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# Size of the universe

Author Topic:   Size of the universe
Percy
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 Message 3 of 248 (545088) 01-31-2010 8:52 PM Reply to: Message 1 by Calypso01-29-2010 10:24 PM

This Wikipedia article describes what you want to know: Observable Universe:
Wikipedia writes:
The age of the Universe is about 13.7 billion years, but due to the expansion of space we are now observing objects that are now considerably farther away than a static 13.7 billion light-years distance. The edge of the observable universe is now located about 46.5 billion light-years away [1].
The 93 billion light year figure you cited is the diameter, twice the 46.5 billion light year radius cited by Wikipedia. There's more detail in a later subsection: Size of the observable universe
--Percy

 This message is a reply to: Message 1 by Calypso, posted 01-29-2010 10:24 PM Calypso has not replied

 Replies to this message: Message 4 by Archangel, posted 09-25-2010 9:20 AM Percy has seen this message but not replied Message 236 by kofh2u, posted 12-01-2012 9:20 AM Percy has replied

Percy
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From: New Hampshire
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 Message 73 of 248 (598545) 01-01-2011 8:56 AM Reply to: Message 67 by Philip Johnson12-30-2010 10:09 AM

Re: Young or old universe
Hi Philip,
Since the diameter of the observable universe grew from effectively 0 light years about 13.7 billion years to about 93 billion light years today, there must have been a time when its size was the same as whatever size Biblical literalists want to claim for it. And you want to characterize this mathematical necessity as a point of agreement between science and Biblical literalism?
There *are* some actual points of agreement between astronomy and Biblical literalists. For example, the Bible says the Earth has a sun and a moon, and astronomers agree. The Bible notes that there are stars, and astronomers agree.
--Percy

 This message is a reply to: Message 67 by Philip Johnson, posted 12-30-2010 10:09 AM Philip Johnson has replied

 Replies to this message: Message 74 by Dogmafood, posted 01-01-2011 11:00 AM Percy has seen this message but not replied Message 75 by Philip Johnson, posted 01-01-2011 6:26 PM Percy has replied Message 237 by kofh2u, posted 12-01-2012 9:26 AM Percy has replied

Percy
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From: New Hampshire
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 Message 77 of 248 (598774) 01-02-2011 7:35 AM Reply to: Message 75 by Philip Johnson01-01-2011 6:26 PM

Re: Young or old universe
Philip Johnson writes:
Is the radius of the universe increasing by at most 1 light year every year since nothing can go faster than the speed of light?
Your mention of radius implies that the universe has a finite size, but we don't know that. It might be finite, it might be infinite, we don't have conclusive evidence either way at this time.
Iblis already provided the correct answer that space/time, being neither matter or energy, is not constrained by the speed of light (c).
If you're wondering what evidence tells us that matter and energy cannot exceed c while the expansion of space can, we can get into that if you like.
--Percy

 This message is a reply to: Message 75 by Philip Johnson, posted 01-01-2011 6:26 PM Philip Johnson has not replied

 Replies to this message: Message 78 by jar, posted 01-02-2011 12:55 PM Percy has seen this message but not replied Message 79 by Dogmafood, posted 01-04-2011 8:55 PM Percy has replied

Percy
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From: New Hampshire
Joined: 12-23-2000
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 (1)
 Message 81 of 248 (599136) 01-05-2011 8:00 AM Reply to: Message 79 by Dogmafood01-04-2011 8:55 PM

Re: Young or old universe
Dogmafood writes:
I don't mean this to be a flippant question. How can something that is neither matter nor energy have any effect on matter or energy?
Cavediver will probably provide a better answer, but you're asking about the nature of space/time. Matter and energy exist within space/time, which means every photon and particle has a 4-dimensional position within space/time (3 spacial dimensions and 1 time dimension) and a 4-dimensional velocity vector. Both the position and the velocity vector will have values that are relative to the observer (that's why they call it relativity).
It turns out that space/time is not fixed, that space is expanding over time at a rate known as the Hubble constant, which is approximately 74 km/sec/Mpc (Mpc is a mega-parsec, a million parsecs, or about 3.2 million light years). Space itself (along with the matter and energy contained within it) that is a mega-parsec away is receding away from us at a rate of 74 km/sec. Space that is 2 mega-parsecs away is receding away from us at twice that rate, 148 km/sec. This recession velocity is due to the creation of new space in the intervening space.
Objects bound together with sufficient force (usually by gravity) are not affected by the expansion and remain together, but objects at great distances from one another exert very little gravity on each other, and the expansion of space is sufficient to carry the objects away from one another. Light is also affected by the expansion of space - it becomes drawn out and lengthened into longer (redder) wave lengths, we observe it as the red shift.
--Percy

