.

In fact, if your line of sight is truly infinite and the universe is homogenous, your line of sight will always extent through an infinite number of active stars.

Even more damning evidence against this model, I'd say.
 
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  • #32
Fascinating, PL. It appears you are asserting 'math' is irrelevant in your odel of the universe.
 
  • #33
Sojourner01 said:
On the subject of star lifetimes:

No, a star does not have to be infinitely long-lived. Suppose it exists for a long time then dies - what then?

Well, since your line of sight extends infinitely far in this model, the probability that there will be an active star somewhere behind the space the first star used to fill will tend towards 1.

In fact, if your line of sight is truly infinite and the universe is homogenous, your line of sight will always extent through an infinite number of active stars.

Even more damning evidence against this model, I'd say.

well.. I´m not going to say that this model should be proven correct. I´m just trying to understand why its wrong... :)

Suppose the life time of a star is 1 year. But star density is the same as it is now. Stars keep popping up and dying out all the time, natural process I guess.

Intuitively, I feel like the average life span of a star in this model determines how bright the nigh sky lights up (also star density is a factor I guess). Now, I know intuition is not always your best friend in science, but sometimes it's all you have,. :)

I don't see how the star's light/radiation continues to move for ever. Perhaps mathematically it does, but a at a certain point it's not practical anymore.

Has there never been done any calculation on the relation between star density, average star life span and the brightness of the night sky? (in an infinite universe, or even in "our" finite big bang universe)
 

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