In the beginning God
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14-03-2014, 02:09 PM
RE: In the beginning God
(14-03-2014 02:00 PM)TubbyTubby Wrote:  
(14-03-2014 01:39 PM)itsnotmeitsyou Wrote:  This requires a bit of clarification. When most people talk about "the universe", they're actually talking about the "observable universe". This is the furthest distance from earth that we can see (approx 13.8 billion light years). We can only see this far because light from further out hasn't had time to reach us.

I thought 13.8 bly was the extent of the observable limit, before that it was sort of 'opaque'? not because that light hasn't had time to reach us. You can't really state that light hasn't had time to reach us, not logical really unless you want to alter the speed of light.

That's not so much an observable space distance as it is an observable time distance - but of course actually it's neither, and really both.

Anyway.

'Age' or 'distance' in such a measure are equivalent; they refer to - roughly - the amount a photon has travelled before we 'see' (detect, observe, infer, whatever) it.

The most 'distant' things we 'see' are those which occurred earliest. From this we can work out how the universe evolved. Now, the reason why we think the universe is slightly older than we can observe is that under our current models for its very early stages, the general mish-mash was of such high energy that free photons did not exist and could not propagate. The oldest photons we see today are those which were emitted and then not disturbed until now. These constitute the cosmic background radiation.

Distant objects - as in, discrete objects like stars - formed yet slightly later.

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14-03-2014, 02:15 PM
RE: In the beginning God
(14-03-2014 02:00 PM)TubbyTubby Wrote:  
(14-03-2014 01:39 PM)itsnotmeitsyou Wrote:  This requires a bit of clarification. When most people talk about "the universe", they're actually talking about the "observable universe". This is the furthest distance from earth that we can see (approx 13.8 billion light years). We can only see this far because light from further out hasn't had time to reach us.

I thought 13.8 bly was the extent of the observable limit, before that it was sort of 'opaque'? not because that light hasn't had time to reach us. You can't really state that light hasn't had time to reach us, not logical really unless you want to alter the speed of light.

Yes and no.

The universe began expanding 13.8 billion years ago. So the furthest ANY light could have travelled is 13.8 bly. We can't actually see ALL the way back to the first moment because prior to 300,000 years after the big bang, the universe was an opaque plasma. So when we look to the edges of the observable universe, what we see is the first light that was able to travel freely.

Currently there are stars, galaxies, light, etc that are further from us than 13.8 bly away. We can't see them yet because the light hasn't reached us yet. Right now, the cosmic background radiation that we call the "limit" to the observable universe is NOT 13.8 bly away, It's actually further away than that, but we can't see farther than that because light has not had enough time to get to us. Remember, when you're viewing anything, you're not seeing it as it is NOW, but as it was when the light was emitted. For instance, when you're looking at a star that is 10000 ly away, you're actually seeing the star as it was 10000 years ago. It could have already exploded and no longer exist.

The universe is expanding in all directions simultaneously. There is no "center" of the universe because ever point in the universe used to be the exact same point and space has expanded around it. No matter where you were standing in the universe, the observable universe would only be 13.8 bly across. Krauss explains it a hell of a lot better than I can on a forum and he has cool diagrams and stuff. Basically, though, because every point in the universe started as the same point, every point in the universe is the center of the observable universe. Yes, you actually ARE the center of the universe. (from your own personal perspective, of course)

Excuse me, I'm making perfect sense. You're just not keeping up.

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14-03-2014, 02:16 PM
Re: RE: In the beginning God
(14-03-2014 02:09 PM)cjlr Wrote:  The most 'distant' things we 'see' are those which occurred earliest. From this we can work out how the universe evolved. Now, the reason why we think the universe is slightly older than we can observe is that under our current models for its very early stages, the general mish-mash was of such high energy that free photons did not exist and could not propagate. The oldest photons we see today are those which were emitted and then not disturbed until now. These constitute the cosmic background radiation.

Distant objects - as in, discrete objects like stars - formed yet slightly later.

I'm well aware of all that. It was the 'We can only see this far because light from further out hasn't had time to reach us' bit that puzzles me.

I don't think that's a correct statement to make thats all.

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14-03-2014, 02:18 PM
Re: RE: In the beginning God
(14-03-2014 02:15 PM)itsnotmeitsyou Wrote:  
(14-03-2014 02:00 PM)TubbyTubby Wrote:  I thought 13.8 bly was the extent of the observable limit, before that it was sort of 'opaque'? not because that light hasn't had time to reach us. You can't really state that light hasn't had time to reach us, not logical really unless you want to alter the speed of light.