 This message is a reply to: Message 79 by Dogmafood, posted 01-04-2011 8:55 PM Dogmafood has replied

 Replies to this message: Message 82 by Dogmafood, posted 01-05-2011 8:43 PM Percy has replied Message 238 by kofh2u, posted 12-01-2012 9:36 AM Percy has replied

Percy
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Posts: 22723
From: New Hampshire
Joined: 12-23-2000
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 Message 83 of 248 (599274) 01-06-2011 9:38 AM Reply to: Message 82 by Dogmafood01-05-2011 8:43 PM

Re: Young or old universe
Dogmafood writes:
It turns out that space/time is not fixed,...
Whoa up there just for a moment. Space/time is neither matter nor energy, as per your words and my own understanding of it. It is not a thing until it is defined by other things that really are things like moons and molecules. I have always considered space to be a sort of ‘not a thing’. Fixed or moving or expanding are qualities that belong to things that are subject to relativity. Are they not?
The normal everyday reality in which we live our lives provides relatively infertile ground for drawing analogies to aid our understanding of other less everyday aspects of reality. I think most people would grant that this is true of both space/time and quantum mechanics.
Common analogies for explaining expanding space/time is the surface of an inflating balloon and a rising bread dough, and you've probably already heard these analogies. If it helps you to think of space/time as analogous to things like balloons or bread dough then good, but I think most would agree with you that space/time is not really a thing. I believe Cavediver, and probably most physicists, prefer a more mathematical view. In other words, they use mathematics instead of language to describe space/time and how it behaves. They can't precisely describe space/time in words, but they can use mathematics to describe precisely how it will behave and what will happen.
Why does the red shift that we observe require the expansion of space? Is it because a galaxy that is 13.7 billion light yrs away appears to be receding at a rate greater than c?
If I could rephrase your question, you're asking what evidence we have that tells us that a distant galaxy receding from us at a great rate is actually receding because of the expansion of space and not simply because it is receding from us at a great rate. In other words, how do we know when a velocity is due to the expansion of space versus when it's simply the object's velocity?
Cavediver can probably provide a better answer, but I'll try anyway. When we peer out into space we observe that the more distant a galaxy the greater its recession velocity. One might conclude from this that we're at the center of the universe and that everything is receding from the center, but if you take the recession velocities we measure from the Milky Way and plug them in for some distant galaxy you find that all galaxies are receding from that galaxy, and again with greater velocity with increasing distance. In other words, no matter where you stand in the universe you'll see all galaxies receding at increasing velocities with increasing distance. This could only be true if space itself were expanding.
That's the best I can do for that, I hope Cavediver can do better. If you want to try a Wikipedia explanation then take a look at the Metric expansion of space article, especially the Theoretical basis and first evidence section.
But let me comment about the part where you ask, "Is it because a galaxy that is 13.7 billion light yrs away appears to be receding at a rate greater than c?" First, we will never measure any velocity greater than c. As far as we know, c is a natural constant that governs the maximum rate of influence of any action or effect, including light and gravity.
But second, sufficiently distant objects are receding from us at a rate greater than c, but we only know this from extrapolation of relativity theory and not from direct observation. I do have a vague recollection of reading about indirectly observing such non-observable objects by their light and gravitational effects on closer objects in earlier eras, maybe Cavediver can confirm whether or not I'm misremembering.
Cavediver has warned me off of considering the BB to be like an explosion but I am finding that difficult to do. Is the nature of the universe, on a universal scale, fundamentally different from what I see around me?
As I said at the opening, the nature of the universe on both very small and very large scales is very different from what we experience in everyday life.
--Percy
Edited by Percy, : Grammar.

