# Thread: Current size of universe

1. Newbie
Join Date
Jul 2008
Posts
1

## Current size of universe

My name is Dave and I'm trying to get a handle on the current dimensions of the Universe. How many miles (or whatever distance figure is appropriate) from the center of the Universe to the outer known limit?

What is the distance from the center of the Universe to Earth?

Assuming the Universe is flat, what is the ratio of the horizontal to the vertical?

What is the distance that our present telescopes can see? To the center? Beyond the center? When aimed along the vertical line, I assume everything is black past a certain point?

Thank you for any information you can send me.

2. Banned
Join Date
Nov 2004
Posts
737
...
What is the distance from the center of the Universe to Earth?
...
No-one has managed to find the centre of the Universe yet.

Or even if they have, it didn't have a sign on it.

3. Originally Posted by Dave Steadman
My name is Dave and I'm trying to get a handle on the current dimensions of the Universe. How many miles (or whatever distance figure is appropriate) from the center of the Universe to the outer known limit?

What is the distance from the center of the Universe to Earth?

Assuming the Universe is flat, what is the ratio of the horizontal to the vertical?

What is the distance that our present telescopes can see? To the center? Beyond the center? When aimed along the vertical line, I assume everything is black past a certain point?

Thank you for any information you can send me.
Firstly as mentioned the centre of the universe is undefined. Secondly the actual true size of the universe would be an estimate based on how far away the outer most detectable objects are. The current estimate IIRC is about 13.7 billion light years from the earth to the furthest most detectable objects. But remember that the universe is inflating at a very high rate and possibly subliminally at the furthest regions. Some of the more knowledgeable folks on this forum will explain it in more detail

4. Established Member
Join Date
Dec 2007
Posts
1,136
If the universe is flat does that mean there would be a physical barrier or wall that defines the end of the universe? Obviously we cannot catch up to the inflation's leading edge but what if we could - What would we see? I just cannot get my head around that concept.

5. Originally Posted by Dave Steadman
My name is Dave and I'm trying to get a handle on the current dimensions of the Universe. How many miles (or whatever distance figure is appropriate) from the center of the Universe to the outer known limit?
As currently conceived, there is no center. As an analogy, imagine the surface of a balloon is the entire universe. No inside, no outside, just the surface. Where is the "center" of such a universe? Well, there's no such thing.

What is the distance from the center of the Universe to Earth?
Since there is no center, some will point out that any point in the universe could be considered a "center," in which case the answer to your question would be zero.

Assuming the Universe is flat, what is the ratio of the horizontal to the vertical?
From all indications and observations, h:v = 1:1.

What is the distance that our present telescopes can see?
The Hubble Ultra Deep Field should give you some idea.... Remarkably, your TV set tuned to an off channel can pick up and display photons that have come from the farthest distance possible - about 13.67 billion lightyears. (That's a lot of miles. )

When aimed along the vertical line, I assume everything is black past a certain point?
When aimed in any direction whatsoever, beyond 13.67 billion lightyears, we cannot see anything, but not because nothing is there. Au contraire, we see nothing because the universe at that time is so hot and dense, it is opaque. The photons that enable us to see anything keep running into other particles and cannot travel any significant distance, so we can't see anything beyond that limit (and never will be able to -- using electromagnetic radiation, which is the generalized term for light).

I haven't checked Wikipedia's Big Bang article lately, and there's always the chance that it contains some misleading statements, but I'm sure you would benefit from looking it over.

6. Banned
Join Date
Dec 2006
Posts
13,423
Just to throw in the inflation factor- 46 Billion Light years is our current estimate .
We can see out to 13.7 billion light years, the rest is pushed out of the visible field because of inflation, but if the universe stopped inflating right now then all of that would be visible in about 46billion years

To expand (pun not intended) on what Cougar said (Although Cougar is more educated than I am- just wanna clarify for Dave), Cougar put the word "surface" in Italics to emphasize what he said about no inside to the balloon. It's an analogy, but describing the current observed state of the universe doesn't really fit with what our brains are accustomed to visualizing. So be wary of trying to ask what's on the other side of the surface There isn't necessarily anything there.