Yes and no.

The universe began expanding 13.8 billion years ago. So the furthest ANY light could have travelled is 13.8 bly. We can't actually see ALL the way back to the first moment because prior to 300,000 years after the big bang, the universe was an opaque plasma. So when we look to the edges of the observable universe, what we see is the first light that was able to travel freely.

Currently there are stars, galaxies, light, etc that are further from us than 13.8 bly away. We can't see them yet because the light hasn't reached us yet. Right now, the cosmic background radiation that we call the "limit" to the observable universe is NOT 13.8 bly away, It's actually further away than that, but we can't see farther than that because light has not had enough time to get to us. Remember, when you're viewing anything, you're not seeing it as it is NOW, but as it was when the light was emitted. For instance, when you're looking at a star that is 10000 ly away, you're actually seeing the star as it was 10000 years ago. It could have already exploded and no longer exist.

The universe is expanding in all directions simultaneously. There is no "center" of the universe because ever point in the universe used to be the exact same point and space has expanded around it. No matter where you were standing in the universe, the observable universe would only be 13.8 bly across. Krauss explains it a hell of a lot better than I can on a forum and he has cool diagrams and stuff. Basically, though, because every point in the universe started as the same point, every point in the universe is the center of the observable universe. Yes, you actually ARE the center of the universe. (from your own personal perspective, of course)

I'm not fucking stupid and I don't disagree with what you're saying, just your initial comment was wrong in my opinion.

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14-03-2014, 02:21 PM
In the beginning God
Why God? Because human beings have a tendency to anthropomorphize everything.

It's not just indoctrination: We tend to view everything from our own point of view. There's a mental mechanism and arrogance blocking the uneducated person from realizing "Well, it must have been a person who did it, but a person that's always existed, everywhere and is all-powerful" is a wildly ridiculous notion.

Talk to your average theist, and they think it's simple, common sense.

“It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.”
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14-03-2014, 02:22 PM
RE: In the beginning God
(14-03-2014 02:15 PM)itsnotmeitsyou Wrote:  
(14-03-2014 02:00 PM)TubbyTubby Wrote:  I thought 13.8 bly was the extent of the observable limit, before that it was sort of 'opaque'? not because that light hasn't had time to reach us. You can't really state that light hasn't had time to reach us, not logical really unless you want to alter the speed of light.

Yes and no.

The universe began expanding 13.8 billion years ago. So the furthest ANY light could have travelled is 13.8 bly. We can't actually see ALL the way back to the first moment because prior to 300,000 years after the big bang, the universe was an opaque plasma. So when we look to the edges of the observable universe, what we see is the first light that was able to travel freely.

Currently there are stars, galaxies, light, etc that are further from us than 13.8 bly away. We can't see them yet because the light hasn't reached us yet. Right now, the cosmic background radiation that we call the "limit" to the observable universe is NOT 13.8 bly away, It's actually further away than that, but we can't see farther than that because light has not had enough time to get to us. Remember, when you're viewing anything, you're not seeing it as it is NOW, but as it was when the light was emitted. For instance, when you're looking at a star that is 10000 ly away, you're actually seeing the star as it was 10000 years ago. It could have already exploded and no longer exist.

The universe is expanding in all directions simultaneously. There is no "center" of the universe because ever point in the universe used to be the exact same point and space has expanded around it. No matter where you were standing in the universe, the observable universe would only be 13.8 bly across. Krauss explains it a hell of a lot better than I can on a forum and he has cool diagrams and stuff. Basically, though, because every point in the universe started as the same point, every point in the universe is the center of the observable universe. Yes, you actually ARE the center of the universe. (from your own personal perspective, of course)
If someone could get far enough away and have a super amazing telescope, could they see their own past?

Swing with me a while, we can listen to the birds call, we can keep each other warm.
Swing with me forever, we can count up every flower, we can weather every storm.
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14-03-2014, 02:22 PM
RE: In the beginning God
And how can there be 'stars, galaxies..' beyond the opaqueness that was the dark hydrogen+helium cloud (that we observe as background radiation)?

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14-03-2014, 02:23 PM
RE: In the beginning God
(14-03-2014 02:18 PM)TubbyTubby Wrote:  
(14-03-2014 02:15 PM)itsnotmeitsyou Wrote:  Yes and no.

The universe began expanding 13.8 billion years ago. So the furthest ANY light could have travelled is 13.8 bly. We can't actually see ALL the way back to the first moment because prior to 300,000 years after the big bang, the universe was an opaque plasma. So when we look to the edges of the observable universe, what we see is the first light that was able to travel freely.