 This message is a reply to: Message 82 by Dogmafood, posted 01-05-2011 8:43 PM Dogmafood has seen this message but not replied

Percy
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 Message 100 of 248 (600679) 01-16-2011 9:41 AM Reply to: Message 98 by Dogmafood01-16-2011 8:13 AM

Re: The void
Dogmafood writes:
I think I get what you mean by no boundary along the surface. Regardless of it's shape does the word 'surface' not denote a boundary? On the surface or not on the surface. Above or below the surface.
Yes, the surface of the sphere represents a boundary between the inside and the outside of the sphere, but the analogy is between space and the surface of the sphere itself. You can travel infinite distances along the surface of a sphere and never reach any boundary. If space is unbounded then you can travel infinite distances in space and never reach any boundary.
--Percy

 This message is a reply to: Message 98 by Dogmafood, posted 01-16-2011 8:13 AM Dogmafood has seen this message but not replied

Percy
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From: New Hampshire
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 Message 198 of 248 (678097) 11-05-2012 7:35 AM Reply to: Message 195 by NoNukes11-04-2012 10:20 PM

Re: lost in space
NoNukes writes:
Almost certainly all of the matter present today was converted back and forth between matter and energy multiple times.
There must have been was a lot of conversion back and forth between matter and energy in the very, very early universe, if that's what you're referring to, but I think much of the hydrogen, helium and lithium are unchanged since first condensed out of the cooling universe. Most of heavier elements formed by stellar processes and by nova and supernova are probably also unchanged since first formed.
--Percy

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Percy
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From: New Hampshire
Joined: 12-23-2000
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 (1)
 Message 213 of 248 (678726) 11-10-2012 8:23 AM Reply to: Message 205 by kofh2u11-09-2012 6:05 PM

Re: lost in space
Hi Kofh2u,
Is your position that any breakdown of events into 7 stages lends support to the accounts in Genesis? Don't you need 6 stages of events followed by a static 7th stage? And doesn't your position mean that any breakdown of events into other numbers of stages argues against the accounts in Genesis?
Or more to the point, isn't the number of stages in anything irrelevant? Shouldn't you be looking for actual correspondences between scientifically verified events and events in the Genesis? For example, in your first diagram the 3rd stage still has no atoms, but on the 3rd day in Genesis there were already plants and trees "of every kind." Seems to me like there's no correspondence at all.
--Percy

 This message is a reply to: Message 205 by kofh2u, posted 11-09-2012 6:05 PM kofh2u has replied

 Replies to this message: Message 218 by kofh2u, posted 11-10-2012 6:24 PM Percy has replied Message 239 by kofh2u, posted 12-01-2012 10:12 AM Percy has replied

Percy
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Posts: 22723
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.8

 (2)
 Message 220 of 248 (678828) 11-10-2012 6:56 PM Reply to: Message 218 by kofh2u11-10-2012 6:24 PM

Re: lost in space
Okay, I think I understand now. You think that numerology is evidence that the Bible knew about the nature of the universe before modern scientists. But numerology is nonsense, plus the events actually described in Genesis lack any correspondence to what actually happened.
--Percy

 This message is a reply to: Message 218 by kofh2u, posted 11-10-2012 6:24 PM kofh2u has replied

 Replies to this message: Message 224 by kofh2u, posted 11-13-2012 12:51 AM Percy has replied

Percy
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From: New Hampshire
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 Message 226 of 248 (679252) 11-13-2012 3:57 AM Reply to: Message 224 by kofh2u11-13-2012 12:51 AM

Re: lost in space
Hi Kofh2u,
You're previous messages could be loosely interpreted as on-topic, but this one isn't even close and so I won't address its content.
If you'd like to discuss how we know how big the universe is then your participation here is very welcome, but if you continue in this way then I'm pretty sure you'll lose your permissions in this forum, too, the Big Bang and Cosmology forum. As a participant I can't moderate this thread myself, but I'm not the only moderator.
--Percy

 This message is a reply to: Message 224 by kofh2u, posted 11-13-2012 12:51 AM kofh2u has replied

