two simple questions

[jureal]

Hi all,

 

I have some questions about the present big bang theory and why the universe is dark. I'm not a creationist, because I don't believe in god or in any deity of whatever kind, so I just need a few seconds of your time and simple answer to my questions.

 

1. We know that light has a speed, we know that light emits in all directions so here is my question: why isn't universe bright then? If we can see a galaxy, than it isn't emitting light in every direction or is it?

 

2. Perhaps there was no big bang at all, but we are on the other side of black hole, which formed 13,7 billion years ago from the stars it devoured?

 

Maybe to you, my questions seem juvenile, but I have to get it off my chest.

 

Thanks,

 

J.

[swansont]

1 is known as Olbers' paradox. It's a problem if the observable universe was infinite and old, but this is not the case with the big bang. The observable universe is finite in size and age, and distant objects (as well as the background radiation) are red-shifted.

[ajb]

This is Oblers' paradox. Have a look at Wikipedia, it should help.

[losfomot]

Hi all,

 

I have some questions about the present big bang theory and why the universe is dark. I'm not a creationist, because I don't believe in god or in any deity of whatever kind, so I just need a few seconds of your time and simple answer to my questions.

 

1. We know that light has a speed, we know that light emits in all directions so here is my question: why isn't universe bright then? If we can see a galaxy, than it isn't emitting light in every direction or is it?

 

2. Perhaps there was no big bang at all, but we are on the other side of black hole, which formed 13,7 billion years ago from the stars it devoured?

 

Maybe to you, my questions seem juvenile, but I have to get it off my chest.

 

Thanks,

 

J.

 

1-

 

Perhaps the first two responders are right in assuming you meant the question in relation to Olber's paradox... I read it differently... so, just in case I am reading it correctly, I will give a different answer:

 

When a star or galaxy emits light, it is emitting countless packets of light energy call photons. These photons are emitted, essentially, in every direction... however you will only see the photons that actually hit your eye (the photons that are moving in your direction). The photons (light) that go in other directions are not visible to you (unless they hit something else and 'reflect' off of it, which is why we can see the moon... some of the photons from the sun that hit the moon will reflect in your direction and hit your eye, allowing you to see the moon... actually that is applicable to almost everything that you see on Earth during the day too.).

 

2-

 

Perhaps you are right. There are many ideas about the origin of the universe... who knows which one is truly correct? But, right now, the Big Bang Theory is the idea that seems to fit the best... and it may not mean what you think it does ( the term 'Big Bang' is a little misleading ).

[md65536]

2. Perhaps there was no big bang at all, but we are on the other side of black hole, which formed 13,7 billion years ago from the stars it devoured?

By "other side" do you mean "inside"?

 

Check this video:

Skip to a question at the end, around 57:33.

 

Special relativity allows observed time and distance to be different for different observers. General relativity says [citation needed] that weird stuff... that interesting stuff... happens inside black holes. One observer can see certain distances expanded to infinite lengths, while another on the other side of an event horizon can see it contracted to infinitesimal lengths (I'm not sure about the math on this).

 

As Krauss suggests, it is possible that from the inside, our universe looks like it does (expanding) AND from the outside it looks like a shrinking black hole. We could be on the inside of a black hole AND have had the big bang happen.

 

We often think of what might be "outside our universe" as some alien observers on some unimaginably large scale looking at our tiny universe within theirs. Personally, I think that if that were possible, then from our point of view, that outer universe wouldn't be a huge thing, it would look tiny to us. I think it's possible (topologically) to have 2 universes inside each other. Suppose that some given black hole is another universe, and you could cross the event horizon intact. I think that what you would see is the black hole universe expanding on one side of you and our universe shrinking on the other side. The event horizon, imagined as a spherical surface on one side of you, would expand until, when you are at the event horizon, it is infinitely large and looks like a plane cutting through you, dividing the black hole universe on one side and our universe on the other, and then once you are past it, it would shrink on the other side of you, encompassing our universe, making it appear to shrink into a black hole. I've described this idea using a sweater as an analogy... the sweater can be turned inside out and have one side "inside" the other, without breaking the sweater. Crossing from one universe to another like this involves turning the universe inside out... not physically, but observationally.

 

I don't know enough about general relativity and topology to tell you how realistic this idea is.

Edited October 15, 2010 by md65536