The Universe is Pretty Big

Psiolent writes "According to a recent article on Space.com, the universe is pretty big (156 billion light years across, to be more precise). Some recent research examining 'primordial radiation imprinted on the cosmos' has led to this conclusion, as well as a few others. This finding is particularly interesting considering the universe is only 13.7 billion years old (which would mean the universe has been expanding faster than light travels), but the article does a good job addressing this seeming paradox."

Comments

Re:The Universe is Pretty Big

[exp(pi*sqrt(163))]

You need to do better than just a copy-and-paste from google. By 1023 I presume you mean 10 to the power of 23. Otherwise I'm distinctly unimpressed.

Re:since light is the FASTEST moving thing

[muon1183]

Um, not quite. If you had RTA, you would understand that the reason the radius of the universe is so large (relative to it's age) is the hubble expansion of the universe. According to current theory, the universe has been expanding since the big bag at an increasing rate. This expansion is not governed by special relativity, and a result of this expansion is that if something travelled 1 light-year in the early universe, it has now travelled something on the order of 1000 light-years. And yes, IAATP (I am a theoretical physicist (in training, at least))

GO TO YOUR ROOM

[Anonymous Coward]

And read the fine article.

The truth is out there.

Re:since light is the FASTEST moving thing

[fredrikj]

The age of the universe is 13.7 (+/- 0.2) billion years, as established by WMAP a year(?) ago. It is perfectly possible for the universe to have expanded faster than the speed of light since the very spacetime might have been expanding; only particle motion "within" it is constrained by the speed of light. Sort of like having a speed limit for the cars on a road while moving the road itself faster than this speed limit.

That's a minimum....

[Rob Carr]

the universe is pretty big (156 billion light years across, to be more precise)

It's worth pointing out that the156 billion lyrs number is a minimum size for the universe. There's nothing in the data that tells us it's only this large.

It also doesn't tell us anything about the shape of the universe. Recent studies of the microwave background have proposed that the universe has a soccer ball or even a Picard (no relation to the TV character) shape. Neither of these have been ruled out, but the minimum size for either of these shapes in our region of space would be 156 billion lyrs. This new result doesn't even tell us if there is a boundary (no, don't ask me what happens at the edge, I don't know) or if the universe "wraps" like the Asteroids game.

Re:That's a minimum....

[Rob Carr]

string theory predics several extra dimensions we can't percieve because they're to small. Any possible relation here?

First off, IANAQP. Most of my modern cosmology and quantum physics comes from SciAm, Brian Greene books, and conversations with Tripoli Rocketry Association member #004. The last time I did tensor calculus was when I looked up Frank Tipler's paper "Rotating Cylinders and the Possibility of Global Causality Violation" twenty years ago. Yes, that is the paper Larry Niven used as the name for a story.

So, based on my rather crude understanding of the whole mess, the answer to your question is "yes." We don't see the extra dimensions in our universe because they are curled up and small. If you look out your window at a telephone wire, the wire appears to be 1 dimensional - it only has length. A closer look shows that the second dimension is "wrapped" around and meets itself.

These dimensions are thought to be exceedingly small, although some string theories allow for the possibility that they could be as big as a millimeter in diameter. The last experiment I remember reading about indicated that, while a millimeter might be too big, they couldn't rule out dimensions on the order of .1 mm. If one of the dimensions is that large, we should soon be able to measure the failure of the inverse square law at very small distances, where gravity leaking into the other dimensions can be seen.

If the four macroscopic dimensions (3 spatial, one time) form closed loops, we might indeed have a strange geometry in space, such as a "horn of plenty."

It's comforting to think that the 4 large dimensions curl up like the small ones. The universe can be "infinite but bounded." There's no messy questions about what happens when you reach the edge of the universe or the universe being infinite in size, although I'd still wonder what's "outside" our universe. There's a symmetry - the big dimensions are simply blown up versions of the small ones and (in some ways) the big dimensions might actually be the same size as the small ones! Measuring the diameter of a dimension can be tricky, since in string theory large and small dimensions are indistinguishable mathematically.

