Exploring the Mystery of Why the Sky is Dark

In summary, the sky is dark because the more distant a light source, the more red-shifted its light. The stars in the sky are all emitting their own light, but 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?
  • #1
lwymarie
90
1
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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  • #2
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).
 
  • #3
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?
 
  • #4
The sky is dark because it is empty, and there is nothing for the light to reflect off.
 
  • #6
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.
 
  • #7
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.
 
  • #8
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 =]
 
  • #9
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.
 

1. Why does the sky appear blue during the day?

The blue color of the sky is due to a process called Rayleigh scattering. Sunlight is made up of a spectrum of colors, with shorter wavelengths (blues and violets) being scattered more easily by the gases and particles in the Earth's atmosphere. This scattered light is what we see as the blue color of the sky.

2. Why does the sky turn red during sunrise and sunset?

During sunrise and sunset, the sun's light has to travel through a thicker layer of atmosphere before reaching our eyes. This causes more scattering and absorption of the shorter wavelengths, leaving mostly red and orange light to reach our eyes, giving the sky its characteristic red and orange hues.

3. Why is the sky dark at night if there are countless stars in the universe?

Despite there being billions of stars in the universe, the sky appears dark at night because the universe is constantly expanding. This expansion causes the light from distant stars to be redshifted, meaning it is shifted towards the longer, less visible wavelengths. As a result, the light from these stars becomes too faint to be seen with the naked eye, making the sky appear dark.

4. Is the sky always dark in space?

No, the sky in space can appear bright depending on the location and the objects around it. For example, near a star or a galaxy, the sky would appear bright due to the light being emitted from these objects. However, in empty space with no nearby objects, the sky would appear dark because there is no atmosphere to scatter and reflect light.

5. How does light pollution affect our view of the night sky?

Light pollution, caused by excessive artificial lighting on Earth, can greatly impact our view of the night sky. It makes it difficult to see stars and other celestial objects, as the artificial light drowns out their faint light. This is why many astronomers and scientists work to reduce light pollution and preserve our view of the night sky.

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