Jetlack, I don't personally hold a belief as to the 'edge of the Universe' if such exists. If it did, I would image that it wouldn't be a wall or anything. First off, I imagine we wouldn't be able to travel there or see anything (Imagine a warp gate that took our ship right up to the edge) because if we 'crossed the edge' we would loop back and find ourselves at our starting point.
However, if we assume we CAN "observe" (somehow) beyond the Universe, we still would see a lot of Nothing. Because there isn't space for light to travel through. there isn't light. If you think the Universe is full of void- that's nothing compared to...uh... Nothing.

7. Originally Posted by Jetlack
If the universe is flat does that mean there would be a physical barrier or wall that defines the end of the universe? Obviously we cannot catch up to the inflation's leading edge but what if we could - What would we see? I just cannot get my head around that concept.
Can anyone?

8. Banned
Join Date
Dec 2005
Posts
14,315
Originally Posted by rtomes
No-one has managed to find the centre of the Universe yet.

Or even if they have, it didn't have a sign on it.
Your statement is true for the actual universe. It's not true for the observable universe.

For the observable universe, the following is true:

How many miles (or whatever distance figure is appropriate) from the center of the Universe to the outer known limit?
About 46 billion light years. In Wikispeak: "The comoving distance from Earth to the edge of the visible universe (also called cosmic light horizon) is about 14 billion parsecs (46 billion light-years) in any direction." (source: Lineweaver, Charles; Tamara M. Davis (2005). "Misconceptions about the Big Bang". Scientific American. Retrieved on 2007-03-05.)

What is the distance from the center of the Universe to Earth?
0.00000 (use any dimensions you wish - it's still zero)

Assuming the Universe is flat, what is the ratio of the horizontal to the vertical?
Flat, how? Like a pancake? If so, the ratio is 1, as it's as nearly spherical as we can tell.

What is the distance that our present telescopes can see?
When speaking of great distance, we speak in terms of time, not distance, as the rate of expansion isn't constant, and going back that far introduces a lot of questions as to the exact distance.

Currently, Hubble's Ultra Deep Field has seen, in visible light, back 13 Billion years distant.

When aimed along the vertical line, I assume everything is black past a certain point?
Black, white, psychodelic purple... We just don't know, as we can't see beyond a certain point.

9. Originally Posted by Neverfly
Just to throw in the inflation factor- 46 Billion Light years is our current estimate.
Thanks for the expansion. In fact, I think you should be saying "expansion" instead of "inflation." Although from all indications the universe is currently "inflating," that term is usually reserved for that brief instant during the first second of time when the universe expanded superluminally before settling down to a more 'relaxed' expansion rate similar to what we see today.

To further e-x-p-a-n-d on the topic for Steadman's benefit, one must differentiate between the visible universe and the 'whole' universe, which may be a lot larger (but since anything outside our visible horizon is... not visible, it's very hard to tell much about it). Nevertheless, Alan Guth, who developed the Theory of Inflation, calculated that the 'whole' universe was 1023 times larger than the visible universe! I mean, the visible universe is pretty darn big, but we're talking 100,000,000,000,000,000,000,000 times bigger! Guth said, "...if the inflationary theory is correct, then the observed universe is only a minute speck in a universe that is many orders of magnitude larger."

Inflationary theory has developed considerably since Guth first proposed it, and it has some observational support, but whether it is correct or not has not really been determined yet.

10. Originally Posted by cosmocrazy
But remember that the universe is inflating at a very high rate and possibly subliminally at the furthest regions.
I'm guessing that's "superluminally" (faster than light) rather than "subliminally" (undetectable by consciousness)?