Alas, there's no guarantee that the 4 macroscopic dimensions have their "ends" meet. String theory can handle infinite dimensions and non-loop strings with end points as well. If you could travel far, far faster than light, you might simply keep going in one direction, never returning to your point of origin.

We may never know the answer. If the universe is far bigger than the 156 billion lyrs minimum, then we'll never see edge effects on the cosmic microwave background. The macroscopic universe might go on forever or loop back around or come to a dead stop at a giant brick wall - and we'll never know.

There are two major problems with current quantum cosmologies. One is that they're exceedingly and increasingly difficult to calculate. What good is an equation that is the "answer to everything" if there's no possible way to solve it or even come up with a decent approximation to an answer? The other problem is that there are probably an infinite number of possible theories, and even if they can be solved, the vast majority predict the same answer at any level we could ever hope to explore in any conceivable experiment.

Think of it as job security for physicists.

I wish I could find a link to George Carlin's riff on the Catholic Church's answer "It's a mystery!" It would be oddly appropriate.

Re:That's a minimum....

[Rob Carr]

What I was thinking was that if a Picard geometry would cause some dimensions to be shrunk to tight circles near it's narrow end, could us being near the narrow end explain why the dimensions predicted by string theory(s) are so tiny.

One of the important points about the Picard geometry discussed in the "horn of plenty" theory is that the universe would look different depending on where you are.

As we look around, the universe appears to be pretty much the same in any direction we look. The fine structure constant and other important physical numbers appear to be same here on earth and in the farthest galaxy we see. There is some question if these constants might have changed over time, but the change is thought to be far, far less than the change one would expect being in the strange part of a Picard universe.

The diameters of the "rolled-up" dimensions are thought to affect the properties of the forces and sub-atomic particles we observe. Why those properties are what they are is one of the great mysteries of Quantum Mechanics and Cosmology. An argument can be made that, if the numbers were different, we wouldn't be here to observe that difference. Some have argued that the numbers are deliberate - that God (or some researcher) caused those numbers to be what they are so that either a) life would exist or b) the universe would be "interesting" (like choosing which rules to use for the game of Life.

Would the diameter of the the rolled-up dimensions be affected in an extreme section of a Picard universe? That's a good question. I'd be tempted to say "no." There are places near a black hole where light orbits - in other words, if you look forward, you can see the back of your head! This is similar to the way the Picard universe behaves at an extreme point. Atoms being torn apart in the accretion disk of a black hole seem to have the same physical constants as atoms on Earth. So that would indicate that no, it doesn't change the smaller dimensions. But who knows? Perhaps a Picard extreme region behaves differently from a black hole region in our section of the universe. Our understanding of why the universe "is the way it is" is primative. My understanding, of course, is far more primative than Hawking, Greene, or Thorne.

I have a crude vision in my mind of a universe where, depending on where you are, you see different dimensions rolled up. Properties would change as you moved from one region of the universe to another - each region being far in excess of 156 billion light years in diameter. My topological intuition begins to fail me, though, and I'm getting a major migrane as a result! I should check to see if my brains are being squeezed out my ears.

I really would suggest that you read Greene's books. In the first one, you might find yourself skipping some of the math. I read through it and humored myself by thinking that I understood the math. I do find that Greene has a wonderful way of tying what you already know into what he's trying to explain.

obligitory Douglas Adams Quote

[Adrick42]

Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the drug store, but that's just peanuts to space.

Douglas Adams

Re:obligitory Douglas Adams Quote

[egomaniac]

"Drug store"? Is there an Americanized version of HHGTTG? My copy says "chemist", not "drug store".

Re:obligitory Douglas Adams Quote

[Uma Thurman]

Babelfish. Duh.

Er, yes

[Wylfing]

This finding is particularly interesting considering the universe is only 13.7 billion years old (which would mean the universe has been expanding faster than light travels)

Sure. There is no restriction to the rate at which spacetime can expand. Relativity only applies to the acceleration of matter.

Re:going backward in time?

[LastToKnow]

Well, that would depend on whose frame of reference you're looking at, in an 'ordinary' FTL situation, but this is kinda different because its not that things are moving FTL with respect to each other, its that the space between things is growing on its own. Apparrantly, according to the article, this can happen FTL without violating causality and such.