Currently there are stars, galaxies, light, etc that are further from us than 13.8 bly away. We can't see them yet because the light hasn't reached us yet. Right now, the cosmic background radiation that we call the "limit" to the observable universe is NOT 13.8 bly away, It's actually further away than that, but we can't see farther than that because light has not had enough time to get to us. Remember, when you're viewing anything, you're not seeing it as it is NOW, but as it was when the light was emitted. For instance, when you're looking at a star that is 10000 ly away, you're actually seeing the star as it was 10000 years ago. It could have already exploded and no longer exist.

The universe is expanding in all directions simultaneously. There is no "center" of the universe because ever point in the universe used to be the exact same point and space has expanded around it. No matter where you were standing in the universe, the observable universe would only be 13.8 bly across. Krauss explains it a hell of a lot better than I can on a forum and he has cool diagrams and stuff. Basically, though, because every point in the universe started as the same point, every point in the universe is the center of the observable universe. Yes, you actually ARE the center of the universe. (from your own personal perspective, of course)

I'm not fucking stupid and I don't disagree with what you're saying, just your initial comment was wrong in my opinion.

I didn't say you were stupid nor did I imply it.

My statement was correct. There is no need to alter the speed of light due to the expansion of the universe. As things are travelling through space, space itself is expanding around them. There will eventually come a point when space will be expanding so fast that relative to earth, the furthest objects will be receding from us at faster than the speed of light. The objects themselves will not be travelling through space at faster than the speed of light, but the amount of expansion between us and them will make space itself push things out faster than light can travel.

Excuse me, I'm making perfect sense. You're just not keeping up.

"Let me give you some advice, bastard: never forget what you are. The rest of the world will not. Wear it like armor, and it can never be used to hurt you." - Tyrion Lannister
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14-03-2014, 02:23 PM
RE: In the beginning God
(14-03-2014 02:18 PM)TubbyTubby Wrote:  
(14-03-2014 02:15 PM)itsnotmeitsyou Wrote:  Yes and no.

The universe began expanding 13.8 billion years ago. So the furthest ANY light could have travelled is 13.8 bly. We can't actually see ALL the way back to the first moment because prior to 300,000 years after the big bang, the universe was an opaque plasma. So when we look to the edges of the observable universe, what we see is the first light that was able to travel freely.

Currently there are stars, galaxies, light, etc that are further from us than 13.8 bly away. We can't see them yet because the light hasn't reached us yet. Right now, the cosmic background radiation that we call the "limit" to the observable universe is NOT 13.8 bly away, It's actually further away than that, but we can't see farther than that because light has not had enough time to get to us. Remember, when you're viewing anything, you're not seeing it as it is NOW, but as it was when the light was emitted. For instance, when you're looking at a star that is 10000 ly away, you're actually seeing the star as it was 10000 years ago. It could have already exploded and no longer exist.

The universe is expanding in all directions simultaneously. There is no "center" of the universe because ever point in the universe used to be the exact same point and space has expanded around it. No matter where you were standing in the universe, the observable universe would only be 13.8 bly across. Krauss explains it a hell of a lot better than I can on a forum and he has cool diagrams and stuff. Basically, though, because every point in the universe started as the same point, every point in the universe is the center of the observable universe. Yes, you actually ARE the center of the universe. (from your own personal perspective, of course)

I'm not fucking stupid and I don't disagree with what you're saying, just your initial comment was wrong in my opinion.

Chill out dude. No one called you stupid.

Swing with me a while, we can listen to the birds call, we can keep each other warm.
Swing with me forever, we can count up every flower, we can weather every storm.
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14-03-2014, 02:25 PM
RE: In the beginning God
(14-03-2014 02:22 PM)TubbyTubby Wrote:  And how can there be 'stars, galaxies..' beyond the opaqueness that was the dark hydrogen+helium cloud (that we observe as background radiation)?

Due to the expansion of space and the time that it takes for light to travel to us.

Ok, so you've got an object that appears to be 13 bly away. Just at the edge of the observable universe. The light you are seeing right now left that object 13 b years ago. During the 13 b year travel time that it took for that photon to leave the object and reach your eye, the object has continued to move away from us. Same thing with the edge of the observable universe.

Excuse me, I'm making perfect sense. You're just not keeping up.

"Let me give you some advice, bastard: never forget what you are. The rest of the world will not. Wear it like armor, and it can never be used to hurt you." - Tyrion Lannister
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