Grant Hutchison

11. Order of Kilopi
Join Date
Jun 2006
Posts
4,794

## Old and Fat and Flat

Originally Posted by Neverfly

We can see out to 13.7 billion light years, the rest is pushed out of the visible field because of inflation, but if the universe stopped inflating right now then all of that would be visible in about 46billion years
Ahem. 'Back' 13.7 billion light years, not 'out' 13.7 billion years. We can see 'back' to the CMB, which was a long time ago and was when the universe was very hot.

Welcome back to the circus, NF.

On other OP stuff:

Many people argue that there are parts of the universe forever inaccesible due to the expansion. Personally, I doubt it, I think the ant on the rubber band analogy holds.

The universe is 'flat' as far as we can tell, to within 2 to 3 percent on cosmological scales. This means it is not closed in 3-space, as is a spherical surface in 2-space embeddded in 3 space, and it is not open in 3 dimensions, as is a hyperbolic (saddle) surface in 2-space embedded in 3-space.

There is also zero, zilch, none, nada physical evidence of more than 3 space dimensions and 1 time dimension, but that's another post.

Regards, John M.

edit: There is no reason currently to think that the universe is not infinite, also.

12. Banned
Join Date
Dec 2006
Posts
13,423
Originally Posted by grant hutchison
I'm guessing that's "superluminally" (faster than light) rather than "subliminally" (undetectable by consciousness)?

Grant Hutchison
Actually, both do apply

13. Originally Posted by Neverfly
Originally Posted by grant hutchison
I'm guessing that's "superluminally" (faster than light) rather than "subliminally" (undetectable by consciousness)?
Actually, both do apply
So you figure that if the car keys in your pocket started to expand faster than light, you wouldn't notice?

Grant Hutchison

14. Banned
Join Date
Dec 2006
Posts
13,423
Originally Posted by grant hutchison
So you figure that if the car keys in your pocket started to expand faster than light, you wouldn't notice?

Grant Hutchison
If it's faster than light, I'm sure I wouldn't notice

15. Originally Posted by Neverfly
If it's faster than light, I'm sure I wouldn't notice
Ah well. I suppose if you're absolutely sure, then that's one less thing for you to worry about.

Grant Hutchison

16. Banned
Join Date
Dec 2006
Posts
13,423
Originally Posted by grant hutchison
Ah well. I suppose if you're absolutely sure, then that's one less thing for you to worry about.

Grant Hutchison
http://www.bautforum.com/1285396-post7.html

17. Originally Posted by Neverfly

Different thing, though: that thread's about the addition of velocities under special relativity; this one refers to superluminal velocities arising from the expansion of space.

Grant Hutchison

18. Banned
Join Date
Dec 2006
Posts
13,423
Originally Posted by grant hutchison

Different thing, though: that thread's about the addition of velocities under special relativity; this one refers to superluminal velocities arising from the expansion of space.

Grant Hutchison
Yeah, I know. Was just being absolute, considering the pocket.
I dunno, somehow it all fit together for a laugh inside my head, but now I can't figure out why.

19. Established Member
Join Date
Jul 2003
Posts
664

## Conceptions

Originally Posted by geonuc
Can anyone?
Hi Geo, the center of the universe, the limits of it,
oh my, where do they come from, the universe is expanding
into null spacetime, dark matter related to the expansion is theory
only, and no evidence to support the idea. Socrates in his law of opposites,
explained, that everything has an opposite, antigravity seems more appropriate
than a dark matter scenario.
Nokton

20. Originally Posted by Neverfly
Yeah, I know. Was just being absolute, considering the pocket.
I dunno, somehow it all fit together for a laugh inside my head, but now I can't figure out why.
I was working my way towards the phrase "pocket universe", myself.

Grant Hutchison

21. Originally Posted by nokton
... the universe is expanding
into null spacetime ...
Would you care to define this "null spacetime"?

Grant Hutchison

22. The observable universe is defined by the distance that the oldest photon we have detected has travelled. That photon has been travelling for 13.7 billion years.

Considering it from the photons point of view, it has crossed a distance that was around 40 million light years when that photon was emitted with the Cosmic Microwave Background Radiation. As we receive that photon, the original coordinate that the photon was emitted from is estimated to have receded to around 46 billion light years in distance.