Excerpt from the Weekly World News ?!?!?

[hajihill]

Somehow this seems like something that should be in the scientific equivalent of the Weekly World News, or the National Enquirer....

Read this quote.... (which seems to provide a basis for other comments)

"The universe is about 13.7 billion years old. Light reaching us from the earliest known galaxies has been travelling, therefore, for more than 13 billion years. So one might assume that the radius of the universe is 13.7 billion light-years and that the whole shebang is double that, or 27.4 billion light-years wide."

What is our frame of reference here.... Are we still assuming we are the center of the universe, even after all the progress we've made in a variety of sciences???

Doesn't this seem to rule out the possibility of light which simply hasn't reached us yet (i.e. if we were NOT located in the middle of the Universe and it was in fact still expanding)?

Re: Excerpt from the Weekly World News ?!?!?

[Corvus9]

The frame of reference is given in the quote; "us". That is, Earth. According to the Big Bang model, the universe expanded from a point. Since every place was once at that same point, every place has an equal claim to be the "center of the universe". Picking Earth is just as valid as picking any other place.

There's another good reason to pick Earth as the center; if the universe is 13.7 billion years old then there is no way that anything - light, gravity, particles, aliens - from farther than 13.7 billion light years has reached us. We are at the centre of a 13.7 billion light year sphere containing everything which we can possibly observe.

Not only does this not rule out the possibility of light which hasn't reached us yet, it is defined by it. This observable universe, which some have called "the cosmos", expands by 1 light year every year, as light further out has time to reach us. The entire universe could well be much larger than this; we can only theorize.

By the way, the observable universe is very symmetrical in every direction, so we can consider ourselves to be at the centre even in a literal geometric sense of the word.

Universe potentially older

[ipoverscsi]

According to a recent Science News article (subscribers only), the universe may actually be older than the aforementioned 13.7 billion years.

The evidence comes from the fact that older stars must fuse carbon, nitrogen and oxygen into helium, unlike their younger bretheren that fuse pure hydrogen. The slowest part of the carbon-nitrogen-oygen reaction comes during the collision of a proton with a nitrogen-14 nucleus. Using particle accelerators to mimic the interior of older stars they have determined that the reaction occurs half as fast as estimated.

Two research teams, one from the National Institute for Nuclear Physics in Padova, Italy, and the other from the University of North Carolina at Chapel Hill, have performed nearly identical experiments and their prelimiary results agree, although their findings have not yet been published.

Re:Universe potentially older

[Floet]

I'm not sure exactly which reaction you're talking about in older stars (ie: fusion or fission) but fusing carbon, nitrogen and/or oxygen into helium is quite impossible. This comes from the fact you should have learned in chemistry that all three aforementioned elements are heavier than helium.

Re:Universe potentially older

[drudd]

As the previous answer noted, you're a little confused about the Carbon-Nitrogen-Oxygen (CNO) cycle. In these set of reactions, the carbon is only used as a catalyst for making helium (so you're still turning H -> He, but you're doing it by repeatedly capturing protons (H) and then beta-decaying). See this article for more information on CNO.

Now the argument that the referenced article is using is that less massive stars will stay on the main sequence longer, due to the reduction in CNO efficiency. Thus older globular clusters will have a bluer turnoff than previously expected.

While this will cause a systematic underestimation of the age of globulars by ~0.7-1.0 Gyr, the uncertainties are so large (+/- 1-1.5 Gyr or so), that they are still consistent with the age of the universe derived from CMB observations.

Doug

Re:The Universe is Pretty Big

[Phronesis]

Of course it would be easier to post "ten to the power of twenty three" if slashdot supported <sup> tags.

Would this work on cops?

[serutan]

No, officer, I wasn't actually going 90 miles an hour. It just seems like it because the spot in the road where I was a minute ago is a mile and a half away now.

Only space expanding?

[DerWulf]

I am no scientist, so please forgive. How come the distances between objects seem to be increasing ( space time expansion or so they say) but not their size? What makes matter so special that the space time between molecules is not expanding as well? What makes our perception so special that only the distances between objects we like to observe ( galaxies, stars) increases but not the distances within them?

