16 replies to this topic

[j6p]

If the universe is boundless, stars and galaxies should be in our line of sight no matter where we look yet the night sky remains dark.

[babyforrest]

Stars and galaxies can be millions and even billions of light years away, and that is why they are not bright enough to see in most cases, let alone brighten up the entire sky.

[Exeter]

[Homer]

Yep, that about sums it up. Clouds of gas, dust and other dark matter block a lot of light; as well as the distances of some of these stars. A widely accepted theory is that as the universe gets older, there will be less stars to see as the expansion makes the distance even further.

Edited by Homer, 04 September 2003 - 12:19 AM.

[j6p]

Well, I would think that at increasing distances there are more and more stars, so their smaller apparent size is made up for by their greater numbers.
As for dust clouds blocking the stars, the dust should absorb the energy radiated by the stars and it should glow. As an example here is the eagle nebula, notice how the surrounding gas and dust glows from the expended radiation of the supernova.

Click Here

[Homer]

There may be more stars at further distances, but they're less luminous than at closer distances. So it isn't possible to light up the sky with stars that are not as luminous.
In regards to dark matter, it's important to understand that most of the matter in the universe is dark matter, meaning it doesn't give off any light.

[Saru]

Just to add to this, the question you've asked J6 is known as Olber's Paradox. It's not dust and gas that are wholly to blame, because there isn't enough to account for the absorption of the light from that many stars.

Here's a brief summary of Olber's Paradox from the Science Line website:

In the past, the absence of light in the night sky has been given as the argument against the idea of a limitless universe containing an infinite number of stars. If this were the case, and if the universe were infinitely old then the light from the limitless number of stars would have had time to reach us and flood the night sky with light.

As this is obviously not the case, Olbers theorised that light from these stars was absorbed by gas and dust occupying deep space. Unfortunately there simply is not enough gas and dust in space to make an appreciable difference to light as it travels from distant stars. So what is the answer?

Today Olber's paradox is explained away by the vastness of the universe. Light has a finite velocity and, put quite simply, the light from the furthest reaches of the universe has not had time to reach us yet. Imagine a universe only 7 minutes old, even the light from the Sun would not have reached us and we would have been wandering around in darkness!

Source :Science Line

[Kaj]

And the earths atmosphere take out some I think, and if there is more dark materia than "normal,light" it should absorbe lots of light or at atleast bend the light to different directions that is "not here"

Thoughts only, no facts.

[Unexplainable]

suppose that space isn't boundless?

[bathory]

a finite universe can still have no end..it depends on its shape

[jimma]

[Athlon64]

Olbers' Paradox is something that I have never understood. Why should the night sky be bright if the vast majority of the stars and galaxies are too far away for us to see ? Also, since the Universe is very likely finite, then there shouldn't even be a paradox !

It is also true that light absorbed by dust and gas between these distant objects and ourselves is generally re-radiated at infrared wavelengths. In other words, HEAT !

[Lionel]

Here is a link that could be a possible answer to this question CLICK HERE

[jimma]

[Unexplainable]

scientists once believed that the Sun orbited around Earth.