So our observable universe can be represented by a sphere around us, currently 13.7 billion years old and 46 billion light years in diameter. The oldest photons we receive were emitted early in the history of the universe when we think it was a lot smaller (around 1100 times smaller) than we think it is today.

There were no galaxies where we are, when the CMBR was emitted, but now we think there will be galaxies in our observable universe at distances up to 46 billion light years away. We have, so far, only observed galaxies what were up to 5.7 billion light years away when they emitted the light we are now seeing.

If our observable universe were all there is, if it is the whole universe, then we can consider ourselves at the centre of everything! If this is not the case, then perhaps anywhere in the universe can be considered to be the centre of things. Maybe the universe wraps around on itself and has no edge - like Pac-Man if you move off one side you come back on the other (this might be true however large the universe is, if it is larger than the observable universe).

Or perhaps the whole universe is many magnitudes larger than our observable portion of it. There may currently be galaxies trillions of light years away. Due to the expansion, no particle from our observable universe can ever reach that galaxy and the same would be true the other way round.

Then again, the whole thing might have been infinite to begin with!

23. Order of Kilopi
Join Date
Jun 2006
Posts
4,794
Grant, NF, if you have a teenage male son as a driver in your house, your car keys will disappear FTL. Just hope that the car doesn't go FTL.

Regards, John M.

24. Banned
Join Date
Dec 2004
Posts
14,782
My name is Dave and I'm trying to get a handle on the current
dimensions of the Universe.
Hello, Dave! I'll try to make this the most concise reply yet.

How many miles (or whatever distance figure is appropriate) from the
center of the Universe to the outer known limit?
There is no indication that the Universe has a center. Theoretically
it does not need to have a center. There are basically two ways that
could be: If the Universe is infinite in all directions (which is entirely
possible theoretically and is not contradicted by observations, but I
think is very unlikely), or if the geometry of the Universe is finite but
unbounded, analogous to the surface of a sphere. There is no point
on the surface of a sphere which can be considered to be the unique
center of that surface, and the surface has no boundaries, or edges.
Analogously, the Universe may have no center point and no edge.

The farthest thing that we can see is the hot plasma which filled the
Universe 13.7 billion years ago. Light from that plasma traveled for
13.7 billion years to reach Earth, and we see it now as the cosmic
microwave background radiation. The light traveled a distance of
13.7 billion light-years to reach Earth.

The space through which the light traveled was expanding. The light
we see now was emitted from a sphere just 40 million light-years in
radius surrounding the particles which would later become the Earth.
Today the sphere of particles from which the light was emitted is
46 billion light-years in radius. So the galaxies and stars and planets
which formed out of the plasma that we see now via the cosmic
microwave background radiation are 46 billion light-years away.
Because of the expansion, we will never be able to see them.

A light-year is approximately 6 trillion miles, so 13.7 billion light-years
is the same as 82,200,000,000,000,000,000,000 miles. 46 billion ly
is the same as 276,000,000,000,000,000,000,000 miles.

If the Universe is finite, it must still be much larger than we can see,
because there is no indication of any overall spacetime curvature
analogous to the curved surface of a sphere. Overall, spacetime
appears to be "flat".

If the Universe does have a center, we see no indication of it, nor
any hint of its direction from us.

What is the distance from the center of the Universe to Earth?
As far as we can tell, nomatter where you are in the Universe, it
looks as if you were in the center of the expansion. We do not know
whether that is actually true or if the Universe is just so big that we
can't see any of the indications we'd expect to see if the Universe
were finite and bounded.

Assuming the Universe is flat, what is the ratio of the horizontal to
the vertical?
That is not what is meant by "flat" when describing the large-scale
geometry of the Universe. What is meant by "flat" is that it follows
the rules of Euclidean plane geometry, rather than something like
spherical geometry or Reimann geometry. Locally, gravity warps
spacetime, making it curve. But on average it appears to be flat.