Re:Only space expanding?

[SofaMan]

My guess is that objects do expand, but since even the biggest objects are infinitesimally small compared to the massive distances between them, we are not going to be talking about objects expanding in the same way we talk about space expanding, since the detectable expansion of objects is likely to be fairly negligible.

I'm not a scientist either, so I'm just making a complete stab-in-the-dark guess, and I'm very happy to be corrected by anyone with a more researched answer. :)

Re:Only space expanding?

[CTachyon]

Yup, over large enough scales. Which is why everyone was concerned (up until a few years ago) about whether or not there might be a "Big Crunch". If the universe ever stops expanding, it must then proceed to collapse -- excepting the unlikely possibility that dark energy weakens but thereafter remains constantly balanced at the equilibrum, as Einstein originally envisioned when he proposed the Cosmological Constant.

Re:Only space expanding?

[PhuCknuT]

Think of it this way... You put 2 magnets on a rubber sheet, stuck together, then you stretch the sheet. The sheet will expand underneath them, putting some force on them, but the magnetic force between them is much stronger and will keep them together.

Now on the scale of molecules, planets, solar systems, even galaxies, expansion is tiny still. The intermolecular forces, electric, magnetic, gravity, whatever will all overpower the expansion by many many orders of magnitude. IIRC the estimates for expansion are something like 20km/s per 1M light years. That works out to 0.00000000000000000211 meters/s per meter of space if I did the math right.

So basically, space is expanding everywhere, even inside you, but it's so slow that your molecules just hold together while expanding space slides out from under them. It's only in the huge empty space between galaxies that it's easily measurable.

Re:Only space expanding?

[Xerxes314]

What makes matter so special that the space time between molecules is not expanding as well?

Matter is held together by electromagnetic forces that are much stronger than the local repulsion due to cosmological expansion.

Re:Only space expanding?

[ggwood]

Expansion is severely reduced near massive objects - thus massive bodies do not expand with the rest of the universe, but at a tiny (or perhaps zero) fraction of the Hubble rate.

My source? I asked this in the context of the distance from the Sun to Pluto increasing over time of John C. Baez, who works on gravity and has written books on it, so I would say he is a good authority.

His response was that space does not expand (much) near massive objects - meaning even between the Sun and Pluto the expansion will not occur at anywhere near the rate it occurs in free space.

Yes, you have to learn general relativity to understand why. It is not simply that local (Newtonian) gravity overcomes it - I asked that specifically. No, I have not taken GR so I cannot give any further insight into this issue.

If the uniform expansion did occur uniformly between the Sun and Pluto, we could measure the Hubble constant by watching Pluto slowly receede from the Sun. It would be measurable using current values of the Hubble constant over years or decades. The effect is tiny beyond measure, apparently.

Note: I cannot recall if there is truely *no* expansion between the Sun and Pluto, or if it is just really small. I have thus opted for the really small in this post as it is the more conservative option.
_________________________________________ ________

Re:Only space expanding?

[nine-times]

This is actually a really great question. Don't let the flurry of responses fool you, the answer to something like this is not so easy or cut-and-dry.

The truth is, no one is completely sure. The replies you've gotten aren't too far off from nice, accepted answers that you might get from a physicist, but it's one of those things where no one really knows.

First, consider the statement "space is expanding". Sounds simple enough, but lets start with the simple: What is space? I mean, what is it that's expanding when space expands? Mostly, our understanding of space usually breaks down, eventually, into putting wooden sticks we call "meter sticks" next to objects, or putting them in-between objects.

Beyond that, some fun questions:

What is gravity?

What is magnatism?

What are the other forces (weak, strong, they seem to be trying to come up with new ones all the time)?

Are those all the forces?

By what means do those forces exert themselves on matter?

What, exactly, is the relationship between gravity and matter?

So, though it's possible to answer your question in a statement to the effect of, "General relativity says electro-magnetism and gravity act on the particle and makes it work like that," but don't think that answers your question. It ends up being like when someone says, "Why do objects, when unhindered, move towards each other? Gravity!" They've effectively given a name to "the force which makes objects move towards each other", but haven't really explained why.