 Replies to this message: Message 232 by kofh2u, posted 11-30-2012 11:16 PM Percy has seen this message but not replied

Percy
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Posts: 22723
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.8

 Message 240 of 248 (682345) 12-01-2012 1:24 PM Reply to: Message 236 by kofh2u12-01-2012 9:20 AM

kofh2u writes:
How could Electromagnetic radiation (not visible light), which came flooding out of the Big Bang 13.5 billion years ago, be any further away than 13.5 BLY?
Because in the 13.5 billion years that that light has been traveling toward us, that region of the universe has continued to recede from us. The light we see today from the most distant reaches of the visible universe is from 13.5 billion years ago when it was much closer. Today it is much further away and in fact has passed over a horizon and is now receding from us faster than the speed of light - we'll never see the most distant parts of the universe as they appear today, no matter how long we wait for the light to arrive.
How could Electromagnetic radiation (not visible light)...
I don't think you meant to say this. Visible light is part of the electromagnetic spectrum. In other words, it *is* electromagnetic radiation.
--Percy

 This message is a reply to: Message 236 by kofh2u, posted 12-01-2012 9:20 AM kofh2u has not replied

Percy
Member
Posts: 22723
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.8

 (1)
 Message 241 of 248 (682349) 12-01-2012 1:37 PM Reply to: Message 237 by kofh2u12-01-2012 9:26 AM

Re: Young or old universe
kofh2u writes:
It seems to me that Genesis was out on a limb until Hubble found support for the claim that the cosmos was NOT always there.
That would be a biggie, wouldn't it?
It certainly isn't a "biggie" in science. In fact, it doesn't merit any attention at all within science.
It seems ill advised for any religion to try to maintain a correspondence between its beliefs and science, because science is ever changing to reflect new evidence or improved insight. First science believed the universe had a beginning, then it believed it was eternal, then that it had a beginning at the Big Bang, and then that it would one day cease expanding and begin falling in on itself into a Big Bounce from which the universe begins again (and again and again), and then that it would expand forever and end in heat death, now there are hypotheses that universes spring out of brane collisions in higher dimensions.
So is it a biggie for your religion if science believes that the universe had a beginning at the Big Bang? I don't know, you tell me. Will it be a biggie for your religion if science eventually comes to believe that there are actually multiple universes, each with its own unique beginning?
--Percy

 This message is a reply to: Message 237 by kofh2u, posted 12-01-2012 9:26 AM kofh2u has not replied

Percy
Member
Posts: 22723
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.8

 Message 242 of 248 (682350) 12-01-2012 1:43 PM Reply to: Message 238 by kofh2u12-01-2012 9:36 AM

Re: Young or old universe
kofh2u writes:
But I thought Dark Energy was deduced because this expansion of Space itself demonstrated that the galaxies were accelerating.
Yes, that's correct. The speed of recession of distant galaxies has been discovered to have begun accelerating a few billion years ago. "Dark Energy" is the label we give to the cause of the accelerating expansion of the universe, but we can only speculate as to the nature of the cause right now.
--Percy

 This message is a reply to: Message 238 by kofh2u, posted 12-01-2012 9:36 AM kofh2u has not replied

Percy
Member
Posts: 22723
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.8

 Message 243 of 248 (682352) 12-01-2012 1:57 PM Reply to: Message 239 by kofh2u12-01-2012 10:12 AM

Re: lost in space
kofh2u writes:
How sure are we about these theories in regard to the size of the Space/time dimensions when astronomers talk about 12 BLY for the most distant galaxies?
The current size of the universe is much more a question of math than theory. Something that was 13.5 billion light years away 13.5 billion years ago has been receding from us for the past 13.5 billion years and so is much further away now than it was 13.5 billion years ago.
Are we to assume that Space has expanded without matter or energy present in the most distant volumes of Space?
The expansion of space is thought to be due to the little understood phenomena of Dark Energy. Quantum theory tells us that no part of the universe can be completely bereft of matter and energy.
--Percy

 This message is a reply to: Message 239 by kofh2u, posted 12-01-2012 10:12 AM kofh2u has not replied

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