Why is the Sky Dark Despite Countless Stars?

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Discussion Overview

The discussion revolves around the question of why the night sky appears dark despite the presence of countless stars. Participants explore various theories and concepts related to this phenomenon, including Olbers' Paradox, the nature of light, and the implications of an expanding universe.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the darkness of the sky is due to the emptiness of space, which does not provide surfaces for light to reflect off.
  • Others reference Olbers' Paradox, suggesting that if the universe were infinite and static, the sky would be uniformly bright.
  • A participant mentions that the light from distant stars becomes redshifted, which may contribute to the perceived darkness.
  • One participant challenges the notion of an infinite universe, arguing that the Big Bang limits how far back one can see, thus affecting star visibility.
  • There is a correction regarding the age of the universe, with some participants debating whether it is 13 billion or 15 billion years old, indicating uncertainty about the current understanding of cosmological time scales.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the reasons for the darkness of the sky, particularly around the implications of Olbers' Paradox and the nature of the universe. The discussion remains unresolved, with no consensus reached on the various claims made.

Contextual Notes

Some claims depend on interpretations of cosmological models and the nature of light, which may not be universally accepted. The discussion includes corrections and clarifications about the age of the universe, highlighting the evolving nature of scientific understanding.

lwymarie
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The stars in the sky are all emitting their own light. The light is reflected for infinitely many times and part of the light energy will be stored in objects. But why is the sky so dark? Why is it not bright?
 
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lwymarie said:
The stars in the sky are all emitting their own light. The light is reflected for infinitely many times and part of the light energy will be stored in objects. But why is the sky so dark? Why is it not bright?
You appear to be a poet by nature, as opposed to a scientist. Light energy is unfortunately not 'stored' in objects. It is either absorbed or refracted (up to the point of being reflected).
 
lwymarie said:
The stars in the sky are all emitting their own light. The light is reflected for infinitely many times and part of the light energy will be stored in objects. But why is the sky so dark? Why is it not bright?

Can you see a light bulb from a mile away? How about 100000000000000000000000000000000000 miles?
 
The sky is dark because it is empty, and there is nothing for the light to reflect off.
 
lwymarie said:
The stars in the sky are all emitting their own light. The light is reflected for infinitely many times and part of the light energy will be stored in objects. But why is the sky so dark? Why is it not bright?
Excellent question, first asked by Kepler 400 years ago! Look up SGT's link.
 
The sky isn't all bright because, for whatever reason, the more distant a light source the more red shifted is its light. When we check low enought frequencies, we even find the light shifted into the radio frequencies.
 
Yes yes I was referring to the Olbers' Paradox. However I do not remember the details so I describe what I still remember about the paradox and see if some goodies can explain to me ;)
Thx a lot =]
 
Olbers' paradox is based upon the false impression of an infinite universe. It supposes that everything has always existed. If such were true, then the sky would be uniformly bright. No matter in which way you look, there would be a star. The Big Bang eliminates that concept, because you can only look as far in space as you can look back in time. The 45 billion years or so that has elapsed since then is not long enough for sufficient star formation to cause infinite light creation. Moreover, the total energy content of the universe precludes the possibility of it ever happening.
 
  • #10
Danger said:
...you can only look as far in space as you can look back in time. The 45 billion years or so that has elapsed since then...
? 45 billion? Did I miss an issue of Sci Am? 13 billion at last count.
 
  • #11
DaveC426913 said:
? 45 billion? Did I miss an issue of Sci Am? 13 billion at last count.
:redface: I usually proof-read these things better, but I was flat-out exhausted when I wrote that. It was supposed to say 15, which is a based upon one study that suggested that it might be as old as 20 billion years. Sorry, and thanks for catching it.
 

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