I'm not being clear either, but I can tell you what's tricky about it. When people talk about general relativity allowing for space to be expanding, it really is something like a reverse-gravity (gravity being when space bends in). Matter seems to produce gravity, or, according to the fancy of an occasional clever thinker, matter is produced by spikes in the gravity field. In any event, it's not clear what either space-time or matter would be without the other, and "gravity" and "space-time expansion" are names for measurements of the interaction between them. Whatever- matter and this "expansive" force are mixed up in weird games. They are linked. Good question.

not symmetrical last time I observed it...

[Roman_(ajvvs)]

The placement of earth in its galaxy has no symmetry and the placement of the galaxies on the observable universe is anything but symmetrical

In addition to this, the observable universe has no visible boundaries which could be deemed symmetrical, as what we observe is not so much the universe itself but the contents thereof. Since the contents aren't spread symmetrically or in any particular order for that matter, any observed boundaries can't be symmetrical.

If you can't see where it ends, does that mean it ends where you no longer see it?

Re:not symmetrical last time I observed it...

[hajihill]

Okay, well.....

I have a couple more questions... which may only serve to indicate my ignorance in both posing the above issue and asking these questions....

Taking this quote into consideration:
"One seemingly paradoxical consequence of Hubble's observation is that galaxies sufficiently far away will be receding from us at a velocity faster than the speed of light. This distance is called the Hubble radius, and is commonly referred to as the horizon in analogy with a black hole horizon."

Wouldn't it be assumed that, while the Universe is definitely expanding, the distance being observed is simply this "Hubble Radius"?

How could we ever make realistic, meaningful observations about the size of the universe when we acknowledge, by means of this and general relativity that at a certain point the expansion of the universe prevents us from observing things more than a specific distance away, for when they reach this distance, defined conceptually by this Hubble radius, they would essentially become unobservable?

To rephrase this you could say that when things get far enough away they will be receding, with the expansion of space-time at a rate faster than the speed of light, and light coming from them will no longer be observable.

Wouldn't this explain why the universe has this 'symmetrical' appearance from our point of observation?

Wouldn't it make more sense to say that this 13.7 billion light-year radius says something not about the size of the universe but in fact about it's rate of expansion?

Re:not symmetrical last time I observed it...

[CodeMonkey4Hire]

The article's meaningful observation is that they have found the minimum size of the universe. They are doing the best that they can, since they can only see out to a point. And by the way:

The edge of the cosmic light horizon is 13.7 billion light years distant. The present distance (comoving distance) to the edge of the observable universe is larger, since the universe has been expanding; it is estimated to be about 50 billion light years (4.7 × 1023 km).

WTF?

[wafwot]

I'm surprised no one has brought this up yet, and I apologize if this seems out of context for me to be commenting, since I'm a musician and a composer, but has anyone read the article and felt that all of this information "makes sense" only if Earth is the center of the creation of universe?

We can measure the distances to far off galaxies to get a "radius", but a "radius" implies a center, primarily the Earth. I have some serious problems with us, because it implies that the "Big Bang" occurred right here, where we are now in the universe. Absolute and utter bull.

Cornish's "explanation" does not make up for the idea that we are not at the center of the creation of the universe. 156 billion light years is not a good number to go by, then, because it doesn't take into account for how far we are from the creation site.

Unless Cornish or anyone else can pinpoint exactly where the Big Bang (or Big Burp or whatever else it's been called over the years) has occurred, this article is completely and utterly pointless.

Please prove me wrong. I study Debussy and Schoenberg, so I may have no right commenting, but this seems like common sense to me.

- wafwot

Re:WTF?

[Anonymous Coward]

I think your question is a fair one, coming from someone with no scientific background and it seems three points need to be cleared:

a) the concept of "radius", or "coordinate system".
b) the concept of "isotropy"
c) the concept of 4D surfaces

a) Radius here is indeed taken as distance to the earth. Cosmologists like to use a spherical coordinate system where the earth sits at the centre, simply because it is *convenient*. Let me first explain isotropy and hopefully it will become clear why this, in this case, doesn't matter:

b) Isotropy says that the *visible* universe is pretty much the same everywhere we go. Cosmologists reached this conclusion based on *observational* evidence. This means (among other things) that the universe is expanding *at the same rate* everywhere in space. This has huge implications.

