Why is the night sky night bright?

[Just Good]

I have a nagging question and hope someone is able to help.

If the boundary of the visible universe expands on a daily basis (that is the light of "new" stars will have been able to catch up with us) does that mean the night sky is brighter each night? Hope this make sense?

Also, As has been explained here problably on many times, when we see the the stars we see what they were like millions of years ago. What I dont understand is that when we look back 13 bill or so years to the start of the universe, where we not there ourselves and why are we seeing the light from such a long time ago when we would have been in the "middle" of it? Finally, how can the Inflation theory be explained as we cannot move faster than the speed of light....

Guys, I am so sorry for the many questions. The above are the ones that I suddenly think I have understood and then suddenly cannot comprehend. Hope someone can explain in simple terms.

[blueshift]

I have a nagging question and hope someone is able to help.

If the boundary of the visible universe expands on a daily basis (that is the light of "new" stars will have been able to catch up with us) does that mean the night sky is brighter each night? Hope this make sense?

There is no "boundary" that is expanding. The space right next to you and inside of you is expanding along with the space everywhere. And the sky is not getting brighter....yet. All the light in the universe has not had enough time to reach us.

Also, As has been explained here problably on many times, when we see the the stars we see what they were like millions of years ago. What I dont understand is that when we look back 13 bill or so years to the start of the universe, where we not there ourselves and why are we seeing the light from such a long time ago when we would have been in the "middle" of it?

We were in the middle of it. Every place was the middle. The light from your next door neighbor to you has not traveled for as long of a time as the light from 13 billion light years away.

Finally, how can the Inflation theory be explained as we cannot move faster than the speed of light....

Things cannot pass each other faster than speed c and information cannot travel faster than speed c. Spatial expansion does permit objects to be stretched away from one another at speeds higher than c and many distant galaxies we see today will disappear from our vision in the future.

Guys, I am so sorry for the many questions. The above are the ones that I suddenly think I have understood and then suddenly cannot comprehend. Hope someone can explain in simple terms.

There is a problem with the word "simple". What is "simple" changes as one's knowledge grows. When the family car broke down during my childhood the "simple" thing to do was to call someone who knew how to fix it. Once I learned how to fix the car the simple thing to think about was experimenting with spark, compression and gas.

[Ken G]

If the boundary of the visible universe expands on a daily basis (that is the light of "new" stars will have been able to catch up with us) does that mean the night sky is brighter each night?
Also, As has been explained here problably on many times, when we see the the stars we see what they were like millions of years ago. What I dont understand is that when we look back 13 bill or so years to the start of the universe, where we not there ourselves and why are we seeing the light from such a long time ago when we would have been in the "middle" of it?

These questions are connected-- when you understand the answer to one, you'll understand the answer to the other. I think a good way to start addressing them is to replace our universe with a much simpler one, where nevertheless those same two questions would appear.

Imagine a universe that does not expand, nor change at all in any way, except that it came into being (say as an infinite homogenous bunch of galaxies) everywhere at once 13.7 billion years ago. That's basically our universe, minus the expansion and the evolution with time, yet both of your questions apply, though the answers come out a bit different. In such a universe, our region of galaxies would have been sending light out for 13.7 billion years, and might be seen by aliens some 13.7 billion light years away. We in turn would be seeing the light they sent out-- neither is seeing their own light, but in a homogeneous universe, it makes no real difference, we see our own past by seeing someone else's. Also, the universe would indeed seem brighter each day, as you are seeing all the same galaxies at the same distances as yesterday, but you are also seeing more distant galaxies (not that one day out of 13.7 billion years would amount to a hill of beans, but I think your question was hypothetical).

Now place those answers into the context of a universe that is expanding and evolving, and is pervaded by a "relic radiation" from a time when light could not propagate freely through space but instead was constantly being absorbed and emitted by ionized hydrogen. Those are really the only three differences from the above case-- we have a "CMB" to look at, but it is not getting brighter every day because it is not still being emitted, it was only emitted over a fairly short era when the universe was a bit less than 400,000 years old, and every day we see the CMB from a little farther away and a little more redshifted, but not from anywhere closer, so it gets dimmer and redder every day. We cannot see the CMB from any greater distance, because at earlier times light did not propagate freely, as though as "shroud" descends if we try to look farther, again making it so that we do not see more CMB light each day, we see the CMB light emitted from regions that were farther away when the "shroud lifted" (and are even farther now) and we stop seeing what was emitted from closer. Farther away means less bright and more redshifted (which is the same thing, when talking about the CMB).

Also, there were no galaxies to see back then, so we don't see more galaxies every day, we've already seen almost the full history that galaxies have to show us. And due to the expansion, the ones we do see get farther every day, so they are each dimmer as well (and are also increasing in redshift at the largest scales, because of the acceleration of the expansion due to "dark energy", but that's a detail you needn't address in your questions). So you can see that the combination of expansion and evolution of the prevailing conditions changes the answer to your questions in important ways, but it still helps to understand what the answers would be without the expansion or evolution.