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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.
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))
There's no sig like SIGSEG
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....
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 AdamsSure. 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.
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.
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.
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.
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?
___
No power in the 'verse can stop me
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?
click-clack, front and back. I'm not moving this car otherwise.
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!!!