Looking Into Deep Space & Back In Time. How does it work?
Discussion
Super Slo Mo said:
50 to the power of 9 
Is that the diameter? If so, that'd mean that the outer reaches of the universe are 25^9 light years from the centre, presumably where it all started.
That would also suggest that it's expanding at a rate faster than the speed of light, or have I grossly oversimplified?
I think the best way I can answer that is like this-Is that the diameter? If so, that'd mean that the outer reaches of the universe are 25^9 light years from the centre, presumably where it all started.
That would also suggest that it's expanding at a rate faster than the speed of light, or have I grossly oversimplified?
Forget about a centre of the universe for a moment, and focus on two individual atoms that are located next to each other at some location in the universe.
Together these atoms are moving away from the Big Bang/centre/Earth at V, but the atoms themselves are also separating relative to each other at V by expansion.
It's hard to put this into words.
Yes Eric.
I understand the idea that it is as if we're on the surface of an expanding balloon which is inflating so that everything is moving away from everything els.
But, if the universe is, say, 20 billion years old and astronomers have detected light from galaxies so far away that it's taken 19 billion years to reach us, then shirley, the bloody thing was only one billion light years away when the light was emitted?
God, I wish I was clever.
I understand the idea that it is as if we're on the surface of an expanding balloon which is inflating so that everything is moving away from everything els.
But, if the universe is, say, 20 billion years old and astronomers have detected light from galaxies so far away that it's taken 19 billion years to reach us, then shirley, the bloody thing was only one billion light years away when the light was emitted?
God, I wish I was clever.
stew-S160 said:
I think the best way I can answer that is like this-
Forget about a centre of the universe for a moment, and focus on two individual atoms that are located next to each other at some location in the universe.
Together these atoms are moving away from the Big Bang/centre/Earth at V, but the atoms themselves are also separating relative to each other at V by expansion.
It's hard to put this into words.
Using that logic, they're expanding away from each other at 2V. Forget about a centre of the universe for a moment, and focus on two individual atoms that are located next to each other at some location in the universe.
Together these atoms are moving away from the Big Bang/centre/Earth at V, but the atoms themselves are also separating relative to each other at V by expansion.
It's hard to put this into words.
Ah, perhaps not, that only applies if they go in opposite directions. If they go in the same direction, but apart, they still are leaving the centre at V, although are of course travelling away from each other too. However, that doesn't explain how the overall 'diameter' of the universe is bigger than it should be unless some things are travelling faster than the speed of light.
Blib said:
Yes Eric.
I understand the idea that it is as if we're on the surface of an expanding balloon which is inflating so that everything is moving away from everything els.
But, if the universe is, say, 20 billion years old and astronomers have detected light from galaxies so far away that it's taken 19 billion years to reach us, then shirley, the bloody thing was only one billion light years away when the light was emitted?
God, I wish I was clever.
Universe age- 13.7 billion years.I understand the idea that it is as if we're on the surface of an expanding balloon which is inflating so that everything is moving away from everything els.
But, if the universe is, say, 20 billion years old and astronomers have detected light from galaxies so far away that it's taken 19 billion years to reach us, then shirley, the bloody thing was only one billion light years away when the light was emitted?
God, I wish I was clever.
Universe observable size- around 50 billion(+/- 3billion) light years diameter.
Actual size of universe beyond observable is about 93billion light years(Good ol expansion)
So what we see now is not the edge as it is now, but as it was then.
This might help some- http://www.science20.com/alpha_meme/einstein_expan...
Ray Luxury-Yacht said:
I watched a recent programme on Discovery channel about the beginning of time and the big bang.
The most mental thing I could not (and still can't) get my head around, is that most scientists say that, before the 'big bang', there was 'nothing'!
Now to me, to have 'nothing' means that you must have 'something' for that 'nothing to be contained within, right?
But no - they say that we have to clear our minds from the accepted sense of 'nothing', and think about 'true nothing' - i.e., absoloutely nothing at all existing, anywhere, ever before...
I still cant imagine that! :/
I love the way we humans as a species - with our puny little ape brains evolved for solving essentially terrestrial problems involving pointy things, fire and meat - think we are entitled to an understanding of these concepts. It's <BrianCox>Amazing</BrianCox> that we understand as much as we do.The most mental thing I could not (and still can't) get my head around, is that most scientists say that, before the 'big bang', there was 'nothing'!
Now to me, to have 'nothing' means that you must have 'something' for that 'nothing to be contained within, right?
But no - they say that we have to clear our minds from the accepted sense of 'nothing', and think about 'true nothing' - i.e., absoloutely nothing at all existing, anywhere, ever before...
