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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."
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.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
ok yea your right 1023 is 10^23
Is it true that more people vote for the winner of American Idol, than vote for the president? -Ali G.
The truth is out there.
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.
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.
This sig seemed like a good idea at the time....
"Drug store"? Is there an Americanized version of HHGTTG? My copy says "chemist", not "drug store".
ZFS: because love is never having to say fsck
Sure. There is no restriction to the rate at which spacetime can expand. Relativity only applies to the acceleration of matter.
Our intelligent designer has never created an animal that we couldn't improve by strapping a bomb to it.
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.
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.
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.
I am one of many. My idea is not unique, nor do I expect my voice alone to sway you. I speak in a chorus of opinion.
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.
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
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).
Let's go Hurricanes!!! 2006 Stanley Cup Champions!!!
Let's go Hurricanes!!! 2006 Stanley Cup Champions!!!
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.
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.
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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.
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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.
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a war on terrorism? How can we end a war on a method?