What is the distance that our present telescopes can see?
To the center? Beyond the center?
The cosmic microwave background radiation is and will likely always
be the most distant thing we can see. It was emitted 370,000 years
after the Big Bang. After that, the Universe was dark until the first
stars and galaxies formed. The most distant galaxies we can see
appear to have formed when the Universe was a few hundred million
years old. Light from them has traveled about 13 billion light-years.
The James Webb infrared space telescope which will be a follow-on
to the Hubble space telescope and is scheduled to launch in 2013
should be able to see even earlier, younger, more distant galaxies.

-- Jeff, in Minneapolis

25. That was concise?

26. Banned
Join Date
Dec 2006
Posts
13,423
Originally Posted by speedfreek
The observable universe is defined by the distance that the oldest photon we have detected has travelled. That photon has been travelling for 13.7 billion years.
Wow, you know him? What a Heroic photon! I would like to meet that photon...
Originally Posted by John Mendenhall
Grant, NF, if you have a teenage male son as a driver in your house, your car keys will disappear FTL. Just hope that the car doesn't go FTL.

Regards, John M.
For now, he's five. But in a few weeks he will be a teenager.
I'm afraid I'm one of the mean ones. I have zero intentions of ever buying him a car.
And I'm not one to let anyone drive my truck. You'll have an easier time getting my spleen than my keys...

27. Newbie
Join Date
Jul 2008
Posts
3
I joined this forum because of this topic. I don't understand how anyone can confidently place a size or age on the universe when we don't have the ability to see the end of it. We could only be in a small portion of it that happens to be expanding because of some other cataclysm besides the big bang. I think it is the height of hubris to theorize on such a grand scale. Every generation produces a new paradigm on this kind of subject. What makes us think we're better? Anyway, glad to meet you all.

28. Banned
Join Date
Dec 2006
Posts
13,423
Originally Posted by sargon
I joined this forum because of this topic. I don't understand how anyone can confidently place a size or age on the universe when we don't have the ability to see the end of it. We could only be in a small portion of it that happens to be expanding because of some other cataclysm besides the big bang. I think it is the height of hubris to theorize on such a grand scale. Every generation produces a new paradigm on this kind of subject. What makes us think we're better? Anyway, glad to meet you all.
Creating a theory is just mans nature. It doesn't make the scientist arrogant for him to observe the evidence, theorize, then observe more and more evidence and compare his theory to that evidence.
In spite of not being able to "see" further back than 13.7 billion liught years, there is still an awful lot of evidence out there.
Do we know for sure? No...
But only a dishonest person would claim to.
But the observational evidence best supports current theory.

29. Originally Posted by sargon
I joined this forum because of this topic. I don't understand how anyone can confidently place a size or age on the universe when we don't have the ability to see the end of it. We could only be in a small portion of it that happens to be expanding because of some other cataclysm besides the big bang. I think it is the height of hubris to theorize on such a grand scale. Every generation produces a new paradigm on this kind of subject. What makes us think we're better? Anyway, glad to meet you all.
*We* are different by going by the scientific method. http://en.wikipedia.org/wiki/Scientific_method

Have been for a couple of centuries now. Its how we got to where we are. If it didn't work, we couldn't have gone to the Moon.

30. Originally Posted by sargon
We could only be in a small portion of it that happens to be expanding because of some other cataclysm besides the big bang. I think it is the height of hubris to theorize on such a grand scale. Every generation produces a new paradigm on this kind of subject. What makes us think we're better? Anyway, glad to meet you all.

You are quite correct that we don't know how much of the universe we can see. You are also quite correct to say that if our observable universe is expanding, that doesn't necessarily mean the whole universe is expanding. We cannot know what is going on outside of our observable universe.

I should have inserted a caveat in my earlier post - "assuming the rest of the universe acts like our section of it seems to" and it is good to point these things out, as we can come across as if we are stating facts.

In general, I think every generation gets a little closer to accurately describing the universe around them (probably with some notable historical exceptions!).

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•