I still cant imagine that! :/
Eric Mc said:
How can you have a distance sepration that is greater than the age of the universe.
You're asking, how can the universe be the size it is (observable 50ish billion) when it's only 13.7 billion years old? It should therefore be around 27.4 billion light years across.Yes?
Expansion/inflation.
This thread is, I think, the same question asked a few months ago.
http://pistonheads.com/xforums/topic.asp?h=0&f...
http://pistonheads.com/xforums/topic.asp?h=0&f...
APanda said:
This thread is, I think, the same question asked a few months ago.
http://pistonheads.com/xforums/topic.asp?h=0&f...
Yeah. But, now that thread is much further away.http://pistonheads.com/xforums/topic.asp?h=0&f...
stew-S160 said:
Eric Mc said:
How can you have a distance sepration that is greater than the age of the universe.
You're asking, how can the universe be the size it is (observable 50ish billion) when it's only 13.7 billion years old? It should therefore be around 27.4 billion light years across.Yes?
Expansion/inflation.
Its size cannot exceed its age - surely?
stew-S160 said:
You're asking, how can the universe be the size it is (observable 50ish billion) when it's only 13.7 billion years old? It should therefore be around 27.4 billion light years across.
Yes?
Expansion/inflation.
I tend to work on the basis that if I can't explain something simply, I haven't understood itYes?
Expansion/inflation.
.From having a quick Google, and sifting through the myriad of crap analogies out there (rasins in dough, FFS!), it seems that in fact it's quite possible for the universe to be expanding faster than the speed of light, contradictory though this may seem.
That doesn't mean that any of the objects in it are travelling faster than the speed of light, but that space itself, which is, of course, nothing, is growing faster than light speed, and taking those objects with it. None of that really makes sense, but it's about the only close to reasonable explanation I could find.
It would kind of suggest that very few people, if anyone, really understands what's going on, but if space is 50^9 light years across, or even bigger as has been suggested, then the only reasonable explanation is that it's expanding at a rate faster than the speed of light.
Eric Mc said:
Correct.
Its size cannot exceed its age - surely?
The answer is inflation. Its size cannot exceed its age - surely?
It is not expanding at a constant velocity. It is speeding up.
As I said in a previous post, all points of the universe are expanding and accelerating away from each other, not just from a central point.
Blib said:
Why would the light from the furthest constellations take billions of years to reach us when all of those billions of years ago, we were sort of next to each other rather than far apart? Surely, we should have 'seen' this light ages ago, when we were close to the distant galaxies.
Others have explained this so I won't repeat what they've said. Once you understand it though, you can draw an even more amazing conclusion about why the night sky is dark.But everywhere you look, the furthest point you can see is 13.7 billion light years away.
And just saying "inflation" does not explain how something can measure across a distance of 50 billion light years when the universe has not existed long enough for anything to move apart by a distance greater than 13.7 billion light years. To move to a further distance implies faster than light movement - which is not possible for material objects.
And just saying "inflation" does not explain how something can measure across a distance of 50 billion light years when the universe has not existed long enough for anything to move apart by a distance greater than 13.7 billion light years. To move to a further distance implies faster than light movement - which is not possible for material objects.
Eric Mc said:
But everywhere you look, the furthest point you can see is 13.7 billion light years away.
And just saying "inflation" does not explain how something can measure across a distance of 50 billion light years when the universe has not existed long enough for anything to move apart by a distance greater than 13.7 billion light years. To move to a further distance implies faster than light movement - which is not possible for material objects.
Maybe you missed the bit that all points of the Universe(I should throw in Spacetime here) are accelerating away from each other, not just from a single common point of origin.And just saying "inflation" does not explain how something can measure across a distance of 50 billion light years when the universe has not existed long enough for anything to move apart by a distance greater than 13.7 billion light years. To move to a further distance implies faster than light movement - which is not possible for material objects.
If the Universe and Spacetime were expanding away at a constant V from a central point in a uniform motion, then sure, 27 lights years across would be about the size of it.
I'll try to explain this in plain language.
First, the present BBT is not settled science it is just the best working model we have at present, but it is not perfect by a long way.
Second, this is by necessity a precis'd version of the BBT and a Cosmologist will wince at the shorthand used but hopefully won't be too offended.
But it goes like this:
First forget the singularity, it's of no consequence to us, but the period we are looking at to solve this dichotomy is the 3 or 4 day after the BB, this is known as the inflationary period. During this time things were not as they are now, we, in the last 13.7 billion years have lived in a stable cosmos as far as the various constants are concerned, the 'Physic' has been stable.