Try this: Find a piece of paper and draw a series of black dots, in a grid, equally spaced. Make one of your dots red. That's the earth. Now imagine your paper is elastic and you take its four corners and pull, so that your paper gets bigger (you'd pull exactly the same amount horizontally and vertically). You'd see that the distance from the red dot to the nearest black dots had increased by a given amount, say D.
If you repeated this exercise having coloured ANY of the other dots red, you'd find the same thing. Meaning, expansion (and measured distances DUE TO EXPANSION are the SAME no matter where you sit in the Universe.
So it doesnt really matter that we're measuring distances due to expansion with a radius relative to the earth. You'd get the same answer if you were sitting on the galaxy M31, measuring distances relative to it.

c) So where is the centre of expansion? Look at your fictitional piece of paper and you'll be able to tell that it's nowhere in the piece of paper. In fact it seems to be everywhere. The right answer gets complicated due to the fact that we live on a curved 3d space. But the answer is again nowhere in our 3d space, and again it seems to be everywhere. We'd have to get into higher dimensions to explain this but the point that I would really like to get across is that there is NO centre of expansion. Not that we can visit

I hope this helped.
--r

WTF back at you

[PatrickThomson]

The big bang did indeed ocurr right where earth is. it also ocurred where alpha centauri is, and where the Andromeda galaxy is. the big bang *was* the universe. Trying to pin it down is like trying to draw on a balloon with a pen the exact location of the unblown balloon.

Re:finite?

[Tango42]

You've got that the wrong way round. A sphere is finite yet unbounded. In other words the surface area of a sphere has a finite value, but there is no edge.

To clarify, when we talk about spheres in this context we mean the surface, not the inside - hence a sphere is 2D, not 3D.

Re:going backward in time?

[stanmann]

Actually, causality isn't violated unless an object is moving FTL in respect to a "fixed" reference point. If two objects are moving at LT light speed away from the "fixed" point. they may be moving FTL in respect to each other. In fact it sorta has to work that way. Just like two cars moving at 60 mph(each) away from a fixed point in opposite directions have a separation speed of 120mph does not mean that one is standing still and the other is moving 120mph. You gotta define the fixed point first.

Re:going backward in time?

[CodeMonkey4Hire]

NOTHING is traveling faster than light. The expansion of the universe is not motion, so special relativity does not apply.

Also, this expansion is not like plate tectonics on earth where there are a couple different areas that are expanding (while there are a couple that are receding). This expansion is happening everywhere at once. So rather than all of the extra space just appearing between New York and London somewhere in the Atlantic, it is as though the earth's diameter started to increase and New York became farther away from Neward and Philidelphia and Boston all at the same time (that could be a good thing).

Oh come on /.'rs I can't be the only one....

[Bitsy Boffin]

who immediatly thought of....

Whenever life get you down, Mrs. Brown,
And things seem hard or tough.
And people are stupid, obnoxious or daft,
And you feel that you've had quite enu-hu-hu-huuuuff!
Just - re-member that you're standing on a planet that's evolving
and revolving at 900 miles an hour,
It's orbiting at 19 miles a second, so it's reckoned,
the sun that is the source of all our power.
The Sun and you and me, and all the stars that we can see,
are moving at a million miles a day,
In the outer spiral arm, at 40,000 miles an hour,
of the Galaxy we call the Milky Way.
Our Galaxy itself contains 100 billion stars,
it's 100,000 light-years side-to-side,
It bulges in the middle, 16,000 light-years thick,
but out by us it's just 3000 light-years wide.
We're 30,000 light-years from galactic central point,
we go round every 200 million years,
And our galaxy is only one of millions of billions
in this amazing and expanding universe.
The universe itself keeps on expanding and expanding,
in all of the directions it can whizz,
As fast as it can go, at the speed of light you know,
twelve million miles a minute, and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
how amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
because there's bugger all down here on Earth.