But for those 3 or 4 days it was not, there was light but it was not visible nor did it illuminate anything, it was trapped, the various forces that hold us and all things together or cause their decay were either combined with other forces as a single entity or were trapped.
These 3 or 4 days all the rules of physics were in flux, jostling for existence or not, whilst this went on inflation occurred, the best guess (but by no means the only one) is that during that time of upheaval the Cosmos expanded to about 36 to 38 billion light years across, the Physics of existence itself was not settled and there was no speed limit on anything.
It settled down after those 3 or 4 days and over the next 400,000 years things became stable, effectively setting the constants and limits we observe today.
In the 13.7 billion years since the settled period began the Cosmos has grown along with the speed limit.
Add 36/38 to 13.7 and you get about 50 billion light years across.
Hope that helps.
Going deeper is fine if you wish, ask away, but in very short order it becomes immensely complex and fiendishly difficult to grasp.
But I think the above answers your question.
Cheers
Gene.
First, the present BBT is not settled science it is just the best working model we have at present, but it is not perfect by a long way.
Second, this is by necessity a precis'd version of the BBT and a Cosmologist will wince at the shorthand used but hopefully won't be too offended.
But it goes like this:
First forget the singularity, it's of no consequence to us, but the period we are looking at to solve this dichotomy is the 3 or 4 day after the BB, this is known as the inflationary period. During this time things were not as they are now, we, in the last 13.7 billion years have lived in a stable cosmos as far as the various constants are concerned, the 'Physic' has been stable.
But for those 3 or 4 days it was not, there was light but it was not visible nor did it illuminate anything, it was trapped, the various forces that hold us and all things together or cause their decay were either combined with other forces as a single entity or were trapped.
These 3 or 4 days all the rules of physics were in flux, jostling for existence or not, whilst this went on inflation occurred, the best guess (but by no means the only one) is that during that time of upheaval the Cosmos expanded to about 36 to 38 billion light years across, the Physics of existence itself was not settled and there was no speed limit on anything.
It settled down after those 3 or 4 days and over the next 400,000 years things became stable, effectively setting the constants and limits we observe today.
In the 13.7 billion years since the settled period began the Cosmos has grown along with the speed limit.
Add 36/38 to 13.7 and you get about 50 billion light years across.
Hope that helps.
Going deeper is fine if you wish, ask away, but in very short order it becomes immensely complex and fiendishly difficult to grasp.
But I think the above answers your question.
Cheers
Gene.
Eric Mc said:
But everywhere you look, the furthest point you can see is 13.7 billion light years away.
And just saying "inflation" does not explain how something can measure across a distance of 50 billion light years when the universe has not existed long enough for anything to move apart by a distance greater than 13.7 billion light years. To move to a further distance implies faster than light movement - which is not possible for material objects.
2 things here. Firstly, there was no visible light at the big bang, that comes later as it is generated by fusion reactions in stars so the first generations stars need time to form, so any expansion prior to that won't be "recorded" by light. Secondly, thinking of "expansion" or "inflation" in terms of "stuff moving apart against a static background" is flawed. You need to think of the background and the stuff expanding/inflating (the dots on a balloon analogy).And just saying "inflation" does not explain how something can measure across a distance of 50 billion light years when the universe has not existed long enough for anything to move apart by a distance greater than 13.7 billion light years. To move to a further distance implies faster than light movement - which is not possible for material objects.
That said, the "inflationary period" is a theory that fits the observed evidence but it still feels like a fudge to me. Of course, a lot of advanced physics is counter-intuitive and yet demonstrably accurate so a theory "feeling like a fudge" isn't a valid reason to reject it.
Edited by ewenm on Wednesday 13th June 11:33
I have to point out in all fairness I have used your 50 billion years... I could use 93 billion years which if you do the maths a different way is just as likely, but we actually don't know for certain of any additional number in actuality... it could be infinite.
It depends if the BBT theory is correct at all in this respect.
It could also have another explanation.
It's rather academic.
But just ponder this, not long ago in human history the Cosmos was not even thought to be 1 light year across (it's a huge distance in miles and would have seemed an impossibly large amount) today we can say with certainty that it is at least 13.7 billion years across beyond that we are playing a bit of game of numbers.
It depends if the BBT theory is correct at all in this respect.
It could also have another explanation.
It's rather academic.
But just ponder this, not long ago in human history the Cosmos was not even thought to be 1 light year across (it's a huge distance in miles and would have seemed an impossibly large amount) today we can say with certainty that it is at least 13.7 billion years across beyond that we are playing a bit of game of numbers.
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